BACKGROUND OF THE INVENTION

This invention deals with non-crosslinked, poly-branched polymers having a comb- burst configuration and a process for preparing such polymers. Macromolecular organic compounds having novel structures have been investigated for many years as academic curiosities and very little attention has been paid to their use in industrial applications. Since the early 1980's, there has been a renewed interest in the study and development of such macromolecular materials in order to control their critical molecular design parameters, for example, size, shape, surface chemistry, flexibility, and topology, for use in industrial applications. These materials have found such diverse uses as demulsifiers for oil-in- water emulsions, as wet strength agents in the manufacture of paper, as agents for modifying viscosities in aqueous formulations, such as paints, and as submicron size cali¬ brators. Certain biological uses have also been suggested for these materials.

Structurally, polymers are classified as either linear or branched wherein the term "branched" generally means that the individual molecular units of the branches are discrete from the polymer backbone, yet may have the same chemical constitution as the polymer backbone. Thus, regularly repeating side groups which are inherent in the monomeric struc¬ ture and are of different chemical constitution than the polymer backbone are not considered as "branches," that is, for example, the methyl groups pendent on a polydimethylsiloxane chain are not considered to be branches of that polymer.

In U.S. Patent No. 4,507,466, issued March 26, 1985, the patentees therein described the preparation of polymers having "branching" in the following manner:

To produce a branched polymer, it is necessary to employ an initiator, a monomer, or both that possess at least three moieties that function in the poly- merization reaction. Such monomer or initiators are often call poly functional.

The simplest branched polymers are the chain branched polymers wherein a linear backbone bears one or more essentially linear pendant groups. This simple form of branching, often called comb-branching, may be regular wherein the branches are uniformly and regularly distributed on the polymer backbone or irregular wherein the branches are distributed in non-uniform or random fashion on the polymer backbone.

An example of regular comb-branching is a comb-branched polystyrene as described by T. Altores et al. in J. POLYMER SCI. , Part A, Vol. 3, 4131-4151 (1965), and an example of irregular comb branching is illustrated by graft copolymers as described by Sorenson et al. in PREPARATIVE METHODS OF POLYMER CHEMISTRY, 2d Ed. , Interscience Pub- lishers, 213-214 (1968).

Another type of branching is exemplified by crosslinked or network polymers wherein the polymer chains are connected via tetravalent compounds, e.g. , polystyrene molecules bridged or crosslinked with divinylbenzene. In this type of branching, many of the individual branches are not linear, in that, each branch may itself contain groups pendant from a linear chain. More importantly in network branching, each polymer macromolecule (backbone) is crosslinked at two or more sites to other polymer macromolecules. Also the chemical constitution of the crosslinkages may vary from that of the polymer macromolecules. In this so-called crosslinked or network branched polymer, the various branches or crosslinkages may be structurally similar (called regular crosslinked) or they may be structurally dissimilar (called irregularly crosslinked). An example of regular crosslinked polymers is a ladder-type poly(phenylsilsesquioxane) .

Sogah et al., in the background of U.S. No. Patent 4,544,724, issued October 1,

1985, discusses some of these types of polymers and gives a short review of the many publications and disclosures regarding them. One of the inventors herein, Donald A. Tomalia, and many of his co-workers, have been working in this field for several years and have issued many patents which disclose various non-crosslinked, macromolecular branched assemblies.

For example, U.S. Patent No. 4,435,548, issued March 6, 1984, discusses branched polyamidoamines; U.S. Patent No. 4,507,466, issued March 26, 1985, U.S. Patent No. 4,558,120, issued December 10, 1985, U.S. Patent No. 4,568,737, issued February 4,

1986, U.S. Patent No. 4,587,329, issued May 6, 1986, U.S. Patent No. 4,713,975, issued December 22, 1987, U.S. Patent No. 4,871,779, issued October 3, 1989, and U.S. Patent No. 4,631 ,337, issued December 23, 1986, discuss the preparation and use of dense star

polymers; and U.S. Patent No. 4,737,550, issued April 12, 1988, and U.S. Patent No. 4,857,599, issued August 15, 1989, discuss bridged and other modified dense star polymers.

Also, other structural configurations of macromolecular materials that have been dis- closed include star/comb-branched polymers, such disclosure being found in U.S. Patent

No. 4,599,400, issued July 8, 1986, and U.S. Patent No. 4,690,985, issued September 1,

1987; and finally, rod-shaped dendrimer polymers are disclosed in U.S. Patent

No. 4,694,064, issued September 15, 1987.

The polyamidoamines referred to supra are also disclosed in U.S. Patent No. 4,758,635, issued July 19, 1988, to Wilson et al.

Hutchins et al., in U.S. Patent No. 4,847,328, issued July 11, 1989, and U.S. Patent No. 4,851,477, issued July 25, 1989, deal with hybrid acrylic-condensation star polymers; and Joseph et al. in U.S. Patent No. 4,857,615, issued August 15, 1989, U.S. Patent No. 4,857,618, issued August 15, 1989, and U.S. Patent No. 4,906,691, issued March 6, 1990, deal with condensed phase polymers which are linear polymers having regularly, or irregularly, spaced polymeric branches, essentially on the order of a comb structure macro¬ molecule.

An excellent presentation of the structures and chemistries of many such macro¬ molecular branched assemblies can be found in Tomalia, D. A. , Naylor, A.M. , and Goddard, W.A. Ill, ANGEWANDTA CHEMIE, 29/2, pp. 138-175 (1990).

However, none of the disclosures of the prior art deal with the novel polymers of the instant invention which are non-crosslinked, poly-branched polymers. For simplicity sake, the polymers of the instant invention can be generally characterized as multiple polymeric branches on multiple polymeric branches.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic in two dimensions of the polymer configuration of the polymers of the instant invention wherein

1 is the initiator core (initiator core molecule); 2 is first grafting and first branching and generation 0;

3 is second grafting and second branching and generation 1 ;

4 is third grafting and third branching and generation 2;

5 is fourth grafting and fourth branching and generation 3;

6 is (i + 1)* grafting and (i + l) ^Λ branching and generation i; and

7 is (i + 2) ^th and all iterative grafting and (i + 2) ^lh and all interative branching, and generation (i + 1) and all subsequent generations.

Fig. 2 illustrates the grafting of oligomer branches to cyclen, and the subsequent grafting of branches upon branches; and

Fig. 3 shows the grafting of oligomer branches onto a polyethyleneamine dendrimer core, and the subsequent grafting of branches upon branches.

THE INVENTION Benefits and other perceived advantages are achieved in accord with the present inven- tion which comprises novel non-crosslinked, poly-branched polymers, and methods for manu¬ facturing such polymers. In its broadest scope, this invention deals with poly-branche polymers having at least one branch referred to herein as a "core branch" emanating fro a core molecule, said branch being essentially linear, and having at least one end chemically coupled to the core molecule, with the other end of the branch terminating in a group fro a molecule used to initiate the reaction by which the branch was prepared, and at least on second branch which is branched from the core branch, said second branch, or branches, being essentially linear, and having at least one end chemically coupled to the core branch with the other end of the branch terminating in a group selected from a molecule used t

prepare the second branch polymer, which when subjected to iterative polymer grafting steps

(i.e., generations which will be delineated further herein), form three-dimensional organizations of ordered organic molecules. These polymers are hereinafter referred to as

"comb-burst" structures in that they are prepared from comb-like core molecules, but after subsequent grafting of additional branches pursuant to the processes of this invention, tend to have the appearance in two dimensions of a woven wire fence, which when viewed in three dimensions gives a topology having a starburst-like appearance. Hence, "comb-burst. "

This invention, therefore, comprises compositions of matter comprising non- crosslinked poly-branched polymers having the general formula: R ^c -{(A ^c )--(B ^c )} _n ^c G ^c

I

G°

I

{(A°)--(B°)} _n ° R° G ¹

I

{(A'MB ¹ )}. ¹ R ¹

I G ²

I

{(A ² )--(B ² )} _n ² R ²

G ³

{(A ³ )--(B ³ )} _n ³ R ³

I

G'

I {(A)'-(B')} _n ' R ¹ wherein R ^c is a non-reactive end group and each R°, R ¹ , R\ R\ and R ¹ is selected from initi¬ ators selected from a group consisting of free radical initiators, cationic initiators, anionic initiators, coordination polymerization initiators, and group transfer initiators; (i) represents repetitive linear polymers having the unit formula {(A')--(B ¹ )}; A ^c , A ⁰ , A ¹ , A ² , A ³ , and A'

are non-reactive comonomers or, oligomers or polymers formed from a polymerizable monomer, said oligomers or polymers being capable of withstanding the conditions required for preparation of a graft polymer; B ^c , B°, B ¹ , B ² , B ³ , and B' are protected or unprotected reactive nucleophilic or electrophilic monomers or, oligomers or polymers formed from a polymerizable monomer, said oligomers or polymers being capable of withstanding the conditions required for preparation of a graft polymer: G is a terminating group or a grafting component and has a value of at least 1 ; n ^c is the degree of polymerization of a core initiator; n° is the degree of polymerization of a first comb-branch; n ¹ is the degree of polymerization of a first generation comb-burst branch; n ² is the degree of polymerization of a second generation comb-burst branch; n ³ is the degree of polymerization of a third generation comb- burst branch; n' is the degree of polymerization of the i* generation comb-burst polymer having at least one branch point; wherein n' > 2 for the case where i = c, °, and 1, and n' > 2 if n' ^{+ 1} is > zero, the largest i for which n' does not equal zero is the total generation level of the polymer wherein the superscripts c, °, 1 , 2, 3, and i designate comb-burst generation level; the unit ratio of A units to B units in any {(A)--(B)} segment of the polymer is O to 1 : 100 to 1.

