含柔性链段的苯并二啞唑类聚合物合成与表征

SYNTHESIS AND CHARACTERIZATION OF POLYBENZO BISOXAZOLES CONTAINING SOFT SEGMENTS

通过溶液缩聚反应,合成了一系列含有刚性苯并啞唑环和柔性脂肪链的刚、柔间隔聚合物.通过FT-IR1、H-NMR和TGA等方法对聚合物化学结构和热失重行为进行了表征.发现聚合物分子链中出现了微量未闭环结构,热分解温度有所降低.聚合物溶液的紫外吸收光谱的最大吸收从PBO的429 nm蓝移到PBOC7的291 nm,同时荧光Stokes位移增大.

A novel series of polybenzazoles with rigid-rod benzobisoxazole cycles and methylene soft segments were designed and synthesized via solution condensation polymerizations from 2, 4-diamino-1, 5-benzenediol dihydrochloride, terephthalic acid and aliphatic dicarboxylic acids. The molecular structures of polymers were characterized by FT-IR,^1H-NMR, WAXD and so on. The polymers are yellowish amorphous powders or solids and own excellent thermal stabilities （Td 〉 470℃）. All the polymers are soluble in strong protonic acid at room temperature, and the intrinsic viscosities [η] are in a range of 0.8 - 0.9 dL/g. A spot of unclosed ring structure fragments in the polymer chain is found via FT-IR and ^1H-NMR,and this is due to the obstacle effect of a-H of the aliphatic dicarboxylic acid in the polymerization process. The photophysical properties of polymers in methanesulfonic acid （MSA） were investigated by UV-Vis absorption and photoluminescence spectra. The UV-Vis absorption spectra of polymers in MSA （4.4×10^-4 g/dL） showed blue-shift from 429 nm for PBO to 291 nm for PBOC7. The photoluminescence emission spectrum of PBO reveals two sharp and strong peaks while the spectra of PBOCx all show one featureless broad diffuse peak. The Stokes shifts enlarge from 7 nm for PBO to I45 nm for PBOC3. One possible reason is that the gap between conduction and forbidden bands increases with the introduction of soft non- conjugation methylene segment. Further study is under way.