Correlating side-chain and backbone dynamics of modified polysaccharide to glass-transition temperatures

Arabinoxylan (AX) is an abundant polysaccharide present in cereals. The AX can be valorized as thermoplastic material by chemical modifications, which supposedly increase polymer mobility of the originally rigid chains. Recently, we developed a strategy that enables the production of highly processible modified AX through a ring-opening reaction, followed by grafting of ether chains (melt extrusion at 150°C and compression molding from 70 °C). The molar ratio of ether to AX required is 1:1 in this process; lower than those for non-ring opened ether/esters which are between 2:1 and 3:1. The mechanical and processing properties of the ring-opened ether AX were also found to be improved when compared to only etherified AX. The material has multiple relaxation behaviors and are also plasticized by water at 50% RH. Our goal is to use QENS to obtain a more refined description of the mechanisms at play in the resulting melt processability. A more complete understanding of the dynamics involved can help evaluate and guide the development of modification reactions for thermoplastic polysaccharide materials in the future.

阿拉伯木聚糖（Arabinoxylan，AX）是谷物中广泛分布的多糖类物质。可通过化学改性将其制备为热塑性材料，该改性手段理论上可提升原本刚性链段的聚合物迁移率。近期，本研究团队开发了一种可制备高可加工性改性AX的策略：先通过开环反应，再接枝醚链，具体工艺为150℃下熔融挤出、70℃下压制成型。该工艺所需的醚与AX的摩尔比为1:1，低于非开环醚/酯改性所需的2:1至3:1的比例。研究表明，相较于仅经醚化改性的AX，开环醚化AX的力学性能与加工性能均得到显著提升。该材料展现出多重弛豫行为，且在50%相对湿度（Relative Humidity，RH）条件下会被水增塑。本研究的目标是通过准弹性中子散射（Quasi-Elastic Neutron Scattering，QENS），对影响该材料熔融加工性能的内在作用机制进行更精准的阐释。对相关动力学过程的全面理解，将有助于未来评估并指导热塑性多糖材料改性反应的开发。