Stereochemical effects on the mechanical and viscoelastic properties of renewable polyurethanes derived from isohexides and hydroxymethylfurfural†
Biomass-derived polyurethanes were synthesized using 2,5-bishydroxymethylfuran (BHMF) and diisocyanate functionalized isohexides, isosorbide bis(3-isocyanatopropanoate) (ISBIP) and isomannide bis(3-isocyanatopropanoate) (IMBIP), at varying feed ratios. PU compositions accurately reflect the feed of ISBIP and IMBIP used as determined by NMR spectroscopy and polarimetry measurements. Differential scanning calorimetry, pycnometry, tensile testing, and rheology reveal that the isosorbide versus isomannide content within the PU effects the glass transition temperature, density, and entanglement molar mass ultimately resulting in different mechanical properties at similar molar mass. Other properties, such as thermal stability and amorphous character, remain similar. The isohexide isomer effects on properties are discussed.