纤维素与乙烯基酯在离子液体介质中的酯交换被认为是常规酯化的一种对环境友好的替代方法。在这项研究中,各种长链纤维素酯(月桂酸酯,Myristate,棕榈酸盐,和硬脂酸酯)在新型可蒸馏离子液体中合成了高达1.8的取代度(DS),[mTBNH][OAC]。这种IL对纤维素有很高的溶解能力,这可以改善均相酯交换。此外,[mTBNH][OAC]具有对再循环的耐久性,并且可以再生并再次用于下一个酯化循环。DMSO用作共溶剂,因为其由于较低的溶剂粘度而能够加速传质。反应参数的优化,如助溶剂含量,温度(20-80°C),反应时间(1-5小时),和反应物的摩尔比(1-5当量。AGU)已报告。发现在研究的反应条件下,DS随着反应时间的增加而增加,温度,并添加乙烯基酯。用FTIR进行结构分析,1H,酰化后的13CNMR表明,对于所有研究样品,都将烷基链引入纤维素中。结果还表明,OH基团的取代顺序为C7-O6>C7-O2>C7-O3。独特,纤维素酯的复杂热和流变学研究表明,随着取代度的增加,无定形相的生长。同时,纤维素与酰基链的均匀取代增加了材料的熔体粘度。发现纤维素酯中的内部增塑是材料熔融加工的机理。长链纤维素酯显示出替代常用的外部增塑纤维素衍生物的潜力。
The transesterification of cellulose with vinyl esters in ionic liquid media is suggested as a prospective environmentally friendly alternative to conventional esterification. In this study, various long-chain cellulose esters (laurate, myristate, palmitate, and stearate) with a degree of substitution (DS) up to 1.8 have been synthesized in novel distillable ionic liquid, [mTBNH][OAC]. This IL has high dissolving power towards cellulose, which can improve homogeneous transesterification. Additionally, [mTBNH][OAC] has durability towards recycling and can be regenerated and re-used again for the next cycles of esterification. DMSO is used as a co-solvent because of its ability to speed up mass transport due to lower solvent viscosity. The optimization of the reaction parameters, such as co-solvent content, temperature (20-80 °C), reaction time (1-5 h), and a molar ratio of reactants (1-5 eq. AGU) is reported. It was found that within studied reaction conditions, DS increases with increasing reaction time, temperature, and added vinyl esters. Structure analysis using FTIR, 1H, and 13C NMR after acylation revealed the introduction of the alkyl chains into cellulose for all studied samples. The results also suggested that the substitution order of the OH group is C7-O6 > C7-O2 > C7-O3. Unique, complex thermal and rheological investigation of the cellulose esters shows the growth of an amorphous phase upon the degree of substitution. At the same time, the homogeneous substitution of cellulose with acyl chains increases the melt viscosity of a material. Internal plasticization in cellulose esters was found to be the mechanism for the melt processing of the material. Long-chain cellulose esters show the potential to replace commonly used externally plasticized cellulose derivatives.