Synthesis of biomass-based comb-shaped polyesters and their thermal properties

Abstract

Novel mono glyceryl ethers (MGEs) were synthesized from biomass-based sources and used as diol monomers for synthesizing comb-shaped polyesters (comb-shaped polymers (CSPs)). MGEs with varied alkyl chain lengths (m values) were polymerized with biomass-based diacids of varied alkyl chain lengths (n values) via polycondensation, yielding a series of (32 kinds of) MGE-based CSPs with diverse m and n combinations. The resulting CSPs had molecular weights > 10 000 g mol⁻¹ (after purification) with a high reaction extent (≥91%). The melting temperatures (T_m) were systematically studied with respect to (1) the branch alkyl chain length (m), (2) the backbone alkyl chain length (n), (3) the branch position in MGE (Sn-1 or Sn-2 positions), and (4) the difference between ether-linked and ester-linked branch chains. Notably, several CSPs showed particularly low T_m (below 0 °C) or even no T_m (with no crystallinity), which is not attainable by linear polyesters. These CSPs may find unique future applications such as low-temperature lubricants.