Ethylene terephthalate statistical copolymers

Statistical copolymerization of ethylene glycol and 1,4-butanediol with dimethyl ter-ephthalate results in products with improved crystallization and processing rates compared to poly(ethylene terephthalate). Polyarylates (trade names Ardel, Arylon, Durel), copolymers of bisphenol A with iso- and terephthalate units, combine the toughness, clarity, and proce-sibility of polycarbonate with the chemical and heat resistance of poly(ethylene terephthalate). The homopolymer containing only terephthalate units is crystalline, insoluble, sometimes infusible, and difficult to process. The more useful copolymers, containing both tere- and isophthalate units, are amorphous, clear, and easy to process. Polyarylates are used in automotive and appliance hardware and printed-circuit boards. Similar considerations in the copolymerization of iso- and terephthalates with 1,4-cyclohexanedimethanol or hexa-methylene diamine yield clear, amorphous, easy-to-process copolyesters or copolyamides,... 

For most of the results discussed below, the following is valid concerning COP, PC and mixtures if not otherwise stated. The thermotropic copolyester derived from p-hydroxybenzoate and poly(ethylene terephthalate) [10] containing 60 mol% PHB was used exclusively as the PLC component because this composition has the best mechanical properties [10,118] of these copolymers. It was obtained from Eastman Kodak, Kingsport, TN, and had an average molar mass estimated from solvent viscosity of about 19000 g mol . The sequence distribution was calculated from C-NMR as described by Lenz et al. [119] and was nearly random the statistical parameter which describes the randomness of the copolymer is = 1 for a block copolymer and P = 0 for a completely random copolymer. The copolymer used for the experiments had P = 0.15. 

Statistical copolymers of ethylene terephthalate (ET) and 1,4-cyclohexylene dimethylene terephthalate (CT) were also found to co-crystallize over a limited composition range [84, 85]. The copolymers rich in ET were found to form a crystalline phase that contained only ET units, while in the copolymers rich in CT, the crystalline phase contained both ET and CT units. The transition between these two crystal phases, as a function of composition, corresponded to a minimum in both copolymer melting temperature and heat of crystallization. It was speculated that the transition occurs at a composition where the energy difference between the melt and the crystal is identical for the two comonomers [85]. 

All of the reactions listed above can be equally applied to the preparation of aromatic copolyesters from almost any combination of hydroxyacids, dicarboxylic acids and biphenols of the types listed in Table 3. In general, the copolymers so obtained are random or statistical in composition. Furthermore, the acidolysis reaction has been successfully applied to preparation of random copolyesters by interchanging monomers and high molecular weight polymers, most notably in the preparation of poly(ethylene terephthalate-co-oxybenzoate) by the insertion reaction of /7-acetoxybenzoic acid with preformed poly(ethylene terephthalate), as follows... 

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