PREPARATION AND KINETIC CHARACTERIZATION OF COPOLYMERS OF ACRYLAMIDE AND POLY(ETHYLENE GLYCOL) (METH)ACRYLATE MACROMONOMERS

Novel comb copolymers were prepared by the free-radical copolymerizati on of acrylamide (AM) and poly(ethylene glycol) (PEG) macromonomers in aqueous solution using potassium persulfate as an initiator. The reac tivity ratios of acrylamide (M(1)) toward macromonomers (M(2)), r(1) = K-p11/K-p12, were estimated at low conversion by using H nuclear magn etic resonance (n.m.r.) spectroscopy and high performance liquid chrom atography (h.p.l.c.) techniques. The values of r(1) ranged between 1.3 5 and 2.2 and were dependent on the PEG pendant chain length in the ma cromonomers. The reactivity of the macromonomers in copolymerization, characterized by (1/r(1)), decreased with the PEG pendant chain length . The reactivity of the macromonomer in homopolymerization, expressed as K-p/K-t(1/2), increased with the PEG pendant chain length. The chan ges of K-p and K-t are probably caused by the shielding effect on the growing radicals by the macromonomer pendant chains. The molecular wei ghts of the copolymers were found to be sensitive to the polymerizatio n temperature. Higher-molecular-weight (> 3 x 10(6)) copolymers were o btained at lower temperatures.