Synthesis and Characterization of Fully Biobased Copolyether Polyols

In the current climate of growing environmental concerns, especially taking into consideration the finite nature of global petroleum resources, biobased polymers are synthetic targets of great interest. In particular, the polyurethane industry is demanding high biobased containing polyols in their raw materials portfolio. While most of the biobased polyols are based on polyesters, the majority of industrial polyurethanes are prepared using polyether polyols due to their low glass transition temperature, T_g, and higher chemical resistance. In this work, we report a series of fully biobased copolyether polyols with low T_g and tunable melting temperatures prepared from the self-condensation of two biobased diols, 1,4-cyclohexanedimethanol and 1,6-hexanediol. By increasing the 1,4-cyclohexanedimethanol content, copolyethers with lower melting temperatures (<50 °C) and degrees of crystallinity are obtained while still showing low T_g values (←40 °C). We also find that the conformation of the 1,4-cyclohexanediol strongly influences the way in which these random copolyethers crystallize. Thus, when 100% trans isomer on 1,4-cyclohexanediol is used, the copolymers show isodimorphic crystallization behavior, showing semicrystalline behavior for all compositions. However, when the cis content is at least 30%, comonomer exclusion occurs and above 50 mol % of 1,4-cyclohexanediol the polyether is fully amorphous. This polycondensation route shows a simple and sustainable way to synthesize fully biobased polyether polyols with comprehensive properties and tunable crystallinity which make them ideal candidates for the preparation of a great variety of polyurethane elastomers.