Side chains affect the melt processing and stretchability of arabinoxylan biomass-based thermoplastic films

Hydrophobization of hemicellulose causes melt processing and makes them stretchable thermoplastics. Understanding how native and/or appended side chains in various hemicelluloses after chemical modification affect melt processing and material properties can help in the development of products for film packaging and substrates for stretchable electronics applications. Herein, we describe a one-step and two-step strategy for the fabrication of flexible and stretchable thermoplastics prepared by compression molding of two structurally different arabinoxylans (AX). For one-step synthesis, the n-butyl glycidyl ether epoxide ring was opened to the hydroxyl group, resulting in the introduction of alkoxide side chains. The first step in the two-step synthesis was periodate oxidation. Because the melt processability for AXs having low arabinose to xylose ratio (araf/xylp<0.5) have been limited, two structurally distinct AXs extracted from wheat bran (AX_WB, araf/xylp = 3/4) and barley husk (AX_BH, araf/xylp = 1/4) were used to investigate the effect of araf/xylp and hydrophobization on the melt processability and properties of the final material. Melt compression processability was achieved in AX_BH derived samples. DSC and DMA confirmed that the thermoplastics derived from AX_WB and AX_BH had dual and single glass transition (T_g) characteristics, respectively, but the thermoplastics derived from AX_BH had lower stretchability (maximum 160%) compared to the AX_WB samples (maximum 300%). Higher araf/xylp values, and thus longer alkoxide side chains in AX_WB-derived thermoplastics, explain the stretchability differences.