Detecting Hydrophobic Interactions in Star-Shaped Amphiphilic Copolymers by the Viscometric Method

The amphiphilic copolymers of N-methyl-N-vinylacetamide and alkylated N-methyl-N-vinylamine combining a hydrophilic backbone and hydrophobic side chains of various lengths and carrying a charge are studied. The results are compared, and the features of the application of known methods for determining the intrinsic viscosity in aqueous and organic solvents are considered. Conclusions are drawn about the intramolecular organization in the molecular chains of the studied copolymers and the manifestation of hydrophobic interactions in macromolecules with different lengths of alkyl radicals. The conditions under which the amphiphilic character of copolymers does not manifest itself are revealed. It is proposed to consider the sign and magnitude of the second derivative of the dependence ln ηr = f(c[η]) as a measure of the hydrophobicity of copolymer chains.