This invention also includes a composition of matter comprising non-crosslinked poly- branched polymers having the general formula

R ^c -{(-CH2CH2NH-)(-CH2CH2N-)} _n ^c G ^c

G° {(CH2CH2NH-)(-CH2CH2N-)} _n ° R°

G ¹

{(CH2CH2NH-)(-CH2CH2N-)} _n ^> R ¹

I

G ²

{(CH2CH2NH-)(-CH2CH2N-)} _n ² R ²

G ³

{(CH2CH2NH-)(-CH2CH2N-)} _n ³ R ³

G ¹

{(CH2CH2NH-)(-CH2CH2N-)} _n ' R ¹ wherein R ^c is a non-reactive end group and each R°, R ¹ , R ² , R ³ , and R' is selected from initiators selected from a group consisting of free radical initiators, cationic initiators, anionic initiators, coordination polymerization initiators, and group transfer initiators; (i) represents repetitive linear polymers having the unit formula {(-CH2CH2NH-)(-CH2CH2N-)}; G is a terminating group or a grafting component and has a value of zero or greater; n ^c is the degree of polymerization of a core initiator; n° is the degree of polymerization of a first comb-branch; n ¹ is the degree of polymerization of a first generation comb-burst branch; n ² is the degree of polymerization of a second generation comb-burst branch; n ³ is the degree of polymerization of a third generation comb-burst branch; n' is the degree of polymerization of the i" ¹ generation comb-burst polymer having at least one branch point; wherein ri > 2

for the case where i = c, °, and 1, and n ¹ > 2 if n' ^{τ l} is > zero, the largest i for which n ¹ does not equal zero is the total generation level of the polymer wherein the superscripts c, ⁰ 1 2 3 and i designate comb-burst generation level; the unit ratio of (-CH2CH2NH-) units to (-CH2CH2N-) units in any (-CH2CH2NH-X-CH2CH2N-) segment of the polymer is 0 to 1: 100 to 1.

There does not seem to be any limit to the size of the dendrimers except that dictated by practicality and/or stereochemistry of the molecules formed. Preferred for this invention are values wherein the molecular weight of the molecules is less than about 1,000,000 and more preferred are those having molecular weights of 250,000 or less. Especially preferred are those molecules having a molecular weight of 100,000 or less, and most preferred as those molecules having a molecular weight of about 30,000.

Values of n^. can be from 2 to a value in excess of 300, but a preferred range for the value of ι is from 2 to 300. Further, the value of n° can have a range of 2 to a value i excess of 100, but the preferred value is from 2 to 100. In addition, values of n ¹ , n ² , an n' can be in the range of 1 to a value in excess of 100, but the preferred range is from 1 t

100.

As indicated above, each of R°, R\ R ² , R ³ , and R' in these inventive polymers i selected as a moiety from a radical initiator, a moiety from a cationic initiator, a moiety fro an anionic initiator, coordination polymerization initiator, or a group transfer initiator. R°-R can be, for example, hydrogen, an alkyl group, Lewis acids, or the like, such materials bein known in the art.

The G' group is the grafting component formed by the reaction of the living end, o a derivative of the living end, of the i* generation oligomer with the reactive groups of th (i-1) generation material. Thus, an anionic oligomer may be reacted directly with an electro philic precursor generator, or it may be terminated by, for example, a halogen, such a chlorine, bromine, or iodine, to create an electrophilic end group for grafting to a nucleo philic precursor. Similarly, a cationic oligomer may be reacted directly with a nucleophili

precursor generation, or terminated with, for example, water, hydrogen sulfide, or an amine to give a nucleophilic end group for reaction with an electrophilic precursor. In the case of G ^c , the "graft" is to a monofunctional molecule, which may be as simple as quenching the active end with a proton or hydroxide, as would be the case with normal termination of ionic oligomers with water, or trapping with a specific molecule in order to introduce a single desired functional group to the molecule. Other telechelic groups suitable for grafting pur¬ poses may be found in Goethals, "Telechelic Polymers," SYN. APPLN. , CRC Press (1989). The oligomeric and polymeric segments of these materials can be homopolymers or copolymers, it being understood that the formulae herein represent bonding of the grafting G groups to either segment A, if it is present, or to segment B, and it being further under¬ stood that the grafting to any A segment is at the terminal end of the molecule, any other segment A grafting would result in the potential for crosslinking the polymers, which is not part of the invention herein. Also, for purposes of this invention, each A segment can be monomeric or, oligomers or polymers formed from polymerizable monomers, the only condi- tion being that the said monomers, oligomers, and polymers must be capable of withstanding the conditions required for preparation of subsequent graft junctures. As illustrated in the formulae, the bond from G to the next generation is indicated by a vertical line about halfway between the A segments and the B segments to illustrate that G can be bonded to either A, if it is present, or to B, which is always present in the molecule. An example of a G group that fits this description would be a urea formed by the reaction of an isocyanate with an amine group. This is formed by the activation of the amines of a poly(vinyl amine) segment with phosgene to create a polyisocyanate precursor molecule which, then, is reacted with an amine terminated poly(vinyl acetamide). The same G group can be formed by treating the poly(vinyl acetamide) with phosgene to form the tele- chelic oligomer with isocyanate end group, followed by reaction with the poly( vinyl amine) precursor molecule.

An example using the A group bonded to the G group would be the use of a copoly- mer of ethyl oxazoline and ethylene oxide. The hydroxyl group on oxyethylene is the

terminal group on the reactive oligomer segment. Activation of the hydroxyl group with phosgene gives a chloroformate which is reacted with the amine of a poly(ethyleneimine) segment on the precursor generation to form a urethane. Thus, the A group of the reactive oligomer is the "unreactive" oxyethylene and the B group is the masked iminoethylene, N- propionyl iminoethylene.

The range of possible G groups is limited only by the types of coupling reactions that are possible. In addition to ureas and urethanes, imide, thiourea, thiocarbamate, and anhydride linkages are readily available from similar reagents. Precursor molecules contain¬ ing olefins that result from polymerization or copolymerization of butadiene or ring opening metatheses polymerization of cyclic olefins can be activated by halogenation for subsequent reaction with a nucleophilic end group, or reacted directly with mercaptans via radical addi¬ tion, or be coupled with a silane end group via catalyzed hydrosilylation methods. Ether and ester linkages can be derived from hydroxyl groups on either the precusor molecule or the reactive oligomer end group. Segments of A include, for example: -CH ₂ ,CH ₂ -, -CH ₂ CH=CHCH ₂ -, -CH ₂ C(CH ₃ ) ₂ -,

-CH ₂ CH(CN)-, -CH-CH-, -CH ₂ CH-, -CH ₂ CH-, -NCH ₂ CH ₂ -, -NCH,CH ₂ CH ₂ -,

I I I I I c=o o o C=O C=O

NH ₂ R C=O R R R

-OCH,CH ₂ -, -SCH.CH,-, -R'-SiO-, -CH-CH-, -OCH.CH-,

OR wherein R' is an alkyl group of 1 to 4 carbon atoms, aryls, arylalkyl, hydrogen, or carbo- alkoxy and R is an alkyl group of 1 to 4 carbon atoms, aryls, or hydrogen;

R -CH ₂ C—

I CO ₂ R" wherein R has the same meaning as set forth above, and wherein R" can be an alkyl group of 1 to 4 carbon atoms.

Preferred as A segments are -CH.CH,-, -NCH.CH ₂ -, -CH2CH-,

I I C=O NH-C=O

R I

R -CH,C(CH ₃ ) ₂ -, -CH.CH-, -CH ₂ CH-O-, -CH-CH,S-, -CH ₂ CH=CHCH,-, -R' ₂ SiO-,

I O=C-NH ₂

-CH.CH-, and -CH-.C-. Most preferred are the A segments

1 ^" i

C _o H ₅ R ₂ and -CH ₂ CH-

I

C ₆ H ₄ CH ₃ .

Examples of the B segment can be monomeric, or oligomers or polymers formed from polymerizable monomers, wherein said monomers, oligomers and polymers must be capable of withstanding the conditions required for preparation of a graft polymer and further, the B segments must contain at least one unit which is nucleophilic or electrophilic in character.

The groups B contain the reactive sites to which the oligomers may be grafted. In many cases, these groups may need to be present in latent or masked form if they would otherwise be incompatible with the oligomerization process. For example, polymerization of ethyleneimine leads to highly branched polyethyleneimine oligomers which are not useful for this invention because the secondary amines formed are also reactive under the polymeri-

zation conditions. Oxazoline polymerization leads to linear polyethyleneimine in a protected form, and the secondary amines can be unmasked for grafting by hydrolysis. For alkylene oxide oligimerizations, hydroxyl groups intended for use as future graft sites would need to be masked as, for example, an ether to preclude the possibility of forming highly crosslinked gel systems. An example of a latent reactive site would be an alcohol group of a polyol which would require activation by conversion to a halide or sulfonate to allow reaction with anionic oligomer.

Thus, B as a nucleophile can be selected from such groups as -NCH.CH,, -CH-.CH-,

I ^" I H NHR

-CH ₂ CH(OH)-, -CH ₂ CH(SH)-, -OCH ₂ CH(CH ₂ OH)-, and -NCH ₂ CH ₂ CH ₂ -,

H while B as an electrophile can be selected from such groups as -O CH— , -O CH— , -CH-CH-, -OO CH— , -CH.CT CH- — ,

I I I I I

CH ₂ C1 CH ₂ (tosylate) CO ₂ R" CH ₂ C1 CH ₂ C1

R R

I I -SiO-, and -SiO~, wherein R and R" have the meanings set forth above.

I I

Cl CH ₂ C1

It should be understood that homopolymers consist of only the B segment, while copolymers can be had by combining the B segments with the A segments. Copolymers can also be prepared by using different monomers for the B segment of different generations, for example B ¹ being different from B ² .

The inventors herein contemplate that for purposes of this invention, there must be at least one B segment and, therefore, the ratio of A segments to B segments ranges from 0 to 1 to 100 to 1.

