Macromolecular Engineering and Additive Manufacturing of Poly(styrene-b-isobutylene-b-styrene)

Abstract

Although polyisobutylene (PIB)-based thermoplastic elastomers (TPEs) possess a combination of unique properties (i.e., low permeability, high environmental and chemical stability, and excellent biocompatibility), they have not been explored for 3D printing. Poly(styrene-b-isobutylene-b-styrene) (SIBS) is one of the most important PIB-based TPEs used in biomedical applications. Herein, we report, for the first time, the development of an efficient and low-cost 3D printing strategy of SIBS by fine-tuning its microstructure and properties. We discovered that blending the polystyrene (PS) homopolymer with SIBS leads to significant changes in its microphase-separated structure. The amount and molecular weight of the added PS significantly affect the micromorphology and 3D printability of SIBS/PS blends. In particular, SIBS/PS blends with high molecular weight PS at relatively high weight fractions show a unique hierarchical salami micromorphology with appropriate properties (improved hardness, modulus, and thermal stability) for 3D printing by fused filament fabrication. SIBS/PS blends with PS molecular weight close to or higher than that of SIBS show better printability than blends with low molecular weight PS. Blending the PIB block copolymer with the homopolymer of its hard block is an efficient and cost-effective strategy for additive manufacturing of PIB-based elastomers with widely tunable properties.