Melt-Spun Fibers Manufactured from α-1,3-Glucan Short- and Long-Chain Mixed Esters

α-1,3-glucan is a linear homopolymer produced through the enzymatic polymerization of sucrose using recombinant glucosyl transferase J (GtfJ) enzyme. Two series of α-1,3-glucan short- and long-chain mixed esters, namely α-1,3-glucan acetate hexanoate and α-1,3-glucan propionate hexanoate, with different ratios of short to long sidechains were synthesized via heterogeneous chemical esterification. α-1,3-glucan propionate hexanoate, with a stable crystalline structure, had a significantly higher melting temperature than α-1,3-glucan acetate hexanoate. Melt-spun fibers of both series of esters were successfully prepared at lower temperatures than those required for conventional α-1,3-glucan homo esters, without decreases in molecular weights. The tensile strength of melt-spun fibers increased as the proportion of the short sidechain increased, reaching 367 MPa (ratio of acetate to hexanoate groups of 2.2:0.8), which was much higher than α-1,3-glucan tripropionate with a tensile strength of 115 MPa. X-ray diffraction analyses indicate that this high tensile strength is due to the high orientation of the molecular chains.