This invention also comprises a process of preparing non-crosslinked poly-branched polymers having the general formula

R ^c -{(A ^c )--(B ^c )} _n ^c G ^c

G°

I

{(A°)--(B°)} _n ° R°

I

G ^l

I

{(A' B ¹ )},, ¹ R ^l

I

G ²

I {(A ² )--(B ² )}„ ² R ²

I

G ³

{(A ³ )-(B ³ )} _n ³ R ³ I

G'

I

{(A)'-(B')} _n ' R wherein R ^c is a non-reactive end group and wherein each R°, R ¹ , R ² , R ³ , and R is selected from initiator types selected from a group consisting of free radical initiators, cationic initia¬ tors, anionic initiators, coordination polymerization initiators, and group transfer initiators; (i) represents repetitive linear polymers having the unit formula {(A')--(B ¹ )}; A ^c , A ⁰ , A ¹ , A ² , A ³ , and A ¹ are non-reactive comonomers or, oligomers or polymers formed from a poly¬ merizable monomer, said oligomers or polymers being capable of withstanding the conditions required for preparation of a graft polymer; B ^c , B°, B\ B ² , B ³ , and B' are protected or unpro¬ tected reactive nucleophilic or electrophilic monomers or, oligomers or polymers formed from a polymerizable monomer, said oligomers or polymers being capable of withstanding the conditions required for preparation of a graft polymer; G is a terminating group or a grafting component having a value of at least one; n ^c is the degree of polymerization of a

core initiator; n° is the degree of polymerization of a first comb branch; n ¹ is the degree of polymerization of a first generation comb-burst branch: n ^: is the degree of polymerization of a second generation comb-burst branch; n ³ is the degree of polymerization of a third generation comb-burst branch; n' is the degree of polymerization of the i" ¹ generation comb- burst polymer having at least one branch point; wherein ri > 2 for the case where i = c, °, and 1 , and ri > 2 if n ^{l+ 1} is > zero, the largest i for which n' does not equal zero is the total generation level of the polymer wherein the superscripts c, °, 1 , 2, 3, and i designate comb-burst generation level; the unit ratio of A units to B units in any {(A)— (B)} segment of the polymer is 0 to 1: 100 to 1, the process comprising (I) forming a linear initiator core having at least one reactive site and having the general formula R ^c -{(A ^c )~(B ^c )} _n ^c G ^c ; (II) reacting all or part of the sites (B ^c ) of (I) with a reactive polymer having the unit formula G°{(A°)— (B ⁰ )} _n ⁰ R° to form multiple branches that contain at least one reactive site on each branch using protection-deprotection reactions to ensure that the unit formula G°{(A°)~ (B°)} _n ° R° reacts only with (B ^c ) sites of (I) and that no reactions occur at the reactive sites B°; (III) repeat (II) sequentially to form successive generations of reactive branches to give the desired non-crossl inked poly-branched polymers.

This invention further comprises a process for preparing non-crosslinked poly- branched polymers having the general formula R ^c -{(-CH ₁ CH ₁ NH-)(-CH,CH,N-)} _n ^c G ^c

I

G°

I

{(CH,CH-NH-)(-CH ₁ CH ₁ N-)} _n ° R°

I

G ¹

{(OLCH.NH-)(-CH,CH,N-)} _n ¹ R ¹

I

G ²

I

{(CH ₂ CH ₂ NH-)(-CH ₂ CH,N-)} _n ² R ²

I

G ³

I

{(CH ₂ CH,NH-)(-CH,CH,N-)} _n ³ R ³

I

G ¹ I

I

{(CH,CH ₂ NH-)(-CH ₂ CH,N-)} _n ⁱ R ¹

I

R wherein the values of the symbols, superscripts, and subscripts are set forth above.

It should be noted by those skilled in the art that the polymer requires an initiator core (initiator core molecule). This initiator core may or may not be a "living polymer" or "liv¬ ing oligomer, " which oligomers and/or polymers are generally known to those skilled in the art. "Living systems" are preferred in order to control polydispersity of the comb-burst dendrimers. Using specific chemistry, the inventors herein can explain this aspect of the invention beginning with reference to "Polymeric Amines and Ammonium Salts, " edited by

E.J. Goelhals, Pergamon Press, (1980). wilh special reference to pages 55 et seq. , wherein there is taught one method of producing living polymers in a paper entitled "Linear Poly- alkylcnimines, " Saegusa, T. and Kobayashi, S.

Using the example of Saegusa, p. 58, one can observe that an initiator, such as methyl iodide, is first reacted wilh an oxazoline in the following sequence to give an oligomeric "living oligomer" having, in this case, two protected reactive sites designated as ~NCII ₂ CII ₂ -:

I ₂ ) ₂

Wilh further reference to Fig. 1 of the instant invention, the initiator core in the spe¬ cific case described just above would bc shown in Fig. 1 as R ^C (B ^C ) _1K G ^c ; where R ^c is methyl and G ^c is as described above.

Reaction sequences are then chosen to dcprotect the nitrogen groups so that each of the two reactive sites adds a reactant possessing its own, new reactive site, or sites, which introduces multiplicity, to obtain a " endrimei " -{(Λ ⁰ )-(B' ^, )} _n ⁿ -R ^,, of generation 0 (see Fig. I), wherein "dendrimer" has the same or similar meaning as that used by Tomalia et al. in the article referenced supra. As can be observed from the reaction sequence set forth above, this process requires that proleclion-deprotection strategies are used to ensure that the

reactant reacts with all reactive (B ^c ) sites, but does not react any (B°) sites. Protection-depro- tection strategies are generally known to those skilled in the art and great detail does not have to be set forth herein. Suffice it to suggest that the living oligomer set forth above has the protective group | on each nitrogen of the oligomer, whereupon the oligomer is then HC=O hydrolyzed with an acid to give polymeric units having reactive amine groups, i.e. ,

Me-(NCH,CH ₂ -) _n -I

I

H which are then used as the reactive sites to form the next generation, it being understood that the reactive sites of the polymer being grafted to me amine groups are protected before this reaction takes place, and that they too are hydrolyzed after the grafting reaction to give addi¬ tional reactive sites for the next generation of branching. Additional iterative sequences involving addition of new reactants having reactive sites is then undertaking in order to add branches onto branches to form the poly-branched polymer of this invention until the poly¬ mers will not form due to stearic hinderance referred to as comb-burst dense packing. The article by Tomalia, et al., referenced supra, sets forth such technical terms.

One of the inventive processes used to prepare polymers of this invention relies on the polymerization of 2-ethyl-2-oxazoline. Methyl p-toluenesulfonate has been shown to polymerize oxazolines and the polymerization mechanism has been determined to be cationic, producing a "living polymer. " This allows the preparation of polymer samples with well- defined molecular weight and low polydispersity. The end of the growing polymer chain contains an oxazolinium ion as disclosed above, that can be trapped by a variety of nucleo- philes. To graft the living poly(2-ethyl-2-oxazoline) chains, they are terminated with the secondary amine groups contained on linear poly(ethyleneimine)(LPEI). After grafting onto the linear poly(ethyleneimine) has been accomplished, hydrolysis of the poly(2- ethyl-2-oxazoline) grafts will generate poly(ethyleneimine) branches. This allows further liv¬ ing poly(2-ethyl-2-oxazoline) chains to be grafted onto the poly(ethyleneimine) branches.

Repetition of the grafting and hydrolysis forms the inventive polymers with the structures shown herein.

Figs. 2 and 3 and Examples 31 and 32 below illustrate branching "0" generation branches onto cores comprising ring compounds and dendrimers, respectively. In Fig. 2, branches which can be generated in the manner described above are attached to the four nitrogens in me ring compound 1,4,7,10-tetraazacyclododecane (cyclen), much as they are grafted to the nitrogens of a poly ethyleneimine core molecule as discussed above. First generation branches are then grafted upon the "0" generation branches, second generation branches are grafted upon the first generation branches, etc. , as discussed above. In Fig. 3, "0" generation branches are grafted to the surface nitrogens of a hyper- terminal-branched or dendrimer core molecule, specifically, a second generation polyethyl- eneamine. At the generation 2 level (designating the first generation as generation 0), such hyper-terminally -branched molecules are typically referred to as "dendrimer. " Hyper- terminal-branched or dendrimer cores can be prepared in various manners known to those skilled in d e art, including, without limitation, by the techniques disclosed in United States Patent No. 4,507,466 entitled "DENSE STAR POLYMER BRANCHES HAVING CORE, CORE BRANCHES, TERMINAL GROUPS"; No. 4,558,120 entitled "DENSE STAR POLYMER," No. 4,568,737 entitled "DENSE STAR POLYMERS AND DENDRIMER"; No. 4,587,329 entitled "DENSE STAR POLYMER HAVING TWO-DIMENSIONAL MOLECULAR DIAMETER"; No. 4,631,337 entitled "HYDROLYTICALLY STATE DENSE STAR POLYAMINE"; No. 4,737,550 entitled "BRIDGED DENSE STAR POLYMER"; No. 4,599,400 entitled "STAR/COMB-BRANCHED POLY AMIDE"; No. 4,690,985 entitled "STAPJCOMB-BRANCHED POLYAMINE"; No. 4,694,064 entitled "ROD-SHAPED DENDRIMER"; and No. 4,857,599 entitled "MODIFIED DENSE STAR POLYMERS. " Similarly, any of the dendrimer molecules described in said patents could be used as the hyper-branched dendrimer core to which oligomer branches are grafted in

reiterative fashion in accordance widi the present invention. One need only develop an appropriate strategy for attaching the oligomer branches to the surface moieties of such hyper-branched cores, and various alternatives will be apparent to those of ordinary skill in the art. For purposes of clarifying terminology, it should be noted that the hyper-terminal- branched core molecule disclosed in Fig. 3 and in Example 32, and those disclosed in the United States Patents discussed above, are built by reiterative terminal branching rather than reiterative comb-branching. That is to say, one attaches subsequent generation branches to the terminal moieties of a previous generation, thus limiting the degree of branching to the functionality of the previous generation terminal moiety, which would typically be two or three. In contrast by branching oligomers upon prior generation oligomer branches in accor¬ dance with the present invention, one can dramatically increase the degree of branching from generation to generation, and indeed can vary the degree of branching from generation to generation. In another preferred embodiment process, the non-crosslinked poly-branched polymers, or hyper-comb-branched polymers, are produced in a remarkably low number of iterations by utilizing a particular combination of process parameters and reactants having certain characteristics. It has been surprisingly discovered that hyper-comb-branched polymers having a molecular weight of about 1 million and up to about 10 million or even higher can be produced in only several reaction iterations by this preferred embodiment process. A hyper-comb-branched polymer product having a molecular weight exceeding 10 million was formed in only 4 iterations from a core of linear PEI 20, and side chains of PEOX 10 for the first iteration and PEOX 100 for the next 3 iterations, by the preferred embodiment process described below. It is contemplated that hyper-comb-branched polymers having a molecular weight ranging from about 10 million to about 50 million could be produced in about 4 iterations. It is further contemplated that even higher molecular weight products could be formed such as products having a molecular weight of about 100 million or more by continuing the iterations. Such remarkably high molecular weight polymers are

produced in a surprisingly few number of iterations primarily by utilizing longer side chains, a particular grafting ratio, shorter reaction time periods, and utilizing a proton trap to increase grafting yields and prevent chain scission of the comb-branched intermediates and resulting hyper-comb-branched polymer product. In another aspect of me preferred embodiment process, a novel separation technique is provided for separating a hyper-comb- branched polymer product from a reaction mixture, that is both economical and rapid.

