This invention relates to processes for radical-initiated polymerization of unsaturated species and for the control of molecular weight of the polymers produced from such processes. Polymers of low molecular weight, or oligomers, are important as precursors in producing other polymeric materials and such polymers have been found to be useful in a variety of products, for example, in the production of high solids (low VOC) surface coatings, in adhesives and as plasticizers in polymeric composites.

In conventional polymerization practice, the manufacture of oligomers requires the use of an initiator which acts as a free radical source, and of a chain transfer agent. The chain transfer agent controls the molecular weight of the polymer by reacting with the propagating polymer radical to terminate its growth. It then initiates a new polymer chain thus transferring the growth process from one discrete polymer molecule to another discrete polymer molecule.

The most commonly used chain transfer agents are alkanethiols, which normally are associated with an objectionable odour and lead to a wide distribution of molecular weight with certain monomers. Also, the residual thiols and the end thio-ether linkage of the polymers may have an adverse effect on the properties of the ultimate product from the polymer.

The present invention helps overcome the disadvantages of polymerizations regulated with thiols by using alternative polymerization regulators. These regulators have good stability and shelf life while maintaining many of the advantages over thiols. In the majority of cases, the materials that are part of the present process present a different range of chain transfer activities, allowing more opportunity for an optimal process to be selected for a given polymerization system of monomers and polymerization conditions. The chain transfer constant that a given regulator possesses is an important consideration in selecting the optimum process for producing low molecular weight

polymers.

This invention provides a process for the free radical polymerization of unsaturated species to provide polymers with lower molecular weight and narrower polydispersity characterised by the use of compounds of Formula (I) as chain transfer agents.

Formula (I) wherein

X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR ⁶ ; C(O)NR ⁷ R ⁸ ; and halogen;

Q is selected from COOR ¹ ; CN; and C(O)NR ⁷ R ⁸ ;

Y is selected from hydrogen; C, to C ₆ alkyl; C, to C ₆ alkyl substituted with one or more substituents selected from hydroxy, amino, C _j to C ₆ alkoxy, C, to C ₆ alkoxycarbonyl, halogen, CN and optionally substituted aryl; C, to C ₆ alkenyl; and C, to C ₆ alkynyl;

Z is selected from COOR ² ; CN; and optionally substituted aryl;

R ³ and R ⁴ may be the same or different and are selected from hydrogen, C, to C ₄ alkyl and halogen; or R ³ and R ⁴ together with the carbon atom to which they are attached form part of a carbocyclic or heterocyclic ring structure;

R is selected from C, to C, _g alkyl; C, to C ₁₂ alkyl substituted with one or more substituents selected from hydroxy, amino, C, to C ₆ alkoxy, phenyl, halogen, NCO, CN, and COOR ⁵ ;

R ¹ and R ² may be the same or different and are selected from C, to C, ₈ alkyl; C, to C ₁₂ alkyl substituted with one or more substituents selected from hydroxy, C, to C ₆ acyloxy, C, to C ₆ alkoxy, amino, halogen, Si(R ⁹ ) ₃ , SiCOR ⁹ ^, optionally substituted aryl, CN and NCO;

R ⁵ is selected from hydrogen and C, to C ₆ alkyl;

R ⁶ is selected from hydrogen and C _] to C, _g alkyl;

R ⁷ and R ⁸ may be the same or different and are selected from C, to C _lg alkyl; and

R ⁹ is selected from C, to C, _g alkyl; C, to C _lg cycloalkyl; and optionally substituted aryl.

A preferred group of compounds of Formula I are the malonates with Q = COOR ¹ and Z = COOR ² having the Formula (IA):

Formula (IA) wherein:

X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR ⁶ ; C(O)NR ⁷ R ⁸ ; and halogen;

Y is selected from hydrogen; C, to C ₆ alkyl; Cj to C ₆ alkyl substituted with one or more substituents selected from hydroxy, amino, C, to C ₆ alkoxy, C to C ₆ alkoxycarbonyl, halogen, CN, optionally substituted aryl; C, to C ₆ alkenyl; and C, to C ₆ alkynyl;

R ¹ and R ² may be the same or different and are selected from C, to C, _g alkyl; C, to C ₁₂

alkyl substituted with a substituent selected from hydroxy, C, to C acyloxy, C, to C ₆ alkoxy, amino, halogen, optionally substituted aryl, CN and NCO;

R ³ and R ⁴ may be the same or different and are selected from hydrogen; C, to C ₄ alkyl; and halogen; and

R, R ⁶ , R ⁷ and R ⁸ are as defined above.

