Department of Chemistry, Wuhan University, Wuhan 430072, China.
Carbohydr Polym. 2013 Feb 15;92(2):1315-20. doi: 10.1016/j.carbpol.2012.10.004. Epub 2012 Oct 12.
Cellulose has been demonstrated to be dissolved in 7 wt% NaOH/12 wt% urea aqueous solution pre-cooled to -12 °C, as a result of the formation of inclusion complexes (ICs) associated with cellulose, urea and NaOH. However, this cellulose solution is meta-stable, and IC aggregate could form. In this work, the influences of solvent composition and temperature on the stability of the cellulose ICs in NaOH/urea aqueous solvent system were investigated by dynamic and static light scattering. The stability of cellulose ICs in NaOH/urea aqueous solvent system was firstly enhanced and then lessened with NaOH concentration increasing. The addition of urea slightly enhanced the stability of ICs. Furthermore, the solvent composition had been optimized to reduce the aggregation phenomenon of ICs. The proportion of single cellulose ICs in 9 wt% NaOH/13 wt% urea system increased to 0.96, indicating a stable and better dispersion system of the cellulose ICs. Moreover, temperature exhibited great effect on the IC stability. The molecular weight of cellulose in 9 wt% NaOH/13 wt% urea system at 10 °C reached a low value about 7.6×10(4) g/mol and the single cellulose ICs were predominant species in this case. This work provided a better pathway to characterize the dilute cellulose in NaOH/urea aqueous solution, in which the single cellulose ICs were predominant species.
纤维素已被证明可溶解于预先冷却至-12°C 的 7wt%NaOH/12wt%尿素水溶液中，这是由于形成了与纤维素、尿素和 NaOH 相关的包合物（IC）。然而，这种纤维素溶液是亚稳的，IC 聚集体可能会形成。在这项工作中，通过动态和静态光散射研究了溶剂组成和温度对 NaOH/尿素水溶剂体系中纤维素 IC 稳定性的影响。随着 NaOH 浓度的增加，NaOH/尿素水溶剂体系中纤维素 IC 的稳定性先增强后减弱。尿素的加入略微增强了 IC 的稳定性。此外，还优化了溶剂组成以减少 IC 聚集体的聚集现象。在 9wt%NaOH/13wt%尿素体系中，单一纤维素 IC 的比例增加到 0.96，表明纤维素 ICs 的分散体系稳定且更好。此外，温度对 IC 稳定性有很大影响。在 10°C 下，9wt%NaOH/13wt%尿素体系中纤维素的分子量达到约 7.6×10(4)g/mol 的低值，并且在这种情况下，单一纤维素 IC 是主要物质。这项工作为在 NaOH/尿素水溶液中表征稀纤维素提供了更好的途径，其中单一纤维素 IC 是主要物质。
