浸泡法和旋涂法对偶氮聚电解质静电吸附自组装膜结构及性能的影响

利用浸泡和旋涂静电吸附自组装技术制备了含有偶氮生色团的聚电解质薄膜,比较了两种方法在自组装膜生长机理、膜结构以及膜光学性能方面的差异.利用紫外光谱和椭偏仪检测自组装膜的生长情况,利用原子力显微镜对膜表面结构进行了表征,并用偏振激光在膜表面进行了写光栅实验.结果表明,采用浸泡法和旋涂法都可以制备出表面光滑均匀的含偶氮生色团的聚电解质自组装膜.但是浸泡法自组装膜的生长速度要比旋涂法快.在自组装膜厚度较小的情况下,旋涂法得到的自组装膜可以写出明显的光栅而浸泡法不可以.随着自组装膜厚度的增加,两种方法得到的自组装膜都可以写出明显的光栅.这些结果说明浸泡法自组装膜内部聚电解质分子的层间穿插比较严重,而旋涂法自组装膜内分子穿插要弱得多.

CONSTRUCTION OF AZO POLYELECTROLYTE SELF-ASSEMBLED MULTILAYERS BY DIPPING AND SPIN-COATING

A series of different methods have been used to fabricate the polyelectrolyte multilayer films through the layer-by-layered adsorption self-assembly method based on electrostatic attraction.In this presentation the multilayer building-up methods through dipping and spin-coating were used to study the influence of the multilayer building-up methods on the multilayers' structure and properties.Experimentally,azobenzene-containing polyelectrolyte PNACN was fabricated into multilayers with counterpart polyelectrolyte PDAC using the layer-by-layer technique based on dipping and spin-coating,respectively.The differences in growth mechanism,structure and photo-sensitive properties of the multilayers fabricated with the two different methods were studied using UV-Vis,ellipsometer and AFM for characterization.Experimental results show that both of the dipping and spin-coating methods could fabricate uniformly layer-by-layered growth multilayer films while the multilayers fabricated by dipping grew faster than those fabricated by spin-coating.Both of the multilayers have relatively smooth surfaces with some spherical structure on them,which is believed to be due to the aggregation of hydrophobic azobenzene chromophores.Interestingly,these two kinds of multilayers have obviously different and complicated responses to the photo irradiation.Under irradiation with interference polarized laser beams,the multilayers by spin-coating could be written with surface relief gratings(SRGs)while not for those by dipping in case that both of the multilayers were less than 100 nm thick approximately.When the multilayers became thicker(for example more than 200 nm)both of the multilayers could be written with obvious SRGs,and the SRGs on the dipping multilayer surface were deeper for its thicker total multilayers.The difference of the multilayers in optical properties is believed to have close relationship with their difference in multilayer structures.Generally,the polymer chains in the multilayers fabricated through dipping are strongly interpenetrated among the ambient layers so that the combination of the interpenetration and electrostatic attraction between the opposite charged polyelectrolytes leads to a crosslinkage-like multilayer structure.On the other hand,the interpenetration of the polymer chains in the multilayers fabricated through spin-coating are much weak for the short time fabrication cycles,and consequently the polymer chains in the multilayers fabricated through spin-coating are more free and mobile.As a result,when the multilayer is relatively thin(less than about 100 nm)the SRGs structure can be formed on the spin-coating multilayer surface,but not on the dipping multilayer surface.