Another preferred group of compounds which possess high chain transfer activities are the compounds of Formula (IB) where Q = COOR ¹ and Z is optionally substituted aryl:

Formula (IB)

wherein:

X, Y, R ¹ , R ³ and R ⁴ are as defined above; and

Z is optionally substituted aryl.

The term "optionally substituted aryl" is used herein to mean an aromatic carbocyclic group which may or may not be substituted with one or more substituents that do not interfere with the polymerization process. Such substituents include alkyl, hydroxyalkyl, aminoalkyl, carboxylic acid, ester, acyloxy, amide, nitrile, haloalkyl, alkoxy, phosphonate, sulfonate, silyl or silyloxy groups.

Preferred aryl groups are phenyl or naphthyl groups.

When X is halogen, chlorine or bromine are preferred.

When R ³ or R ⁴ is halogen, chlorine or fluorine are preferred.

The following compounds of Formula I are novel and form part of the invention:

ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate; ethyl 2,4-bis(ethoxycarbonyl)-2-ethyl-4-pentenoate; ethyl 2-benzyl-2,4-bis(ethoxycarbonyl)-4-pentenoate; ethyl 2-ethoxycarbonyl-2-methyl-4-phenyl-4-pentenoate; ethyl 2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl)-4-penteno ate; and ethyl 2-phenyl-4-(t-butoxycarbonyl)-4-pentenoate .

The process of this invention uses the compounds of Formula (I) as alternatives to thiols or other chain transfer agents for the control of molecular weight. The process of this invention may be operated in a similar manner to conventional processes using thiols. The compounds of Formula I can be prepared easily from inexpensive starting materials. Unlike thiols, they do not, in general, possess an objectionable odour.

The materials of this invention exhibit unexpectedly good chain transfer activities in general. For example, compound ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (lb) of this invention possesses significantly higher activity when compared with the methyl 4-methoxycarbonyl-2,2-dimethyl-4-pentenoate (MMA dimer or dimethyl 2,2- dimethyl-4-methylene glutarate) (refer to Table 5) in methyl methacrylate, acrylate and styrene polymerizations. The advantages of this invention will become more apparent by referring to the illustrative non-limiting examples shown below.

Preparation of Chain Transfer Agents

The allylic malonate derivatives [Formula (IA)] are synthesized in good to excellent yield in a one-step reaction between the corresponding allylic halides (II) and malonates (IIIA). The reaction is carried out in the presence of base and solvent. Acetonitrile, N,N-dimethylformamide (DMF), dried THF or diethyl ether are suitable solvents. Although many (inorganic and organic) bases are suitable, sodium hydride, sodium

alkoxide, sodamide, potassium alkoxides are preferred bases. The use of sodium hydride is found to provide better results than sodium alkoxide for the synthesis of these types of compounds.

Similarly, the allylic compounds of Formula IB [e.g., compound (Ii)] can be synthesized in good yield in a one-step reaction between the corresponding allylic halide (II) and arylacetate (IIIB). The reaction is carried out in the presence of base and solvent.

l

(ID me OB)

Typical compounds (Ia & lb) used in the process of this invention and their preparation are further illustrated by the following non-limiting preparative examples.

Preparative Example 1: Ethyl 2.4-bisfethoxycarbonylV4-pentenoate (Ia) [Formula (IA), X = COOCH ₂ CH ₃ ; Y = R ³ = R ⁴ = H; R ¹ = R ² = CH ₂ CH ₃ ]. [Typical procedure].

To a suspension of sodium hydride (80% dispersion in oil, 0.36g, 12mmol) in acetonitrile (lOmL), was added diethyl malonate (1.60g, lOmmol). The resulting suspension was allowed to stir at room temperature for 15 minutes. A solution of ethyl α-(bromomethyl)acrylate [obtained from a modified procedure of S. E. Drewes, G. Loizou and G. H. P. Roos, Synthetic Communications, 1987, 17(3 ^' ). 291-298] (1.93g, lOmmol) in acetonitrile (5mL) was then added slowly to the above suspension. Stirring was maintained for 2 hours and then the reaction mixture was poured into water, and

extracted (3x) with diethyl ether. The extracts were combined and dried over anhydrous Na-SO^ filtered and evaporated to dryness. Distillation of the crude product under reduced pressure gave (Ia) as a colourless liquid (b.p.~140°C/0.1mmHg) (1.90g, -70%). Η-NMR (CDC1 ₃ ) δ(ppm) 1.21 (t, 6H), 1.25 (t, 3H), 2.85 (d, 2H), 3.67 (t, IH), 4.15 (q, 4H), 4.20 (q, 2H), 5.60 (br. s, IH) and 6.18 (br. s, IH). ¹³ C-NMR (CDC1 ₃ ) δ(ppm) 13.98, 31.34, 50.76, 60.81, 61.37, 127.56, 136.68, 166.38 and 168.67.

