This invention relates to compounds having at least one perfluorovinyl group and at least one other functional group and to polymeric compositions prepared from such compounds.

High molecular weight enhances the physical properties of engineering thermoplastics such as polycarbonates, polyesters, polyamides, and polyethers. However, high molecular weight also increases melt viscosity which often causes difficulty in processing these polymers into useful articles. One way to overcome the difficulty is to build lower molecular weight polymers which are easily fabricated, then to increase chain length after or during fabrication by a continuation of the condensation reaction on which polymer formation is based. However, these condensation reactions almost always produce small molecule by¬ products such as water, hydrogen chloride, or salts which are difficult to remove from a finished article and which are almost always detrimental to the properties of the final product.

This undesirable situation can be overcome by capping lower molecular weight polymers (oligomers) with molecules (capping agents) which contain terminal functional groups which will react with each other when the molded article is heated above a given temperature or during the molding operation itself. However, almost all capping agents have terminal functionality such as ethenyl or ethynyl groups which under high temperature conditions create a cross-linked, thermoset polymer system. This often produces a brittle material which forfeits many of the desirable qualities of thermoplastic polymers.

Acetylene terminated systems (ATS) illustrate such capping and are reported by Hergenrother et al. in SAMPE Journal Sept./Oct. 1984 pp. 18-23; ChemTech, 1984, pp. 496-502; and Polymer Preprints, Amer. Chem. Soc. 1983, Vol. 24, no. 2, pp. 16-17; and J. Macromolecular Sci, Reviews in Macromolecular Chemistry C19(1), 1 _> (1980). These materials are frequently brittle due to high crosslink densities and must be carefully purified to avoid lowered thermooxidative stability. (Abrams et al., in Organic Coatings and Applied Polymer Science Proceedings, Vol. 48, pp. 909-913 (1983).)

It would be very desirable to have a capping agent to react with oligomers such that these oligomers would have a terminal functionality which, when heated, would extend the polymer chain linearly, without crosslinking, and without the consequent formation of volatiles or salts.

In one aspect, the present invention is a compound of the following Formula I:

(G) _n -R-(X-CF=CF2)m Formula I

wherein R represents an optionally substituted hydrocarbyl group, X represents any group which links R and a perfluorovinyl group; n is an integer of at least 1 , m is an integer of at least 1 , and G represents any reactive functional group or any group convertible into a reactive functional group.

In another aspect, the present invention is a process for preparing a compound of Formula I comprising the steps of:

(a) preparing a 2-halotetrafluoro compound of the following Formula III:

( ^Q -CF2-CF2-X-)m-R-(G")n Formula III

wherein X, R, m and n are as defined for Formula I, and Q is bromine, chlorine or iodine; and G" is a functional group G, as previously defined, or a functional group suitable for conversion into G;

(b) chemically modifying group G" to produce functional group G when G" is a functional group suitable for conversion into G; and

(c) dehalogenating the 2-halotetrafluoro compound to form the corresponding trifluorovinyl compound.

In yet another aspect, the present invention is the reaction product of a compound of Formula I with a second compound having at least one functional group reactive with the reactive functional group G of the first compound.

Compounds of the present invention are particularly useful in reacting with such second compounds as oligomers, di- or poly-functional compounds and relatively low molecular weight polymers to produce materials having a perfluorovinyl group. Advantageously, such materials with perfluorovinyl groups are cyclodimerized to increase the molecular weight of the materials. Cyclodimerization is a particularly useful means of increasing molecular weight because it links molecules, particularly oligomers and polymers linearly rather than crosslinking them and does so without production of volatile by-products which can cause undesirable bubbles in polymeric materials.

The present invention includes compounds having at least one perfluorovinyl group and at least one functional group suitable for forming condensation polymers or a group suitable for conversion into such a functional group. The functional group is preferably attached indirectly to the perfluorovinyl group via some linking structure thereto. More preferably, the compounds of the present invention have structures represented by the following Formula I:

(G)n-R(-X-CF=CF2)m Formula I

wherein R represents an optionally substituted hydrocarbyl group, X represents any group which links R and a perfluorovinyl group; n is the number of G groups, preferably an integer of at least 1 , more preferably an integer of from 1 to 4, most preferably an integer of from 1 to 2; m is the number of (-X-CF=CF2) groups, preferably an integer of at least 1 , more preferably an integer of from 1 to 3, most preferably an integer of from 1 to 2; G represents any reactive functional group _Q or any group convertible into a reactive functional group, preferably any functional group suitable for reaction with di- or poly-functional compounds to form polymers, which functional group G is, more preferably, insufficiently nucleophilic to react undesirably with 5 perfluorovinyl groups at room temperature (for example 25°C), most preferably at temperatures used in subsequent reactions of the compound. Alternatively, G is a group suitable for chemical conversion into a functional group suitable for reaction to form a 0 polymer.

G is preferably selected from the group consisting of functional groups including hydroxyl c groups (both alcoholic and phenolic); carboxylic acid groups; acyl halides such as chlorides; isocyanates; acyl azides; acetyl groups; primary or secondary amines; sulfide groups; sulfonic acid groups; sulfonamide groups; ketones; aldehydes; epoxy groups; primary or 0 secondary amides; halo groups (for example chloro, bromo, iodo, and fluoro groups); nitro groups; cyano groups; anhydrides; imides; cyanate groups; vinyl; allyl; acetylene groups; and esters including thiocarboxylic and carboxylic esters, preferably lower alkyl esters such as methyl and ethyl esters;

trihalomethyl groups including trichloromethyl groups; silicon-containing substituents such as alkyl silanes, siloxanes, chlorosilanes; phosphorus-containing groups such as phosphines, phosphate, phosphonate; boron- containing groups such as boranes; and alkyl groups and alkoxy groups preferably containing from 1 to 12 carbon atoms when R is aromatic. Most preferably, for ease in preparation of the compounds and polymers thereof, G is selected from hydroxyl, carboxylic or thiocarboxylic acid ester groups, carboxylic acid groups, acyl chlorides, isocyanates, alkyl groups when R is aromatic, and primary or secondary amines.

X is any linking group such as an oxygen atom, carboxylic and thiocarboxylic ester groups, other sulfur containing structures, perfluoroalkylene, perfluoroalkylene ether, alkylene, acetylene, phosphorus containing groups such as phosphines, carbonyl and thio carbonyl groups; seleno; telluro; nitrido; silicon- containing groups such as silanediyl, trisilanediyl tetrasilanetetrayl, siloxanediyl, disiloxanediyl, trisiloxyl, trisilazanyl, or silylthio groups; boron- containing groups such as boranediyl or methylboranediyl groups; a combination thereof, or any other group which is inert, which molecularly links R to a perfluorovinyl group, and which provides a molecular structure in which the perfluorovinyl group is sufficiently reactive to form a perfluorocyclobutane ring. For instance, X is preferably other than a perfluoroalkylene group because perfluorovinyl groups attached to perfluoroalkylene groups generally require temperatures greater than about 300°C to dimerize and are subject to isomerization.

Preferably, X is independently selected from the group consisting of groups having at least one non- carbon atom between the perfluorovinyl groups and R, such as groups containing oxygen, sulfur, selenium atoms, tellurium atoms, silicon, boron, phosphorus or nitrogen between R and the perfluorovinyl group, for example, oxygen atoms, sulfur atoms, (thio) carboxylic ester groups, phosphines, (thio) carbonyl groups, seleno, telluro, silanediyl, trisilanediyl, trisilazanyl or silylthio, boranediyl groups. Preferred groups have S, 0, Si, N or P, more preferably S, 0, or Si between R and the perfluorovinyl group, such as carbonyl, thiocarbonyl, sulfone, sulfoxy, silanediyl, amines, (optionally inertly substituted) oxygen or sulfur atoms. Most preferably there is a single atom other than carbon between R and each perfluorovinyl group; even more preferably the single atom is oxygen or sulfur, among those groups preferably an ether or sulfide linkage, because monomers having such linking structures advantageously form perfluorocyclobutane groups at lower temperatures than are needed with such groups as perfluoroalkyl groups and are more stable than monomers where the perfluorovinyl group is attached directly to R, particularly when R is aromatic. Monomers having such linking structures are also relatively easily prepared.

