聚乳酸离子凝胶结构的形成及其调制

发布时间：2018-01-02 01:09

  本文关键词：聚乳酸离子凝胶结构的形成及其调制　出处：《东华理工大学》2016年硕士论文　论文类型：学位论文

  更多相关文章： 聚乳酸 离子凝胶 环带球晶 高模量 多孔膜

【摘要】：聚乳酸(PLA)又称聚丙交酯,是由乳酸分子缩聚而成的聚酯族可降解高分子材料,可以由玉米、土豆等再生资源发酵而来,具有良好的机械性能且易加工成民生用品,因而越来越受到广泛关注。聚乳酸离子凝胶是聚乳酸分子所形成的网状结构间隙中充满离子液体介质的一类凝胶。离子液体的不挥发性、高离子电导率赋予了聚乳酸离子凝胶较好的电化学性能,同时聚乳酸使离子凝胶具备了生物相容性,两者结合兼具电性能,机械强度,生物性能,在生物材料和电化学智能材料领域有着广泛的应用前景。本文阐述了聚乳酸离子凝胶中环带球晶及形成机理,提高聚乳酸离子凝胶模量的物理改性方法,以及相分离法制备聚乳酸离子凝胶纳孔膜等三个方面,分别从原理、方法和应用进行了深入研究,为聚乳酸离子凝胶制备和应用提供了实验依据。主要研究结果如下:(1)一般情况下聚乳酸不易形成环带球晶,而与离子液体共混后可形成环带球晶,通过观察聚乳酸离子凝胶的结晶形貌,提出了影响环带球晶形成的因素,即链解缠结。离子液体的存在降低了非晶层的粘度和聚乳酸的链缠结,有利于片晶扭转进而在混合物中形成环带球晶。另一方面混合物中环带球晶的形成依赖于结晶温度和离子液体的含量,并且与片晶扭转的不平衡应力的变化密切相关。(2)通常离子凝胶的电导率与模量成反比,电导率高时其凝胶的机械强度往往非常弱,而在电化学元器件应用中一般要求凝胶有高的电导率和较强的模量。通过在聚乳酸离子凝胶中加入成核剂,可有效提高凝胶模量并且不影响离子电导率。聚乳酸在离子液体中结晶形成孤立的球晶结构,从而得到模量较低的凝胶。加入成核剂后可以显著的提高PLA结晶的成核密度,构成网络结构,使得凝胶的模量提高了三个数量级,电导率的大小与成核剂的加入无关,只与离子迁移数有关。这项研究为通过PLA结晶来提高离子凝胶的模量找到了一种简单易行的方法。(3)在多孔材料中聚乳酸常常是作为被除去的一相,然而聚乳酸其本身的天然可降解性使其多孔材料在日常生活中有举足轻重的作用,因此开发出聚乳酸纳孔膜材料仍是一个挑战。通过调控离子凝胶膜中聚乳酸和离子液体的相分离程度,并选择性地除去离子液体,得到了不同孔结构的聚乳酸纳孔膜。实验证明结晶温度和离子液体的浓度可有效调节相分离程度,低温有利于形成小孔,高浓度有利于形成大而连通的孔,但是结晶温度过低或离子液体含量过少并不利于具有双连续多孔聚乳酸膜的形成,结果证明结晶温度为4℃时,离子液体含量为70wt%,所制备聚乳酸纳孔膜对蛋白的截留率可达96%以上,效果最佳。
[Abstract]:Polylactic acid (PLA), also known as poly (lactide), is a kind of degradable polymer material made from lactic acid molecules, which can be fermented from corn, potato and other regenerative resources. With good mechanical properties and easy to process into daily necessities. Polylactic acid ionic gel is a kind of gel filled with ionic liquid medium in the network structure gap formed by polylactic acid molecule. The ionic liquid is not volatile. High ionic conductivity endows better electrochemical performance of polylactic acid ionic gel, and polylactic acid makes ionic gel have biocompatibility. The combination of the two has both electrical properties, mechanical strength and biological properties. It is widely used in the field of biomaterials and electrochemical intelligent materials. In this paper, the formation mechanism of ring spherulites of polylactic acid ion gel and its physical modification methods to improve the modulus of polylactic acid ionic gel are described. The principle, method and application of the preparation of polylactic acid ion gel nanpore membrane by phase separation were studied in detail. The main results are as follows: (1) in general, polylactic acid is not easy to form ring spherulites, but mixed with ionic liquids can form ring spherulites. By observing the crystalline morphology of polylactic acid ionic gel, the factors affecting the formation of ring band spherulites, I. e., chain untangling, were proposed. The existence of ionic liquids reduced the viscosity of amorphous layer and the chain entanglement of polylactic acid. On the other hand, the formation of ring spherulites in the mixture depends on the crystallization temperature and the content of ionic liquids. The ionic gel conductivity is inversely proportional to the modulus, and the mechanical strength of the gel is very weak when the conductivity is high. In the application of electrochemical components, it is generally required that the gel have high conductivity and strong modulus, by adding nucleating agent into the polylactic acid ionic gel. Polylactic acid crystallizes in ionic liquids to form isolated spherulites. After adding nucleating agent, the nucleation density of PLA crystal can be significantly increased, and the network structure can be formed, which makes the modulus of gel increase by three orders of magnitude. The conductivity is independent of the addition of nucleating agent. This study has found a simple and easy way to improve the modulus of ionic gels through PLA crystallization) Polylactic acid is often removed as a phase in porous materials. However, the natural degradability of polylactic acid makes its porous materials play an important role in daily life. Therefore it is still a challenge to develop polylactic acid nanoporous membrane materials by regulating the phase separation of polylactic acid and ionic liquids in ionic gel membranes and selectively removing ionic liquids. The results show that the crystallization temperature and the concentration of ionic liquid can effectively adjust the degree of phase separation, the low temperature is favorable to the formation of small pores, and the high concentration is conducive to the formation of large and connected pores. However, too low crystallization temperature or too little ionic liquid content is not conducive to the formation of polylactic acid membrane with double continuous pores. The results show that the content of ionic liquid is 70 wt% when crystallization temperature is 4 鈩，

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