Preparative Example 2:

Ethyl 2.4-bis( ^' ethoxycarbonyl ^' )-2-methyl-4-pentenoate (lb) [Formula A), X = COOCH ₂ CH ₃ ; Y = CH ₃ ; R ³ = R ⁴ = H; R ¹ = R ² = CH ₂ CH ₃ ]. This compound was prepared using a similar procedure to that described above. Pure ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (lb) was obtained (60% yield) after column chromatography on silica-gel (diethyl ether : n-hexane 1 :4 as eluent). ¹ H-NMR (CDCI ₃ ) δ(ppm) 1.20 (t, 6H), 1.25 (t, 3H), 1.33 (s, 3H), 2.95 (s, 2H), 4.15 (m, 6H), 5.56 (br. s, IH) and 6.22 (br. s, IH). ¹³ C-NMR (CDC1 ₃ ) δ(ppm) 13.91, 14.06, 35.98, 53.88, 60.78, 61.23, 128.61, 136.29, 166.67 and 171.57.

Preparative Example 3:

Ethyl 2.4-bisfethoxycarbonyl -2-ethyl-4-pentenoate (Ic) [Formula (IA), X = COOCH ₂ CH ₃ ; Y = CH ₂ CH ₃ ; R ³ = R ⁴ = H; R ¹ = R ² = CH ₂ CH ₃ ].

This compound was prepared in -80% yield using a similar procedure to that described in Example 1. Η-NMR (CDC1 ₃ ) δ(ppm) 0.85 (t, 3H), 1.20 (t, 6H), 1.30 (t, 3H), 1.85 (q, 2H), 2.95 (s, 2H), 4.15 (m, 6H), 5.58 (br. s, IH) and 6.25 (br. s, IH). ¹³ C-NMR (CDCI ₃ ) δ(ppm) 8.58, 14.06, 14.16, 25.46, 32.98, 58.32, 60.89, 61.15, 128.42, 136.53, 167.05 and 171.09.

Preparative Example 4:

Ethyl 2-benzyl-2.4-bis(ethoxycarbonvD-4-pentenoate (Id) [Formula (IA), X = COOCH ₂ CH ₃ ; Y = CH ₂ C ₆ H ₅ ; R ³ = R ⁴ = H; R ¹ = R ² = CH ₂ CH ₃ ].

This compound was prepared by a procedure similar to Example 1, using diethyl

benzylmalonate as the starting material; the product was isolated in 76% yield as a colourless syrup. 'H-NMR (CDC1 ₃ ) δ(ppm) 1.20 (t, 6H), 1.30 (t, 3H), 2.95 (s, 2H), 3.25 (s, 2H), 4.15 (m, 6H), 5.65 (br. s, IH), 6.25 (br. s, IH) and 7.20 (m, 5H). ^,3 C-NMR (CDC1 ₃ ) δ(ppm) 13.82, 14.11, 30.40, 39.63, 43.30, 58.75, 60.84, 61.20, 126.87, 128.11, 128.55, 130.08, 167.40 and 170.56.

Preparative Example 5:

Ethyl 4-chloro-2-ethoxycarbonyl-2-methyl-4-pentenoate (Ie)

[Formula (IA), X = CI; Y = CH ₃ ; R ³ = R ⁴ = H; R ¹ = R ² = CH ₂ CH ₃ ]. To a suspension of sodium hydride (25.2g, 0.84 moles, 80% dispersion in oil) and diethyl methylmalonate (104.5g, 0.60 moles) in acetonitrile (500mL), a solution of 2,3- dichloropropene (66.6g, 0.60 moles) in acetonitrile (lOOmL) was added slowly over 20 minutes with stirring at room temperature. The resulting mixture was allowed to stir at room temperature overnight. Water (250mL) was added, and the mixture extracted three times with diethyl ether (200mLx3). The combined organic layers were washed successively with water (200mL) and brine (200mL), they were then dried over anhydrous MgSO ₄ . After removal of the organic solvent, distillation of the crude product under reduced pressure afforded the product (Ie) as a colourless liquid (91.6g, 61.5% yield), b.p. 77-78°C (O.lmmHg). Η-NMR (CDC1 ₃ ) δ(ppm) 1.22 (t, 6H), 1.42 (s, 3H), 3.00 (s, 2H), 4.18 (q, 4H), 5.20 (s, IH) and 5.30 (s, IH).

