Solvent-dependent rheological behavior of concentrated solutions of a cationic acrylic terpolymer containing self-assembled chains

Abstract

AbstractIt has been proved that alcohol molecules exist as cyclic and chain aggregates of different sizes in pure or mixed solvent systems. Here, it will be shown that these aggregates can radically change the rheological properties of a concentrated polymer solution containing self-assembled chains. In a previous study by the same authors, the existence of self-assembled structures in dilute solution of poly(dimethylaminoethyl methacrylate-co-methyl methacrylate-co-butyl methacrylate) in an alcoholic solvent mixture was shown according to small angle X-ray scattering results, showing that these structure were much more compact than those in acetone. This finding is based on the role of alcohol aggregates as physical cross-linkers. Here, the existence of self-assembled structures in concentrated solutions of the same terpolymer was confirmed by atomic force microscopy and rheology results both in acetone (a good solvent) and in a solvent mixture composed of acetone, ethanol and 1-propanol. For the terpolymer solutions in the solvent mixture, very little decrease in complex viscosity and shear thickening were observed at high strains and frequencies, respectively. It can be concluded that the alcohol aggregates can cause the formation of strong self-assembled structures that can even resist high shear forces or strains.