Copolymers of N-vinyl-2-pyrrolidone and 2-(dimethylamino)ethyl methacrylate, 3. Viscosity of quaternized copolymers in aqueous solution

N‐Vinyl‐2‐pyrrolidone (VP) — 2‐(dimethylamino)ethyl methacrylate (DMAEM) copolymers were quaternized with octyl, dodecyl or hexadecyl bromide. The behaviour of the modified copolymers in aqueous solutions was studied by viscosimetry. As typical of classical polyelectrolytes, by increasing the ionic strength of the solutions, their viscosity decreases. Since the DMAEM mole fraction in the modified copolymers is low, the pH of the solutions does not have a great influence on the extension of the macromolecules. The influence of the size of the alkyl chains and of the mole fraction of quaternized units were studied: the formation of hydrophobic microdomains is easier for copolymers which have a low fraction of long quaternized units than for copolymers with a high mole fraction of short quaternized units.