The present inventors have discovered that grafting yields may be significantly increased by utilizing a particular grafting ratio of living chain ends to secondary amines, and in some instances, by also employing a proton scavenger during grafting operations. Prior to the present discovery, when producing comb-branched polymers from PEI cores and PEOX 5 to PEOX 10 as grafting chains at a grafting ratio of 0.3 living chain ends per secondary amine, grafting yields typically ranged from about 10% to about 15% . In the present preferred process, it is preferred to utilizing a grafting ratio of from about 0.8 to about 1.2 living chain ends per secondary amine, and most preferred to utilizing a grafting ratio of about 1 : 1 of living chain ends to secondary amines. These grafting ratios result in significantly improved grafting yields.

At these grafting ratios, i.e. about 0.8 to about 1.2:1, it has been found that it is also beneficial to utilize a proton scavenger during grafting to trap or scavenge protons which are generated during grafting, such as when a living PEOX chain is grafted onto a secondary amine such as PEI. Without such scavengers, expelled protons are transferred to basi secondary amine sites along the PEI polymer backbone, thereby blocking and thus renderin those sites inaccessible for further grafting. In the preferred embodiment process, the us of a proton scavenger and a grafting ratio of about 1 : 1 has been found to significantl increase grafting efficiency, such as up to about 75% to 95% when grafting PEOX 5 o PEOX 10 branches onto a PEI core.

Proton scavengers may comprise nearly any suitable base that is compatible with th core and side chain reactants. A preferred proton scavenger for use when grafting PEO chains onto PEI is a relatively hindered, tertiary amine such as ϊ-Pr ₂ NEt. However, it i

contemplated that a wide array of suitable bases could be utilized instead of, or in addition to t-Pr ₂ NEt, such as triisobutylamine, triisooctylamine and triethylamine. The proton scavenger is preferably utilized in the grafting mixture in a concentration of from at least about 1 to about 2 equivalents of the proton scavenger for every living or reactive chain end. It is envisioned that even higher ratios may be utilized in certain instances.

As previously noted, the remarkably high molecular weight polymeric products are produced in a surprisingly few number of iterations by increasing grafting yield, and by preventing chain scission of me comb-branched intermediates and resulting hyper-comb- branched polymer products. In the case of utilizing PEOX and PEI to produce a hyper- comb-branched polymer, chain scission often occurs when there exists an excess of chain ends to secondary amines in the reaction environment. An excess of chain ends to secondary amines promotes the formation of quaternary amines along the polymer backbone, which readily undergo Hofmann degradation to produce undesirable lower molecular weight fragments upon heating. The present inventors have discovered that chain scission may be essentially prevented or significantly minimized by employing one or more of the following practices: (a) utilizing shorter reaction periods, (b) utilizing relatively long chains for grafting onto polymer backbones, (c) ensuring that NaOH or other salts are completely removed, or nearly so, from the reaction mixture(s) throughout the various stages of the process, and (d) ensuring that the resulting hyper-comb-branched product is maintained at relatively low temperamres and not exposed to high temperatures. It is preferred to employ all of these practices to prevent chain scission, and most preferred to employ all of these practices in conjunction with utilizing the previously described grafting ratios and proton scavenger during grafting operations to increase grafting yields. Shorter reaction periods are utilized for both polymerization of the reactants, e.g. core and branches, and grafting operations in the preferred embodiment process since shorter reaction periods have been found to reduce the tendency for quaternary amines to be formed. Quaternary amines, as previously noted, are prone to undergo Hofmann degradation and

thereby cause chain scission. When forming PEOX side chains from PEOX 10 or PEOX 20, for later use in preparing hyper-comb-branched polymers, it is preferred to utilize a time period of less than about 5 hours for the polymerization of PEOX. When forming PEOX side chains from PEOX 100, longer time periods may be required such as up to about 10 hours. It is particularly preferred to employ relatively short time periods during grafting operations, such as a grafting reaction time of less than about 1 hour for grafting polymerized PEOX chains onto a PEI core.

In addition to forming side chains from PEOX, it is possible to utilize a wide array of monomer units such as, but not limited to any 2-, 4-, or 5-substituted oxazoline;

any 2-unsubstituted 5,6-dihydro-4H-l,3-oxazines;

ι any 2-substituted 5,6-dihydro-4H-l,3-oxazines;

1 or any block copolymers containing 5,6-dihydro-4H-l ,3-oxazines and 2-alkyloxazolines. Hyper-comb-branched polypropyleneimine polymer obtained by hydrolysis of poly(5,6- dihydro-4H-l ,3-oxazines), both 2-substituted and 2-unsubstituted, were found to exhibit a relatively high degree of thermal stability as compared to those having PEI side chains.

The tendency for chain scission is further reduced by utilizing relatively long chains for grafting onto a polymer backbone. Once a long side chain is grafted onto a secondary amine to generate a tertiary amine site along the polymer backbone, it is nearly impossible to introduce another chain, particularly another long chain, at this tertiary amine site due to steric inhibition. In the case of forming hyper-comb-branched polymers from PEOX and PEI, it has been discovered that the preferred length for PEOX side chains or branches are at least about 50 monomer units, and most preferably at least about 100 monomer units.

In another preferred embodiment, relatively short chains are utilized during the early stages in forming the hyper-comb-branched product, i.e., generation 0, (GO) and relatively long side chains are utilized during later stages, i.e. , generations 1 (Gl) and above. This practice has been found to increase interior branching density, and reduce the previously described tendency for chain scission to occur at higher generations.

Chain scission may also occur after initial formation of the poly-branched polymer or hyper-comb-branched polymer, such as during or after neutralization of the hydrolyzed polymer product. After formation of the comb-branched polymer product and addition of acid to hydrolyze the product, the polymer product is neutralized and separated from the reaction mixture by adding base to form an oily layer containing the polymer product. This is typically accomplished by adding a base such as NaOH followed by heating until an oily layer separates from the mixture, that layer containing the high molecular weight product. The oily layer is then cooled to harden or solidify it, wherein it can be readily removed. It has been discovered that after neutralization with NaOH, the PEI moieties in the polymer product tend to chelate the sodium cations, thereby freeing hydroxyl ions and increasing the pH of the environment, and further promoting Hofmann degradation of any quaternary amines present upon heating, which in turn leads to chain scission. Additionally, unwanted amounts of NaOH or other salts may contaminate the reactants used in forming the polymer product, such as linear PEI. Such contamination can later promote chain scission. Removal of NaOH or other salts from the poly-branched polymer, and/or from die components used to form such product, has been discovered to reduce the tendency of chain scission of die

poly-branched or hyper-comb-branched polymer. NaOH or otiier salts may be removed from the reaction mixmre at various points of me process by a wide variety of techniques such as exhaustive washing with water of precipitated polymer product or of the reactants used to form the polymer product which are believed to contain NaOH. and then dissolving the polymer product in toluene, in which NaOH is insoluble, heating to remove water by azeotropic distillation, then filtering or otherwise separating the hot polymer product from the NaOH and/or other salts. The various points of the process in which it is desirable to remove NaOH or any other salts include the stage in which the reactants are polymerized to form chains for subsequent grafting onto the polymer core or backbone, and the stage in which the grafting occurs.

Chain scission is also minimized in accordance with the preferred embodiment process by not exposing me resulting poly-branched or hyper-comb-branched polymer product to temperamres that are significantly above room temperature, such as when drying by ovens in which case, temperamres of 100°C or more are often reached. Conventional drying procedures in which PEI polymer was dried at 80 °C in an oil bam and under vacuum overnight were found to degrade the comb-branched polymer into undesirable numerous smaller fragments. Thus, it is preferred that PEI poly-branched or hyper-comb-branched polymer product is dried at temperamres less than about 60 °C, and it is most preferred that the PEI product be stored at room temperamres, i.e. about 20 °C. It has been found mat PEOX-PEI comb-branched polymers exhibit greater thermal stability than PEI comb-branched polymers. Thus, it is preferred to store hyper-comb-branched polymers in me PEOX-PEI stage and hydrolyze the polymers to PEI hyper-comb-branched polymers prior to use.

In another aspect of the preferred embodiment process, a novel separation technique is provided for separating a poly-branched or hyper-comb-branched polymer product from a reaction mixmre containing lower molecular weight products that is both economical and rapid. Currently known techniques for separating high molecular weight, highly branched polymers from reaction mixtures generally involve some type of ultrafiltration process. Ultrafiltration, although satisfactory in many respects, is undesirable in view of the relative

high cost of ultrafiltration equipment and me inefficiencies associated with separating high molecular weight products from undesired low molecular weight products. The present inventors have discovered a separation technique, whereby ultrafiltration is avoided and the polymer product is separated by a polymer refractionation technique. The preferred polymer refractionation technique is performed by separation of hyper- comb-branched polymer product from a reaction mixmre comprising the product and unwanted lower molecular weight components at me PEOX-PEI stage, by a first addition of an alcohol solvent in which both high molecular weight and low molecular weight products are soluble, and a second incremental addition of a poor solvent in which the high molecular weight product is less soluble than the unwanted low molecular components. Addition of the poor solvent to the alcohol and dissolved components causes the high molecular weight polymer product to precipitate from solution. Examples of suitable poor solvents include, but are not limited to, diethyl ether or other ether-based solvents and hexane.