When carbon-containing structures are associated with X or G, such as in ester groups and siloxane groups, those carbon-containing structures suitably have any number of carbon atoms, but preferably have from 1 to 50, more preferably from 1 to 12 carbon atoms.

R is suitably any inert hydrocarbyl group (that is a group having at least one carbon atom bonded to a hydrogen atom, such as methylene, phenylene, or pyridinyl group), preferably a hydrocarbyl group which facilitates formation of perfluorocyclobutane rings and/or imparts desirable physical properties to polymers or oligomers prepared from compounds of Formula I. For the purpose of imparting desirable physical properties to polymers, R preferably contains at least one carbon atom. (Preferably, the carbon atom is in the molecular chain between X and G because compounds having at least one carbon atom between X and G tend to have desirable stability and to produce polymers having desirable physical properties.) Alternatively, the carbon atom is in a side chain; for instance, -R- can be -N(CH3)-, -N(CH2CH3)-, -P(CH3>- or -P(CH2CH3)-. The carbon atom(s) in R are suitably in aliphatic, cycloaliphatic, aromatic, heterocyclic groups or combinations thereof. Additionally, R optionally contains groups or has substituents which are inert, that is, which do not undesirably interfere with the formation of perfluorocyclobutane rings from perfluorovinyl groups. Inert substituents include ,for example, ether, carbonyl, ester, tertiary amide, carbonate, sulfide, sulfcxide, sulfone, nitrile, alkyl phosphonate, tertiary amine, alkyl phosphate, alkyl silyl, chlorine, bromine, fluorine, alkyl, arylalkyl, alkylaryl, cycloalkyl, aromatic, heterocyclic, alkoxyl and aryloxy groups. Carbon-containing inert substituents on R preferably contain from 1 to 50, more preferably from 1 to 12 carbon atoms because of the stability and ease of working with monomers of lower molecular weight. R, including inert substituents, preferably has a molecular weight (MW) of from 14 to 20,000, more preferably from

75 to 15,000 and most preferably from 75 to 5,000. These ranges include monomeric and oligomeric R groups. In the case of monomers which are other than oligomeric, R preferably has from 1 to 50, more preferably from 6 to 25 carbon atoms because molecular weights of R groups having carbon atoms above these quantities reduce the contribution to properties made by the fluorine- containing substituents when R is alkyl or aromatic hydrocarbon. As previously discussed, the nature of R as well as the perfluorocyclobutane content of the polymers can vary broadly according to the type of products desired.

Preferably, for polymers having good plastic properties such as tensile strength and flexibility, at least one carbon atom of R is in the molecular chain between X and G and is part of an aromatic nucleus. Aromatic groups are desirable because of improved physical properties of the polymers and ease of manufacture of the monomers. For both ease of manufacture of the monomer and monomer stability, when R is aromatic, each X is preferably a group having only non-carbon atoms, more preferably one non-carbon atom, most preferably one non-carbon atom having sulfur or oxygen between R and the perfluorovinyl group. The aromatic group can be any molecular structure having aromatic character, advantageously having at least one six-membered aromatic ring, suitably having any number of such six-membered rings fused together or connected by bonds or linking structures. R preferably has from 1 to 50 such rings, more preferably from 1 to 10 rings (more preferably containing from 6 to 25 carbon atoms) most preferably R has at least 2 to 4 aromatic rings to impart properties such as hardness and/or stiffness to a

polymer. The aromatic rings are suitably unsubstituted or inertly substituted. Inert substituents on an aromatic R include, for instance, the inert substituents listed for R generally. Exemplary aromatic molecular fragments or groups include, for instance, perchlorophenylene, phenylene, biphenylene, naphthylene, dichlorophenylene, nitrophenylene, p,p' (2,2-diphenylene propane) [-C6H4-C(CH3)2-C6H4]; p,p'-(2,2-diphenylene- 1,1,1,3,3,3 hexafluoropropane) [-C6H -C(CF3)2-C6H_H» preferably biphenylene; phenylene; 9,9'-diphenyl- fluorene; oxydiphenylene; thiodiphenylene; 2,2-diphenylene propane; 2,2'-diphenylene; 1,1,1,3,3,3-hexafluoropropane; 1,1-diphenylene-1-phenyl ethane; naphthalene; and anthracene. Molecular weights of aromatic ring containing polymers are preferably at least about 10,000. Such aromatic groups are preferably present because they generally impart high temperature glass transition properties (Tg) and good mechanical strength (for example as measured by differential scanning calorimetry (DSC) and tensile/flexural tests) to the polymer.

Most preferably, at least one aromatic carbon atom of R is bonded directly to X because perfluorovinyl groups bonded to X, said X being bonded to aromatic groups are generally more reactive in forming perfluorocyclobutane rings.

Compounds of the present invention having a perfluorovinyl group and a functional group are advantageously formed by (i) chemically reacting a compound having a perfluorov- iyl group with a compound having a suitable functional group or a molecular structure suitable for conversion to a functional group

(for example by techniques disclosed in such references as Antonucci, High Polymers, Vol. XXV, "Fluoropolymers," Chapter 2, "The Synthesis and Polymerization of Fluorostyrenes and Fluorinated Vinyl Phenyl Ethers," pp. 33-82 (1972); or, preferably (ii) by forming a compound having a functional group or a molecular structure suitable for conversion to a functional group and a molecular structure suitable for conversion to a perfluorovinyl group, then converting that structure to the perfluorovinyl group. In either case, a molecular structure suitable for conversion to a functional group is converted to the functional group when conversion is required to obtain a desired functional group.

Preferably, a process for preparing a compound of Formula I comprises the steps of:

(a) preparing a 2-halotetrafluoro compound of the following Formula III:

( ^Q -CF2-CF2-X-) _m R-(G")n Formula III

wherein X, R, m and n are as previously defined; Q is bromine, chlorine or iodine; preferably bromine or iodine, most preferably bromine; and G" is a functional group G, as previously defined, or a functional group suitable for conversion into G;

(b) chemically modifying group G" to produce functional group G when G" is a functional groups suitable for conversion into G; and

(c) dehalogenating the 2-halotetrafluoro compound to form the corresponding trifluorovinyl compound.

Step (b) optionally precedes or follows step (c), or steps (b) and (c) are carried out simultaneously. The sequence of steps (b) and (c) generally depends on the relative ease of the reactions required and the relative sensitivity of the 2-halotetrafluoro group or the trifluorovinyl group to the chemical reactions required for step (b).

Generally, the trifluorovinyl group is sensitive to materials more nucleophilic than amines such as metal hydroxides (for example potassium and sodium hydroxide), metal alkcxides, metal sulfides, metal alkylthiolates, metalamides, metal alkylamines and organometallics. Reactions involving such materials are avoided after formation of the trifluorovinyl group.

Compounds of Formula III are suitably prepared by any method within the skill in the art such as by processes taught by Rico et al. in U.S. Patent No. 4,377,711; by Carl et al. in U.S. Patent No. 4,423,249; by Antonucci in High Polymers, Vol. XXV, ed. Walls, Wiley Interscience (1972) and references therein; or by Xingya in Tetrahedron Letters, 1984, 25 (43), 4937-4940 and references therein.

Preferably compounds of Formula III are prepared by a process including the steps of:

(1) forming a salt having an anion represented by the following Formula IV:

( -X ) _m -R- ( G" ) _n Formula IV

wherein X, m, R, G" and n are as previously defined in Formula I; and

(2) reacting the salt formed in step (1) with a 1 ,2-dihalo-1 , 1 ,2,2-tetrafluoroethane wherein the halo

(halogen) groups are as defined for Q in Formula III, but at least one of the halo groups is bromine or

_l ₀ iodine.

