【摘要】：纖維素是現(xiàn)如今最為豐富的可再生聚合物資源。然而,由于纖維素分子間和分子內(nèi)強氫鍵作用的限制,使得纖維素很難溶解于水和有機溶劑,也不能被熔融,這嚴重阻礙了它以各種形式進行非衍生化和衍生化的均相反應(yīng)[1]。對于纖維素的改性和利用,一個關(guān)鍵的問題是如何實現(xiàn)纖維素的成功溶解�？捎糜诶w維素溶解的體系相當有限,離子液體(IL)體系是少數(shù)能直接溶解纖維素的溶劑,已被廣泛研究。但其價格昂貴,溶解效率低。本實驗選擇將環(huán)狀碳酸丙烯酯(PC)與離子液體1-乙基-3-甲基咪唑醋酸鹽(EmimOAc)混合,構(gòu)建了纖維素直接溶解與利用的新型混合體系,研究了溶液性質(zhì)及用于材料制備的可行性,實驗結(jié)果如下:1.基于EmimOAc/PC體系,研究了該體系的溶解能力及溶液性質(zhì)。當反應(yīng)溫度為80℃時,混溶劑中只需離子液體摩爾含量χIL=0.3的EmimOAc,反應(yīng)20 min,能實現(xiàn)15%微晶纖維素的溶解。使用溶致變色的Reichardt’s染料進行了溶劑極性參數(shù)測定,結(jié)果表明,將EmimOAc加入PC后可以顯著提高PC的極性。當χIL增加到0.4時,ET(30)的值可從47.501增加到50.132。2.基于EmimOAc/PC體系,用得到的纖維素溶液成功制備得到的非衍生化的纖維素凝膠。對凝膠的結(jié)構(gòu)和形貌的觀測結(jié)果表明,再生后的纖維素化學結(jié)構(gòu)未發(fā)生變化,晶型結(jié)構(gòu)由纖維素I型轉(zhuǎn)變?yōu)槔w維素II型。將纖維素含量為4%的水凝膠恒溫靜置,其相應(yīng)的平衡溶脹率可達2066%,這種纖維素水凝膠溶脹過程中不完全遵循Fickian擴散原理,其載藥率為0.24%。對其進行冷凍解凍循環(huán)后,所得凝膠的透過率最高可達91.0%,加水再生后凝膠的熱穩(wěn)定性能略有提高。3.基于EmimOAc/PC體系,溶解10%的纖維素后,使用新戊酸乙烯酯、苯甲酸乙烯酯、月桂酸乙烯酯與纖維素溶液進行轉(zhuǎn)酯化反應(yīng)。當反應(yīng)溫度為80℃,反應(yīng)4 h可以得到取代度為1.29的纖維素新戊酸酯�？傊�,本研究構(gòu)建了EmimOAc/PC纖維素直接溶解體系,制備了纖維素凝膠和纖維素酯,為纖維素均相的衍生化和非衍生化提供了一種新的思路。
[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，

本文編號：2209822