Polymer, Vol.40, No.11, 3025-3031, 1999
Blends of side-chain liquid crystalline polymers: towards self-assembled interpenetrating networks
The possibility of using various types of non-covalent cross-linking, to promote the structure of interpenetrating networks in blends based on side-chain liquid crystalline polymers, was investigated. The polymers used included: (I) random copolymers of liquid crystalline polyacrylates containing benzoic acid units for hydrogen-bond cross-linking through the formation of intermolecular dimers; (2) liquid crystalline polyacrylate-ionomers bearing sodium salt groups for cross-linking through ionic aggregates; and (3) a styrene-butadienestyrene triblock copolymer having a network structure with polystyrene microdomains as cross-links. The preparation method consists of making a dilute solution of two polymers, then evaporating the solvent and drying the mixture. No evidence of network interpenetrating was observed. The results suggest, however, that blends composed of two components having a network structure, for both H-bond/ionic-aggregate and H-bond/triblock-copolymer combinations, have a greater miscibility, compared with blends containing only one component capable of forming a network structure through non-covalent cross-linking. The improved miscibility is characterized by reduced domain sizes and, for blends of two liquid crystalline polymers, changes in the phase transition behavior.