Formation of liquid‐crystalline morphologies in dilute solutions of a charged random terpolymer

Abstract

Formation of micellar morphologies in aqueous solutions of charged random copolymers has been reported in several studies. This paper reports on liquid crystallization of the cationic random acrylic terpolymer i.e., poly[(dimethylaminoethyl methacrylate)‐co‐(methyl methacrylate)‐co‐(butyl methacrylate)] containing no mesogenic groups. The viscometric behaviour of the terpolymer solutions deviated in several ways from ordinary behaviour of polyelectrolytes supporting the possibility of self‐assembly of this cationic random terpolymer in a solvent mixture containing acetone, ethanol and 1‐propanol or each of these solvents separately. The existence of nano‐sized liquid‐crystalline structures was demonstrated using small‐angle X‐ray scattering (SAXS) analysis of the terpolymer solutions. Morphology and sizes of the liquid‐crystalline structures were determined according to the SAXS results and confirmed by dynamic light scattering and atomic force microscopy findings. Liquid crystallization was reasoned on the basis of the existence of a segregated chain microstructure as for polyelectrolytes containing folded parts connected to each other by monomer strings. In a random amphiphilic copolymer or the terpolymer under investigation, the folded parts and strings must be hydrophilic and hydrophobic, respectively. The role of alcohol aggregates should be considered in self‐assembly of the terpolymer chains. The alcohol aggregates can act as physical crosslinkers leading to the formation of more compact liquid‐crystalline structures. The deviations observed in the viscometric behaviour of the terpolymer solutions are suggested as the result of the ability of terpolymer chains to self‐assemble. © 2013 Society of Chemical Industry