Conversion of Chloro-substituted Aromatic Polyamides into Polybenzoxazoles by Heat-treatment

Abstract

The three kinds of chloro-substituted aromatic polyamides (PC1P-BEA, PC1P-TA, and PC1P-C1TA) were prepared by low-temperature solution polycondensation of chloro-pphenylenediamine with bis[4-(chloroformyl)phenyl] ether, terephthaloyl dichloride, chloroterphthaloyl dichloride. The convers ion of these aramids into the corresponding polybenzoxaboles by heat-treatmet is investigated by CHN elemental analysis, pyrolysis/gas chromatography/mass spectrometry, dnynamic viscoelastic properties, IR spectroscopy, and UV spectroscopy. The summarized data of PC1P-BEA are the follows ( 1 ) Untreated PC1P-BEA was dissolved i n N, N-dimethylacetamide and N-methy1-2pyrrolidone, but PC1P-BEA treated at 250 °C was insoluble in those solvents. ( 2 ) The value of dynamic storange modulus E' of 2-fold-drawn PC1P-BEA film was decreased in the range from room temp. to around 250 C and increased in the range from around 250 to 380 °C. ( 3 ) In the pyro lysis products of PC1P-BEA, there is a peak in the chromatogram for a compound with mfe-=.195 attributed to 2-phenylbenzoxazole. ( 4 ) The values of CHN elemental percentage compositions of PC1P-BEA treated at 450 °C for 30 min were similar to those calculated from constitutional repeating unit of the corresponding polybenzoxazole. ( 5 ) In the IR spectra of PC1P-BEA treated at 450 °C, the absorptions at 3400 (NH), 1630 (vc=0), 1370 and 1290 (pc-N and Oc_N) cm-1 decreased with an increase in time of treatment. ( 6 ) In the UV spectra of PC1P-BEA treated from 380 to 450 °C, the absorption peak near 300 nm was shifted toward the long wavelength region with an increase in temperature. The data of PCP-TA and PC1P-C1TA shows the same tendencies as those of PC1P-BEA. The above data show that PC1P-BEA, PC1P-TA, and PC-C1TA were slowl y converted into the corresponding polybenzoxazols by heat-treatment at temperatures of around 250 °C and above.