POLYMERS DERIVED FROM HEXAFLUOROACETONE

Teaching Old Polymers New Tricks: Improved Synthesis and Anomalous Crystallinity for a Lost Semi-Fluorinated Polyaryl Ether via Interfacial Polymerization of Hexafluoroacetone Hydrate and Diphenyl Ether

A practical and direct electrophilic polymerization of hexafluoroacetone hydrate with diphenyl ether toward the preparation of semi-fluorinated polyaryl ethers (PAE) is reported. Electrophilic aromatic substitution (EAS) polymerization under interfacial conditions with phase transfer catalyst (Aliquat 336) proceeds in trifluoromethanesulfonic anhydride by generation of trifluoromethanesulfonic acid and the protonated hexafluoroacetone (HFA) in situ affording 1,1,1,3,3,3-hexafluoroisopropylidene (6F) PAE with high regioselectivity (4,4'-DPE) and high molecular weight (≈60 kDa). Although first reported in a 1966 US Patent by DuPont using harsh conditions, improved synthetic methods or modern characterization has not been disclosed until now. Despite the presence of the 6F group, known to impart disordered morphology, this simple semi-fluorinated PAE exhibits anomalous crystallinity with polymorphic melting points (T_m ) ranging from 230-309 °C, high solubility in common organic solvents, a glass transition (T_g ) of 163 °C, and thermo-oxidative stability above 500 °C. Tough optically clear films prepared from solution give transmittance higher than 90% throughout the visible region. Synthesis, mechanistic aspects, and characterization including surface and dielectric properties are discussed.

Synthesis and properties of fluorinated poly(ester-imide)s

A series of new, fluorinated poly(ester-imides)s has been synthesized by solution condensation, in a high-boiling-point solvent, of dihydroxy compounds containing imide and hexafluoroisopropylidene units with diacid chlorides containing preformed ester groups. Solutions of these polymers in NMP or in a mixture of trifluoroacetic acid with chloroform were cast into colourless, thin, flexible films having a low dielectric constant. These polymers show high thermal stability, with the initial decomposition temperature being over 400cC. The glass transition temperature is in the range 215-272C for fully aromatic structures and is about 170 TC for those polymers containing some ethylene groups along with aromatic ones. All these characteristics are discussed and compared with those of related poly(esterimide)s which do not contain 6F groups.

Fluorinated Poly(Phenylquinoxaline–Imide–Amide)S

Poly(phenylquinoxaline–imide–amide)s have been synthesized by solution polycondensation of aromatic diamines containing preformed phenylquinoxaline rings with a diacid chloride incorporating preformed imide rings and hexafluoroisopropylidene (6F) groups. These polymers do not decompose up to 400 °C and have glass transition temperatures in the range of 284–308 °C. They are soluble in polar amidic solvents, such as N-methyl-pyrrolidone, and in less polar solvents such as pyridine and tetrahydrofuran, and give flexible films by casting from solutions.

Synthesis and Properties of Polyamide-Imide Based on 2, 2-Bis[4-(4-Aminophenoxy)Phenyl]Hexafluoropropane and 2, 2-Bis[4-(4-Aminophenoxy)Phenyl]Propane

Aromatic polyamide-imides having hexafluoroisopropylidene and isopropylidene groups in the main chain of the polymer were prepared by reacting 4-chloroformylphthalic anhydride (CPA) and fluorine or non-fluorine containing diamines using low-temperature polycondensation. Polyamide-imides were obtained with high molecular weight and high yield. Thermal decomposition temperature and glass transition temperatures of polymers were above 460 °C and 275 °C respectively. Fluorine and non-fluorine containing polyamide-imides were cast into transparent films which were characterized by mechanical and water absorption analysis.

Preparation of soluble polyimides containing pendent imide groups

Polyimides containing imide and (p-phenoxy)imide side groups were obtained by the interaction of new aromatic tetramines, bis[3-amino-4-(p-aminophenoxy)]arylenes, with equimolar amounts of aromatic tetracarboxylic acid dianhydrides and twofold molar amounts of aromatic dicarboxylic acids anhydrides. Structures and properties of the final polyimides depend on the nature of starting monomers and subsequent introduction of monomers to the reaction mixtures. Polyimides thus obtained demonstrate good solubility in organic solvents, high glass transition temperatures and good stability.

Study of the crosslinking process in fluorinated poly(imide-amide)s containing pendant cyano groups

Fluorinated poly(imide-amide)s containing pendant cyano groups have been synthesized by solution polycondensation of aromatic diamines which contain cyano groups with diacid chlorides which have both hexafluoroisopropylidene and imnide groups. Thermal crosslinking of these polymers has been attempted in NMP, or by heating the polymer films up to 370-400 'C. The solubility, thermal stability, glass transition temperature and dielectric constant of both linear and crosslinked polymers have been studied.

