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Chemical modification of cellulose by TEMPO-mediated oxidation

通过 TEMPO 介导的氧化对纤维素进行化学改性

基本信息

批准号：
15380116
负责人：
ISOGAI Akira
金额：
$ 8.96万
依托单位：
THE UNIVERSITY OF TOKYO
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Details about chemical modifications of native cellulose by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation were studied in this project. Carboxylate and aldehyde groups introduced into native celluloses by the TEMPO-mediated oxidation were determined in terms of oxidation conditions such as reaction time and the amount of sodium hypochloride added as a co-oxidant to the cellulose/water suspensions. Linter cellulose was used to begin with as the starting native cellulose. Microscopic observation showed that the original fibrous morphology of linter cellulose was unchanged before and after the TEMPO-mediated oxidation, and recovery ratios of the TEMPO-oxidized linter cellulose were almost 100% by filtration. Carboxylate and aldehyde contents in the TEMPO-oxidized linter cellulose reached to 35 times and 1000 times as much as those of the original linter cellulose, respectively. Crystallinity and crystal size of the native cellulose I structure of the original lint … More er cellulose were unchanged even after the TEMPO-mediated oxidation, which was proved by X-ray diffraction and solid-state ^<13>C-NMR analyses of the oxidized products. Thus, TEMPO-mediated oxidation allows to introduce carboxylate and aldehyde groups only on the surface of cellulose microfibrils quite efficiently, maintaining the microfibril structure of native cellulose. Such surface-modified celluloses prepared by the TEMPO-mediated oxidation showed specific adsorption behavior of metal ions. Especially, carboxylate ions in the TEMPO-oxidized cellulose form metal salt structures at molar ratio of 1:1 with either calcium, silver or lead ion. When the TEMPO-mediated oxidation was applied to wood chemical pulp, bacterial cellulose, tunicate cellulose, ramie cellulose and wood holocellulose, each cellulose had characteristic carboxylate and aldehyde contents even under the same TEMPO-mediated oxidation conditions, depending on the original cellulose used. Particularly, we have succeeded in preparation of transparent cellulose microfibril dispersion gels by TEMPO-mediated oxidation under quite mild conditions followed by mechanical treatments. These transparent gels consisted of independently-dispersed cellulose microfibrils with nano-size width in water, differing from the conventional cellulose microcrystals dispersed in water or cellulose derivatives molecularly dissolved in water, and thus behaved quite high viscosities even at low consistencies. These new cellulose nano-materials dispersed in water are expected to show some unique functionalities. Less

本课题研究了2，2，6，6-四甲基哌啶-1-氧自由基（克里思）对天然纤维素的化学改性。通过TEMPO介导的氧化引入天然纤维素中的羧酸根和醛基根据氧化条件如反应时间和作为共氧化剂添加到纤维素/水悬浮液中的次氯酸钠的量来确定。棉绒纤维素开始用作起始天然纤维素。显微镜观察表明，TEMPO介导的氧化前后短绒纤维素的原始纤维形态没有变化，过滤回收率几乎为100%。TEMPO氧化后的纤维素中羧酸根和醛的含量分别达到原纤维素的35倍和1000倍。天然纤维素的结晶度和晶体尺寸 ...更多信息通过对氧化产物的X-射线衍射和固态1H-NMR分析证明，即使在TEMPO介导的氧化后，纤维素也没有变化<13>。因此，TEMPO介导的氧化允许仅在纤维素微纤丝的表面上相当有效地引入羧酸根和醛基，保持天然纤维素的微纤丝结构。通过TEMPO介导的氧化制备的这种表面改性纤维素对金属离子表现出特异性吸附行为。特别地，TEMPO氧化纤维素中的羧酸根离子与钙、银或铅离子以1：1的摩尔比形成金属盐结构。当TEMPO介导的氧化应用于木材化学纸浆，细菌纤维素，被囊纤维素，苎麻纤维素和木材综纤维素，每种纤维素具有特征的羧酸根和醛含量，即使在相同的TEMPO介导的氧化条件下，取决于所使用的原始纤维素。特别是，我们已经成功地制备透明的纤维素微纤维分散凝胶TEMPO介导的氧化在相当温和的条件下，然后通过机械处理。这些透明凝胶由在水中独立分散的具有纳米尺寸宽度的纤维素微纤丝组成，不同于分散在水中的常规纤维素微晶或分子溶解在水中的纤维素衍生物，因此即使在低粘度下也表现出相当高的粘度。这些分散在水中的新型纤维素纳米材料有望显示出一些独特的功能。少