This work pertains to the development of high strength elastomers potentially useful as nonthrombogenic cardiovascular prostheses. Triblock copolymers of the styrene-butadiene-styrene type have been subjected to surface hydroxylation via intermediate epoxides providing reactive sites at the surface for the subsequent coupling of heparin while retaining the unique mechanical properties of the SBS copolymers.

Curves of hydroxyl content versus the copolymer film thickness demonstrated the effect of swelling in the surface region on the product distribution and on the time dependence of the hydroxylation process. The results indicatedthat swelling in the surface region is modified by stress transfer to the unreacted, nonswelling core, giving rise to a lower hydroxyl content in thicker films than in thinner films due to separate effects on both the epoxidation agent and on the cleavage agents and an exponential time dependence with the appearance of a significant induction time.

Detailed quantitative analysis of the infrared spectra of surface reacted samples indicated the presence of a thickness dependent diffusion lag between the cleavage agents and the peracid, confirming the observation of a decreased hydroxyl content in thicker films. Delamination of surface reacted samples occurred on swelling in chloroform. Through analysis of the weights of the resulting fractions, the depth of penetration and the shape of the reaction front was estimated as a function of time, temperature and the composition of the reaction bath.

The general applicability of this surface modification scheme to biomaterial development and the use of SBS triblock copolymers as potential biomaterials was also evaluated.