Preparative Example 6:

Ethyl 2-ethoxycarbonyl-4-phenyl-4-pentenoate (If)

[Formula (IA), X = Phenyl; Y = R ³ = R ⁴ = H; R ¹ = R ² = CH ₂ CH ₃ ]. This compound was prepared in -20% yield (not optimized) according to a similar procedure to that described in Example 1. The reaction was carried out between α- (bromomethyl)styrene [obtained from the reaction of α-methylstyrene and N- bromosuccinimide in carbon tetrachloride according to the published procedure by H. Pines, H. Alul and M. Kolobielski, J. Org. Chem., 1957, 22, 1113-1114] and diethyl malonate in the presence of sodium hydride (1 eq.). Η-NMR (CDC1 ₃ ) δ(ppm) 1.25 (t, 6H), 3.10 (d, 2H), 3.50 (t, IH), 4.17 (q, 4H), 5.15 (br. s, IH), 5.35 (br. s, IH) and 7.35 (m, 5H).

Preparative Example 7:

Ethyl 2-ethoxycarbonyl-2-methyl-4-phenyl-4-pentenoate (Ig) [Formula (IA), X = Phenyl; Y = CH ₃ ; ^' R ³ = R ⁴ = H; R ¹ = R ² = CH ₂ CH ₃ ]. This compoxind was prepared in -60% yield by reacting α-(bromomethyl)styrene [obtained by method of H. Pines, H. A , M. Kolobielski, J. Org. Chem., p. 1113 (1957)] and diethyl methylmalonate in the presence of sodium hydride (2 eq.) in acetonitrile solvent. Η-NMR (CDC1 ₃ ) δ(ppm) 1.10 (t, 6H), 1.30 (s, 3H), 3.18 (s, 2H), 3.90 (m, 4H), 5.10 (br. s, IH), 5.27 (br. s, IH) and 7.30 (m, 5H).

Preparative Example 8:

Ethyl 2-ethoxycarbonyl-2.3-dimethyl-4-( ^' t-butoxycarbonyl -4-pentenoate (Ih) [Formula (IA), X = COOC(CH ₃ ) ₃ ; Y = CH ₃ ; R ³ = H; R ⁴ = CH ₃ ; R ¹ = R ² = CH ₂ CH ₃ ].

The starting material, t-butyl (Z)-2-bromomethyl-2-butenoate, was prepared via literature procedures [H. Hoffmann and J. Rabe, Helvetica Chimica. Ada, 67(2), p. 413 (1984)].

A stirred solution of diethyl methylmalonate (1.5g, 8.6mmol) in distilled THF was cooled to -5°C and sodium hydride (0.52g) added portionwise. The resultant suspension was stirred below 0°C for an hour, then t-butyl (Z)-2-bromomethyl-2-butenoate added dropwise. The mixture was stirred below 0°C for a further two hours before being allowed to warm to room temperature and stirred overnight. Solvent was removed under reduced pressure, water added and the product extracted with ether (3x50ml), and the combined organic layers dried over anhydrous magnesium sulphate. Upon removal of ether under reduced pressure, a pale yellow oil was obtained (2.02g, 72%). •H-NMR spectrum revealed the presence of two isomers in a ratio of 4:1, with the preferred isomer being the major product (Ih). Column chromatography on silica gel (9:1, pet. spirit 40-60°C : ethyl acetate) gave slight separation of the two isomers. The fraction containing the highestlevel of ethyl-2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl) pent-4-enoate (Ih) was used for the following spectroscopic data. 'H-NMR (CDC1 ₃ ) δ(ppm): 6.25, s, IH; 5.55, s, IH; 4.2, m, 4H; 3.7, q, IH; 1.2-1.6, m, 21H. ¹³ C-NMR (CDClj) δ (ppm): 171.7, 171.2, 166.6, 143.5, 125.2, 80.5, 61.1, 57.5, 36.7, 28.0, 17.5, 17.0, 14.0, 13.9.

