Hydroquinone polycarbonate

Polycarbonates were first prepared by Einhom in 1898 by reacting the dihydroxybenzenes, hydroquinone and resorcinol, separately with phosgene in solution in pyridine. The hydroquinone polycarbonate was an infusible and insoluble crystalline power whereas the resorcinol polymer was an amorphous material melting at about 200°C. The third dihydroxybenzene, catechol, yields a cyclic carbonate only, which is not surprising bearing in mind the proximity of... 

Hydroquinone polycarbonates, 19 800-801 Hydroquinone-substituted anthraquinones, 19 285 Hydrosilation... 

A reexamination of polycarbonate chemistry was carried out about 50 years after the first aromatic polycarbonates of resorcinol and hydroquinone were discovered. In independent investigations at Bayer AG and General Electric, it was discovered that the polycarbonates of BPA could be prepared (eq. 2). Unlike the ahphatic polycarbonates prepared earlier, which were either hquids or low melting sohds, the aromatic polycarbonates were amorphous sohds having elevated glass-transition temperatures. 

Thermotropic polycarbonates have been prepared from mixtures of 4,4 -dihydroxybiphenyl and various diphenols (10). Nematic melts were found for copolycarbonates prepared from methyfliydroquiaone, chlorohydroquiaone, 4,4 -dihydroxydiphenyl ether, and 4,4 -dihydroxybenzophenone. Slightly crystalline polycarbonates have been prepared from mixtures of hydroquinone and BPA (T = 154°C, =313°C, AH = 11.0 J/g (2.63 cal/g)), and... 

Polycarbonates are polyesters of phenols and carbonic acid. Polycarbonates are polymer containing O CO O groups. They were prepared accidentally in 1989 by Einhom by the action of phosgene with hydroquinone. He also prepared a resin by reacting phosgene with resorcinol. Bischoff and Hedenstrom in 1902 reacted dihydricphenols with diphenylcarbonate to get insoluble materials. Carothers and others prepared aliphatic Polycarbonates in 1930 but they were of no commercial importance. 

Mahabadi and Alexandru [74] have published data on thermotropic copolycarbonates of biphenol (BP) and diethylene glycol (DEG) with hydroquinone (HQ), methyl hydroquinone (MHQ), f-butyl HQ, oxydiphenol (ODP) or bis(4-hydroxyphenyl)methane (DPM) or bisphenol A. The tabulated compositions and calculated MI values are recorded with the published data on mesophase transitions in Table 4. Mesophases appear only to be present when the MI score >10.1. However, the gap in values between mesogenic materials and non-mes-ogenic materials in the three series reported is about +1 and therefore it cannot be claimed on this evidence alone that polycarbonates have a similar critical value to polyesters and polyamides. 

Cholesteric polycarbonates derived from DAS bis(phenyl carbonate), methyl hydroquinone, and 4,4 -dihydro-biphenyl were better obtained by polycondensation in pyridine-containing organic solvents, as reported by Kricheldorf et al. [39]. Trichloromethylchloroformate (TCF) was successfully used for all these polycondensations. The use of solid TCF is advantageous over phosgene because it is easy to apply in stoichiometric amounts, easy to store, and commercially available. 

Kricheldorf H.R., Sun S.J., Gerken A., Ch. Chang T., Polymers of carbonic add 22. Cholesteric polycarbonates derived from (S)-[(2-methylbutyl)thio]hydroquinone or isosorbide. Macromolecules, 29, 1996, 8077—8082. 

Kricheldorf H.R., Sun Sh.J., Chen Ch.R, Chang T.Ch., Polymers of carbonic acid. XXIV. Photoreactive, nematic or cholesteric polycarbonates derived from hydroquinone-4-hydroxybenzoate 4,4 -dihydroxychtilcone and isosorbide, J. Polym. Sci. Part A Polym. Chem., 35, 1997, 1611-1619. 

Early developments in aliphatic and aromatic polycarbonates. The first significant documentation of aromatic polycarbonates synthesis began with Einhom [24]. He reacted hydroquinone, resorcinol, and catechol with phosgene in a pyridine solution, obtaining linear polymers from hydroquinone (an insoluble crystalline powder that melted above 280°C) and resorcinol (an amorphous material that melted with decomposition at 190 to 200°C), and a cyclic carbonate from catechol. Subsequent research was focused on finding more efficient preparation methods and on improving material properties [25]. 

A reexamination of aromatic polycarbonate chemistry was carried out about 50 years after the first polycarbonates of resorcinol and hydroquinone were... 

Aromatic polycarbonates were first disclosed by A. Einhorn in 1898. He reacted pyridine solutions of hydroquinone, resorcinol and catechol with phosgene to produce respectively... 

The first aromatic polycarbonates were prepared more than a century ago by reacting hydroquinone or resorcinol with phosgene in pyridine, but the crystalline polymers produced were brittle and difficult to process. After 50 years, a crosslinked resin was introduced, prepared by a free-radical polymerisation using a peroxide as initiator and an unsaturated carbonate derivative as a monomer. 

Polycarbonates are polyesters of carbonic acid formed by reaction of diols (aromatic, aliphatic or a mixture of both) with a derivative of carbonic acid. The first preparations of polycarbonates were reported by Einhorn in 1898 [155], by reaction of phosgene with resorcinol or hydroquinone in a pyridine solution. Bischoff and van Hedenstrom in 1902 [156] obtained the same aromatic polycarbonates via transesterification with diphenyl carbonate (DPC). Thus the main routes to polycarbonates were established early, but the properties of the products seemed uninteresting. Around 1930 aliphatic polycarbonates were studied by Carothers and van Natta [157]. These carbonates have low melting points and thermal resistance and are not commercially interesting as stand-alone thermoplastics. Low molecular... 

---