| SYNTHESIS |
PCPP was synthesized as described in Example I and in the general discussion by conversion of its dicarboxylic acid precursor to a mixed anhydride followed by thermal condensation of the mixed anhydride into the polymeric form following the procedure of Cottler et al [Chemis Weekblad 63:113 (1967)]. The PCPP prepolymers were purified by recrystallization in acetic anhydride repeatedly until a snowy white prepolymer was obtained. Were this repeated recrystallization step not done, the polymer would appear as a dark brown solid as a result of contamination and decomposition during the polymerization process conducted at high temperature. After purification in this manner, the white prepolymer in a polymerization tube was immersed in a paraffin oil bath in a dry nitrogen environment under dynamic vacuum of less than 1 torr. The polymer thus-obtained was only slightly yellow and crystalline in structure. Using methods of gel permeation, chromatography and solution viscometry, the polymer was demonstrated to have an average weight molecular weight of 15,000 daltons and a polydispersity of 3.6. Molecular weight species less than 15,000 daltons dissolved in tetrahydrofuran, dimethylformamide and other polar solvents. The glass transition temperature and melting temperature obtained using DSC measurements were 92.degree. C. and 240.degree. C. respectively |
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