Preparative Example 9:

Ethyl 2-ρhenyl-4-(t-butoχycarbonylV4-pentenoate (Ii)

[Formula (IB), X = COOC(CH ₃ ) ₃ ; Y = R ³ = R ⁴ = H; R ¹ = CH ₂ CH ₃ ; Z = phenyl] The starting allylic bromide material, t-butyl 2-(bromomethyl)propenoate was prepared via a modified procedure of S. E. Drewes, G. Loizou and G. H. P. Roos, Synthetic Communications, 1987, 17f3 291-298 using t-butyl acrylate.

Ethyl phenylacetate (6.66g, 40.6 mmol) was dissolved in dry THF (20 mL) and sodium hydride (1.09g, 36.5 mmol) added portionwise. The resulting suspension was stirred at room temperature for 30 minutes then cooled on ice while t-butyl 2- (bromomethyl)propenoate (4.49g, 20.3 mmol) was added dropwise under nitrogen atmosphere. On completion of the addition, the reaction mixture was allowed to reach room temperature then heated under reflux for 8 hours. The THF solvent was removed under reduced pressure, water added and the product mixture extracted with diethyl ether (3x50 mL). After removal of organic solvent, the excess ethyl phenylacetate was removed by vacuum distillation and the residue was chromatographed on a silica-gel column using 5% ethyl acetate in petroleum spirit as eluent. The pure product (Ii) was obtained as a very pale yellowish liquid (2.5g, 41%). Η-NMR (CDC1 ₃ ) δ(ppm): 1.10, t, 3H; 1.45, s, 9H; 2.65, dd, IH; 3.00, dd, IH; 3.85, dd, IH; 4.10, m, 2H; 5.35, s, IH; 6.00, s, IH; 7.25, s, 5H.

Operation of the Process

The process of this invention may be adopted by the users of conventional processes using thiols with little change to reaction conditions other than the substitution of the appropriate quantity of compound of general Formula (I) for the thiol. The proportion of compound of Formula (I) used may be in the range of 0.01 to 30 mole percent based on total monomer, with a preferred range of 0.1 to 10 mole percent.

The process may be operated at any of the reaction conditions appropriate to free radical polymerization, ie., temperatures from -100°C to 200°C and pressures from below atmospheric to substantially above atmospheric.

The polymerization process can be carried out in bulk, solution, emulsion, suspension or other conventional polymerization modes. Source of radicals for polymerizations are well known in the art and they include α,α'-azobisisobutyronitrile, 4,4'-azobis(4- cyanovaleric acid), 2,2'-azobis(2,4-dimethylpentanenitrile), benzoyl peroxide, t-butyl peroxybenzoate, ammonium persulfate, potassium persulfate.

Any unsaturated monomers susceptible to free radical polymerization may be used although it should be noted that the chain transfer constant will vary with the monomer used. Suitable unsaturated monomers include acrylic esters, methacrylic esters, vinyl esters, vinyl aromatics, unsaturated or polyunsaturated hydrocarbons, or mixtures of these. Examples of these monomers are methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, w-butyl methacrylate, 2-ethylhexyl methacrylate, vinyl acetate, styrene, 7-chloromethylstyrene, 2-vinylpyridine, 4-vinylpyridine, N-vinylpyrrolidone, vinyl halides of the formula CH ₂ =CHX where X is CI or F, vinylidene halides of the formula CH ₂ =CX ₂ wherein X is independently CI or F, vinyl ethers CH ₂ =CHOR where R is alkyl, and allyl monomers such as allyl ethers, allyl carbonates or diallyl carbonates.

Compounds of general Formula (I) used in the process of this invention display an unexpected high activity in controlling molecular weight in polymerization reactions and have chain transfer constants that may be superior to those of thiols, particularly with styrene and acrylates. Their activity is such that their chain transfer constants can approach the optimum values of 1.0 for batch polymerizations and this activity is not as highly dependent as that of thiols on the structure of the propagating radical.

The process is applicable to the manufacture of synthetic rubbers, and other polymer formulations where reduced molecular weight aids processing and improves properties. The process can also be used to produce low molecular weight polymers, oligomers, macromonomers and functional polymers for a variety of applications such as high-solids surface coatings, paints, and adhesives. Furthermore, the process can be used to enable better control over the polymerization kinetics, e.g., delaying the onset of gelation in cross-linking systems.