Salts having anions of Formula IV are suitably formed by any method which associates a metal cation with such an anion such as replacing hydrogen atoms of 15 compounds such as those of the following Formula V:

(HX) _m -R-(G")n Formula V

wherein x, m, R, G" and n are as defined for Formula I

20 with metal cations. Suitable methods include reaction with bases such as sodium hydroxide or potassium hydroxide when the compound has an acidity reactive with a hydroxide, such as when R is aromatic carbocyclic or c aromatic heterocyclic. Compounds which have acidity too low to react readily with a hydroxide are reacted, for instance, with metals such as sodium or their hydrides. Among hydroxides, potassium hydroxide is generally preferred because potassium salts of alkoxides or

30 aryloxides are more reactive than are lithium or sodium salts. Sufficient hydroxide or metal to form the salt is used, preferably at least about 1.0 equivalents of hydroxide of metal per equivalent of compound of Formula V. Temperatures and pressures are determined without undue experimentation and are conveniently atmospheric

pressure and a temperature maintained below about 140°C to avoid ring halogenation when there is an aromatic ring in the compound. Temperatures are preferably from -10°C to 125°C for an aromatic compound (R is aromatic) and of from -25°C to 25°C for an alkyl compound.

Suitably, both the compound of Formula V and the hydroxide are slurried or dissolved in an easily removable medium such as methanol before reaction for convenience in mixing the reactants. Alternatively, and preferably, the hydroxide is mixed directly into a solution of the compound of Formula V in a solvent such as methanol, a glyme, water or mixtures thereof.

Alternatively, salts having an anion of Formula

IV may be formed by reacting compounds of Formula V with metals or their hydrides such as Group I metals including sodium and potassium, or any metal or its hydride which reacts to form salts with compounds of Formula V at temperatures of from -25°C to 150°C. These reactions are particularly useful when (HX) _m -R-(G")n is unreactive toward metal hydroxides. Use of metals and their hydrides is within the skill in the art and a description of such use is found, for instance, in the following reference: Fieser and Fieser, Reagents for Organic Synthesis, Wiley-Interscience, New York (1967).

Although it is generally preferable, for convenience, to maintain reactants in a slurry or solution for subsequent reaction, any liquid medium, for example methanol or glyme, which is used as a solvent herein is suitably, alternatively, removed before the next reaction step. Removal of protic media is necessary. Removal is within the skill in the art.

Methanol, for instance, is conveniently removed by rotary evaporation followed by heating to 100°C to 140°C under vacuum until the salt is dry. Other media are conveniently removed, for instance, by filtration, spray-drying particularly of water solutions, or freeze- drying.

The salt having an anion of Formula IV is then reacted with a 1 ,2-dihalo-1 , 1 ,2,2-tetrafluoroethane which is commercially available.

The dihalotetrafluoroethane has a structure represented by the following Formula VI:

Q-CF ₂ -CF ₂ -Q Formula VI

wherein Q and Q represent halogens other than fluorine. Q and Q are preferably selected such that the dihalotetrafluoroethane reacts readily with the anion (preferably of Formula IV), leaving one residual halogen (Q or Q and that residual halogen is later readily eliminated to form a perfluorovinyl group. Q and Q are, therefore, preferably selected from Cl, Br, and I and at least one of Q and Q' is Br or I; more preferably Q and Q' are independently Br or I; most preferably Q and Q' are Br. 1,2-dibromo-1, 1 ,2,2-tetrafluoroethane is preferred because it is liquid at room temperature, stable, and readily available.

The 1 ,2-dihalotetrafluoroethane is preferably reacted with the salt in a liquid reaction medium which is, for instance, suitably a solution or slurry of the salt in an aprotic solvent such as an ether, (for example diethyl ether), dioxane, dimethyl sulfoxide

(DMSO), glyme, diglyme, tetraglyme, tetrahydrofuran, dimethyl formamide (DMF), or acetonitrile. The glymes, DMSO, and DMF are preferred, with DMSO most preferred but DMF most preferred at low temperatures below which DMSO begins to freeze. When the reaction medium is a slurry it is preferably stirred sufficiently to maintain the slurry and contact between the dihalotetrafluoroethane and the salt. Sufficient solvent to homogeneously disperse both the dihalotetrafluoroethane and the salt is used, preferably from 1 to 99, more preferably from 25 to 75 weight percent solvent relative to weight of salt, for convenience. Sufficient salt is reacted with the dihalotetrafluoroethane to form a predetermined degree of substitution; preferably from 0.1 to 10.0 equivalents of salt per equivalent of dihalotetrafluoroethane is supplied, more preferably from 0.75 to 1.1 equivalent of salt per equivalent of dihalotetrafluoroethane. The dihalotetrafluoroethane is preferably added as a liquid at room temperature or with cooling and/or pressure if necessary to maintain the liquid phase.

The reaction temperature is preferably maintained above -30°C to achieve reaction at a convenient rate and below 125°C to avoid by-products. More preferably the temperature is maintained between -10°C and 125°C, most preferably between 0°C and 125°C when R is aromatic and X is -0-, -S-, -S0 ₂ - or -SO-; most preferably between -10°C and 25°C when R is alkyl. These temperatures are preferably used at atmospheric pressure which is preferable for convenience. Alternatively sub- or super-atmospheric pressure is used and temperature adjustments within the skill in the art are made. The temperature of the reaction is also

dependent on the nature of a substituent group. In general, electron donating substituents enhance the reaction, and cooling is necessary to keep the reaction temperature down. Electron donating substituents also activate the aromatic ring toward halogenation which can be a significant side reaction at elevated temperatures. The reactions are preferably run at the lowest temperature possible to prevent ring halogenation. Electron withdrawing substituents, however, retard the reaction and deactivate the ring toward halogenation. Reactions involving deactivated phenols are preferably heated to obtain a convenient reaction rate. The deactivated phenols can be heated much hotter than the activated phenols, because the deactivating groups also retard ring halogenation. In all cases the reaction is advantageously kept substantially free of protic materials, which are preferably at concentrations of less than about 0.1 weight percent, most preferably in no detectable concentrations. Protic materials can cause production of an undesirable side product (i.e., -OCF2CF2H instead of -0CF2CF2Br). Protic materials include, for example, water, alcohols and phenols.

When aromatic ethers are formed, the ease of the reaction of a phenol salt and 1,2-dihalo- tetrafluoroethylene is correlatable to the pKa (acidity) of the parent phenol. The presence of an electron- withdrawing substituent retards the reaction, and decreases the pKa of a phenol; increasing temperatures are required to obtain ether formation. A comparison of the pKa's of substituted phenols and reaction temperature for ether formation is shown in Table 4.

Table K

Some substituent groups, for example, ketones and aldehydes, are capable of reacting with a hypobromite 5 intermediate. These reactive substituent groups are best protected (for example as acetals) prior to reaction. It is observed that meta-substituted phenoxides, in most cases, react at lower temperatures than corresponding para-substituted phenoxides. 0

Reaction of a 1,2-dihalotetrafluoroethane and the salt forms a 2-halotetrafluoroethyl compound. The 2-halotetrafluoroethyl compound is either separated from the liquid media or slurry or is further reacted in the medium. Removal is by means within the skill in the

art, such as by pouring the slurry into an equal volume of water and removing the product in a lower, oily layer which is then purified by vacuum distillation. If a liquid medium such as tetraglyme which does not completely dissolve in water is used, the product is conveniently distilled therefrom under vacuum. Otherwise, the product in a solvent such as a glyme (including multiple glymes such as diglyme and tetraglyme) is conveniently filtered from the precipitated salts, and isolated by distillation or used without purification in the dehalogenation reaction. It is preferable to remove the solvent if a different solvent is preferred for the dehalogenation reaction. Also, any unreacted dihalotetrafluoroethane is preferably removed prior to dehalogenation to avoid production of by-products.

