LiCl/DMAc溶剂中活化处理对不同类型纤维素静电纺丝效果的影响

Study on electro⁃spin performance of different types of cellulose by activation in the solvent of LiCl/DMAc

纤维素纳米纤维在生物医用产品、增强材料、过滤吸附材料、柔性电极材料和储能器件等领域具有广阔的应用前景。静电纺丝法是目前能直接且连续制备微纳米纤维的主要方法之一,由于纤维素中极强的氢键网络导致的高结晶度,使得直接使用纤维素静电纺丝制备纳米纤维较难。笔者以微晶纤维素、纸浆纤维素为研究对象,通过氯化锂/二甲基乙酰胺(LiCl/DMAc)溶剂体系溶解并进行活化处理,加入不同含量聚丙烯腈(PAN)对纤维素进行静电纺丝制备纤维素纳米纤维,探究纤维素类型、N,N-二甲基甲酰胺(DMF)活化处理前后、PAN加入量对纤维素溶解性、纺丝液性参数和纺丝效果影响。结果表明:DMF活化处理可有效提升纤维素在LiCl/DMAc溶剂体系中的溶解性,在相同溶解温度下获得更加均匀透明的纤维素溶液。在该溶剂体系下,纺丝液黏度、电导率和表面张力分别高于1 300 mPa·s、2 000μs/cm和34.5 mN/m,可获得连续的电纺纤维素纳米纤维。活化微晶纤维素纳米纤维膜比活化纸浆纤维素纳米纤维膜表面更光滑且纤维直径分布更均匀。活化微晶纤维素与PAN质量比为2∶8时可获得表面光滑无珠状物,纤维均一程度高,直径分布小(185~245 nm)的纤维素纳米纤维膜。

Cellulose is the most abundant biomass resource on the earth.It is one of the most important alternative raw materials for replacing petroleum-based polymer materials due to its excellent biocompatibility,biodegradability and sustainability.The nanofibers produced by electrospinning technology have a great potential in the applications of biomedical products,reinforcing fillers,filter and adsorption materials,flexible electrode materials and energy storage devices with the advantages of large specific surface area,well fiber network connectivity and excellent mechanical properties.Electrospinning is currently the only way that can directly and continuously produce the micro or nanofibers.Generally,it is difficult to prepare the cellulose nanofibers directly using the electrospinning method due to the high crystallinity caused by the extremely strong hydrogen bonding network in cellulose molecular chains.Usually,the cellulose is derivatized and then electro-spun to obtain nanofibers.Lithium chloride/N,N-dimethylacetamide(LiCl/DMAc)solvent system can dissolve different kinds of cellulose with relatively large content without other side reactions.In order to directly obtain the cellulose nanofiber with good quality and small diameter distribution by electrospinning,in this study,the microcrystalline cellulose and pulp cellulose firstly were pretreated by the N,N-dimethyl-Formamide(DMF)activation,then were dissolved in the LiCl/DMAc solvent system and electro-spun by adding different contents of Polyacrylonitrile(PAN).The effects of cellulose type,activation treatment,addition amount of PAN on the cellulose dissolution and performance of electro-spun nanofibers were comparatively investigated.The DMF activation can effectively improve the solubility of cellulose in the LiCl/DMAc solvents and obtain a more uniform and transparent cellulose solution.The continuous electro-spun cellulose nanofibers can be obtained when the viscosity,electrical conductivity and surface tension of spinning solution were over 1300 mPa·s,2000μs/cm and 34.5 mN/m,respectively,in the LiCl/DMAc solvent.The electro-spun nanofiber membranes prepared using the activated microcrystalline cellulose were smoother with a more uniform distribution of nanofiber diameter than the activated pulp cellulose.When the ratio of activated microcrystalline cellulose and PAN was 2∶8,the optimum cellulose nanofiber membrane with uniform nanofibers ranging from 185 to 245 nm can be obtained.This can provide important data support and preliminary theoretical analysis for the direct construction of high-quality cellulose nanofibers by electrospinning.