Homology Violation in a Series of Amphiphilic Comb-Like Statistical Copolymers of N-Methyl-N-vinylacetamide and N-Methyl-N-vinylamine with Moderate Density of Grafting of Side Dodecyl Groups

A series of water-soluble comb-like copolymers of N-methyl-N-vinylacetamide and N-methyl-N-vinylamine (MVAA‒со‒MVA) bearing hydrophobic dodecyl side groups С₁₂Н₂₅ has been investigated by means of molecular hydrodynamics (viscometry, translational diffusion, and analytical ultracentrifugation) in dilute solutions in 0.1 M NaCl, under conditions of suppression of the polyelectrolyte effects. The issues of homology of these amphiphilic copolymers have been considered. The viscometry data plotted as lnη_r as function of c[η] have allowed to distinguish between macromolecules of the copolymers according to their hydrophobicity. Positive values of the second derivative B₂ determined from the initial parts of these curves have served as a measure of hydrophobicity of the amphiphilic copolymers. The noticeable differences in the B₂ values for different copolymers have shown that they do not form true homologous series. For the quasi-homologous series of the MVAA–со–MVAC₁₂H₂₅·HI copolymers with close values of B₂, the Kuhn–Mark–Houwink–Sakurada relationships have been obtained and the equilibrium rigidity of the chains has been assessed using the modified Gray–Bloomfield–Hearst equation.