纤维素凝胶的制备及性能研究
发布时间：2018-08-28 15:29
【摘要】：纤维素是现如今最为丰富的可再生聚合物资源。然而,由于纤维素分子间和分子内强氢键作用的限制,使得纤维素很难溶解于水和有机溶剂,也不能被熔融,这严重阻碍了它以各种形式进行非衍生化和衍生化的均相反应[1]。对于纤维素的改性和利用,一个关键的问题是如何实现纤维素的成功溶解。可用于纤维素溶解的体系相当有限,离子液体(IL)体系是少数能直接溶解纤维素的溶剂,已被广泛研究。但其价格昂贵,溶解效率低。本实验选择将环状碳酸丙烯酯(PC)与离子液体1-乙基-3-甲基咪唑醋酸盐(EmimOAc)混合,构建了纤维素直接溶解与利用的新型混合体系,研究了溶液性质及用于材料制备的可行性,实验结果如下:1.基于EmimOAc/PC体系,研究了该体系的溶解能力及溶液性质。当反应温度为80℃时,混溶剂中只需离子液体摩尔含量χIL=0.3的EmimOAc,反应20 min,能实现15%微晶纤维素的溶解。使用溶致变色的Reichardt’s染料进行了溶剂极性参数测定,结果表明,将EmimOAc加入PC后可以显著提高PC的极性。当χIL增加到0.4时,ET(30)的值可从47.501增加到50.132。2.基于EmimOAc/PC体系,用得到的纤维素溶液成功制备得到的非衍生化的纤维素凝胶。对凝胶的结构和形貌的观测结果表明,再生后的纤维素化学结构未发生变化,晶型结构由纤维素I型转变为纤维素II型。将纤维素含量为4%的水凝胶恒温静置,其相应的平衡溶胀率可达2066%,这种纤维素水凝胶溶胀过程中不完全遵循Fickian扩散原理,其载药率为0.24%。对其进行冷冻解冻循环后,所得凝胶的透过率最高可达91.0%,加水再生后凝胶的热稳定性能略有提高。3.基于EmimOAc/PC体系,溶解10%的纤维素后,使用新戊酸乙烯酯、苯甲酸乙烯酯、月桂酸乙烯酯与纤维素溶液进行转酯化反应。当反应温度为80℃,反应4 h可以得到取代度为1.29的纤维素新戊酸酯。总之,本研究构建了EmimOAc/PC纤维素直接溶解体系,制备了纤维素凝胶和纤维素酯,为纤维素均相的衍生化和非衍生化提供了一种新的思路。
[Abstract]:Cellulose is the most abundant renewable polymer resource nowadays. However, due to the restriction of strong hydrogen bonding between and within molecules, cellulose is difficult to dissolve in water and organic solvents and cannot be melted, which seriously hinders its homogeneous reactions in various forms of non-derivation and derivation [1]. A key problem for cellulose modification and utilization is how to successfully dissolve cellulose. The system that can be used to dissolve cellulose is very limited. The ionic liquid (IL) system is a few solvents which can dissolve cellulose directly and has been widely studied. But its price is expensive, dissolving efficiency is low. In this experiment, the cyclic propylene carbonate (PC) was mixed with ionic liquid 1-ethyl-3-methylimidazole acetate (EmimOAc) to form a new mixed system for the direct dissolution and utilization of cellulose. The properties of the solution and the feasibility of its application in the preparation of the material were studied. The results of the experiment are as follows: 1. Based on the EmimOAc/PC system, the solubility and solution properties of the system were studied. When the reaction temperature is 80 鈩，
本文编号：2209822
[Abstract]:Cellulose is the most abundant renewable polymer resource nowadays. However, due to the restriction of strong hydrogen bonding between and within molecules, cellulose is difficult to dissolve in water and organic solvents and cannot be melted, which seriously hinders its homogeneous reactions in various forms of non-derivation and derivation [1]. A key problem for cellulose modification and utilization is how to successfully dissolve cellulose. The system that can be used to dissolve cellulose is very limited. The ionic liquid (IL) system is a few solvents which can dissolve cellulose directly and has been widely studied. But its price is expensive, dissolving efficiency is low. In this experiment, the cyclic propylene carbonate (PC) was mixed with ionic liquid 1-ethyl-3-methylimidazole acetate (EmimOAc) to form a new mixed system for the direct dissolution and utilization of cellulose. The properties of the solution and the feasibility of its application in the preparation of the material were studied. The results of the experiment are as follows: 1. Based on the EmimOAc/PC system, the solubility and solution properties of the system were studied. When the reaction temperature is 80 鈩，
本文编号：2209822
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