The non-fluorine halogen atom and a fluorine atom are then eliminated from the product 2-halo¬ tetrafluoroethyl compound to form the perfluorovinyl compound. The elimination is suitably conducted by any effective means. Preferably, a metallic reagent such as magnesium or zinc, (more preferably zinc) is reacted with the 2-halotetrafluoroethyl compound, preferably in a liquid medium such as the ones suitable for formation of the salt. Alternatively, some reactants are sufficiently liquid for convenient reaction in the neat form. More preferably, the 2-halotetrafluoroethyl compound is added to a hot (75°C to 140°C) preferably

110°C to 115°C slurry of (preferably granular) zinc most preferably in a dry glyme, or other liquid medium which is aprotic. The reaction is exothermic and the temperature is regulated by the speed of the addition of reactants. Most preferably, the halotetrafluoroethyl

compound is mixed with the metallic agent in a dry glyme and refluxed at 85°C to 90°C with stirring until the perfluorovinyl compound is formed, generally several hours, conveniently overnight. Better yields are generally observed in glymes. Zinc is preferred not only because of its effectiveness but also because few substituent groups (other than possibly nitro groups) on aromatic portions of the molecule react with zinc. Granular zinc is convenient to work with, but size has little effect on the reaction except that powdered zinc increases reaction rate to vigorous level. The zinc is preferably cleaned by washing with dilute acid (for example hydrochloric acid), rinsing with water and drying under vacuum. This method enhances initiation of the elimination reaction and accelerates the rate of that reaction.

Efficient stirring is important to avoid occluding the active metallic reagent in a heavy precipitate of metallic salts. Dehalogenation is exothermic, and if carried out at 110°C to 115°C, the addition rate of a dihalotetrafluoroethyl ether to the reaction mixture is preferably controlled to avoid overheating. It is preferable to adjust the rate of addition so that the reaction maintains itself at 110°C to 115°C without external heating.

After completion of the reaction, any precipitated materials, for example metal salts are removed, by methods within the skill in the art, conveniently by centrifugation because the precipitates are often very fine. If diglyme, tetraglyme or a higher boiling solvent is used, the product is preferably fractionally distilled from the mixture. If glyme or a

lower boiling solvent is used, the solvent is conveniently removed by rotary evaporation and the product is preferably purified by distillation.

In a preferred embodiment of the invention, compounds having a structure corresponding to Formula I, are reacted with other materials suitable for incorporation into polymers. The materials include, for example, reactive oligomers, difunctional compounds and polyfunctional compounds. Polyfunctional compounds suitably have any number of reactive functional groups, preferably from 2 to 10, more preferably from 2 to 4 functional groups. Such reactions are referred to herein as "capping reactions", and the compounds of Formula I so used are referred to herein as "capping agents". Preferably, the compounds of Formula I are reacted with oligomers (polymers having from 2 to 100 repeating units and, preferably, a molecular weight of from 300 to 30,000); or alternatively, with di- and poly-functional compounds (such that at least one group suitable for reaction to form a polymer remains). These compounds, oligomers or relatively low molecular weight polymers, are then preferably thermally reacted such that the perfluorovinyl groups form perfluorocyclobutane groups and the molecular weight of a resulting material is increased. Use of such compounds is given in further detail in copending U.S. Patent Application Serial No. 364,667 filed June 9, 1989 and U.S. Patent Application Serial No. 364,665 filed June 9, 1989.

Compounds of the present invention are reacted with relatively low molecular weight (for example from 300 to 30,000, preferably from 1,000 to 20,000, more preferably from 1,000 to 5,000) oligomers or polymers to

form perfluorovinyl terminated polymers or oligomers. The polymers or oligomers are preferably those that have a low viscosity relative to their higher molecular weight counterparts, suitably low molecular weight polymers containing perfluorocyclobutane rings, addition polymers (including addition polymers of perfluorovinyl compounds) or condensation polymers such as polyethers, poly(carboxylic acid derivatives) including polyesters, polyurethanes, epoxy resins, polysulfones, polycarbonates and polyamide-polyimides; preferably polycarbonates, polyesters, polyamides, and polyimides, more preferably polyimides, liquid crystal polymers, especially polyesters, aromatic polyesters, aromatic polyamides and aromatic polycarbonates which are frequently intractable or ha - high melting points and poor melt flow characteristics at temperatures commonly used in shaping or molding polymers, when advanced to high molecular weights such as molecular weights greater than about 10,000. To be useful in reacting with compounds of Formula I having functional group G, the oligomers or polymers must have a group reactive with G. Examples of suitable terminal groups of the oligomers or polymers include carboxylic acid groups and their derivatives such as salts, acid halides, or esters; amines, either primary or secondary; hydroxyl; chloroformate or any number of other nucleophilic or electrophilic groups. When one of either the compound of Formula I or the polymer or oligomer has a given reactive group, the other has a functional group of opposite reactivity, i.e., nucleophilic with electrophilic. Preferably the perfluorovinyl group is incorporated as a perfluorovinyl ether, more preferably a perfluorovinyl aromatic ether, most preferably as the perfluorovinyl ether of an aromatic ester, as for

example CF2=CF-0-Ar-C0-0-oligomer where Ar is an aromatic group. An example of the latter method of preparing the monomer and subsequently the polymer of the present embodiment of the present invention is the reaction of polycarbonate oligomer or other oligomer having terminal phenolic groups with 4-trifluoro- vinyloxybenzoyl chloride. The resulting oligomeric compound is terminated with trifluorovinyl groups connected to the oligomer via ester groups formed in the reaction of the phenolic end groups with the acid chloride reactive site of the trifluorovinyl compound. The reaction is conveniently conducted by methods of forming esters from phenolics and acid chlorides. Oligomers, thus capped, are then thermally polymerized to a higher molecular weight polymer wherein the oligomer fragments are linearly linked by perfluoro¬ cyclobutane rings. Polymers, thus formed, retain substantial property similarity to high molecular weight resins of the oligomer structure. The 4-trifluorovinyl- oxybenzoyl chloride referred to above and related compounds are prepared from phenolic substituted aromatic esters by techniques taught in U.S. Patent No. 4,423,249 followed by hydrolysis to the acid and then conversion to the corresponding acid chloride.

Alternatively, the compounds of Formula I are similarly reacted with di- or poly-functional compounds such as diphenols, for example 4,4'-biphenyldiphenol; dianilines; diacyl chlorides, for example terephthaloyl chloride; and hydroxy carboxylic acids, for example hydroxy benzoic acid.

Reaction products of such reactions are generally useful in further reactions, including

polymerization. For instance, compounds having two or more perfluorovinyl groups are useful for polymerization according to the teachings of U.S. Patent Application Serial No. 364,667 filed June 9 , 1989.

Alternatively, products of the reaction of Formula I with polyfunctional compounds having more than one type of functional group, less than all of which are reactive with the compound of Formula I have perfluorovinyl groups and remaining functional groups. The functional groups are useful for reacting for example with oligomers polymers or compounds to form compounds suitable for coupling or polymerization to form higher molecular weight compounds by thermally forming perfluorocyclobutane rings. Alternatively, perfluorocyclobutane rings are formed before the functional groups are reacted.

Alternatively, compounds having a perfluorocyclobutane group and at least two functional groups are prepared by thermally dimerizing compounds of the present invention and converting the suitable groups to the functional groups as appropriate.

Thus, compounds of Formula II are formed by a process comprising steps (a) through (c) explained above and step (d) after step (c), thermally dimerizing the trifluorovinyl compound to form a compound having a perfluorocyclobutane group.

^τ 2—CF ₂ Formula II

G-R-X-CF—CF-X'-R'-G*

wherein X, R and G are as previously defined and X' is independently defined as is X, R ^f is independently defined as is R, and G' is independently defined as is G. More detail regarding these novel compounds is given in U.S. Patent Application Serial No. 364,686, filed June 9, 1989.

In the process, step d follows step (c), but step (b) optionally precedes or follows step (c) or (d), depending on the relative sensitivity of the groups present to subsequent reactions. Determining suitable order of reaction steps is within the state of the art without undue experimentation.

The perfluorovinyl compounds are preferably thermally dimerized by heating the compounds to a temperature and for a time sufficient to form perfluorocyclobutane rings. Temperatures suitable for forming perfluorocyclobutane rings differ with the structure of the perfluorovinyl compound. In general, temperatures above about 40°C are suitable for formation of perfluorocyclobutane rings, preferably the temperature is above about 50°C, more preferably above about 100°C, because these temperatures result in formation of the rings at successively faster rates. Dimerizations are preferably carried out by stirring and

heating the neat perfluorovinyl compounds under nitrogen to approximately 195°C for several hours. Temperatures above about 450°C are preferably avoided because perfluorocyclobutane rings are thermally unstable at such temperatures.

