Characterization of the chromium (III) crosslinked collagen poly(butry acrylate) graft copolymer

The redox, free radical‐initiated graft polymerization of butyl acrylate onto chromium (III)‐crosslinked collagen has been investigated previously. In the experiments reported here we set out to determine whether true grafting had occurred and, if so, the molecular weight of the synthetic polymer that was grafted to the collagen. The butyl acrylate grafted product was successively extracted with acetone and ethyl acetate to remove homopolymers. The solvent‐extracted product was then subjected to enzymatic degradation, followed by chloroform fractionation, and finally gel permeation chromatography of the chloroform‐soluble fraction. Viscosity studies of the final fractionated product indicated that the molecular weight was about 1 million. Viscosity studies of the two homopolymers extracted with acetone and ethyl acetate show that the molecular weights of these homopolymers were somewhat less than that of the isolated polymer–peptide fragment. The fractionated polymer–peptide unit contained 2.83% amino acids, indicating that there are about 288 amino acids in the peptide attached to the polymer molecule. This polymer is composed of approximately 8100 monomer units. The IR spectra confirmed that this fraction is principally poly(butyl acrylate) with amide, OH, and NH absorption bands contributed by the peptide. The isolation and characterization of the polymer–peptide fragment provided proof of graft polymerization onto the collagen molecule.