Synthesis and Characterization of Polybenzazoles Containing Hexafluoroisopropylidene

A series of three polybenzazoles containing hexafluoroisopropylidene (HFIP-PBZs) were produced in order to study the effect of including the HFIP group into the rigid PBZ backbone. The monomers, 2,5-diamino-1,4-benzenedithiol dihydro-chloride and 4,6-diamino-1,3-benzenediol dihydrochloride, were synthesized and puri-fied. The monomer 1,2,4,5-tetraaminobenzene tetrahydrochloride is commercially avail-able and was purified by recrystallization. These mononmers were polymerized with 2,2-his(4-carboxyphenyl)-I1,,1,3,3,3-hexafluoropropane (6F-diacid) by a polycondensation reaction in polyphosphoric acid employing the P205 adjustment method to give polymers in good yields with inherent viscosities ranging from 0.33 to 1.18 dl/g. These polymers show an increase in solubility over non-HFIlP containing PBZs and display excellent thermal stability by thermogravimetric analysis (540-568°C in argon). Isothermal aging in air of the polymers for 300 h afforded weight losses between 3.27 and 12.0%.

New Aromatic Diacids Containing the Trifluoromethyl Group and their Polyamides

A series of new fluorinated, high-temperature polymers has been prepared from 1, 1, - bis( p-carboxyphenyl)-2, 2, 2-trifluoroethanol (3FOH). This diacid was synthesized by oxidation of 1, 1-di( p-tolyl)-2, 2, 2-trifluoroethanol, which was obtained from p-bromotoluene and ethyl trifluoroacetate. The 3FOH was also reacted with dimethyl sulphate to yield 1-methoxy-1, 1- bis( p-carboxyphenyl)-2, 2, 2-trifluoroethane (3FM), and with SOCl2 to produce 1-chloro-1, 1- bis( p-chloroformylphenyl)-2, 2, 2-trifluoroethane (3FCl). These two diacids, as the acid chlorides, were polymerized with six aromatic and four aliphatic diamines to produce polyamides which had viscosities ranging from 0.32 to 1.52 dl g−1, thermal stabilities up to 518 °C in nitrogen and glass transition temperatures from 165 °C to 337 °C. The dielectric constants of these polyamides ranged from 2.64 to 2.99. The 3FM- and 3FCl-containing polyamides were compared with the 6F (hexafluoroisopropylidene) analogues and found to be somewhat less thermally stable and had equal or lower Tgs.

Synthesis and Properties of Hexafluoroisopropylidenecontaining Polyarylates and Copolyarylates

A homologous series of four aromatic polyesters and two series of copolyarylates were synthesized under phase-transfer conditions from monomers containing the isopropylidene (IP) and/or the hexafluoroisopropylidene (HFIP) moiety. The homopolymers were obtained in good yields, were soluble in common organic solvents, and would readily form clear, colorless films from solution. Thermal stabilities in air (dynamic-10% weight losses at 440°C-490°C; isothermal-100 h at 350°C, 7%-86% weight loss) revealed that resistance to thermo-oxidation was highest when the HFIP group replaced the IP moiety in the bisphenol rather than in the diacid. Other properties of the homopolymers which were measured were water absorption of 0.07%-0.35% (by weight), and the dielectric constant of 2.32 for the fully fluorinated polymer. Copolymers were prepared from mixtures of bisphenols A and AF, and each of the two diacids. The thermal stability and water absorption of both series were measured as functions of BPAF content. No significant change in properties was observed for copolymers with less than 70 mol.% BPAF comonomer.

The Influence of Conformational Parameters on Some Physical Properties of Polyamides Containing Pendant Acetoxybenzamide Groups

Conformational parameters of some aromatic polyamides containing pendant acetoxybenzamide groups have been calculated by Monte Carlo method taking into consideration the hindered rotation produced by the side groups. Several physical properties such as solubility, glass transition temperature, initial decomposition temperature and dielectric constant were studied with regard to the rigidity of the chain of these polyamides. It has been shown that glass transition temperature is correlated with chain rigidity, whereas initial decomposition temperature and dielectric constant are not.

Synthesis and properties of novel poly(ether ether ketone) copolymers with (3,5-ditrifluoromethyl)phenyl and (4-phenoxy)phenyl side groups

A new nonfluorinated bisphenol monomer 2-(4-phenoxyphenyl)-1,4-diphenol was prepared via a four-step synthesis process. A series of poly(ether ether ketone) copolymers (6FPOP-PEEKs) were derived from 4,4′-difluorobenzophenone via a nucleophilic aromatic substitution polycondensation with various molar feed ratios of bisphenol monomer, 2-(4-phenoxyphenyl)-1,4-diphenol to (3,5-ditrifluoromethyl)phenylhydroquinone. The molecular weights ( Mn values), polydispersities and Tg values of 6FPOP-PEEKs increase as the molar feed ratio of 6FPH/(6FPH+POPH) increases. These 6FPOP-PEEKs show very high thermal stability. At a wavelength of 1550 nm, the refractive indices of the 6FPOP-PEEKs films are in the range of 1.5992–1.6396 and birefringences are in the range of 0.0034–0.0043. The near-infrared spectra show that the 6FPOP-PEEK films have small light absorption at the telecommunication wavelengths of 1300 and 1550 nm.