Prospects for Using Styrene-Isobutylene-Styrene (SIBS) Triblock Copolymer as a Cusp Material for Leaflet Heart Valve Prostheses: Evaluation of Physicochemical and Mechanical Properties

Search for promising polymer materials as a base for cusps of leaflet heart valve prostheses is a topical problem from the viewpoint of limited durability of fixed biological material. For this purpose, styrene-isobutylene-styrene (SIBS) triblock copolymer was prepared by controlled cationic polymerization. The synthesized SIBS is characterized by the number-average molecular mass M n = 33 000 and narrow monodisperse molecular-mass distribution ( M w / M n = 1.3). The ultimate strength of the polymer film was lower than that of xenopericard and ePTFE in the longitudinal direction by a factor of 3.30 and 6.36, respectively ( p < 0.05); it was lower than that of ePTFE in the transverse direction by a factor of 4.58 ( p < 0.05) and did not differ significantly ( p = 0.65) from that of xenopericard in the transverse direction. The relative elongation and Young’s modulus of the SIBS film exceeded those of ePTFE and xenopericard in the longitudinal direction by a factor of 3.00 and 5.68 and in the transverse direction by a factor of 6.50 and 3.86, respectively (p < 0.05). The contact angle for different sides of the SIBS film was 101.6° ± 2.9°/104.4° ± 0.9°. According to the data of atomic force microscopy, the height difference on the SIBS surface usually did not exceed 1 µm, with separate pits of 20–40 µm size. The results of studying the physical properties of the surface and the mechanical properties determining the primary biocompatibility factors in comparison with control materials show that SIBS polymers are promising for making leaflet heart valve prostheses.