Preparation and solution behaviour of graft copolymers with cationic groups in polyoxyethylene side chains

Abstract

Novel, cationic graft copolymers with charged polyoxyethylene (PEO) side chains were prepared from the alternating copolymer poly(phthalimidoacrylate- co-styrene). Substitution of the good leaving phthalimido ester groups with α-trimethylammonioethyl-ω-aminopolyoxyethylene resulted in graft copolymers with PEO side chains end-functionalized with quaternary ammonium groups. In a two-step synthetic procedure the same precursor polymer was modified with 3-dimethylaminopropylamine. Then the tertiary amine groups were quaternized with α-methoxy-ω-bromopolyoxyethylene or with α-trimethylammonioethyl-ω-bromopolyoxyethylene to yield graft copolymers with cationic groups close to the backbone or bearing bifunctional side chains. The effect of ionic group location on the behaviour of the copolymers in a low-polarity and a polar solvent was studied by viscosity, GPC and static light scattering measurements. In a low-polarity solvent (tetrahydrofuran) the factors determining the solution properties of the cationic graft copolymers are the intramolecular side chain and ion-pair attractions which shrink the polymer chains. In a polar solvent ( N, N-dimethylformamide) the behaviour of the graft copolymers with low degree of grafting is determined by the balance between the intramolecular side chain attraction and the electrostatic interactions of the dissociated ion-pairs. The ionic groups located at the end of the side chains cause polyelectrolyte behaviour.