The operation of this process is demonstrated by the following non-limiting examples. In these examples molecular weight measurements were performed on a Waters Associates liquid chromatograph equipped with differential refractometer and six μ- styragel columns of 10 ⁶ , 10 ⁵ , 10 ⁴ , 10 ³ , 500 and 100 A pore size. Tetrahydrofuran solvent was used at a flow rate of 1 mL/min. Results were derived by comparison with polystyrene standards using the Chromatix GPC-1 program.

The conversions were determined from the mass of the polymers isolated after precipitation in solvents where appropriate or after removal of all the volatiles in vacuo, and after subtracting the mass of the chain transfer agent.

Example 1: Polymerization of Methyl Methacrylate

α,α'--Azobisisobutyronitrile (23.4 mg) was dissolved in freshly distilled inhibitor-free methyl methacrylate (MMA) (25 mL). Aliquots (4 mL) were removed and added to ampoules containing weighed amounts of the allylic chain transfer agent of Formula (I). The contents of the ampoule were either degassed by three freeze-evacuate-thaw cycles and sealed under vacuum or by bubbling nitrogen through the solution. The mixtures were then polymerized at 60 °C for one hour. The contents of the ampoules were then added dropwise to methanol and the precipitated polymers were collected and dried in a vacuum oven to constant weight. A small portion of each polymer was examined by gel-permeation chromatography (GPC) to determine its molecular weight.

Table 1

Molecular Weight and Conversions for Methyl Methacrylate Polymerizations

Carried Out in the Presence of Chain Transfer Agents (CTA)

Temp. Time 10 ³ [CTA]/ %

Entry CTA (°C) (hr.) [Monomer] Conv. H, ^*

1 Ia 60 1.00 0.00 15.80 327160

2 Ia 60 1.00 10.20 14.70 287300

3 Ia 60 1.00 22.80 13.30 253630

4 lb 60 1.00 0.00 14.95 159200

5 lb 60 1.00 16.80 13.35 104100

6 lb 60 1.00 31.30 12.80 89900

7 lb 60 1.00 68.30 11.20 58700

8 Ic 60 1.00 0.00 16.30 254350

9 Ic 60 1.00 14.32 12.10 195900

10 Ic 60 1.00 28.37 9.95 190150

11 Ic 60 1.00 56.73 8.30 153150

12 If 60 1.00 0.00 14.72 266800

13 If 60 1.00 9.82 2.44 89000

14 If 60 1.00 19.64 1.30 64875

15 If 60 1.00 38.58 1.22 50800

16 Ig 60 1.00 0.00 11.49 299000

17 Ig 60 1.00 9.89 4.48 113400

18 Ig 60 1.00 19.03 0.42 91990

19 Ig 60 1.00 36.34 1.47 57530

20 Ii 60 1.00 0.00 12.74 248860

21 Ii 60 1.00 9.89 11.52 131020

22 Ii 60 1.00 18.15 11.61 100900

23 Ii 60 1.00 34.50 10.30 71120

# Number-average molecular weight determined by GPC, calibrated with polystyrene standards.

Example 2: Polymerization of Styrene

Polymerizations of styrene (Sty) were carried out similarly for three hours at 60°C. α,α'-Azobisisobutyronitrile (21.6 mg) was dissolved in freshly distilled styrene (50 mL). Aliquots (10 mL) were removed and transferred to ampoules containing weighed amounts of chain transfer agent. After the degassing and polymerization, the contents of ampoules were poured into methanol and the precipitated polymers were collected, dried, and examined as before.

Table 2

10 Molecular Weight and Conversions for Styrene Polymerizations Carried Out in the Presence of Allylic Malonate Chain Transfer Agents and MMA Dimer

(Methyl 4-methoxycarbonyI-2,2-dimethyl-4-pentenoate)

