DMSO/DBU/CO2溶剂体系中原位有机功能催化纤维素碳酸酯的合成及其性质研究

Synthesis and property study of cellulose methyl carbonate in DMSO/DBU/CO_2 system via in situ organocatalysis

纤维素是地球上储量最丰富的生物可再生资源,具有价格低廉、易改性、可生物降解等特点.纤维素衍生化是拓展纤维素应用的重要手段之一.纤维素碳酸酯是重要的纤维素衍生物之一,在包装材料、热塑性材料、固体电解质等领域具有重要的应用潜力.本文基于1,8-二氮杂二环十一碳-7-烯(DBU)/二甲基亚砜(DMSO)/CO_2体系溶解活化纤维素,通过原位DBU的有机功能催化作用催化纤维素与碳酸二甲酯之间的转酯化反应,合成了纤维素甲基碳酸酯.结果表明,碳酸二甲酯与纤维素脱水葡萄糖单元(AGU)摩尔比为8:1,反应温度为60℃,反应时间为12 h时,可得到取代度(DS)1.09的纤维素碳酸酯,并通过核磁共振、红外光谱、热重分析(TGA/DSC)等表征方法研究纤维素碳酸酯结构与热性能的关系.DSC/TGA结果显示,当纤维素甲基碳酸酯的取代度为1.09时,其玻璃化转变温度为62.9℃,起始降解温度为305.5℃.

Cellulose is the most abundant biorenewable resource on the earth, and is also characterized by its low price,easy derivatization and good biodegradable property. It is believed that derivatization is an important strategy to extend its applications. Cellulose carbonate is one of the most important classes of cellulose derivatives, as they have good potential in the field of green packaging film materials, thermoplastics, solid electrolyte, and so on. In this study,cellulose methyl carbonate has been synthesized successfully after the dissolution of cellulose in the novel 1,8-diazabicyclo[5.4.0]undec-7-ene（DBU）/DMSO/CO2 system followed by the addition of dimethyl carbonate via the insitu organocatalysis by DBU. The structure and thermal properties of the as prepared cellulose methyl carbonate were systematically characterized by NMR, FTIR, TGA and DSC. The results show that cellulose methyl carbonate with a DS of 1.09 was achieved after 12 h at 60 ℃ with molar ratio of dimethyl carbonate/AGU at 8：1. The DSC/TGA results show that the cellulose methyl carbonate with DS=1.09 has a Tgof 62.9 ℃ and starts thermal degradation at 305.5 ℃.