Dependence of In-Plane Anisotropy in Polyimide Langmuir-Blodgett Films on Molecular Weight of Polyamic Acid

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Abstract
The relation between molecular weight of polyamic acid and inplane anisotropy in the LB films was investigated. As the molecular weight increases, orientation order of the polymer chains to the dipping direction in the LB films and that of the liquid crystal on the LB films become uniform. The orientation of liquid crystal is seemed to reflect that of the polymer chains. The experimental results can be qualitatively explained by the flow orientation model. It is assumed that origin for orientation of the polymer chains is attributed to the flow in vicinity of a substrate during dipping. The spreading solution stored for over a week results in inferior quality LB film as an alignment layer. Refering to the molecular weight dependence, it is thought that the degradation of the solution is caused by lowering of the molecular weight of polyamic acid due to hydrolysis.