Phase separation of aqueous solution of methylcellulose
Phase separation of aqueous solution of methylcellulose
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DOI：
10.1007/s003960050116
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发表时间：
1997-06-01
影响因子：
2.4
通讯作者：
Axelos, MAV
中科院分区：
文献类型：
--
作者：
Chevillard, C;Axelos, MAV
用温度浊点法目测，甲基纤维素在水溶液中的共存相曲线属于低临界溶液温度(LCST)型。流变动力学测试表明，存在三个凝胶区。凝胶(I)在低浓度和低温下定位在均相中，是一种非常弱的凝胶，其中交联链是由于主链上最疏水的区域：三甲基嵌段之间的两两疏水作用所致。第二种凝胶(II)出现在高浓度区，低于LcST，这可能归因于起交联点作用的微晶的形成。第三种凝胶伴随着微相分离。在这些混浊的凝胶中，水合作用随着时间的推移发展缓慢：温度越高，浓度越低，水合作用越快。在三个溶胶-凝胶转变附近，观察到损耗和存储模数与频率的幂函数关系，粘弹性指数Delta(G‘类似于G’‘，类似于omega(Delta))分别为0.76和0.8，高浓度时达到1。
As we determined visually by the temperature cloud point method, the coexistence phase curve of methylcellulose in aqueous solution belongs to the LCST (low critical solution temperature) type. Rheological dynamic measurements reveal the existence of three gel domains. The gel (I) localized in the homogeneous phase at low concentration and low temperature, is a very weak gel, where the cross-links are attributed to pairwise hydrophobic interactions between the most hydrophobic zones of the backbone: the trimethyl blocks. The second gel (II) was revealed in the high concentration regime and below the LCST, it may be attributed to the formation of crystallites which play the role of cross-linking points. The third gel was concomitant to the micro-phase separation. In these turbid gels, syneresis develops slowly with time: the higher the temperature and the lower the concentration: the faster the syneresis. Near the three sol-gel transitions, a power law frequency dependence of the loss and storage moduli was observed and the viscoelastic exponent Delta(G' similar to G '' similar to omega(Delta)) was found to be 0.76 and 0.8 and to reach 1 at high concentration.