Preferably, especially when the perfluorovinyl compounds are capable of addition polymerization, like formation of polytetrafluoroethylene, conditions conducive to free radical polymerization, for example presence of oxygen, ozone, peroxygen compounds and other free radical generating compounds, are avoided so that the perfluorovinyl groups will dimerize into perfluorocyclobutane groups rather than addition polymerizing. Compounds known in the art for stabilization against free radical polymerization are alternatively used. Such compounds include limonene and phenolic compounds. Similarly, especially when the perfluorovinyl groups are capable of addition polymerization in the presence of anions or cations, compounds which supply such anions or cations are avoided. For instance, fluoride (for example from carbonyl fluorides), chloride, hydroxide, phenoxide ions and the like are preferably avoided. To avoid such compounds as carbonyl fluorides, oxidative conditions such as presence of oxygen, hypochlorite, dichromate or permanganate are preferably avoided because perfluorovinyl groups are known to oxidize to form carbonyl fluorides. Perfluorovinyl ethers, thioethers, sulfones or sulfoxides are relatively stable with regard to addition polymerization and oxidation; and, therefore, such precautions are generally unnecessary when these perfluorovinyl compounds are used.

Advantageously, the perfluorovinyl compounds are stirred while they are heated. Perfluorovinyl compounds or admixtures thereof are preferably neat or, alternatively are in admixture with other materials such as in solution, in emulsion, in dispersions or in any other form in which perfluorovinyl compound molecules can be contacted with one another to form a dimer. Liquid admixtures are advantageous for maintaining contact between perfluorovinyl compound molecules such that dimers are formed.

Dimerizing suitably takes place at any pressure. Pressures of about one atmosphere are generally preferable for convenience when the perfluorovinyl compounds and any solvents and/or dispersing media remain liquid at the temperatures used for dimerizing. Other pressures are also suitably used, and are especially useful when the perfluorovinyl compounds have boiling points below the optimum dimerization range. Unreacted perfluorovinyl compounds along with any tetrafluoroethyl byproducts are preferably removed from the high boiling dimer by distillation at reduced pressure. The dimer is conveniently then distilled under high vacuum for further purification. Alternatively, other purification methods within the skill in the art are used.

The perfluorovinyl compounds may contain functional groups as described for G and G' in Formulas I and II such as alkoxy and alkyl when R is aromatic, halide, ester, acid, ketone, aldehyde, nitro, nitrile, alkylthio groups which do not react undesirably with the perfluorovinyl compound or interfere with formation of

its dimer, the perfluorocyclobutane compound. Alternatively, the perfluorovinyl compound can have a molecular structure suitable for conversion to a functional group (G" in Formula III). Conversion after dimer formation is preferred when the functional group for condensation polymerization is reactive with a perfluorovinyl group or would undergo polymerization at reaction temperatures. Exemplary of such groups are esters which are convertable to acid chloride by saponification followed by treatment with oxalyl chloride (for perfluorovinyl group compounds) or thionyl chloride for perfluorocyclobutane compounds according to the procedures disclosed by J. Cason Org. Syn. , Coll. Vol. 3, 169 (1955); methoxy groups which are convertible to hydroxy groups by treatment with Nal and Me^SiCl in CH^CN according to the proced _^ ^es disclosed by Olah in J. O g. Chem. 1979, 44 _> 1247-1251; ethyl groups on perfluorocyclobutane compounds which are convertable to ethynyl groups by procedures detailed in examples of the present invention; esters which are convertable to acid chloride and subsequent conversion to isocyanates by Curtius rearrangement according to the procedures disclosed by P. Smith in Organic Reactions, Vol. 3, P 337-449, Wiley, NY ed. Adams (1946); to amines by

Curtius reaction according to the procedures disclosed by P. Smith in Organic Reactions, Vol. 3, p 337-449, ed. Adams, Wiley, NY (1946). Those skilled in the art are familiar with other such conversions. The examples of the present invention provide additional detail with regard to useful conversions.

Details of forming and using such dimers are given in copending U.S. Patent Application Serial No. 364,686 filed June 9, 1989.

The following examples are offered to illustrate but not to limit the present invention. In each case, percentages are by weight unless otherwise indicated. Examples (Ex.) of the present invention are indicated numerically, while Comparative Samples (C.S.) are not examples of the present invention and are indicated with letters.

In each case, gas chromatographic (GC) analyses are done on a Varian 3700 GC using a 30 m DB210 megabore column (commercially available from J&W Scientific) and a flame ionization detector. The conditions are: injector, 150°C; detector, 250°C; temperature program: 50°C for 3 minutes, then increase 10°C/minute to 180°C and hold; initial column pressure 20 psig (pounds per square inch guage). Proton nuclear magnetic resonance (NMR) spectra are taken on a EM-360 or T-60 (Varian) nuclear magnetic resonance spectrometer. Fluorine (19 F) NMR's are taken on a Varian EM-360 modified for 19F NMR using trifluoroacetic acid (TFA) as the external zero reference. The 19F NMR spectra of the 2-bromotetrafluoroethylethers appears as two triplets within the ranges of: (CF2Br)-10.2 to -9 ppm (J approximately 7-9Hz) and (CF2O) 7.8 to 9.5 ppm (J cis approximately 7-9Hz). The 19F NMR spectra of the trifluorovinyl ether appears as 3 doublets of doublets within the ranges of: (=CF, cis to F) 39 to 45 ppm, (J approximately 60 Hz, J gem approximately 100 to 107 Hz). (=CF, trans to F) 45 to 52 ppm, (J trans approximately 112 to 120 Hz, J gem approximately 100 to

107 Hz); (OCF) 55 to 60 ppm, (J trans approximately 112 to 120 Hz, J cis approximately 60 Hz). The 19F NMR spectra of the substituted perfluorocyclobutane rings appears as broad multiplets at ^i: 3 to 55 ppm. Infrared analyses are performed on a Beckman IR-33 or a FTIR (Fourier transform infrared spectrometer) to obtain spectra characteristic of the respective functional groups and characteristic of a perfluorovinyl group at 1845 cm-1. Thermal data are obtained on a Perkin-Elmer 7 Series Thermal Analysis System according to manufacturer's directions. Gas chromatography/mass spectrometry (GC/MS) is performed on a Finnigan 1020 using a 30 m RLS 150 capillary column. Conditions are varied to give the best combinations of retention time and resolution.

Example 1 : Preparation of Methyl 4-Trifluoroethenyloxy- benzoate, Dimerization and Derivation to Form 1,2-bis(4- Chloroformylphenoxy)hexafluorocyclobutane

Methyl p-hydroxybenzoate was converted to its potassium salt by reaction with a stoichiometric amount of potassium hydroxide in methanol. The salt was isolated by evaporation and dried under vacuum. The dried salt was slurried in an equal weight of dry dimethyl sulfoxide. The mixture was stirred and heated to about 50°C and a slight excess of 1,2-dibromotetra- fluoroethane was added slowly. The reaction temperature was maintained at 60°C to 70°C. An efficient condenser was necessary to condense the dibromotetrafluoroethane. After addition was complete, the mixture was warmed for an additional hour, cooled and poured into an equal volume of water. The product (methyl 4-(2-bromotetra- fluoroethoxy)benzoate) separated as a brown oil which

was distilled under vacuum (85°C to 90°C, 0.3 mmHg (39.3 Pa)) to yield a colorless oil (85 percent to 95 percent yield) .

The bromotetrafluoroethylether was dehalogenated by combining it with a stoichiometric amount of granular zinc in glyme and refluxing overnight. After removal of the glyme by evaporation, the product, methyl 4-trifluoroethenyloxybenzoate, was distilled under vacuum (85°C to 90°C/8 to 10 mmHg (1330 Pa), 85 percent to 100 percent yield).

