正电子湮没谱研究聚烯烃聚氨酯的自由体积、微观结构和溶剂的扩散行为

Free-volume, Microstructure and Solvent Diffusion Behavior of Polyolefine Based Polyurethane Studied by Positron Annihilation Lifetime Spectroscopy

用正电子湮没技术(PAS)结合示差扫描量热法(DSC)研究了聚烯烃聚氨酯的自由体积特征和微相分离结构的关系.结果表明,硬段含量增加,自由体积孔洞平均半径和自由体积分数减小;丁腈聚氨酯相分离程度小,相应自由体积孔洞平均半径和自由体积分数小,而丁羟聚氨酯的情况正好相反.石英弹簧法对苯和乙醇蒸气的溶解和扩散行为的研究表明,聚烯烃聚氨酯的自由体积孔洞平均半径和自由体积分数与苯和乙醇溶剂蒸气的无限稀释扩散系数呈正相关,但它们的无限稀释扩散系数和自由体积分数关系无法用Fujita的自由体积模型描述,可能归因于它们对聚烯烃聚氨酯复杂的溶胀行为.

A series of polyurethane(PU) films made from TDI, 1,4-BDO and hydroxyl-terminated polybutadiene(HTPB) or hydroxy-terminated polybutadiene/acrylonitrile(HTBN) was synthesized by solution polymerization. Positron annihilation lifetime(PAL) spectroscopy and DSC were applied to investigate their free volume and morphology. The free volume fraction(f_v) decreased with the increase of hard segment content. The HTBN based PUs showed smaller values of f_v, which may be attributed to its lower degree of microphase separation, while the HTPB based PUs were antithetical. Sorption experiments showed that the diffusion coefficients(D_0) of the 'infinitely diluted' benzene and ethanol vapor through the PU film exhibited positive correlation with free volume fraction, but did not fit to the Fujita free-volume theory, which might be attributed to the ethanol and benzene having complicated effect of swelling.