【作者】 刘崴崴；

【导师】 郁铭芳； 王华平；

【作者基本信息】 东华大学 ， 材料加工工程， 2008， 博士

【摘要】 离子液体是一种完全由离子（一般是有机阳离子,有机或者无机阴离子）构成的化合物。一般来说,熔点在100℃以下的熔融盐都可以称为离子液体。由于具有不挥发、热稳定性好、易于回收等优点,离子液体作为一种绿色溶剂被科学家们广泛关注,在化学合成、材料加工、电化学和化学分离等方面都有广泛的应用前景。本论文主要研究内容包括离子液体的合成与表征、离子液体/水溶液的物理性质、纤维素在离子液体中的溶解性和溶解过程、纤维素/离子液体浓溶液的流变特性以及纤维素/离子液体/水体系的溶液纺丝成型。首先,在实验室中合成了咪唑基离子液体1-丁基-3-甲基-咪唑氯化盐（[BMIM]Cl）、1-乙基-3-甲基-咪唑溴化盐（[EMIM]Br）、1-丁基-3-甲基-咪唑溴化盐（[BMIM]Br）、1-丁基-3-甲基-咪唑四氟硼酸盐（[BMIM]BF₄）和1-烯丙基-3-甲基-咪唑氯化盐（[AMIM]Cl）,并通过红外光谱、核磁共振和元素分析手段进行表征。结果表明,合成的产物就是纯度较高的离子液体。第二,研究了这几种离子液体水溶液的物理性质,包括在整个液态范围内的密度、折光指数、粘度、表面张力和电导率。根据所测量的数据计算出摩尔电导率、电离度,并与理想溶液体系、强电解质体系和弱电解质体系等进行比较,发现了离子液体在水中的聚集特性,并用激光光散射实验进行进一步的证明。根据实验结果,把离子液体/水溶液分为富水区、富离子区和富盐区,为离子液体回收等研究提供理论基础。第三,研究了不同的聚合物在各种离子液体中的溶解性,最终选择纤维素/离子液体[BMIM]Cl、[AMIM]Cl体系进行研究。测定了纤维素在[AMIM]Cl和[BMIM]Cl中的溶解度和溶解速率,结果发现,相同条件下,纤维素在[AMIM]Cl中具有较大的溶解度和较快的溶解速率;随着纤维素聚合度的增大,纤维素在离子液体中的溶解度降低。进一步通过WXRD、FTIR、¹³C-NMR和粘度法分析了溶解前后纤维素的化学结构、结晶结构和聚合度,结果表明,纤维素在离子液体中的溶解属于直接溶解,纤维素经离子液体溶解和再生后,晶型由纤维素Ⅰ转变为纤维素Ⅱ;溶解时间和温度对再生纤维素的聚合度有较大的影响,随着溶解时间的延长（5小时以上）和溶解温度的提高（100℃以上）,再生纤维素聚合度明显降低。第四,研究了纤维素/离子液体浓溶液的稳态和动态流变行为。在高剪切速率区,纤维素/离子液体溶液的表观粘度随着剪切速率的增大而降低,表现为切力变稀的流变行为。低剪切速率时,随着浓度的升高,纤维素/离子液体溶液的表观粘度增大,剪切速率增大到一定程度后,高浓度的纤维素/离子液体溶液反而具有较低的粘度。我们推测这可能是由于纤维素/离子液体溶液在剪切作用下,呈现出一种有序的超分子结构。纤维素/离子液体溶液的粘度随着温度的升高和聚合度的降低而减小,纤维素离子液体溶液的粘流活化能较大,温度对粘度的影响较大。纤维素溶液的弹性随着溶液浓度的增大、温度的降低和聚合度的增大而增大。稳态和动态流变数据的关联表明,在高剪切速率下,Cox-Merz规则不适用于纤维素/离子液体溶液体系。最后,以纤维素浆粕为原料,离子液体为溶剂,水为凝固剂,采用干喷湿纺技术成功地制备了纤维素纤维,并对纤维的纤度、取向度、断裂强度等结构性能进行了表征。这种纤维素纤维的截面接近于圆形,但是与莱赛尔纤维相比,表面还有较多的杂质和缺陷。所得纤维素纤维的断裂强度为1.83 cN/dtex,断裂伸长率为6.17%。更多还原