An example of the preferred refractionation technique is as follows. An alcohol solvent such as methanol is added to die reaction mixmre, until all of the components in the mixmre, including unwanted low molecular weight components and the high molecular weight polymer product, are dissolved and are in solution. Then, a poor solvent such as diethyl ed er, is incrementally added to preferentially precipitate the desired high molecular weight components from the alcohol phase containing the low molecular weight products. Poor solvent is added until all, or substantially all, of the high molecular weight product is in the precipitate. Periodically, the resulting oil sludge bottom product, i.e. precipitate, and/or top layer containing the dissolved low molecular weight products are analyzed for the presence of the high molecular weight polymer product. Analysis may be performed by SEC (size exclusion chromatography) methods. Once the high molecular weight polymer product no longer precipitates from the resulting mixmre of alcohol solvent, poor solvent, and low molecular weight components, and thus is in the precipitate, addition of the poor solvent is halted. The mixmre remaining above the precipitate and containing the low molecular weight product, is then removed. The high molecular weight poly-branched or hyper-comb-

branched product remains in the bottom precipitate layer and can be redissolved in water and subsequently dried by lyophilization. Example i

A 250 ml one-necked, round-bottomed flask equipped with a magnetic stirring bar and a Dean-Stark trap that was surmounted with a reflux condenser was charged with 2.84 gm (15.3 mmole) of methyltosylate and 125 ml of toluene. The mixmre was heated at reflux and solvent was collected until all water had been removed. At this time, 30.0 gm (303 mmoles) of freshly distilled 2-ethyl-2-oxazoline was added all at once and me mixmre was refluxed for approximately 4 hours. During this time, in a separate flask, 1.64 gm (38.1 mmole of repeat units) of linear poly (ethyleneimine) (LPEI) was azeotropically dried with toluene. When me poly (ethyleneimine) was dry, it was added to the round-bottomed flask containing the oxazoline oligomer and men allowed to reflux for an additional 3 hours. Any ungrafted living poly(2-ethyl-2-oxazoline) chains were neutralized by die addition of 2.0 ml of water wi refluxing for an additional 1 hour. Toluene was removed under reduced pressure to leave a yellowish oily solid mat was dissolved in chloroform and precipitated dropwise into diemyl ether. The yellow solid was filtered from solution and dried overnight in a vacuum oven to yield 29.7 gm (94% yield) of grafted poly(2-ethyl-2-oxazoline) (PEOX) as a yellow powder. Example 2 Into a 500 ml one-necked, round-bottomed flask was placed 21.6 gm of the oxazoline from Example 1 and 350 ml of water. When the polymer had completely dissolved, 35 ml of concentrated sulfuric acid was added. The flask was equipped widi a distillation head and die mixmre was heated at reflux and distillate was collected until propionic acid could not be detected. Water was added to me distilling pot when me volume was reduced to less than approximately 75 ml. Upon removal of the propionic acid, the distillation head was replaced wim a reflux condenser surmounted wim a pressure equalized addition funnel charged with 5N NaOH. The base was slowly dripped into the reaction mixmre maintained at reflux. When the pH of me reaction mixmre was approximately 12, heating was discontinued.

While standing at room temperature, a solid formed at me surface of the aqueous mixmre. This solid was removed and placed in a 250 ml round-bottomed flask wi 175 ml of toluene. The water was removed from the water-toluene azeotrope by distillation. When water removal was complete, the solid became soluble in me refluxing toluene. The hot toluene solution was poured into a 250 ml round-bottomed flask leaving behind insoluble salts. Toluene was removed under reduced pressure to leave a brownish, waxy solid. The sample was dried for approximately 24 hours under vacuum to give 9.14 gm (97% yield) of polymer sample. Example 3 Using the general metiiod of Example 2, hydrolysis of the graft polymers, was carried out on a separate batch of the graft polymers in the following manner. Five grams (5.0 gm) of the graft copolymer were placed in a 250 ml round-bottomed flask wim 100 ml of water and 10 gm of sulfuric acid. The flask was heated widi a heating mantle to give a slow distillation of Λe propionic acid/water azeotrope. The distillation was continued for 2 days, wim water being added as necessary to maintain the reaction volume. Approximately 200 ml of distillate was collected over me course of the hydrolysis. The heating was discontinued and 50% NaOH was added slowly to bring die pH to 10. The free polyamine was insoluble in the saturated salt solution, giving a separate phase on top of the aqueous solution. The phases were separated and the polyamine was placed in a 250 ml round-bottomed flask. One hundred fifty ml of toluene was added and a Dean-Stark trap was attached. After reflux overnight (about 16 hours), no more water was being removed and the polyamine had dissolved in the hot toluene. The hot solution was filtered and die solvent was removed from me filtrate using vacuum and agitation to give branched poly(ethyleneimine) weighing 2.2 gm (100% of theory) as an orange oil. The ¹³ C-NMR spectrum showed a peak for linear poly(ethyleneimine) (49.4 ppm/intensity 8075), residual unhydrolyzed propionamide (9.5 ppm/intensity 156), 26.3 ppm intensity 180), and primary amine end group (41.7 ppm/intensity 61). No peak for a hydroxy terminal group was observed. While me intensities may not be interpreted as a quantitative measure of the groups present,

qualitatively, hydrolysis was 80 to 90% complete and grafting was complete within the limits of detection. Example 4

A 2-liter, 3-necked, round-bottomed, glass flask was used wid a shaft driven stirrer, instead of magnetic stirring. The initial loading was: water - 250 ml, material prepared essentially by the method of Example 3 - 125 gm, sulfuric acid - 150 gm. Additional sulfuric acid, 100 gm was added halfway through the hydrolysis to improve solubility. Internal flask temperature was monitored and a solenoid valve was rigged to add water whenever the temperature rose above 107 °C. Thus, constant attention was not necessary and the distillation could be left unattended overnight. The heating mantle was also set to shut off at the same temperature so that the flask would not overheat if me water reservoir ran out of water. After 2 days of continuous distillation, 1.6 liters of distillate was collected. The reaction mixmre was neutralized and die polymer phase was separated. The crude polymer was purified by dissolving in hot water ( 1 liter) and precipitated by slow addition to cold water. After two precipitations, the supernatant solution was neutral to Hydrion ^R paper. The resulting hydrated polymer was dehydrated via toluene azeotrope as described above to give LPEI (51 gm 94% yield). The ¹³ C-NMR spectrum showed LPEI wi residual amide carbon intensities 0.5 % of the LPEI intensity. Primary amine end group intensity was 0.4% of the LPEI intensity. Example 5

Into a 250 ml round-bottomed glass flask was placed p-toluenesulfonic acid monohydrate (2.0 gm, 11 mmole) and toluene (100 ml). A Dean-Stark trap was attached and die mixmre was heated at reflux until water removal was complete. Ethyl oxazoline (10 gm, 100 mmole) was added all at once and die reflux was continued for 2 hours. LPEI (1.0 gm, 23 meq.) was placed in toluene (25 ml) and me mixmre was heated to boiling to dissolve me polymer and azeotropically remove trace water in the polymer. The hot LPEI solution was added all at once, to the cloudy oligomer suspension. An orange oil began to precipitate immediately. After 1 hour at reflux, me mixmre was cooled and me solvent stripped using

vacuum. The residue was dissolved in CH ₂ C1 ₂ (40 ml) and precipitated by a slow addition to ether (500 ml). The solid was collected by filtration and dried in a vacuum oven at 40° to 50°C to give me grafted polymer (12 gm, 92% yield) as a yellow powder. At higher M/I ratios, me oligomerization time had to be increased to allow complete conversion of the ethyl oxazoline. For example, intermediated degree of polymerization runs (M/I = 200, olig. time

= 3 hours, or M/I = 400, olig. time = 6 hours) had low yields due to incomplete conversion. Increasing the reaction time to 12 hours and 24 hours respectively, gave higher conversions and yields. The highest M/I (1000) run, had an oligomerization time of 36 hours, which was not long enough for complete conversion. This gave a material with actual oligomer dp of 700. The ¹³ C-NMR spectrum of the poly-branched polymer derived from this material showed a peak for primary amine end groups which was approaching me limits of detection for me signal/noise ratio. No hydroxyl terminal group was detectable.

Example 6 Preparation of Morpholine Terminated Linear

Polyemyleneimine Having a Degree Of Polymerization (dp) of 20.

A mixmre of Methyltosylate (7.46 g, 40 mmole) in 200 ml of toluene was azetroped to dryness with a Dean-Stark trap for about 10 to 15 minutes. To this mixmre which had cooled to about 90°C was added ethyl oxazoline (79.3 g, 800 mmole) and the mixmre was refluxed for 18 hours. To this mixmre which had been cooled to about 90° C was added moφholine (4 g, 161 mmole). This mixmre was refluxed for 16 hours. This mixmre was evaporated of volatiles on a rotary evaporator. This crude mixmre was hydrolyzed with 400 ml of 50% H-SO ₄ by azeotroping the water-propionic acid mixmre with a Dean-Stark trap until about 500 ml were collected or until me pH of the distillate was neutral. This hot mixmre was slowly poured into a 50% KOH mixmre under an atmosphere of N ₂ . The resulting heterogenous mixmre was made homogeneous by heating to reflux. The product floated to the top of this mixmre as a clear liquid. This hot mixmre was allowed to cool under N ₂ to room temperature. The solid cake that formed on me surface of this mixmre was dissolved in 600 ml of deionized water by heating to reflux, allowed to cool and

ultracentrifuged (8000 rpm) for 10 minutes. The clear liquid was decanted and the remaining white solid- water mixmre was mixed with toluene. This mixmre was azeotroped of water to form a dry toluene-LPEI mixmre. The toluene was removed from this mixmre by a rotary evaporator followed by high vacuum (0.2 mm Hg) at 80°C for 2 hours to give 34 g (88% yield) of the title compound.

Example 7 Preparation of Comb-Branched PEI Wherein N _c is 20, N _b is 5, and G is Zero.

A mixmre of Methyltosylate (MeTOs) (3.7 g 20 mmole) in 50 ml of toluene was azeotroped to dryness with a Dean-Stark trap under nitrogen for 10 minutes. To this mixmre cooled to 90°C was added emyl oxazoline (10 g, 100 mmole). This mixmre was stirred for 10 hours at 90°C. To diis mixmre was added N-morpholine terminated LPEI (dp of 20) (0.53 g, 0.55 mmole, 11 mmole NH) dissolved in 20 ml of hot (90°C) toluene which had been dried by azeotropic distillation for about 15 minutes. This was immediately followed by me addition of diisopropylemylamine (12 g, 93 mmole, 8 equivalents of amine per NH). This mixmre was refluxed for 48 hours. The volatiles were removed from mis mixmre and me resulting residue dissolved in deionized water. After ultrafiltration (MW > 1000), me retentate was refluxed in 400 ml of 50% H ₂ SO ₄ for 18 hours. The cooled reaction mixmre was made basic to a pH ≤ 14 with KOH to produce a clear colorless liquid that floated to d e top of the mixmre. Upon cooling the liquid solidified. The solid was removed from the mixmre and dissolved in 500 ml of hot deionized water. This mixmre was allowed to cool forming a white suspension. This resulting mixmre was ultracentrifuged at about 8000 rpm for about 10 minutes. The clear liquid was decanted from the white precipitate. The white precipitate was refluxed wid toluene with an attached Dean-Stark trap to dry the product. The toluene mixmre was evaporated of volatiles on a rotary evaporator. The remaining volatiles were removed at 0.1 mm Hg at 50°C to give 1.8 g (70%) of the title compound. A ¹³ C-NMR spectrum of mis mixmre in CDC1 ₃ indicated a 65% grafting of PEOX onto LPEI as shown by integration of me terminal methyl signals versus the methylene carbon signals.

