纤维素LiCl/DMAc体系的溶液特征

Solution characteristics of cellulose in lithum chloride and N, N-dimethylacetamide

本文研究了纤维素LiCl／DMAc体系的溶液特征。实验结果证明该体系具有良好的时间稳定性和热稳定性，能在常温下近30天内没有明显的粘度降低；在100℃高温下，4h不降解。同时测定了溶液的特性粘数和Huggins常数，Huggins常数在0．4～0．6之间，对比纤维素的铜乙二胺（Cuen）溶液，发现特性粘数[η]LICI/DMAc＞[η]Cuen，无扰尺寸ALiCi／DMAc＞ACuen，可见在LiCl／DMAc体系中，溶剂与纤维素分子表现出更强的相互作用力，分子链充分伸展。该体系的特性粘数、粘度常数不仅与温度、溶剂有关，而且是LiCl浓度的函数，具有与聚电解质溶液相类似的性质。这可能是因为纤维素分子链上的H质子和溶液中的Cl-离子相互作用，而使纤维素分子带上部分电荷，相互排斥而引起的。因此利用M－H方程测分子量，粘度常数的确立必须考虑诸多因素的影响，否则会导致分子量的高估。

The solution characteristies of cellulose in mixtures of lithum chloride (LiCl)and N, N-dimethylacetamide (DMAc) are discussed. The effects of aging and heat on the viscosity of the solution were studied, No obvious loss in viscosity was observed af ter about 30 days at 30℃ and no degradation for 4hrs even at 100℃. Viscometer was used for measurement of the intrinsic viscosity number and Huggins constant K (K =0. 4~0. 6). In contrast to cellulose solution in Cuen, we found that [η]LiCl/DMAc> [η]Cuen,ALiCl/DMAc>ACuen (A means the undisturbed dimension). This means more intense interaction between macromolecular chains and molecule of the solvent LiCl/DMAc and the more intense interaction produces larger end distance of the chains. Similar to polyelectrolyte, the intrinsic viscosity number and viscosity parameter is affected by not only temperature and solvent but also the concentration of LiCl, which may be due to the repulsive interactions of the chloride anions associated with backbone. In all, the M-H equation application must depended on many factors, or molecule weight may be overestimated.