Synthesis and characterization of α-1,6-graft-α-1,3-glucan ester derivatives

Abstract

α-1,6- graft - α -1,3-glucan, produced by enzymatic polymerization, comprises a main chain of α -1,6-glucan and a side chain of α -1,3-glucan. In the present study, we synthesized α -1,6- graft - α -1,3-glucan ester derivatives with acyl groups ranging from acetate to octanoate, and evaluated their thermal, mechanical, and optical properties. We compared the mechanical and optical properties of cast films of the derivatives with those of cast films of α -1,6-glucan butyrate, α -1,3-glucan butyrate, and their blend. The graft glucan ester films had the flexibility of α -1,6-glucan and the rigidity of α -1,3-glucan, and their haze values were much lower than those of the α -1,3-glucan butyrate and blend films. Differential scanning calorimetry and polarized microscopy revealed that the prepared graft glucan ester derivatives were amorphous, although they were partially pseudo-crystallized. This suggests that the main chain limited the crystallization of the α -1,3-glucan ester side chain. This inhibition of crystallization resulted in the flexibility, toughness, and transparency of the solvent-cast films. • α -1,6- graft - α -1,3-glucan, which comprises a main chain of α -1,6-glucan and a side chain of α -1,3-glucan, was esterified with acyl groups ranging from acetate to octanoate. • The α -1,6- graft - α -1,3-glucan ester films had the flexibility of α -1,6-glucan and the rigidity of α -1,3-glucan. • The α -1,6-glucan ester main chain limited the crystallization of the α -1,3-glucan ester side chain, and this inhibition of crystallization resulted in the flexibility, toughness, and transparency of the films.