Example 8 Preparation of a Comb-Burst PEI Wherein N _c is

20, N _b is 5, and G is 1.

The compound dendrimer was prepared in me same manner as in the Example 7 using

MeOTs (3.7 g, 20 mmole), 300 ml of toluene, ethyl oxazoline, (10 g, 100 mmole), diisopropylethylamine (12 g, 93 mmole) and comb-branched PEI where N _c is 20, N _b is 10 and G is zero (1.0 g, 23 mmole NH maximum). Ultrafiltration, hydrolysis and drying gave

5.0 g (80% yield) of the title compound. The ¹³ C-NMR spectrum was consistent with the proposed structure.

Example 9 Preparation of a Comb-Burst PEI Wherein N _c is 20, N _b is 5, and G is 2.

This example shows die use of the material formed in Example 8 which was refluxed wim two equivalents of PEOX having a dp of 5 per NH and 11 equivalents of diisopropylemylamine for two days. This mixmre was worked up differently man the previous example. The crude PEOX-comb-burst PEI was hydrolyzed directly, without ultrafiltration, to give 8.6 g of a comb-burst and linear polyethyleneimine (PEI). This mixmre was dissolved in hot deionized water. Upon cooling the product crystallized from me mixmre. The mixmre was ultracentrifuged at 8000 rpm and the white precipitate was azeotropically dried with toluene to give 4.5 g for a yield of 72%.

Example JO Preparation of a Comb-Burst PEI Wherein N _c is 20, N _b is 5, and G is 3.

The preparation of comb-burst PEI where G is 3 incoφorated improvements in the grafting step by using two equivalents of PEOX per NH and 26 mmoles of diisopropylemyl¬ amine per NH. The crude material was hydrolyzed as before and the resulting mixmre precipitated from PEI by making basic with KOH. Recrystallization of the cake of product floating on the KOH mixmre from deionized water followed by ultracentrifugation at 8000 φm and azeotropic drying of the white solid with toluene gave 5.6 g for a 90% yield.

Example ϋ Preparation of a Comb-Burst PEI Wherein N _c is

20, N _b is 5, and G is 4.

The comb-burst PEI was prepared in a manner similar to me previous example, using two equivalents of PEOX per NH, and 23 equivalents of diisopropylethylamine per NH and refluxing two days. The crude mixmre was not ultrafiltered but hydrolyzed with H ₂ SO ₄ , removed from solution by KOH and recrystallized twice from deionized water. Eac recrystallization involved dissolving the product in hot water, allowing the mixmre to coo to 25 °C and ultracentrifugation at 8000 rpm, 10 minutes. The clear supernatant wa decanted from me white solid and the white solid was azeotropically dried wid toluene. Th isolated yield from the second recrystallization came to 4.9 g for a yield of 78% . The firs recrystallization gave 5.5 g, for a yield of 87% .

Example 12 Preparation of Comb-Burst PEI Wherein N _c is

20, N _b is 5, and G is 5.

The next generation (G) was prepared at twice the scale of all me other graftin experiments (2.0 g of starting material versus 1.0 g of starting material). Only 4 to equivalents of diisopropylemylamine per NH were used along widi two equivalents of PEO per NH and refluxing two days. After evaporating the volatiles the crude mixmre wa dissolved in deionized water and ultrafiltered using a spiral wound cartridge Amicon S1Y

(3000 MWCO). Hydrolysis of the retentate gave an 85% yield of the title compound. Th ultrafiltration with this membrane was not tried on earlier generations of G = 1 to 4.

Example 13 _. Preparation of Comb-Burst PEI Wherein N _c is

20, N _b is 5, and G is 6.

This generation was prepared in a similar manner as before using two equivalents o

PEOX per NH, six equivalents of diisopropylethylamine per NH and refluxing two days The workup again was done by ultrafiltration in deionized water using a spiral wound S1Y membrane. The isolated yield of PEOX-comb-burst after ultrafiltration came to one-half th amount normally obtained from an 80 to 90% grafting experiment. Hydrolysis of the mix

ture as before followed by treatment with NaOH and azeotropic drying with toluene gave only a 32% yield of the G = 6 product. A repeat of this same experiment except with two recrystallizations in water instead of an ultrafiltration gave a 38% yield of the title compound. Example .14 Preparation of a Comb-Branched PEI Wherein

N _c is 20, N _b is 10, and G is Zero.

A mixmre of MeOTs (7.4 g, 40 mmole) in 100 ml of toluene was azeotroped to dryness with a Dean-Stark trap under nitrogen for 10 to 15 minutes. To mis mixmre, cooled to about 90°C, was added ethyl oxazoline (39.7 g, 400 mmole). This mixmre was refluxed under nitrogen for 18 hours. To this mixmre was added N-moφholine terminated LPEI hav¬ ing a dp of 20 (1.0 g, 1.1 mmole, 23 mmole of NH) dissolved in 50 ml of hot (100°C) toluene which had been dried by azeotropic distillation for 15 minutes. This was immedi¬ ately followed by the addition of diisopropylethylamine (24 g, 186 mmole, 8 equivalents amine per NH). This mixmre was refluxed for 48 hours. The mixmre was cooled, dissolved in methanol and evaporated of volatiles on a rotary evaporator and the resulting mixmre was dissolved in deionized water (about 60 ml). This mixmre was ultrafiltered using an Amicon spiral wound cartridge S1Y3 wim the above volume as a retentate until 12 liters of permeate had been obtained (20 recirculations). The retentate was refluxed in 400 ml of 50% H ₂ SO ₄ with a Dean-Stark trap collecting about 400 to 500 ml of distillate (replenishing the equiva- lent water) until me distillate was neutral to pH paper. This hot mixmre was made basic by pouring slowly into a 50% KOH mixmre under a blanket of nitrogen. The heterogenous mixmre was heated to a homogeneous mixmre that produces a liquid mat floats to the top of me mixmre. Upon cooling the liquid solidified. The solid was removed from the mixmre and dissolved in 500 ml of hot deionized water. This mixmre was allowed to cool forming a white suspension. This resulting mixmre was ultracentrifuged at 8000 φm for about 10 minutes. The clear liquid was decanted from me white precipitate. The white precipitate was refluxed with toluene with an attached Dean-Stark trap to dry me product. The toluene mixmre was evaporated of volatiles on a rotary evaporator. The remaining volatiles were

removed at 0.1 mm Hg at 50°C to give 1.8 g (70% ) of the title compound. A ¹³ C-NMR spectrum of this mixmre in CDC1 ₃ indicated a 65% grafting of PEOX onto LPEI as shown by integration of the terminal methyl signals versus die methylene carbon signals.

Example .15 Preparation of a Comb-Branched PEI Wherein N _c is 20, N _b is 10, and G is Zero.

A mixmre of moφholine-terminated LPEI having a dp of 20 (1.04 g, 22 mmole),

PEOX oligomers having a dp of 10 (47.5 g, 40 mmole) and diisopropylethylamine (20 g, 6 to 7 equivalents per NH) were refluxed under nitrogen obtained from a nitrogen cylinder

(constant pressure and no flow) and an Hg bubbler for 48 hours. The volatiles were removed from the mixmre and me resulting yellow orange residue was dissolved in 1 liter of deionized water. The mixmre was ultrafiltered wim an Amicon spiral wound cartridge using 700 ml of retentate and 8.5 liters of permeate to give 24 g of me PEOX-comb- branched PEI copolymer. The material was hydrolyzed with 50% H ₂ SO ₄ and the resulting mixmre added to an excess of 50% KOH. The cake floating on the KOH was mixed wim toluene and azeotropically dried under nitrogen to give 10.1 g (90%) of the comb-branched

PEI dendrimer.

Example 16 Preparation of a Comb-Burst PEI Wherein N _c is

20, N _b is 10, and G in One.

The preparation of G= l of this comb-burst PEI series was identical in all respects to the preparation of G=0. The isolated yield of me title compound from 1.1 g of G=0 comb-branched PEI was 10.5 g (84%). The ¹³ C-NMR system showed a little more of the carbinol signal at 60.1 ppm than before, plus a signal at 59.46 ppm.

Example 17 Preparation of Comb-Burst PEI Wherein N _c is

20, N _b is 10, and G is 2. This material was prepared as described in me previous preparations utilizing an

Amicon S1Y10 spiral wound ultrafiltration cartridge (10,000 MWCO) (600 ml retentate/9 liters of permeate). From 1.1 g of comb-burst PEI wherein G = 1, there was obtained 10.8 g (86%) of the title product. The ¹³ C-NMR spectrum indicated more of the signal at 60.1 ppm than at 59.67 ppm.

Example 18 Preparation of a Comb-Burst PEI Wherein N _c is

20, N _b is 10, and G is 3.

The material was prepared as described before using an Amicon S1Y10 spiral wound ultrafiltration cartridge (10,000 MWCO) and filtration volumes as described before. From 1.1 g (25 mmole NH) of comb-burst PEI dendrimer wherein N _c is 20, N _b is 10, and G is 2 diere was obtained 10.3 g (82%) of the comb-burst PEI dendrimer wherein N _c is 20, N _b is

10, and G is 3. The ¹³ C-NMR spectrum of the material again indicated carbinol signals at

60.1 ppm and 57 ppm.

Example .19 Preparation of Comb-Burst PEI Wherein N _c is 20, N _b is 10, and G is 4.

This material was prepared as described above using an Amicon S1Y10 spiral wound ultrafiltration cartridge widi the volumes indicated above. From 1.1 g (25 mmole NH maxi¬ mum) of comb-burst PEI dendrimer wherein N _c is 20, N _b was 10, and G was 3, diere was obtained 10.1 g of the title compound (80% yield). Example 20 Preparation of a Comb-Burst PEI Wherein N _c is

20, N _b is 10, and G is 5.

