Chemical Modification of Poly-α-1,3-Glucan

Abstract

Sustainability is becoming a primary consideration in the development of new materials. Specifically, renewability and biodegradability are desirable properties for materials in a variety of applications, including packaging and personal care products. α-1,3-glucan is a biodegradable polysaccharide found naturally in fungi and bacteria. It can also be synthesized enzymatically from sucrose to have a controlled structure and molecular weight. Similar to cellulose, α-1,3-glucan has a high degree of crystallinity which hinders its interaction with other materials. The objective of this research is to investigate the chemical modification of α-1,3-glucan with the goal of changing its properties so it would become suitable to be manufactured into a valuable material.

α-1,3-glucan, dissolved in N,N-dimethyl acetamide/lithium chloride, is functionalized with octenylsuccinic anhydride. Reaction conditions are varied and their effects on the structural and thermal properties of the esterified α-1,3-glucan are explored. Modified α-1,3-glucan samples are also qualitatively analyzed for melt flow behaviour and interaction with oil and water mixtures. The optimal reaction conditions for maximizing the degree of substitution and minimizing chain degradation consist of a temperature of 50 °C and a molar ratio of octenylsuccinic anhydride to anhydroglucose units of 3:1. Increasing the reaction temperature was found to cause degradation of the polysaccharide backbone. The addition of pyridine is found to increase the degree of substitution and alter the extent of chain degradation depending on the reaction conditions. A decrease in lithium chloride concentration leads to an increase in degree of substitution and increased molecular weight loss. Esterified α-1,3-glucan samples do not show thermal transitions in calorimetry measurements but samples with sufficient extent of modification flow under the simultaneous application of heat and force. Due to the amphiphilic nature of octenylsuccinic anhydride, α-1,3-glucan modified at elevated temperature shows potential as an emulsifying agent.

α-1,3-glucan continues to show promise as a renewable and biodegradable material. Chemical modification via functionalization of the hydroxyl groups has been shown to successfully alter the material properties. Additional experimentation is recommended to further explore the effects of catalyst and lithium chloride concentrations on the reaction efficiency and material properties. Continued investigation of the emulsifying capacity should be performed to verify the conclusions drawn from preliminary testing.