角蛋白作为一种纤维状、可再生、可降解的蛋白质资源，来源相当丰富，其中羊毛中角蛋白的含量高达95 %。再生角蛋白是高性能生物医用材料和化妆品的优质原料，而每年有大量的羊毛被废弃，因此废弃羊毛中角蛋白资源的回收问题需要亟待解决。由于羊毛角蛋白大分子的结构复杂、分子内存在多种作用力，从羊毛中提取角蛋白难度较大。传统溶剂对角蛋白的结构和分子量具有严重的破坏作用，不利于再生角蛋白的高值化应用。近年来，离子液体作为一种绿色溶剂，在溶解生物高分子方面表现出良好的溶解性能，因此可将离子液体应用于羊毛角蛋白的溶解。另外，目前有关离子液体溶解角蛋白方面的报道并不多，且角蛋白的溶解机理尚不明确。因此，本研究主要通过系统考察离子液体的阴、阳离子结构对羊毛角蛋白溶解的影响以及对再生角蛋白结构和性质的影响，初步获得离子液体溶解角蛋白的规律，确定适合溶解羊毛角蛋白的离子液体，并进一步考察了离子液体角蛋白溶液的流变性质以及离子液体中水含量对离子液体溶解性能的影响，具体内容如下：（1） 对比1-丁基-3-甲基咪唑氯盐（[Bmim]Cl）、 四丁基季鏻氯盐（[P4444]Cl）、 四丁基季铵氯盐（[N4444]Cl）、1-丁基吡啶氯盐（[BPy]Cl）四种不同阳离子结构氯盐类离子液体；咪唑环上烷基侧链长度（1-烷基3-甲基咪唑氯盐 [Cnmim]Cl, n=2, 4, 6, 8）；以及1-乙基-3-甲基咪唑磷酸二甲酯（[Emim]DMP）、1-丁基-3-甲基咪唑乙酸（[Bmim]OAc）、三乙基甲基季铵磷酸二甲酯（[N2221]DMP）等不同阴离子结构的离子液体对羊毛角蛋白的溶解效果。在相同的溶解条件下，即溶解温度为130 oC，羊毛角蛋白与离子液体的质量比为8 wt%，对比了这些离子液体对羊毛角蛋白的溶解时间。得到阳离子的溶解能力大小顺序是 [Bmim]+> [P4444]+>> [N4444]+、[BPy]+；咪唑环上烷基侧链长度对离子液体的溶解效果没有明显影响；阴离子的溶解能力大小顺序是OAc-> DMP-> Cl-> FeCl4-> SCN-。另外，比较1-乙基-3-甲基咪唑氯（[Emim]Cl）中引入羟基官能团（[EtOHmim]Cl）对角蛋白的溶解的影响，发现羟基官能团的引入不利于角蛋白的溶解。（2） 对离子液体溶解后的角蛋白进行再生，并通过13C-NMR、FT-IR、XRD、SEM、TGA等手段对再生角蛋白的结构和性质进行表征。发现从这些离子液体中再生的角蛋白主要结构均保持完整，但二级结构发生了变化。其中[Bmim]OAc溶解再生的角蛋白二级结构变化最大，α-螺旋结构被破坏，含量降低到45.5%，热稳定性也明显降低，热分解温度为206 oC；而[Emim]DMP溶解再生的角蛋白二级结构与原羊毛角蛋白的相近，α-螺旋的含量为90.7 %，且再生角蛋白的稳定性有所提高，热分解温度为244 oC。因此，综合考虑溶解能力和再生角蛋白的结构和性质等因素，确定比较适合溶解羊毛角蛋白的离子液体是磷酸酯类，即 [Emim]DMP。（3） 对离子液体溶解后得到的角蛋白溶液进行流变性质测定，考察了温度以及角蛋白含量对溶液流变性质的影响。得到的结果是角蛋白含量越高，溶液的非牛顿指数越小，不利于纺丝；温度对角蛋白溶液流变性质的影响有极值，磷酸酯类的角蛋白溶液一般在40~60 oC可纺性更高。 （4） 考察了水含量（水：离子液体的摩尔比为0：1，0.2：1，0.4：1，0.6：1，0.8：1，1.0：1，2.0：1，3.0：1）对离子液体结构、性质以及羊毛角蛋白溶解的影响。通过对比羊毛角蛋白在不同水含量离子液体混合体系中的溶解时间，以及1H-NMR、DSC、密度粘度等手段对离子液体混合体系结构和性质的变化进行表征。最终得到：水分子的存在会降低离子液体的溶解效果，且随着水含量的增加，这种影响变得更明显，离子液体的溶解时间变化规律为先缓慢再明显的趋势。这主要是因为水分子在离子液体内的扩散并与离子液体形成氢键作用导致的。随着水分子的增多，水分子的扩散加快，其与离子液体形成的氢键增强，离子液体与角蛋白的氢键作用就会减弱，导致离子液体溶解性能降低。另外，对离子液体进行5次循环回收利用，回收的离子液体结构保持完整且溶解性能不变，5次回收率高达96 %。

Keratin is a kind of fibrous, renewable and biodegradable protein with wide resources. Wool consists of 95 % keratin. Keratin is a high quality raw material for biomedical materials and cosmetics. However，numbers of wool have been currently discarded every year, and the recycling of waste wool keratin resources needs to be solved urgently. While the interactions between keratin macromolecules is complex making it difficult to extract keratin from wool. Traditional solvents would seriously damage structure and molecular weight of keratin, not conducive to high value of application of regenerated keratin. Since ionic liquids as green solvents, have exhibited excellent solubility in the dissolution of biological macromolecules, so it will be better for dissolving wool keratin by ionic liquids. However, there are very few reports about dissolving keratin by ionic liquids and the dissolution mechanism of keratin is also unclear. Therefore, our work is to investigate the effects of ionic liquids structures on the dissolving capability of wool keratin and structures-properties of regenerated keratin. Based on that, we would find the dissolution law of ionic liquids and optimal ionic liquid for dissolving wool keratin. Moreover, we have investigated rheological properties of keratin/ionic liquids solution and the effect of water concentration on the solubility of ionic liquids. Details are as following:(1) This work has investigated the dissolving capability of ionic liquids with various cations (1-butyl-3-methylimidazolium chloride ([Bmim]Cl), tetrabutylphosphonium