Meltable fatty acid esters of α-1,3-glucan as potential thermoplastics

Biosynthetically produced α-1,3-glucan dissolved in N,N-dimethyl acetamide/LiCl was allowed to react with lauric-, palmitic-, and stearic acid in presence of the activation agents p-toluenesulfonic acid chloride (TsCl), N,N′-carbonyldiimidazole (CDI), or the iminium chloride (ImCl) obtained from N,N-dimethyl formamide and oxalyl chloride. The highest degree of substitution (DS) of ester groups of 2.20 was obtained by reacting the glucan with 5 mol lauric acid and 5 mol ImCl per mole repeating unit within for 4 h at 100 °C. Formation of 6-deoxy-6-chloro moieties (as a known side reaction) is less pronounced in case of ImCl compared the use of TsCl for activation. The glucan esters melt except those synthesized with CDI as activation agent. The melting temperature is lower in case of higher DS, longer carboxylic acid, and lower molar mass. Products which do form a melt were shaped to films and could be used as basis for hot-melt adhesive to bond wood.