Temp . Time 10 ³ [CTA]/ %

15 Entry CTA CQ (hr.) [Monomer] Conv. H* ^#

1 Ia 60 3.00 0.00 9.80 130000

2 Ia 60 3.00 13.20 8.40 119250

3 Ia 60 3.00 26.20 9.30 114300 onv

4 lb 60 3.00 0.00 8.30 127000

5 lb 60 3.00 14.86 4.20 20400

6 lb 60 3.00 32.78 3.65 12500

7 lb 60 3.00 43.11 3.20 11400

8 Ih 60 3.00 0.00 8.4 103995

9 Ih 60 3.00 8.75 6.3 43755

10 Ih 60 3.00 16.90 5.8 28222

11 Ih 60 3.00 30.40 5.2 18682 in

12 Ii 60 3.00 0.00 9.0 112525

13 Ii 60 3.00 9.01 8.3 102660

14 Ii 60 3.00 18.35 7.4 89260

15 Ii 60 3.00 38.69 6.5 80940

16 MMA Dimer 60 3.00 0.00 10.5 120010

17 MMA Dimer 60 3.00 12.50 7.0 59855

18 MMA Dimer 60 3.00 25.00 5.8 41220

19 MMA Dimer 60 3.00 49.88 5.7 27830

# Number-average molecular weight determined by GPC, calibrated with polystyrene standards.

Example 3: Polymerization of Acrylate Esters

Polymerizations of methyl acrylate (MA) (or ethyl acrylate, EA) were carried out using a stock solution prepared from α,α'-azobisisobutyronitrile (6.34 mg) and distilled thiophene-free benzene (25 mL). Aliquots (6 ml) were removed and added to ampoules containing freshly distilled methyl acrylate (4 mL), thiophene-free benzene (10 mL) and weighed amounts of the activated allylic malonate chain transfer agents. After degassing, the mixtures were polymerized at 60°C for one hour; or at 80°C for 30 minutes; or at 90°C for 30 minutes. The volatiles were then removed on rotary evaporator and the polymers were dried in vacuo to constant weight and examined by GPC.

Table 3 Molecular Weight and Conversions for Acrylate Polymerizations Carried Out in the Presence of Chain Transfer Agents (CTA)

Temp .Time 10 ³ [CTA]/ %

Entry Monomer CTA CQ (br.) [Monomer] Conv. M/

1 MA Ia 80 0.50 0.00 38.70 183900

2 MA Ia 80 0.50 10.00 36.60 137500

3 MA Ia 80 0.50 20.60 31.90 95750

4 MA Ia 80 0.50 39.75 25.60 67400

5 EA lb 60 1.00 0.00 8.80 235000

6 EA lb 60 1.00 4.33 4.60 89400

7 EA lb 60 1.00 5.87 3.85 53100

8 EA lb 60 1.00 12.81 2.30 33500

9 MA Ie 60 1.00 0.00 26.3 493150

10 MA Ie 60 1.00 3.73 25.3 467300

11 MA Ie 60 1.00 14.67 21.8 362400

MA If 60 1.00 0.00 28.2 388450

MA If 60 1.00 9.43 -0.0 31455

MA If 60 1.00 20.61 -0.0 8140

MA If 60 1.00 34.18 -0.0 5810

MA If 80 0.50 0.00 46.0 133300

MA If 80 0.50 8.70 0.39 22630

MA If 80 0.50 18.10 1.60 11540

MA If 80 0.50 34.44 -0.0 4375

MA ig 60 1.00 0.00 21.44 657800

MA ig 60 1.00 8.84 0.47 13260

MA ig 60 1.00 21.32 0.14 4885

MA ig 60 1.00 37.33 0.0 3495

MA ig 80 0.50 0.00 17.36 187500

MA ig 80 0.50 9.43 0.30 7960

MA ig 80 0.50 20.73 0.21 3860

MA ig 80 0.50 38.79 0.12 2560

MA Ih 60 1.00 0.00 20.5 926S32

MA Ih 60 1.00 6.54 22.6 66231

MA Ih 60 1.00 13.30 27.5 37180

MA Ih 60 1.00 26.50 12.9 21243

MA Ih 80 0.50 0.00 40.6 176925

MA Ih 80 0.50 6.91 38.3 48525

MA Ih 80 0.50 13.30 32.1 26285

MA Ih 80 0.50 26.50 28.4 16074

36 MA Ii 60 1.00 0.00 23.4 739090

37 MA Ii 60 1.00 7.49 3.2 151740

38 MA Ii 60 1.00 14.29 1.7 98120 39 MA Ii 60 1.00 29.24 0.2 52940

40 MA Ii 90 0.50 0.00 55.6 83145

41 MA Ii 90 0.50 6.93 20.9 46055

42 MA Ii 90 0.50 14.91 16.4 28680 43 MA IIii 9900 00..5500 2288..9999 1144..99 18100

# Number-average molecular weight determined by GPC, calibrated with polystyrene standards.

Example 4 : Polymerization of Vinyl Acetate

Polymerizations of vinyl acetate (VAc) were carried out in vacuo at 60°C for one hour or at 80°C for one hour using the following procedure. α,α'-Azobisisobutyronitrile (20.5 mg) was dissolved in freshly distilled vinyl acetate (25 mL). Aliquots (4 mL) were removed and added to ampoules containing weighed amounts of the chain transfer agents. After the polymerization, the volatiles were removed and the polymers were dried and examined as before.

