低取代羟乙基纤维素在碱溶剂中的溶解行为及其机制

Dissolution behavior and mechanism of hydroxyethyl cellulose with low molar substitution in alkali solvent

为改善纤维素在氢氧化钠(NaOH)水溶液中的溶解性能,通过醚化改性制备了低取代羟乙基纤维素(HEC),并借助光学显微镜、核磁共振仪、差热扫描量热仪和透射电子显微镜等测试手段,研究了HEC在质量分数为8%的NaOH水溶液中的溶解行为及溶解机制。结果表明:低温下NaOH溶剂和水分子可结合形成尺寸合适、结构稳定的NaOH水合分子,与HEC大分子上的羟基键合形成HEC-NaOH-H_2O缔合结构,切断了HEC大分子间氢键,HEC直接溶解;醚化改性后亲水性侧链的引入减弱了HEC分子间作用力,增强了HEC与NaOH水合分子之间的作用强度,加强了缔合结构稳定性,促进了HEC在NaOH溶剂中的良好溶解;沿纤维长度方向HEC最外层膜溶胀成球形并逐渐破裂溶解,最终以长度为微米级、宽度为10～80 nm的微纤维形式分散在溶剂中。

In order to improve the solubility of cellulose in NaOH solution,hydroxyethyl cellu-lose(HEC)with low molar substitution was prepared.The interactions between HEC(8%)and NaOH in solution were investigated by optical microscopy,nuclear magnetic resonance,differential scanning calorimetry and transmission electron microscopy.The results show that at low temperatures(below 0℃)NaOH solvent combines with water molecules to form NaOH hydrated molecules with proper size and stable structure,which are bonded with hydroxy on HEC molecules to form HEC-NaOHH 2O water association structure.HEC is gradually dissolved following with the breakage of intermolecular hydrogen bond of HEC.After etherification,the introduced hydrophilic side chains weakens the interactions between HEC molecules but strengthens interactions between HEC chains and NaOH hydrated molecules,enhancing the stability of association structure and promoting the dissolution of HEC in NaOH solvent,then HEC is gradually dissolved and finally dispersed in the form of microfiber with the length of micron\|scale and the width of 10-80 nm.