一锅法合成纤维素乙酰丙酸混合酯

Cellulose Levulinate and Its Mixed Esters: One Pot Synthesis and Properties

在1,8-二氮杂二环十一碳-7-烯/二甲基亚砜/二氧化碳(DBU/DMSO/CO_(2))溶剂体系中,有机碱DBU既作为溶剂组分又作为催化剂可以实现纤维素的-OH与α-当归内酯(α-AL)的转酯化反应,制备高取代度、水溶性的纤维素乙酰丙酸酯.本文中以纤维素和α-AL、酸酐为原料,在该溶解体系中通过一锅法制备了纤维素乙酰丙酸混合酯.并系统地研究了反应时间、温度和α-AL/酸酐/-OH的摩尔比对单体转化率和取代度(DS)的影响.结果表明,在80℃下反应3 h,可以获得DS为3.0的纤维素乙酰丙酸混合酯.采用核磁谱图、傅里叶红外光谱、热重分析及示差扫描量热测试等研究纤维素乙酰丙酸混合酯的结构及热性能,结果表明材料具有良好的热稳定性,其玻璃化转变温度随着侧链烷基延长而降低.不仅如此,纤维素乙酰丙酸混合酯薄膜显示出良好的力学性能,纤维素乙酰丙酸乙酸酯(CLE-A)薄膜最大拉伸强度可达32.02 MPa,纤维素乙酰丙酸丁酸酯(CLE-B)薄膜断裂伸长率达到65.83%.

Due to the depletion of petroleum resources and the development of the emerging bioeconomy,the conversion of biomass into renewable chemicals for the preparation of advanced materials is believed to reduce modern society's dependence on fossil resources.The abundant hydroxyl groups on cellulose make it easy to modify,and it has the advantages of wide source,renewable,biodegradable and excellent bio-co MPatibility.Therefore,the preparation of novel cellulose-based functional materials based on cellulose skeleton has broad application prospects.In 1,8-diazabicyclo[5.4.0]undec-7-ene/dimethyl sulfoxide/CO_(2)(DBU/DMSO/CO_(2))solvent system,the transesterification between the hydroxyl groups of cellulose andα-angelicolactone(α-AL)were processed catalyzed by DBU.During this solvent system,the organic base DBU acted as solvent component and catalyst,the cellulose levulinate with high substitution degree(DS)and water solubility could be prepared successfully.In this study,cellulose,α-AL and acid anhydride are used as raw materials to prepare cellulose levulinic acid mixed ester by one-pot method in the same solvent system.The effects of reaction time,temperature and molar ratio ofα-AL/anhydride/-OH on monomer conversion rate and DS were studied systematically.The results showed that cellulose levulinic acid mixed ester with DS of 3.0 could be obtained after reaction at 80℃for 3 h.The structure and thermal properties of cellulose levulinic acid mixed ester were studied by magnetic resonance spectroscopy(1H-NMR,13C-NMR),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).And the relationship between structure and properties of cellulose levulinic acid mixed ester was studied in depth.The results showed that the material had good thermal stability and the glass transition temperature decreased with the extension of side chain alkyl.The mechanical properties of cellulose levulinic acid mixed ester films were investigated by stress-strain experiments.And the results showed that the maximum tensile strength of the CLE-A film reached 32.02 MPa,the elongation at break of CLE-B was 65.83%showing strong and tough characteristics.