2,3-Butanediol as a Biobased Chain Extender for Thermoplastic Polyurethanes: Influence of Stereochemistry on Macromolecular Architectures and Properties

2,3-Butanediol (2,3-BDO) is a short diol, easily bioproduced by different native bacteria from sugars or lignocellulosic biomasses at low cost. In this study, the potential of the different stereoisomers of 2,3-BDO as chain extenders in thermoplastic polyurethanes (TPUs) was evaluated for the first time. Several partially biobased TPUs were synthesized from a long biobased diol based on fatty acid dimers, 4,4′-methylene bis­(phenyl isocyanate), and the different stereoisomers of 2,3-BDO as chain extenders. The stereochemistry of 2,3-BDO was found to have a dramatic influence on the structuration of the TPUs and consequently on their physical properties. The favorable orientation of the methyl side chains of the meso form of 2,3-BDO allows strong hydrogen bonding, leading to the formation of crystalline hard segments and to large-scale structuration into separated hard segment domains, leading to strong mechanical and thermomechanical properties. On the other hand, (+)- and (−)-2,3-BDO present an unfavorable orientation of the methyl groups that precludes crystallinity and leads to lower structuration and mechanical properties.