Surface hydroxylation of styrene–butadiene–styrene block copolymers for biomaterials

Abstract

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.

Anti‐thrombogenicity of styrene‐butadiene‐styrene triblock copolymer grafted with poly(ethylene glycol)s

“…Ishihara and Iwasaki et al [9][10][11][12][13] synthesized a copolymer of 2-methacryloyloxyethyl phosphorylchloline (MPC) and nbutyl methacrylate (BMA), which is similar to bio-membranes, and they found that the copolymer is the best excellent anti-thrombogenic material in the world, and SPUs coated the copolymer shows the improved blood compatibility. 14 Sefton et al 15 prepared a styrene-butadienestyrene tri-block copolymer (SBS), which has also excellent mechanical properties and is able to mold at melt state, grafted with hydrophilic heparin molecules on the poly(butadiene) (PB) domains of SBS. After approximately two decades, Yang et al 16,17 grafted vinyl pyridine by radiating ultraviolet light on the surfaces of PB domains of SBS cast film and found that this surface reduced the adhesion of protein molecules and resulted in good anti-coagulation property of blood.…”

“…Sefton et al15 prepared a styrene‐butadiene‐styrene tri‐block copolymer (SBS), which has also excellent mechanical properties and is able to mold at melt state, grafted with hydrophilic heparin molecules on the poly(butadiene) (PB) domains of SBS. After approximately two decades, Yang et al16, 17 grafted vinyl pyridine by radiating ultraviolet light on the surfaces of PB domains of SBS cast film and found that this surface reduced the adhesion of protein molecules and resulted in good anti‐coagulation property of blood.…”

Ex vivo and in vitro Blood Response to Surface-Modified Poly(styrene-b-butadiene-b-4-vinylpyridine) Triblock Polymers

“…The ratio of the surface hard to soft segments appears to be an important parameter in determining blood response. A number of researchers have examined the blood compatibility of ABA triblock polymers.10- 13 Okano et a/. 14 have proposed that the hydrophilic-hydrophobic balance between the blocks is the principal determinant of the thrombogenicity of these materials.…”