Solution properties of an aqueous poly(methacryl oxyethyl trimethylammonium chloride) and its poly(oxyethylene) grafted analog

Cationic poly(methacryl oxyethyl trimethylammonium chloride), PMOTAC, and its poly(oxyethylene), POE, grafted analog have been synthesised. The molar mass of the POE grafts was M w = 200 g/mol, and the grafting degrees of the synthesised copolymers were 2, 5, and 15 mol %. The effect of the POE grafts on the solution properties and the conformation of the polycation has been investigated in aqueous NaNO 3 by means of dynamic and static light scattering, viscometry, and Raman spectroscopy. It was found that the polyelectrolyte properties are more pronounced for the homopolymer than for the POE-grafted copolymers. The increase of the POE-grafting degree dramatically decreases the hydrodynamic radius of individual macromolecules and causes intermolecular association. It also suppresses the conformational response of the copolymers upon changing the ionic strength with respect to that of the homopolymer. DFT calculations have been used to estimate a possible mechanism of interaction between the POE grafts and the MOTAC repeating units. It has been revealed that the POE grafts are capable of forming intramolecular hydrogen bonds with the MOTAC groups. The latter was confirmed experimentally; addition of free POE chains to a solution of PMOTAC results in formation of intermolecular PMOTAC/POE complexes. Increasing the POE concentration decreases the solution viscosity. At the same time, the bimodal distributions of the hydrodynamic radius, which are typical for polyelectrolytes in salt-free solutions, become monomodal representing the PMOTAC/POE complexes.