Gavillon Roxane, Budtova Tatiana
Centre de Mise en Forme des Matériaux, Ecole des Mines de Paris, UMR CNRS 7635, BP 207, 06904 Sophia-Antipolis, France.
Biomacromolecules. 2007 Feb;8(2):424-32. doi: 10.1021/bm060376q.
The regeneration kinetics of cellulose from cellulose--NaOH--water gels immersed in a nonsolvent bath is studied in detail. Cellulose concentration, bath type, and temperature were varied, and diffusion coefficients were determined. The results were compared with data measured and taken from the literature on the regeneration kinetics of cellulose from cellulose--N-methylmorpholine-N-oxide (NMMO) monohydrate solutions. Different theories developed for the transport behavior of solutes in hydrogels or in porous media were tested on the systems studied. While the diffusion of NaOH from cellulose--NaOH--water gels into water has to be described with "porous media" approaches, the interpretation of NMMO diffusion is complicated because of the change of NMMO's state during regeneration (from solid crystalline to liquid) and the high concentration of NMMO in the sample. The activation energies were calculated from diffusion coefficient dependence on temperature for both systems and compared with the ones obtained from the rheological measurements. The activation energy of cellulose--NaOH--water systems does not depend on cellulose concentration or the way of measurement. This result shows that whatever the system is, pure NaOH--water solution, cellulose--NaOH--water solution, or cellulose--NaOH--water gel, it is NaOH hydrate with or without cellulose in solution, which is moving in the system. The swelling of cellulose in different nonsolvent liquids such as water or different alcohols during regeneration was investigated and interpreted using the Hildebrand parameter.
详细研究了纤维素 - NaOH - 水凝胶浸入非溶剂浴中时纤维素的再生动力学。改变了纤维素浓度、浴液类型和温度，并测定了扩散系数。将结果与从文献中获取的关于纤维素从纤维素 - N - 甲基吗啉 - N - 氧化物（NMMO）一水合物溶液中再生动力学的数据进行了比较。针对溶质在水凝胶或多孔介质中的传输行为所提出的不同理论，在本研究体系中进行了验证。虽然NaOH从纤维素 - NaOH - 水凝胶向水中的扩散必须用“多孔介质”方法来描述，但由于NMMO在再生过程中的状态变化（从固态晶体变为液态）以及样品中NMMO的高浓度，NMMO扩散的解释较为复杂。计算了两个体系中扩散系数对温度的依赖性所对应的活化能，并与流变学测量得到的活化能进行了比较。纤维素 - NaOH - 水体系的活化能不取决于纤维素浓度或测量方式。该结果表明，无论体系是纯NaOH - 水溶液、纤维素 - NaOH - 水溶液还是纤维素 - NaOH - 水凝胶，在体系中移动的都是溶液中含有或不含有纤维素的NaOH水合物。利用希尔德布兰德参数研究并解释了再生过程中纤维素在不同非溶剂液体（如水或不同醇类）中的溶胀情况。
