Self-assembly and Electrorheological Effect of Phthalocyanine-Based Liquid Crystalline Polysiloxanes

A series of phthalocyanine-based liquid crystalline polysiloxanes (PLCPs) were synthesized by use of poly(methylhydrogeno)siloxane (polymer matrix), a sulfonic acid-containg monomer 4-(allyloxy)benzenesulfonic acid, a liquid crystal monomer cholesteryl 4-(allyloxy)benzoate and a phthalocyanine-containing monomer zinc tetraaminophthalocyanine. The chemical structure, liquid crystal, dielectric and electrorheological properties were characterized via various experimental techniques. With increase of phthalocyanine in the supermolecular systems, the mesophases of PLCPs change from chiral nematic phase to discotic hexagonal columnar mesophase. Furthermore, the dielectric constant increases with increase of phthalocyanine component in the polymer systems. All the PLCPs exhibit electrorheological (ER) effect. For the ER fluid of PLCPs prepared by the same method, the ER effect strengthens firstly and then weakens with increase of phthalocyanine component in the polymers. The ER effect is strongest when the molar ratio of phthalocyanine and cholesteryl mesogens in the polymer is 8:2. This suggests some synergistic effect is occurred between semiconducting property and molecular orientation in these phthalocyanine-based liquid crystalline polysiloxanes.