chloride ([P4444]Cl), tetrabutylammonium chloride ([N4444]Cl), 1-butylpyridinium chloride ([BPy]Cl)) and different anions (1-ethyl-3-methylimidazolium dimethylphosphate ([Emim]DMP), 1-butyl-3-methylimidazole acetate ([Bmim]OAc), triethylmethylammon- ium dimethylphosphate ([N2221]DMP)). Meanwhile, the effects of side chain lengths of imidazole cation ([Cnmim]+, n=2, 4, 6, 8) on the dissolving capability are also investigated. This paper has studied the dissolution time of ionic liquids with the same temperature 130 oC and mass ratio 8 wt%. It is found that the dissolving capability of cations follow the decreasing order of [Bmim]+> [P4444]+> >[N4444]+, [BPy]+, and the anions follow the decreasing order of OAc-> DMP-> Cl-> FeCl4-> SCN-. While side chains lengths of imidazole cation have little effect on the dissolving capability. In addition, the effect of hydroxyl group is also investigated, such as [EtOHmim]Cl, and the results show that the introduction of hydroxyl groups is not conducive to the dissolution of wool keratin.(2) The structures and properties of regenerated keratin are characterized by 13C-NMR, FT-IR, XRD, SEM, TGA, et al. The results show the main structures of regenerated keratin are intact, but the secondary structures have changed. The σ-helix structure of regenerated keratin from [Bmim]OAc has been destroyed decreasing to 45.5 %, the thermal stability of regenerated keratin has reduced and thermal decomposition temperature is 206 oC. The secondary structures of regenerated keratin from [Emim]DMP is similar to raw material, the content of σ-helix structure is 90.7 %, thermal stability has improved and thermal decomposition temperature is 244 oC. Therefore, comprehensive consideration of dissolving capability and properties of regenerated keratin, dimethylphosphate ionic liquids ([Emim]DMP) are chosen as the optimal ionic liquids for dissolving wool keratin.(3) Rheological properties of keratin/ionic liquids solutions are investigated by changing test temperature and keratin concentration. The results show that the higher the keratin concentration is, the smaller the non-Newton index is, which is not conducive to the spinning. It also has found that temperature between 40~60 o C is more advantage to spinning for keratin/dimethylphosphate solutions.(4) The effect of water concentration (between 0:1 to 3:1) on the dissolving capability of ionic liquids is studied. Compared with the dissolution time and structures-properties of ionic liquids with different water concentrations, it has been found that the presence of water molecules will reduce the dissolving capability of ionic liquids, and variation of dissolution time is slow first, then changes obviously with the increase of water content. It mainly because of the diffusion of water molecules in ionic liquids and forming hydrogen bonds with ionic liquid. With the increasing of water molecules, the diffusion of water molecules in ionic liquids speed up, the numbers of hydrogen bonds increase and it will prevents ionic liquids forming hydrogen bonding with keratin, reducing the dissolving capability of ionic liquids. In addition, 5 times recycle and characterization of the structure of ionic liquids show that dimethylphosphate ionic liquids have exhibited good performance with recycling rate as high as 96 %.