Influence of Electrostatic Long-Range and Short-Range Effects on the Conformations of Flexible-Chain Linear Polyelectrolyte Macromolecules with Different Charge Density in Salt-Free Aqueous Solutions

A series of copolymers of N-methyl-N-vinylacetamide and N-methyl-N-vinylamine hydrochloride with an average content of charged groups of (4.4 ± 0.2) mol % and molecular mass in the range of 22 < M × 10–3, g/mol < 630 are synthesized and characterized. Fractions are studied by sedimentation-diffusion methods in 0.2 mol/L NaCl under almost suppressed polyelectrolyte effects. In salt-free aqueous solutions, their viscous flow is investigated and intrinsic viscosity is determined as [η] ≡ lim(∂lnηr/∂c) at c → 0. The results are compared with the previous data obtained for the copolymer containing (15.7 ± 0.5) mol % of charged groups and the homopolymer. It is shown that the type of intrinsic viscosity dependence on the molecular mass of the copolymer containing 4.4 mol % of charged groups is typical of chains manifesting intrachain volume interactions, while at a 15.7 mol % content of charged groups the type of the dependence is characteristic of chains demonstrating intrachain short-range effects; hence, the chains behave as rigid-chain, permeable. The statistical segment lengths of copolymer macromolecules in salt-free solutions and in 0.2 mol/L NaCl are determined. The data are analyzed in terms of the normalized Kuhn–Mark–Houwink–Sakurada relation.