【Abstract】 Ionic liquids（ILs）are a class of compounds composed of organic cations and organic or inorganic anions.Broadly speaking,such organic compounds which melt at or below 100℃are considered ionic liquids. Because of its extremely low volatility,good thermal stability and it is easy to be recycled,some of the RTILs are promising environment-friendly solvents in a range of science and technology applications such as media for organic and inorganic reactions,materials processing,electrochemistry and chemical separation.The main content of this dissertation includes synthesis and characterization of ionic liquids,physical properties of aqueous solution of ionic liquids,dissolution of cellulose in ionic liquids,rheological behavior of cellulose/ionic liquids concentrated solutions and cellulose fiber processing of cellulose/water/ionic liquids system.Firstly,ionic liquids based on imidazolium,1-butyl-3-methylimidazolium chlorides（[BMIM]Cl）,1-ethyl-3-methylimidazolium bromides（[EMIM]Br）,1-butyl-3-methylimidazolium bromides（[BMIM]Br）,1-butyl-3-methylimidazolium tetrafluoroborate（[BMIM]BF₄）,1-allyl-3-methylimidazolium chlorides（[AMIM]Cl）was synthesized.They were characterized by FTIR,H¹-NMR and elementary analysis.The results show that the ionic liquids synthesized are object products.Secondly,physical properties of aqueous solutions of ionic liquids were studied.The measurements of densityρ,refractive index△n, viscosityη,specific conductanceκand surface tensionγwere made over the whole concentration range.The equivalent conductivity∧_m, ionization degree a were calculated.Comparing with the ideal solution, strong and weak electrolyte solution,the aqueous solution of ionic liquids showed a typical aggregation behavior.The experiment of laser light scattering proved this structure further more.The data and evolution of the solution will support the chemical engineering process such as recycle of ionic liquids.Thirdly,the solubility of different kinds of polymers in ionic liquids we synthesized was studied.According to the result,cellulose/ionic liquid [AMIM]Cl and[BMIM]Cl were chose to studied further.The solubility and the dissolution rate of cellulose in two ionic liquids were investigated. The results showed that the solubility and dissolution rate of cellulose in [AMIM]Cl was higher than in[BMIM]Cl.The solubility of cellulose in ionic liquids decreased with the increase of degree of polymerization （DP）.The crystalline structure,chemical structure and DP were characterized by X-Ray diffraction,FT-IR spectroscopy,¹³C-NMR spectroscopy and viscosity method.It was shown that ionic liquids are direct solvents for cellulose.The crystalline form of cellulose transforms from celluloseⅠto celluloseⅡafter regeneration from ionic liquids.The DP of cellulose decreased with increase of dissolution time and temperature.Fourthly,the steady and dynamic rheological behaviors were investigated.The cellulose/ILs solutions act as non-Newtonian fluids at high shear rate.With increasing concentration of the solution the apparent viscosity of solution increases at low shear rate while the viscosity of high concentration solutions was lower than that of low concentration at high shear rate.The viscosity increased with the increase of the DP of cellulose and decrease with the increase of temperature.The higher activation energy E_ηof cellulose/ionic liquids solution indicated that the shear viscosity of solution is more sensitive to temperature.The elasticity of cellulose solutions increased with increasing concentration and DP of cellulose while decreased with increasing temperature.The correlation of dynamic and steady flow viscosity revealed that the Cox-Merz rule did not fit these cellulose solutions at high shear rate.Lastly,the spinning experiment was conducted with the cellulose pulp as raw material,ionic liquids[BMIM]Cl as solvent and water as coagulation bath.The cellulose fiber was obtained by dry-jet wet-spinning technology.The structure and properties of the cellulose fiber were characterized.It is shown that the cross section of the fiber is circle and uniform.The tensile strength is 1.83 cN/dtex and the elongation at break is 6.17%.更多还原