Polyelectrolyte behavior of copolymers of 2-deoxy-2-methacrylamido-d-glucose with cationic comonomers in water and dimethylsulfoxide solutions

Abstract

Copolymers of 2-deoxy-2-methacrylamido-d-glucose with N,N-dimethyl aminoethyl methacrylate were synthesized. Triple copolymers containing N,N-dimethyl-N-dodecyl-N-methacryloyl oxyethyl ammonium iodide units were obtained by alkylation of tertiary amino groups. These copolymers were studied by hydrodynamic and optical methods in various solvents. It was revealed that polyelectrolyte effect in salt-free aqueous solutions is far less pronounced than that in dimethyl sulfoxide (DMSO) solutions. The values of equilibrium rigidity A of alkylated macromolecules in salt-free solutions obtained from viscosimetry data is equal to ∼ (150±50)Å in aqueous solutions and to (750±250)Å in DMSO solutions. Change in intrinsic anisotropy of alkylated macromolecules in DMSO solutions demonstrated that in the concentration range from 2.5 to 0.5g/dL, electrostatic interactions lead to isotropic increase in dimensions of macromolecular coils. In the concentration range from 0.5 to 0.02g/dL, increase in equilibrium rigidity by almost a factor of 4 is observed. It was established that in water-salt solutions of copolymers which contain more than 10mol.% of dodecyl groups, compact structure is formed; in this structure, intramolecular fragments of polymer chain are hindered. In dimethylsulfoxide solution, in the presence of a salt, the value of intrinsic viscosity [η] increases by more than a factor of 6–8 as compared to that in water-salt solutions. The observed differences in conformation, optical and relaxation properties of the triple copolymers in aqueous and DMSO solutions are related to hydrophobic interactions between alkyl substituents. These interactions lead to the formation of hydrophobic “core” and shielding the charged quaternary ammonium groups (N+) in aqua solutions.