Antithrombogenicity and oxygen permeability of block and graft copolymers of polydimethylsiloxane and poly(alpha-amino acid).

A-B-A-type block copolymers consisting of poly(alpha-amino acid) as A component and polydimethylsiloxane as B component and graft copolymers consisting of polydimethylsiloxane as trunk polymer and poly(alpha-amino acid) as branch polymer were synthesized. gamma-Benzyl-L- or DL-glutamate, epsilon-benzyloxycarbonyl L-lysine, and sarcosine were used as alpha-amino acid. Different microphase-separated structures were found on the film surface according to the copolymer composition and the casting conditions. In vitro antithrombogenicity test showed higher antithrombogenicity of block or graft copolymers than homopolymers. The best antithrombogenicity was independent of the kind of alpha-amino acid and the degree of polymerization of copolymers. The best ratio was 65-75% in block copolymer and 40-50% in the case of graft copolymer. The oxygen permeability of block and graft copolymer film was intermediate between those of homopolymers and varied with changing the composition of the copolymer. These experiments showed that the microphase-separated structure on the film surface was most important both for the antithrombogenicity and oxygen permeability of these copolymer films.