苯并二噁唑系列聚合物的合成及表征

以4,6-二氨基-1,3-苯二酚盐酸盐为原料,分别和对苯二甲酸、1,4-萘二甲酸、2,6-萘二甲酸、2,5-噻吩二甲酸、4,4-′(1,2-二苯基乙烯)二甲酸在多聚磷酸介质中反应,合成单环的聚(1,4-亚苯基)苯并二噁唑(PBO)、稠环的聚(1,4-亚萘基)苯并二噁唑(1,4-PNBO)和聚(2,6-亚萘基)苯并二噁唑(2,6-PNBO)、杂环的聚(2,5-亚噻吩基)苯并二噁唑(PTBO)及含有两个苯环的聚-4,4′-亚(1,2-二苯乙烯基)苯并二噁唑(4,4′-PDPEBO).采用傅立叶红外光谱、热重分析、元素分析、特性黏数分析对系列聚合物进行了表征.研究结果表明PBO、1,4-PNBO、4,4-′PDPEBO、2,6-PNBO和PTBO 5种聚合物的耐热性能依次降低,特性黏数依次为25.40、16.76、20.63、15.38和14.63 dL/g.

SYNTHESIS AND CHARACTERIZATION OF A SERIES OF POLYBENZOBISOXAZOLES

A series of polybenzobiso xazoles,including PBO,poly(1,4-naphthalene benzobisoxazole)(1,4-PNBO),poly(2,6-naphthalene benzobi soxazole)(2,6-PNBO),poly(2,5-thiophene benzobisoxazole)(PTBO)and poly-4,4'-(1,2-diphynylethylene benzobisoxazole)(4,4'-PDPEBO),were synthesized by polycondensation of 4,6-diamino-1,3-benzenediol dihydrochloride with terephthalic acid,1,4-naphthalene dicarboxylic acid,2,6-naphthalenedicarboxylic acid,2,5-thiophenedicarboxylic acid and 4,4'-(1,2-diphynylethylene)dicarboxylic acid in polyphosphoric acid,and the relationship between the resulting polymer chain structures and the properties of the polybenzobisoxazoles was investigated.The results showed that the target polymers were successfully synthesized proved by Fourier transform infrared spectra and elemental analysis.And the thermal stability of PBO,1,4-PNBO,4,4'-PDPEBO,2,6-PNBO and PTBO decreased in turn from thermal gravimetric analysis.The reasons are that 1,4-phenylene chains in the PBO possesses the best rigidity among all the polybenzobisoxazole chains.And C=C bonds in ethylidene of 4,4'-PDPEBO are easy to be broken under high temperature,even though 4,4'-PDPEBO has two phenylene chains,and so 4,4'-PDPEBO has worse thermal resistance compared with PBO and 1.4-PNBO.Bond energy of C-S bonds in PTBO chains is less than that of C=C bonds or C-C bonds in other polybenzobisoxazoles,and so PTBO possesses the worst thermal resistance among all the polybenzobisoxazoles.The intrinsic viscosity of PBO,4,4'-PDPEBO,1,4-PNBO,2,6.PNBO and PTBO decreased in turn,and the data were 25.40,20.63,16.76,15.38,14.63 dL/g,respectively.The main reasons are that linearity and symmetry of 1,4-phenylene group,4,4'-(1,2-diphynyl)ethylene group,1,4-naphthalene group,2,6-naphthalene group and 2,5-thiophene group decreased in turn,and the stereo-hindrance effect of these groups increased in turn.