Aliphatic Polyester Materials from Renewable 2,3-Butanediol

Abstract

2,3-Butanediol has emerged as a promising bio sourced monomer for polyester synthesis. However, it has received limited attention as monomer for semicrystalline polyesters, due to the lower reactivity of secondary alcohols often resulting in low molecular weight polymers. Furthermore, the methyl branches of 2,3-butanediol reduce the crystallinity of resulting polyesters, leading to lowered melting temperatures. We report the synthesis of semicrystalline polyesters from 2,3-butanediol with long-chain aliphatic dicarboxylate monomers ranging in chain length from C10 to C48. With appropriate reaction conditions, high molecular weights up to 59,000 g mol–1 were obtained. Polyester-b4.48 (b4 = 2,3-butanediol-based repeat units) features a high melting point of 103 °C and orthorhombic polyethylene-like crystal structure, while shorter dicarboxylate-based polyesters have different crystal structures and polyester-b4.10 is amorphous. Tensile tests of polyester-b4.18 reveal a modulus of elasticity of 290 MPa and elongation at break of 430%. The combination of b4/C10 noncrystallizing repeat units with the well-crystallizable C48 repeat units provides 2,3-butanediol-based thermoplastic elastomers. Faster enzyme-catalyzed hydrolysis rates were measured for polyester-b4.18 compared to the linear polyester-4.18, indicating an increase in biodegradability with decreasing polymer melting points and crystallinities.