Characterization of the collagen–vinyl graft copolymers prepared by the ceric ion method. I. Solution properties

Abstract

Graft copolymerization of vinyl monomers on to collagen was carried out by the ceric ion method. The grafted vinyl polymer chains were isolated by both acid and enzymatic hydrolysis of the collagen backbone in order to characterize the graft copolymers. Proof of grafting was obtained through the detection of amino acid endgroups in the grafts isolated by both the methods. The grafts isolated gave the characteristic blue color normally associated with the presence of amino acids. The presence of amino acid endgroups was further confirmed by dinitrophenylation of the isolated grafts. The absorption spectra of the dinitrophenylated(DNP) grafts showed absorption maximum in the ultraviolet region of 340–360 mμ, characteristic of DNP-amino acids. Soluble collagen grafted with polyacrylamide(PAA) formed fibrils on heating to 37°C at neutral pH but, unlike the native collagen, these fibrils did not redissolve on cooling at 2°C. These results show that the redispersion property of soluble collagen was impaired, probably by attachment of the PAA side chains to the collagen molecule. The turbidimetric titration behavior of the grafts, their general behavior of swelling in different solvents, and the intrinsic viscosity of the copolymers in mixed solvents also provided additional proof of grafting.