光致取向调控偶氮苯侧链液晶聚合物的阻隔特性研究

BARRIER PROPERTY OF POLARIZED LIGHT ORIENTED AZOBENZENE CONTAINING SIDE-CHAIN LIQUID CRYSTALLINE POLYMER

研究了液晶分子的排列方式对聚合物膜阻隔特性的影响,采用473 nm线偏振光照无定形偶氮液晶聚合物,使其介晶基元发生从无序到有序的取向排列.用膜透射率变化和锥光干涉图表征了分子的取向,其锥光干涉图为粗黑十字,说明在线偏振光下作用下液晶分子取向形成了单相畴沿面内排列的有序态.用金属表面氧化法进一步研究了取向态聚合物膜的阻隔性能.实验结果表明,取向后膜对水和氧气的阻隔性约为多相畴热致液晶相的1.25倍,是无定型态膜的2.5倍.光致取向使光照区域内所有介晶基元沿偏振光电矢量垂直方向排列,形成为整体的单相畴有序区,相当于消除了热致液晶相中多相畴液晶微相区之间的可渗透的无序区,因此光致取向能显著提高液晶聚合物膜的阻隔性能.

Barrier properties of light-induced ordered phase and thermo-induced ordered phase of azobenzene containing side-chain liquid crystalline polymers were investigated by a ferrous matrix surface oxidation method.Different mesogen distributions were obtained by linear polarized light irradiation and by annealing the as-cast film,and were characterized by polarized light microscopy（POM） under conoscopic observation.Upon a 473 nm linear polarized light irradiation,an interference figure was observed suggesting the formation of an in-plane arranged single-domain ordered phase.In contrast,the thermo-induced polydomain liquid crystalline（LC） phase showed a bright field vision when the sample was annealled at a temperature below its clear transition point,suggesting the formation of a randomly orientated multi-domain LC phase.Their permeation rates were obtained by measuring the surface oxidation rate of the ferrous matrix covered with differently arranged liquid crystalline polymer films.It was found that the barrier value of the orientated film was 2.5 times higher than those of the amorphous film,and about 1.25 times higher than that of the thermotropic liquid crystalline phase.Combining the conoscopic observation results,the gas permeation behavior in the liquid crystalline polymer films was proposed.Linear polarized light induced mesogens orientation and assembled a single-domain order phase,which eliminated the permeable boundary existed in the thermotropic polydomain liquid crystalline phase.Thus,the low value of permeability was attributed to a low diffusion coefficient in the ordered phase.