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Date of Publication:2022-10-06

Journal:高分子学报

Affiliation of Author(s):化工学院

Issue:2

Page Number:173-177

ISSN No.:1000-3304

Abstract: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.

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