Table 4

Molecular Weights and Conversions for Vinyl Acetate Polymerizations

Carried Out in the Presence of Chain Transfer Agents (CTA)

Temp. Time 10 ³ [CTA]/ %

Entry CTA CQ (br.) [Monomer] Conv. M»*

1 Ie 80 1.00 0.00 60.2 62700

2 Ie 80 1.00 1.87 29.9 54700 3 Ie 80 1.00 3.72 18.9 38300

4 Ie 80 1.00 7.43 12.6 25900

5 Ig 60 1.00 0.00 5.37 193500

6 Ig 60 1.00 12.90 0.08 8200 7 Ig 60 1.00 23.90 0.02 5740

8 Ig 60 1.00 39.10 0.03 3260

# Polystyrene standard equivalent number-average molecular weight.

Table 5 summarizes the results of chain transfer constants in polymerizations of common monomers using the allylic chain transfer agents [(la), (lb), (Ic), (Ie), (If), (Ig) and (Ih)].

Table 5

Chain Transfer Constants (CJ for Polymerizations of Common Monomers in the Presence of Allylic Transfer Agents and MMA Dimer

CTA Monomer Conditions Chain Transfer Constants

(CJ

Ia MMA 60°C 0.004

MA 80°C 0.020

Sty 60°C 0.004 lb MMA 60°C 0.015

Sty 60°C 0.148

EA 60°C 0.203 MMA EMA 60°C 0.007 Dimer EA 60°C 0.120

Sty 60°C 0.057

Ic MMA 60°C 0.004 Ie VAc 80°C 0.274 MA 60°C 0.005

If MMA 60°C 0.060

MA 60°C 0.450

MA 80°C 0.560

Ig MMA 60°C 0.040 MA 60°C 0.670

MA 80°C 0.850 VAc 60°C 7.010

Ih MA 60°C 0.150 MA 80°C 0.180 Sty 60°C 0.150

Ii MMA 60°C 0.029

MA 60°C 0.053 MA 90°C 0.130 Sty 60°C 0.009

Example 5: Polymerization of Styrene

A multi-necked reactor was equipped with a stirrer, thermocouple, and condensor. The reactor was held under nitrogen positive pressure and the following ingredients were used.

Part 1

Styrene 2ml

MEK 4ml

Transfer agent (lb) 370mg

Part 2

Styrene 8ml

MEK 12ml

Part 3

AIBN 14mg

MEK 2ml

Part 4

MEK 2ml

Part 1 was charged to the reactor and heated to 80°C. When the temperature stabilized at 80°C, part 2 (the monomer feed) was charged to the reactor concurrently with part 3 (the initiator feed) over 90 minutes via a syringe pump. Then part 4 was charged to the reactor as a single shot feed to rinse the syringe pump and the reaction mixture was held at 80°C for further 120 minutes. The solvent and unreacted monomer were then distilled off. The result is summarized in Table 6.

Table 6

CTA(Ib) H* H, Dispersitv

Control 0 20400 39350 1.93

Example 5 370mg 14900 29600 1.94

Examples 6-8: Polymerization ofn-Butyl Methacrylate/Hydroxypropyl Acrylate

A multi-necked reactor was equipped with a stirrer, thermocouple, and condensor. The reactor was held under nitrogen positive pressure and following ingredients were used in three separate polymerizations.

PART INGREDIENTS Example 6 Example 7 Example 8

I. Xylene 20.94 g 20.94 g 20.94 g

Transfer Agent lb 0.00 g 3.47 g 6.94 g

II. n-BMA 51.17 g 47.70 g 44.23 g

HPA 18.23 g 18.23 g 18.23 g

III. Xylene 9.07 g 9.07 g 9.07 g

VAZO 67 0.60 g 0.60 g 0.60 g

Part I was charged to the reactor and heated to 90 C. When the temperature stabilized, Part II was charged to the reactor concurrently with Part III over 240 and 260 minutes, respectively. The reaction mixture was held for 60 minutes following the completion of the feeding of Part III. The monomer conversion was determined by solids analysis and molecular weight was determined by GPC. The results are summarized in Table 7.

Table 7

Example Wt% Mn Mw Dispersity . Conversion

Number CTA(Ib)

6 0 27180 65950 2.43 100% (control)

7 5.0% 16410 37940 2.31 98%

8 10.0% 12730 26750 2.10 100%