The methyl 4-trifluoroethenyloxybenzoate was cyclodimerized by heating at 195°C for several hours. The dimerized product was isolated by distillation

(135°C to 150°C/0.025 mmHg (3-3 Pa), 97 percent yield, with the remainder being unreacted vinyl compound). The overall yield from methyl p-hydroxybenzoate was

80 percent.

The dimer was saponified to the diacid with 2.1 molar equivalents of sodium hydroxide in methanol. Upon acidification with concentrated hydrochloric acid the diacid precipitated and was filtered from the liquid as an insoluble white powder with a melting point above 300°C. Yields were quantitative. The diacid was converted to the diacid chloride by slurrying it in approximately a 6 molar equivalent of thionyl chloride and warming the mixture to 50°C to 75°C. The product diacid chloride was soluble in dichloromethane and was purified by dissolving the crude reaction product in dichloromethane and filtering the diacid chloride solution from unreacted diacid (which was insoluble). The product was identified by 19F NMR, 1H NMR and

infrared (IR) spectra. IR 1790, 1755 cm-1 (C=0), no C02H absorption.

Example 2: Preparation of 4-Trifluoroethenyloxyanisole, Dimerization and Derivation to Form 1 ,2-bis(4-Hydroxy- phenoxy)hexafluorocyclobutane

4-Methoxyphenol was converted to its potassium salt by reaction with a stoichiometric amount of potassium hydroxide in methanol. The salt was isolated by evaporationand dried under vacuum. The dried salt was slurried in an equal weight of dry dimethyl sulfoxide. The mixture was stirred and cooled in an ice bath as a slight excess of 1 ,2-dibromotetrafluoroethane was added slowly to maintain thereaction temperature at less than 30°C. After addition was complete, the mixture was warmed to 50°C for an additional hour, cooled and poured into an equal volume ofcold water. The product, 4-(2-bromotetrafluoroethoxy)anisole, separated as abrown oil which was distilled under vacuum (85°C to 100°C, 3.5 mmHg (465.5 Pa)) to yield a colorless oil (88.2 percent yield).

The bromotetrafluoroethylether was dehalogenated by combining it with a stoichiometric amount of granular zinc in glyme and refluxing overnight. After removalof the glyme by evaporation, the product, 4-trifluoroethenyloxyanisole, was distilled under vacuum (70°C/2.75 mmHg (364.7 Pa), 73 percent yield). This vinyl ether was cyclodimerized by heating at 195°C for six hours. The dimerized product,

1,2-bis(4-methoxy-phenoxy)hexafluorocyclobutane, was

isolated bydistillation (120°C to 130°C/0.05 mmHg (6.6 Pa), 91.3 percent yield).

The bis(methyl ether) was converted to the bis(trimethylsilyl)ether by treatment with four equivalents of trimethylchlorosilane and sodium iodide in refluxing acetonitrile for 48 hours. The bis(trimethylsilyl)ether was then hydrolyzed to the bisphenol by the addition of water, and the bisphenol was extracted with ether. The ether extracts were washed with sodium thiosulfate and concentrated to yield 1,2-bis(4-hydroxyphenoxy)hexafluorocyclobutane as yellowish crystals. The crystals were slurried in methylene chloride, chilled, and filtered to yield white crystals of 1,2-bis(4-hydroxyphenoxy)hexafluorocyclo- butane (73 percent conversion, 94 percent yield, with the remainder of the material being 1-(4-hydroxy- phenoxy)-2-(4-methoxyphenoxy)hexafluorocyclobutane. Identity of the product was verified using 19F NMR, 1H NMR, and IR spectra. Melting point of the bisphenol was 137°C to 152°C.

Example 3: Preparation of Methyl 4-(2-Bromo- tetrafluoroethoxy)benzoate and its Conversion to the Corresponding Benzoic Acid and 4-Trifluoroethenyl- oxybenzoic Acid, and the Benzoyl Chloride Thereof.

Methyl 4-hydroxybenzoate (304.3 g, 2 mole) was dissolved in 800 L of methanol and was converted to the potassium salt by the slow addition of potassium hydroxide (132.02 g, 2 mole, 85 percent purity). The resulting mixture was stirred and cooled as necessary to maintain the temperature below 50°C. The solvent was

then removed by rotary evaporation and the crystalline salt was dried under vacuum overnight at 140°C.

The dried salt was allowed to cool and transferred to an oven dried 2 L flask under nitrogen. The flask was fitted with a mechanical stirrer, thermometer, heating mantle, condenser and pressure- equalizing addition funnel. Dry dimethylsulfoxide (DMSO) (550 g) was added and the mixture was stirred and warmed to 60°C as 1 ,2-dibromotetrafluoroethane (537 g, 2.06 mole) was added slowly. (No appreciable reaction was observed at lower temperatures.) Reaction temperature was maintained at 65°C to 70°C for two hours after addition was complete. The mixture was then heated to 90°C and allowed to cool overnight.

Product was isolated by extracting the mixture with 500 mL of water to remove salts and DMSO. The product separated as an orange oil which was washed with water to remove residual DMSO. (The upper aqueous layer was extracted with methylene chloride and the methylene chloride solution was evaporated to yield about 40 g of product which was added to the rest of the product prior to the water washes.) The product (623 g) was distilled at 85°C/0.3 mmHg (39.9 Pa) to yield 561 g of colorless oil, 85 percent yield. The product, methyl 4-(2-bromo- tetrafluoroethoxy)benzoate, was identified by 19F NMR, 1H NMR, and IR spectra.

To form the benzoic acid, methyl 4-(2-bromo- tetrafluoroethoxy)benzoate (33.11 g, 0.1 mol) was weighed into a 250 mL round-bottomed flask along with potassium hydroxide (85 percent, 8.77 g, 0.13 mole), water (5 mL) and methanol (100 mL). The mixture was

stirred overnight and then acidified by the addition of 16 mL of concentrated hydrochloric acid. Product, 4-(2-bromotetrafluoroethoxy)benzoic acid, precipitated as white flocculent crystals. The methanol was removed by rotary evaporation and the product was dissolved in methylene chloride and washed with water. The methylene chloride solution was dried over magnesium sulfate, filtered and concentrated to yield 28.66 g of white crystals (yield 90.4 percent, melting point 170°C to 173°C). The product was identified by 19F NMR, 1H NMR, and IR spectra.

To form a salt suitable for formation of the perfluorovinyl ether, another sample of methyl 4-(2-bromo-tetrafluoroethoxy)benzoate (66.25 g,

0.2 mole) was weighed into a 4-necked 500 mL round- bottomed flask fitted with a condenser, thermometer, mechanical stirrer, and heating mantle. Methanol (300 mL) and sodium hydroxide (8.05 g, 0.2 mole) were added to form a mixture which was stirred and heated to reflux for three hours. A sodium carboxylate formed and began to precipitate early in the reaction and was gelled into an almost solid mass after 1.5 hours. The mass was allowed to settle overnight and the solvent was then removed by rotary evaporation.

The sodium carboxylate was dissolved in warm water. A warm solution of zinc acetate (26.35 g, 0.12 mole) in 40 mL of water was added to precipitate the carboxylate as the zinc salt. The salt slurry was then cooled, and the zinc salt was filtered from the solution and dried under vacuum to yield 65.6 g (94 percent yield).

The dried zinc salt was transferred to a dry 4-necked 500 mL round-bottomed flask containing zinc metal (10 mesh, 13.0 g, 0.198 mole). Dry glyme (160 mL) was added by a canula and the flask was fitted with a condenser, mechanical stirrer, and thermometer. The mixture was stirred and heated to reflux under nitrogen overnight. The mixture was acidified by the addition of 18 mL of concentrated hydrochloric acid (HC1), concentrated by rotary evaporation, and then partitioned between methylene chloride and water. The methylene chloride solution of the acid was dried over magnesium sulfate, filtered and concentrated to yield 40.02 g of 4-trifluoroethenyloxybenzoic acid as white crystals (97.6 percent yield, melting point 139°C to 140°C). The product 4-trifluoroethenyloxybenzoic acid was identified by 19F NMR, 1H NMR, and IR spectra.