This material was prepared as described above utilizing 1.1 g (25.5 mmole NH) of comb-burst PEI wherein N _c is 20, N _b is 10, and G is 4, 47.5 g (40 mmole) of PEOX oligomer, and 25 g (8 equivalents of amine per NH) of diisopropylemylamine. Workup as before using an Amicon S1Y10 spiral wound cartridge (700 ml of retentate, and 9 liters of permeate) gave 18 g of the PEOX-comb-burst copolymer. Hydrolysis with 50% H ₂ SO ₄ and treatment with excess NaOH gave a cake of material that floated on the caustic mixmre with a lot of trapped NaOH and sodium sulfate salts. The cake was heated in 300 ml of deionized water to boiling and allowed to cool giving a white precipitate. This mixmre was ultracentri- fuged at 8000 φm for 10 minutes and me resulting clear liquid was poured from the settled white solid. This white solid was mixed wim toluene and dried by azeotropic distillation to give 7.0 g (56%) of die title compound.

Example 21 Preparation of a Comb-Branched PEI Wherein

N _c is 20, N _b is 20, and G is Zero.

A PEOX oligomer having a dp of 20 was prepared from MeOTs (7.5 g, 40 mmole) and ethyl oxazoline (80 g, 800 mmole) by refluxing under tank nitrogen using an Hg bubbler. The LPEI (0.5 g, 0.52 mmole, 10 mmole per NH) in hot toluene was added to me PEOX oligomer followed by diisopropylediylamine (74 g, 574 mmole, 29 mmole per NH). This mixmre was refluxed for 72 hours. The volatiles were removed and the resulting residue was dissolved in deionized water. This mixmre was ultrafiltered using a S1Y3 cartridge. Workup as before gave 9.8 g of a PEI product (tiieory 9.1 g). The ¹³ C-NMR spectrum of this material indicated a significant amount of a carbinol signal at 60.2 ppm.

Example 22 Preparation of a Comb-Branched PEI Polymer

Wherein N _c is 20, N _b is 20, and G is Zero.

In diis experiment, two equivalents of PEOX oligomer per NH of the PEI and diiso¬ propylethylamine (30 equivalents per NH of PEI) were refluxed for five days. A very large stir bar was used to get more efficient stirring of the mixmre than was obtained in me above experiment. The mixmre was stripped of volatiles and die resulting residue dissolved in deionized water. Ultrafiltration of this mixmre using the S1Y3 spiral wound cartridge gave no separations as determined by SEC. The SEC plot indicated two peaks. Upon co-injection wim authentic PEOX oligomer having a dp of 20, one of me peaks was enhanced. The ultra- filtration was then carried out on a S1Y10 (10,000 MWCO) spiral wound cartridge. The SEC plot of the retentate was identical to the S1Y3 cartridge retentate.

The ultrafiltration was switched to an Amicon flat stock stirred cell system using a YM10 (10,000 MWCO) cartridge. After 1.5 liters of permeate only a small amount of the presumed PEOX oligomer having a dp of 20 had been ultrafiltered. The material was then ultrafiltered wim the flat stock stirred cell using a YM30 membrane (30,000 MWCO) (100 ml, retentate; 2000 ml permeate) to give a good separation by SEC. The retentate evaporated to 18 g (42%) of the PEOX-comb-branched PEI copoly- mer. This material hydrolyzed to 7.0 g (38%) of the comb-branched PEI. The ¹³ C-NMR

spectrum of the comb-branched PEI indicated only a minor amount (about 10%) of the carbinol signal at 60.1 ppm relative to the methyl terminated signal at 36.5 ppm.

Example 23 Preparation of a Comb-Burst PEI Polymer

Wherein N _c is 20, N _b is 20, and G is One. This material was prepared with two equivalents of PEOX oligomer having a dp of

20 and refluxing with diisopropylethylamine for three days. The reaction parameters were to be held constant to permit a reasonable analysis of the chemistry. An analysis of the crude reaction mixmre by SEC at 48 hours, 72 hours and 96 hours indicated a progressive increase in molecular weight. Ultrafiltration of me crude material in water with the Amicon flat stock stirred cell using a YM30 (30,000 MWCO) membrane as before (100 ml, retentate; 2000 ml permeate) gave a 74% yield of me PEOX-comb-burst PEI copolymer. Hydrolysis and treat¬ ment with NaOH, recrystallization from water, and azeotropic drying in toluene, gave a 68% yield of me title compound.

Example 24 Preparation of a Comb-Branched PEI Polymer Wherein N _c is 20, N _b is 100, and G is Zero.

Further exploration of the PEOX chain length on the grafting efficiency was done.

A PEOX having a dp of 100 was prepared (24 hrs at reflux) and refluxed 65 hours widi PEI

(1 equivalent PEOX per NH) with 11 equivalents of diisopropylemylamine per NH. The mixmre was evaporated of volatiles, dissolved in deionized water and ultrafiltered widi SI Y30 (30,000 MWCO) cartridge. Hydrolysis of the retentate and workup gave a 31 % yield of a white amoφhous powder. Hydrolysis of the permeate gave a white crystalline material, LPEI having a dp of 100. Example 25 Preparation of a Styrene Core Polymer.

The styrene core polymer precursor was prepared by polymerization of 20 g (192 mmole) of styrene in benzene (20 ml), initiated by s-butyl lidiium (4 mmole). After 4 hours, the reaction was terminated by addition of methanol (1 ml). Chloromethylation of the prod¬ uct polymer (10 g polystyrene, 60 ml chloromethyl me yl ether, and 1 ml stannic chloride in 500 ml of carbon tetrachloride for 48 hours) gave the chloromethylated core polymer.

Example 26 Preparation of a Comb-Branched Polystyrene

Wherein G is Zero.

Living polystyrene oligomer was generated by initiation of 20 g of styrene by 4 mmole of s-butyl lithium, as in example 25. After 4 hours at room temperature, 6 mmole of diphenylethylene in 350 ml of tetrahydrofuran was added. The chloromethylated polystyrene core was added portionwise, over 30 minutes, until most of the orange color of the carbanion had disappeared. After an additional 30 minutes, residual carbanions were terminated by the addition of 1 ml of methanol. Evaporation of the solvent and fractionation in toluene/methanol gave an 80% yield of die title compound. Example 27 Preparation of a Comb-Burst Polystyrene

Polymer Wherein G is Equal to One.

The product of Example 26 was chloromethylated as described in Example 25. Graft¬ ing was carried out as described in Example 26, substituting the chloromethylated-comb- branched material for the linear-chloromethylated-poly styrene core. Example 28 Preparation of a Comb-Burst Polystyrene

Polymer Wherein G is 2.

The product of Example 27 was chloromethylated as described in Example 25. Graft¬ ing was carried out as described in Example 26, substituting the chloromethylated-comb-burst material for the linear-chloromethylated-polystyrene core. Example 29 Preparation of Rod-Shaped Comb-Burst PEI

Wherein N _c is 200, N _b is 5, and G is 3.

This material was prepared as described above using N-moφholine terminated PEI as an initiator core. Repeated grafting (4 times) with Methyltosylate (3.7 g, 20 mmole) and ethyl oxazoline (10 g, 100 mmole) in 100 ml of toluene, followed by hydrolysis wim 150 ml of 50% H ₂ SO ₄ gave the dendrimers in a 70 to 80% yield. These products were characterized by ¹³ C-NMR spectroscopy, titration, and electrophoresis and shown to be d e titled material.

Example 30 Preparation of Spherically-Shaped Comb-Burst

PEI Wherein N _c is 10, N _b is 100, and G is 3.

This material was prepared in me same manner as die rod-shaped dendrimer using

LPEI (dp of 10) as an initiator core. The branches were constructed with PEOX (dp of 100), initiated as shown in the examples above.

Example 3J _. Synthesis of Ring Core Hyper-Comb-Branched

Polymers.

AZACROWN™ (1 ,4,7, 10-tetraazacyclododecane, cyclen) was obtained from The Dow

Chemical Company, and was further recrystallized from toluene. The purified AZACROWN™ is a white needle-like crystal.

A mixmre of methyltosylate (MeOTs) (0.922 g, 4.95 mmole) in 100 ml of toluene was azeotroped to remove water wim a distillation head under Ar for 10 minutes. After cooling to ~ 90°C, 2-ethyloxazoline (10 ml, 99.06 mmole) was cannulated in and the mix¬ mre was allowed to reflux for 5 hours. To mis mixmre was added an AZACROWN™ core (0.214 g, 4.95 mmole of NH), which was dried by azeotropic distillation from toluene, fol¬ lowed by immediate addition of diisopropylethylamine (i-Pr ₂ NEt)(2-4 eq.). The mixmre was refluxed for 1 hour, cooled, and men dissolved in methanol ( - 100% grafting yield as determined by SEC). After rotary-evaporation of the solvents, me crude product was either purified by ultrafiltration widi Amicon spiral wound cartridges S1Y3 (3,000 MWCO), or fractionated by methanol/diethyl ether mixmre to remove the unreacted monomers, oligomers, and catalysts. The entire separation process was monitored by size exclusion chromatography (SEC). The purified product was rotary-evaporated and lyophilized to give a ring-branched polyethyloxazoline-polyediyleneimine (PEOX-PEI) polymer as a white powder. The higher generations of die ring core comb-burst polymers can be prepared in a similar manner as described in die linear core case as described above. All d e products were analyzed by size exclusion chromatography (SEC), capillary electrophoresis (CE), nuclear magnetic resonance (NMR), and electrospray mass spectroscopy (ES-MS).

Example 32 Synthesis of Hyper-Terminal ly Branched Core

Hyper-Comb-branched Polymers.

