Self-Assembly and Molecular Electrical Switching Property of Phthalocyanine-Based Liquid-Crystalline Poly(Styrene Sulfonic Acid) Compounds

A series of phthalocyanine-based liquid-crystalline poly(styrene sulfonic acid) compounds (LCPCs) are synthesized using cholesterol, dicarboxylic acid, amino- zinc phthalocyanine, and polystyrene sulfonic acid. The chemical structure, thermal property, liquid-crystalline behavior, direct current conductivity, and temperature-controlled molecular electronic switch property are investigated by use of various techniques. The LCPCs show both columnar phase (Col_h) induced by the phthalocyanine moieties and nematic discotic (N_d) phase formed by the collapse of the columnar phase structure. The temperature-dependent conductivity of the LCPCs is associated with the activation energy evaluated by Broido's graphical procedure according to the thermogravimetric analytical curves. The LCPCs show low conductivity derived from 1D charge migration through phthalocyanine cores in the col_h phase, but exhibit high conductivity due to 3D ionic charge transport in the N_d phase. A temperature-controlled molecular electronic switch is fabricated on the basis of the temperature-dependent conductivity property, which can be useful for some potential applications.