To form the 4-trifluoroethyloxybenzoyl chloride, 4-trifluoroethenyloxybenzoic acid (79.4 g,

0.36 mole) was transferred to a 1 L round-bottomed flask. Dry methylene chloride (250 mL) was added, and the resulting mixture was stirred under nitrogen as oxalyl chloride (62.5 g, 0.49 mole) was added. The mixture was stirred overnight and then concentrated by rotary evaporation. The brown liquid was distilled at

60°C to 65°C/0.2 mmHg (26.6 Pa) to yield 82.94 g of colorless liquid (97.4 percent yield). The product was identified by 19F NMR, 1H NMR, and IR spectra.

Example 4: Reaction of Polycarbonate Oligomer with Trifluoroethenyloxybenzoyl Chloride and Chain Extension of Polycarbonate Oligomers by Cyclodimerization of Trifluorovinyl Groups

Low molecular weight polycarbonate oligomer

(2000 MW) terminated with bisphenol A groups (7.5 g, about 7.8 x 10-3 mole of phenolic OH) was weighed into a

100 mL flask with trifluoroethenyloxybenzoyl chloride (1.84 g, 7.8 x 10-3 mole) as prepared in Example 3. Dichloromethane (30 mL) was added to dissolve the oligomer, and the mixture was stirred as triethylamine (0.81 g, 8 x 10-3 mole) was added via syringe. A fine white precipitate formed in the mixture almost immediately. Dichloromethane was added to dissolve the precipitate. The resulting solution was extracted with water to remove triethylamine hydrochloride. The dichloromethane solution was dried over 4A molecular sieves, and concentrated to yield 9.06 g (100 g) of oligomer capped with trifluoroethenyloxybenzoyl groups. Structure was verified by 19 F NMR (trifluorovinyl ether pattern), H-NMR (2 protons of the aromatic benzoate were shifted downfield to 8 to 8.3 ppm from the aromatic polycarbonate protons), and FT-IR (C=0 stretch at 1739 cm-1, distinct from the C=0 stretch of polycarbonate at 1774 cm-1).

A sample of the capped oligomer was heated to 300°C (under differential scanning calorimetry (DSC) analysis) to effect chain extension. The sample was cooled and reheated to determine the Tg, which was observed at 140.4°C (representative of high molecular weight polycarbonate). For comparison a sample of the uncapped oligomer heated to 300°C, cooled, and reheated,

exhibited a Tg of only 106.8°C. The increase of 33.6°C in the Tg was attributed to the production of high molecular weight by linear chain extension through cyclodimerization of the trifluorovinyl groups to form perfluorocyclobutane groups.

Examples 5-14: Preparation and Dimerization of Substituted Phenylperfluorovinyl Ethers

For each of Examples 5-14 the following procedure was followed with the details of solvent and reaction temperatures noted in Tables 1-3. A phenol starting material having the substituent indicated in

Table 1 was dissolved or slurried in methanol to form an admixture. A methanolic solution of one equivalent of potassium hydroxide was added to the stirring admixture.

The admixture was cooled to maintain a temperature below

40°C. Stirring and cooling was maintained for about

15 minutes after addition was complete.

The methanol was then removed by rotary evaporation and a resulting wet salt was transferred to a suitable container and dried under vacuum at 100°C to 140°C to produce a dry salt. The dry salt was transferred to a dry flask and an equal volume of dry solvent as indicated in Table 1 was added to form a slurry. The flask was fitted with a mechanical stirrer, thermometer, efficient condenser, and pressure- equalizing addition funnel.

The salt slurry was stirred and heated or cooled as indicated in Table 1 as a slight excess (1.1 equivalents) of 1 ,2-dibromotetrafluoroethane was added slowly. Reaction temperature was dependent on the

nature of the substituent group (see Table 1). The reaction temperature was maintained for about 2 hours after addition was complete or until analysis indicates that the phenoxide was consumed and a 2-bromotetrafluoroethyl ether was formed.

The 2-bromotetrafluoroethyl ether was isolated by pouring into an equal volume of water. When the solvent was DMSO, the ether separates as a lower layer of oil and was purified by vacuum distillation. (When the solvent was tetraglyme the product was distilled from the reaction mixture under vacuum.)

Table 1

*Product boiling points (b.p.) were uncorrected as determined using a Kugelrohr bulb to bulb distillation apparatus and measuring container (oven) temperature, m.p. is melting point in °C.

A perfluorovinyl ether was synthesized by adding the 2-bromotetrafluoroethyl ether into a hot slurry of granular zinc in a dry glyme. When diglyme or tetraglyme was used (as indicated in Table 2) the glymes are about 105°C to 115°C when the ether was added. When glyme was used, the bromotetrafluoroethyl ether was combined with granular zinc in dry glyme and refluxed at 85°C to 90°C with stirring overnight. The reaction was exothermic and the temperature was regulated by the speed of the addition. For very large reactions the bromotetrafluoroethyl ether was added in portions. This method eliminated the exotherm problem and simplified product isolation.

After completion of the reaction, the precipitated zinc salts were removed by centrifugation. If diglyme or tetraglyme was used as the solvent, the product was fractionally distilled from the mixture. If glyme was used, the solvent was removed by rotary evaporation and the product was purified by vacuum distillation.

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TABLE 2

*b.p. is boiling point

** ^" m.p. is melting point

The indicated trifluorovinyl compounds are cyclodimerized by heating to 180°C to 195°C for several hours, approximately 6 to 8 hours. Low boiling

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impurities and unreacted perfluorovinyl compound are removed by vacuum distillation. The products are distilled under high vacuum and have the characteristics reported in Table 3.

Table 3

*prepared by saponification of diester.

25

Example 15: Preparation of 4-Trifluoroethenyloxyaniline via the Amide

4-(2-Bromo-tetrafluoroethoxy)benzoic acid 30 prepared as in Example 1 (26.6 g, 0.083 mole) was transferred to a 250 mL round-bottomed flask along with 150 mL of methylene chloride. Oxalyl chloride (11.64 g, 0.92 mole) was added and the mixture was stirred under nitrogen overnight to form a turbid solution which was concentrated by rotary evaporation and distilled at 80°C

to 90°C/0.1 mmHg (13.3 Pa) to yield 20.88 g of 4(2-bromotetra-fluoroethoxy)benzoyl chloride as a colorless liquid, leaving 6.16 g of unreacted acid (76.8 percent conversion, 96.5 percent yield). The benzoyl chloride was added slowly with stirring to 8 mL of cold ammonium hydroxide (0.12 mole). The product amide precipitated as fine white needles which were filtered and dried under vacuum to yield 14.74 g of 4-(2-bromotetrafluoro-ethoxy)benzamide (75 percent conversion, 99 percent yield, melting point 150.5 to 151.5°C), along with 4.8 g of 4-(2-bromotetrafluoro- ethoxy)benzoic acid which was recovered from the mother liquor (24.3 percent recovery).

The crystalline amide (10 g, 0.316 mole) was transferred to a 250 mL round-bottomed flask along with 48 mL of cold potassium hypochlorite (K0C1) solution (0.667 M) containing 2 g of potassium hydroxide. The resulting mixture was stirred until most of the solids have dissolved. The mixture was then warmed in a 50°C to 70°C water bath to effect the rearrangement to the amine. The mixture was extracted with methylene chloride and the extracts were dried over magnesium sulfate and concentrated by rotary evaporation. The resulting brown oil was distilled at 60°C to

80°C/0.05 mmHg (6.6 Pa) to yield 4.85 g of

4-(2-bromo-tetrafluoroethoxy)-aniline as a colorless oil (53-3 percent yield).

A mixture of 4-(2-bromotetrafluoroethoxy)- aniline (1.44 g, 5 mole), dry glyme (15 mL), and zinc (10 mesh, 0.4 g, 5.5 mole) was formed and stirred with heating to reflux under nitrogen overnight. The mixture was filtered to remove insoluble zinc salts, and then

concentrated to yield a cream colored solid material which was found to be the zinc complex of 4-trifluoroethenyloxyaniline.