A mixmre of MeOTs (0.39 g, 1.98 mmole) in 100 ml of toluene was azeotroped to remove water with a distillation head under Ar for 10 minutes. After cooling to ~ 90°C, 2-ethyloxazoline (10 ml, 99.06 mmole) was cannulated in and d e mixmre was allowed to reflux for 5 hours. To this mixmre was added a hyper-branched polyethylene amine core (0.214 g, 4.95 mmole of NH), which was dried by azeotropic distillation from toluene, followed by immediate addition of _-Pr ₂ NEt (large excess). The mixmre was refluxed for 3 hours, cooled, and the top toluene solution was decanted off. The remaining viscous oil was redissolved in a small amount of MeOH and reprecipitated out in diethyl ether (Et ₂ O). After the top Et ₂ O solution was decanted, the bottom precipitate was redissolved in methanol (MeOH) and dried over rotary evaporator and high vacuum to give a light yellow polyethyl- oxazoline-polyethyleneamine (PEOX-PEA) polymer. The higher generations of the hyper- branched core comb-burst polymers can be prepared in a similar manner as described in die linear core case described above. All the products were analyzed by SEC and NMR. Instrumental for Examples 3,1 and 32

SEC measurements were performed on a series of Beckman TSK 4000 PW (or POLY-OH, Polymer Laboratory), 3000 PW, and 2000 PW columns using Waters 510 HPLC pump, Thermo Separation Products AS 3000 Autosampler, Wyatt DAWN DSP-F Multi Angle Laser Light Scattering Detector, and Wyatt interferometer refractometer (Optilab 903). 'H and ¹³ C-NMR spectra were obtained on Brucker 360 MHz or Varian Unity 300 MHz NMR spectrometer using either CDC1 ₃ or MeOD as solvents. Purity of monomers was checked by GC (HP 5890, He as carrier gas). Ultrafiltration was achieved using eidier an Amicon 3,000 or 10,000 molecular weight cut off (MWCO) membrane. CE was performed on Beckman P/ACE System 2050 (Software System Gold). The polymer MWs were also measured by ES-MS (Finnigan Mat TSQ 700).

Example 33 Preparation of Poly (2-Ethyloxazoline) and Polyethyleneimine

Linear Polymers (DP= 10, 20, 50, 100, and 200).

Med yl p-toluenesulfonate, 2-ethyloxazoline, moφholine and diisopropyl emylamine were purchased from Aldrich. Mediyl p-toluenesulfonate was purified by distillation, while 2-ethyloxazoline, moφholine, diisopropyl ed ylamine and toluene were stirred over CaH ₂ and distilled prior to use. All d e reactions were performed under an ultra pure Ar atmosphere. The synthesis of poly (2-ethyloxazoline), (PEOX20, DP =20) is described to illustrate the general procedure for the preparation of linear PEOX. To a 250 ml two-neck round- bottom flask was added methyl p-toluenesulfonate (7.45g, 40 mmole) and dry toluene (150 ml). A distillation head (vacuum type) was attached and trace amounts of water in the mixmre were removed by azeotroping with toluene for 10-15 minutes. After cooling to about 90°C, ethyloxazoline (80.8 ml, 800 mmole) was cannulated in, and d e mixmre was allowed to reflux for 10 hours before termination wim excess moφholine. During me polymerization, a cloudy PEOX suspension was formed. After the termination with moφholine, me solution become clear again. The crude mixmre was rotary -evaporated and men hydrolyzed wim 500 ml of 50% H ₂ SO ₄ , followed by azeotroping the water-propionic acid mixmre with a Dean-Stark trap until the pH of the distillate was neutral. This hot acidic solution was slowly added (widi a separatory funnel) into a 50% NaOH solution cooled by an ice bath. This solution (pH > 11) was heated to boil under N ₂ , and the product (linear PEI) floated on top as an oily layer. After cooling to room temperamre, the top layer became a solid cake on the surface which was subsequently removed and redissolved in 600 ml deionized, boiling water. After slow sedimentation overnight, the white precipitate was filtered by suction funnel.

In order to completely remove excess NaOH, cold water was used to exhaustively wash the precipitate until pH of the filtrate solution was neutral. Pure polymer was obtained by azeotropic removal of water from a toluene solution of the polymer, followed by a gravity filtration and then rotary evaporating the toluene at 60 ^C C. Such polymer was further dried under high vacuum overnight (33 g., 85.8% yield, MW = 1,130, MWD = 1.05). Linear

PEOX and PEI 10, 50, 100, and 200 were prepared in a similar manner (PEOX yield >

90%, PEI yield > 80%). All the polymers were analyzed by SEC, ES-MS, NMR. CE. and

PAGE.

Example 34 Synthesis of Comb-branched Polymers (GO). The syndiesis of PEOX10-g-PEI20 is provided as a general procedure for the preparation of comb-branched PEOX-PEI and PEI polymers. A mixmre of MeOTs (7.38 g, 39.62 mmole) in 150 ml of toluene was azeotroped to remove water wid a distillation head under Ar for 10 minutes. After cooling to about 90°C, 2-ethyloxazoline (40 ml, 396.24 mmole) was cannulated in and the mixmre was allowed to reflux for 5 hours. To mis mixmre was added moφholine terminated LPEI 20 (1.90 g, 39.62 mmole of NH), which was dried by azeotropic distillation from toluene, followed by immediate addition of i-Pr ₂ NEt (1 to 2 eq.). The mixmre was refluxed for 1 hour, cooled, and men dissolved in methanol (about 75% grafting yield as determined by SEC). After rotary-evaporation of the solvents, d e crude product was ei ier purified by ultrafiltration wid Amicon spiral wound cartridges S1Y3 (3,000 MWCO), or fractionated by medianol/diethyl ether mixmre to remove the unreacted monomers, oligomers, and catalysts. The entire separation process was monitored by SEC. The purified product was rotary-evaporated and lyophilized to give a comb- branched PEOX-PEI polymers as a white powder. This white powder was further hydrolyzed in 50% H ₂ SO ₄ at 100°C and purified as described before to provide a PEI comb- branched polymer as a white viscous oil (MW=2,500, MWD = 1.22). Comb-branched PEOX20-g-PEI20, PEOX10-g-PEI50, PEOX50-g-PEI20, PEOX100-g-PEI50, PEOX200-g- PEI50, and PEOX20-g-l,4,7,10-Tetraazacylododecane) (PEOX20-g-Azacrown) were also prepared in a similar manner. All the products were analyzed by SEC-multi angle laser light scattering, CE, NMR, ES-MS and PAGE. Example 35 Synthesis of Comb-branched Polymers (Gl).

A mixmre of MeOTs (0.738 g, 3.962 mmole) in 150 ml of toluene was azeotroped to dryness widi a distillation head under Ar for 10 minutes. After cooling to about 90°C, 2- ethyloxazoline (40 ml, 396.24 mmole) was cannulated in and the mixmre was allowed to

reflux for 10 hours. To this mixmre was added comb-branched PEI (0.209g, about 3.962 mmole of NH) dried by azeotropic distillation from toluene, followed by immediate addition of i-Pr ₂ NEt (1-2 eq.). The mixmre was refluxed for 1 hour, and then cooled to room temperamre. The top toluene solution was decanted off and me bottom polymer product was redissolved in methanol. This crude product was purified by refractionation with a methanol/diemyl ether mixmre to remove the unreacted monomers, oligomers, and catalysts. The entire separation was monitored by SEC. The purified product was rotary -evaporated and lyophilized to give die comb-branched PEOX-PEI polymer as a white powder (MW=260,000, MWD = 1.10). The grafting yield depends on the length of the side chains (normally around 40% -80% as determined by SEC). Shorter side chains give a higher grafting yield. This white powder was further hydrolyzed in 50% H ₂ SO ₄ at 100°C and purified as described before to provide a PEI comb-branched polymer as a white solid (80% yield, MW= 138,800, MWD = 1.34). Example 36 Synthesis of Comb-branched (G2). A mixmre of MeOTs (0.738 g, 3.962 mmole) in 150 ml of toluene was azeotroped to dryness with a distillation head under Ar for 10 minutes. After cooling to about 90°C, 2-ethyloxazoline (40 ml, 396.24 mmole) was cannulated in and the mixmre was allowed to reflux for 10 hours. To this mixmre was added comb-branched PEI polymer (0.200g, about 3.962 mmole of NH) dried by azeotropic distillation from toluene, followed by immediate addition of i-Pr ₂ NEt (1-2 eq.). The mixmre was refluxed for 1 hour, and dien cooled to room temperamre. The top toluene solution was decanted off and die bottom polymer product was redissolved in med anol. This crude product was purified by refractionation with a methanol/diethyl ed er mixmre to remove the unreacted monomers, oligomers, and catalysts. The entire separation was monitored by SEC. The purified product was rotary - evaporated and lyophilized to give d e comb-branched PEOX-PEI polymer as a white powder (MW=2,182,000, MWD= 1.50). This white powder was further hydrolyzed in 50% H ₂ SO ₄ at 100° C and purified as described before to provide PEI comb-branched polymers as a white

solid (85% yield, MW = 1,078,000, MWD = 1.47). All the products were analyzed by SEC, CE, NMR and PAGE, viscometry, TGA, and DSC. Example 37 Synthesis of Comb-branched (G3)

The G3 comb-branched polymer was synthesized in a similar manner as above. The molecular weight of the resulting product was 10,400.000 and me molecular weight distribution was 1.20. The higher generation comb-branched polymers and od er comb- branched polymers wid different shapes due to the different side chains and initiator cores used were prepared in a similar manner. Instrumentals for Examples 33-37 SEC measurements were performed on a series of Beckman TSK 4000 PW (or

POLY-OH, Polymer Laboratory), 3000 PW, and 2000 PW columns using Waters 510 HPLC pump, Thermo Separation Products AS 3000 Autosampler, Wyatt DAWN DSP-F Multi Angle Laser Light Scattering Detector, and Wyatt interferometer refractometer (Optilab 903). 'H and ¹³ C-NMR spectra were obtained on Brucker 360 MHz or Varian Unity 300 MHz NMR spectrometer using either CDC1 ₃ or MeOD as solvents. Purity of monomers was checked by GC (HP 5890, He as carrier gas). Ultrafiltration was achieved using an Amicon 3,000, 10,000, or 100,000 molecular weight cut off (MWCO) membrane. Thermal analysis was performed on DuPont Thermal Gravimetric Analyzer (Model 951) wid TA Instrumental Software (2000 Series). CE was performed on Beckman P/ACE System 2050 (Software System Gold). The polymer MWs were also measured by ES-MS (Finnigan Mat TSQ 700). PAGE analysis was performed on Gradipore gradient microgel (5-40% T) with a BioRad 500/200 power supply. The viscosity measurements were achieved on a Cannon-Ubbelohde semi-micro viscometer.