DDM-PMDA-HAB噁唑酰亚胺共聚物的合成及其耐热性

Preparation and Heat-Resistance of DDM-PMDA-HAB Benzoxazole-Imide Copolymers

用4，4′-二氨基二苯基甲烷（DDM），3，3′-二羟基联苯胺（HAB），与均苯四甲酸二酐（PMDA）在N，N-二甲基乙酰胺中室温缩聚，制备了3种共聚酰胺酸（CPAA）；CPAA膜经热处理失水环化，形成共聚酰亚胺（CVI）；在N2气下经500℃热处理，重排转变为DDM．PMDA．HAB噁唑酰亚胺共聚物（CPBI）。ATR光谱显示了CPI和CPBI膜的特征结构。TGA分析佐证了噁唑化转变。CPBI膜均显示优良的耐热性（用质量损失5％时的温度Td表示）。比相应的CPI高93～138℃；比二元聚合物PMDA-HAB聚苯并噁唑（PBO）高65～86℃。廉价的DDM在二胺单体中所占摩尔分数为75％时，CPBI仍保持优良的耐热性（Td为573℃）。

Three poly （ amic acid ） copolymers （CPAAs） were synthesized from 4,4′-diamino diphenyl methane （ DDM）, 3,3′-dihydroxy-4,4′-diamino-biphenyl （ HAB ） and pyromellitic dianhydride （ PMDA ） by condensation in N, N-dimethylacetamide at room temperature. Thermal cyclodehydration of CPAA cast films led to the formation of copolyimides （ CPIs）, which were rearranged to DDM-PMDA-HAB benzoxazole-imide copolymers（CPBIs） by further thermal treatment at 500℃ under nitrogen. ATR spectra showed the characteristic structure of CPIs and CPBIs. TGA analysis confirmed the rearrangement to the formation of Polybenzoxazoles（PBOs）. All the CPBI films displayed excellent thermal stability, shown by Td, the temperature at which the mass loss of the polymer is 5%. Td values of CPBI films are 93 - 138℃ higher than that of correspending CPIs, and 65 - 86℃ higher than that of PMDA-HAB PBO. The molar ratio of cheap DDM among diamines can increase up to 75%, while the CPBIs still have the excellent heat resistance（ Td is 573℃ ）.