The product amine was isolated by redissolving the complex in glyme and adding saturated aqueous sodium bicarbonate (NaHC03) to the solution to precipitate the zinc ion as its bicarbonate salt. The amine was extracted with methylene chloride, dried over sodium sulfate, and distilled at 45°C/0.025 mmHg (3.31 Pa) to yield 0.83 g of 4-trifluoroethenyloxyaniline (88 percent yield) as a colorless liquid. The product was identified by 19F NMR, 1H NMR, and IR spectra.

Example 16: Preparation of 4-Trifluoroethenyloxyphenol

A sample of 4-trifluoroethenyloxyanisole prepared as in Example 2 was treated with two equivalents of trimethylchlorosilane and sodium iodide in refluxing acetonitrile to give 4-trifluoroethenyloxy¬ phenol. The product was extracted with ether, washed with sodium thiosulfate solution to remove iodine, and then concentrated by rotary evaporation.

Example 17: Synthesis of 4-Trifluoroethenyloxyphenyl Acetate from Hydroquinone Monoacetate, Dimerization of the Phenyl Acetate and Conversion to the Corresponding Phenol

Hydroquinone monoacetate (205.4 g, 1.35 mole), available from p-isopropylphenyl acetate by the method of Van Sickle (Ind. Eng. Chem. Res. 27, 440-447 (1988)), was dissolved in 800 mL of methanol and cooled to less than 10°C with stirring. A solution of potassium

hydroxide (90.9 g, 1.38 mole) in 200 mL of methanol was added slowly with cooling, keeping the reaction temperature below 20°C. The mixture was stirred for 30 minutes, then concentrated by rotary evaporation. The resulting wet salt was transferred to a crystallizing dish and dried overnight under vacuum at 120°C. The resulting dry salt was transferred to a dry 2 L, 4-necked flask fitted with a mechanical stirrer, thermometer, condenser, and pressure-equalizing addition funnel. Dry DMSO (520 g) was added to form a reaction mixture which was stirred and cooled to 10°C. The reaction mixture was stirred and maintained at 10°C to 20°C as 1,2-dibromotetrafluoroethane (421 g, 1.62 mole) was added slowly. After addition was complete, the mixture was heated to 60°C for 1 hour, cooled and poured into an equal volume of water.

Product, 4-(2-bromotetrafluoroethoxy)phenyl acetate was separated as an oily lower layer, which was washed with water to remove residual DMSO, dried over 4A molecular sieves, and distilled under vacuum (85°C/0.5 mmHg (66.5 Pa)) to yield product 4-(2-bromotetrafluoroethoxy)-phenyl acetate as a colorless oil (60 to 85 percent yield).

The product was dehalogenated by combining it with 1 to 2 volumes of dry glyme as solvent and 1 to 1.1 equivalents of zinc and refluxing with stirring overnight. The solvent was then removed by rotary evaporation, and resulting product and zinc salts were slurried in hexane or dichloromethane. The zinc salts were removed from the product by filtration, and the product 4-trifluoroethenyloxyphenyl acetate was isolated by vacuum distillation at 70°C to 80°C/3 mmHg (399 Pa) to

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give the purer product as a colorless oil. The acetate was converted to 4-trifluoroethenyloxyphenol by treatment with 0.1 M hydrochloric acid in methanol.

4-Trifluoroethenyloxyphenyl acetate was dimerized to 1 ,2-bis(4-acetoxyphenoxy)hexafluorocyclo- butane by stirring and heating to 195°C for 6 to 8 hours. The product was distilled under vacuum to yield 1,2-bis(4-acetoxyphenoxy)hexafluorocyclobutane as a low melting crystalline solid (melting point 60°C to 80°C).

1 ,2-Bis(4-acetoxyphenoxy)hexafluorocyclobutane was converted to 1 ,2-bis(4-hydroxyphenoxy)hexafluoro- cyclobutane by treatment with two molar equivalents of sodium hydroxide in methanol. The methanol was removed by rotary evaporation, and a product bisphenol was dissolved in ether, washed with water, dried over 4A molecular sieves, and concentrated to yield 1 ,2-bis(4-hydroxyphenoxy)hexafluorocyclobutane.

Example 18: Reaction of 4,4'-Biphenol and Trifluoro¬ vinyloxybenzoyl Chloride

Dihydroxybiphenyl (0.7888 g, 0.00423 mole) was placed in a dry 250 mL round bottom flask with a magnetic stirring bar. The flask was capped with a rubber septum. Dry methylene chloride (25 mL) and trifluorovinyloxybenzoyl chloride as prepared in Example

3 (2.000 g, 0.00846 mole) were each added to the flask via syringe. The mixture was stirred as triethlyamine

(0.86 g, 0.0085 mole) was added dropwise. The mixture was stirred at room temperature for 2 hours, then filtered. A white precipitate was obtained and washed

several times with methylene chloride to remove residual triethlamine hydrochloride. A white crystalline product was obtained and had a melting point of 225°C to 228°C. Qualitative solubility tests indicated that this product was nearly insoluble in methylene chloride, acetone, acetonitrile, hexane, methanol, water, and benzene, only slightly soluble in hot tetrahydrofuran, and moderately soluble in carbon tetrachloride.

Infrared analysis (using a potassium bromide KBr pellet) gave the following spectrum (reported in cm-1): 1830, indicative of a trifluorovinyl group; 1723, indicative of a benzoate ester; 1600 and 1495, indicative of aryl carbon-carbon double bond; 1315 and 1267, indicative of carbon-fluorine bonds.

Thermal analysis (DSC) of the monomer indicated a crystalline melt beginning at 223°C, followed immediately by a slight exotherm as the monomer underwent polymerization. A second scan of the sample showed no thermal activity up to and including 350°C

The melted monomer exhibited possible liquid crystalline behavior during it's short lived melt phase. As viewed under a cross-polarized light microscope, the melted monomer phase (at 230°C) exhibited birefringence suggestive of liquid crystalline behavior, followed by rapid polymerization to a crystalline solid. This solid did not melt, but underwent discoloration and apparent decomposition when heated in air at temperatures above 400°C.

Example 19: Synthesis of 1-Bromo-2,4-di(2-Trifluoro- ethenyloxy)benzene from Resorcinol

Resorcinol (412.9 g, 3.75 mole) was dissolved in 1800 mL of DMSO and 670 mL of toluene to form a mixture in a 3-necked, 5 L flask fitted with an overhead stirrer, moisture trap and condenser, and nitrogen sparge. The mixture was stirred and sparged with nitrogen as potassium hydroxide (495.1 g, 7.5 mole) was added in 5 g portions. The mixture was then heated to reflux to remove water by azeotropic distillation. After the water was removed, the mixture was cooled to 15°C as 1,2-dibromotetrafluoroethane (2144 g, 8.25 mole) was added rapidly, and the mixture was stirred overnight. The mixture was then stirred and heated to 90°C for three hours. The mixture was then cooled and diluted with an equal volume of water. The product separated as an oily lower layer, which was fractionally distilled under vacuum to yield 190.3 g of 1-(2-bromo- tetrafluoroethoxy)-3-( 1, 1 ,2,2-tetrafluoroethoxy)benzene (3 percent yield), 895.5 g of 1,3-di(2-bromotetrafluoro- ethoxy) enzene (51 percent yield), and 340.8 g of 1-bromo-2,4-di(2-bromotetrafluoroethoxy)benzene (17 percent yield). The products were identified by 19 F NMR, 1H NMR, and IR spectra.

1-Bromo-2, -di(2-bromotetrafluoroethoxy)benzene (18.06 g, 35 mole) was added dropwise to a hot (110°C) mixture of zinc (4.74 g, 72.5 mole) in dry tetraglyme (20 mL). Product 1-bromo-2,4-bis(trifluoroethenyloxy)- benzene was fractionally distilled from the mixture under vacuum (95°C to 100°C/1 mmHg (133 Pa), 6.57 g,

59 percent yield). The product was identified by 19 F NMR, 1H NMR, and IR spectra.