温度和pH双重敏感型聚氨酯膜的制备及其可控分离特性与机理

The polyurethane membrane materials with thermal and pH sensitive properties have been widely used in the fields of collagen purification, cell separation, antibiotic purification and so on. Currently, the surface grafting technology is adopted in the preparation of thermal and pH sensitive polyurethane membrane materials. However, due to the limitation of the grafting monomers and grafting technology, the control of the thermal and pH responsive properties of polyurethane membrane has been severely affected. In this project, a new method for the preparation of thermal and pH sensitive polyurethane membrane materials would be proposed by the directional block copolymerization. The phase transition temperature of the soft segment of polyurethane membrane will be set in the range from 0 to 40℃ and the acid/alkali functional groups will be introduced in the side chain of hard segment. The relationship of microstructure properties of the polyurethane membrane with the temperature and pH value will be analyzed. The regulatory mechanism of temperature and pH responsive threshold of membrane will be explored. The mechanism of selective separation of collagen with different sizes by membrane will be studied. A new method for the preparation of thermal and pH sensitive membrane materials and the basic theory of controllable separation will be build. This study will provide a new method for the development of novel intelligent polymer membrane materials and its application in controllable separation.

具有温度和pH双重敏感特性的聚氨酯膜材料，已在胶原蛋白纯化、细胞分离、抗生素精制等领域显示了广阔的应用前景。目前，温度和pH双重敏感型聚氨酯膜材料的制备多采用表面接枝技术。然而，由于受到接枝单体和接枝技术的限制，温度和pH双重敏感型聚氨酯膜材料的开发与功能应用受到了严重的影响。本课题拟运用定向嵌段共聚技术，将聚氨酯软段的相态转变温度设置在0～40℃，且在硬段侧链中引入适量的易离子化的酸碱官能团，探索温度和pH双重敏感型聚氨酯膜材料制备的新方法；系统研究膜材料的微观结构随环境温度和pH值的响应规律，探究膜材料的温度和pH响应特性的调控机制；研究膜对胶原蛋白提取液中不同尺寸物质选择性分离的机理，构建温度和pH双重敏感型聚氨酯膜的可控分离基本理论。该研究将为新型智能高分子膜材料的开发及其可控分离应用提供新思路。

具有温度和pH双重敏感特性的聚氨酯膜材料在胶原蛋白纯化、物料分离等领域具有广阔的应用前景。本项目采用定向嵌段共聚技术，在第一步中加入聚酯（醚）二元醇后作为软段提供聚氨酯材料的温度敏感特性，第二步中加入低分子量的二元醇（扩链剂）的酸（碱）官能团提供聚氨酯材料的pH 敏感特性，合成了MDEA型温度和pH双重敏感特性的聚氨酯材料，该聚氨酯具有典型的三维网状结构，有助于提高聚氨酯的平衡溶胀度和对酸性大红GR的平衡吸附量以及去除率。系统研究了该聚氨酯材料随环境温度和pH值的响应规律，当温度和初始pH值较低（T=25 ℃，pH=2.5）时，聚氨酯对酸性大红GR的吸附效果最佳，平衡吸附量和去除率可达29.66mg/g和99.4%；当温度和pH值较高（T=60 ℃，pH=11.5）时，聚氨酯对酸性大红GR的吸附效果较差，体现出了温度和pH敏感特性，实现了聚氨酯对水体中酸性大红GR的可控分离。利用湿法转相技术，通过添加TPU将上述聚氨酯制备成温度和pH敏感性聚氨酯膜材料，选用K+、甘氨酸、BSA为模拟物质，分别考察了温度与pH敏感特性聚氨酯膜对不同尺寸的物质的可控分离性能的影响。结果表明，甘氨酸的渗透率受外部温度的影响，但对K+和BSA的渗透率则变化不明显，说明通过外界温度变化能够调控聚氨酯膜的渗透性能与阻滞性能，从而实现可控分离。在不同pH条件下，K+能够轻易地通过聚氨酯膜完成渗透，BSA由于较大分子尺寸而无法透过聚氨酯膜，甘氨酸则受初始pH值的聚氨酯膜的渗透率受影响较大，这说明调节初始pH值对甘氨酸可实现有效的调控作用。本项目系统地研究聚氨酯膜材料的微观结构、孔洞尺寸、透过通量、分离选择性等随温度、pH变化的规律，获得了温度和pH双重敏感型聚氨酯膜的可控分离基本理论，为胶原蛋白等混合物质体系的可控分离提供了新思路。