發(fā)布時間：2018-01-02 01:09

  本文關(guān)鍵詞：聚乳酸離子凝膠結(jié)構(gòu)的形成及其調(diào)制　出處：《東華理工大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 聚乳酸 離子凝膠 環(huán)帶球晶 高模量 多孔膜

【摘要】：聚乳酸(PLA)又稱聚丙交酯,是由乳酸分子縮聚而成的聚酯族可降解高分子材料,可以由玉米、土豆等再生資源發(fā)酵而來,具有良好的機械性能且易加工成民生用品,因而越來越受到廣泛關(guān)注。聚乳酸離子凝膠是聚乳酸分子所形成的網(wǎng)狀結(jié)構(gòu)間隙中充滿離子液體介質(zhì)的一類凝膠。離子液體的不揮發(fā)性、高離子電導(dǎo)率賦予了聚乳酸離子凝膠較好的電化學(xué)性能,同時聚乳酸使離子凝膠具備了生物相容性,兩者結(jié)合兼具電性能,機械強度,生物性能,在生物材料和電化學(xué)智能材料領(lǐng)域有著廣泛的應(yīng)用前景。本文闡述了聚乳酸離子凝膠中環(huán)帶球晶及形成機理,提高聚乳酸離子凝膠模量的物理改性方法,以及相分離法制備聚乳酸離子凝膠納孔膜等三個方面,分別從原理、方法和應(yīng)用進行了深入研究,為聚乳酸離子凝膠制備和應(yīng)用提供了實驗依據(jù)。主要研究結(jié)果如下:(1)一般情況下聚乳酸不易形成環(huán)帶球晶,而與離子液體共混后可形成環(huán)帶球晶,通過觀察聚乳酸離子凝膠的結(jié)晶形貌,提出了影響環(huán)帶球晶形成的因素,即鏈解纏結(jié)。離子液體的存在降低了非晶層的粘度和聚乳酸的鏈纏結(jié),有利于片晶扭轉(zhuǎn)進而在混合物中形成環(huán)帶球晶。另一方面混合物中環(huán)帶球晶的形成依賴于結(jié)晶溫度和離子液體的含量,并且與片晶扭轉(zhuǎn)的不平衡應(yīng)力的變化密切相關(guān)。(2)通常離子凝膠的電導(dǎo)率與模量成反比,電導(dǎo)率高時其凝膠的機械強度往往非常弱,而在電化學(xué)元器件應(yīng)用中一般要求凝膠有高的電導(dǎo)率和較強的模量。通過在聚乳酸離子凝膠中加入成核劑,可有效提高凝膠模量并且不影響離子電導(dǎo)率。聚乳酸在離子液體中結(jié)晶形成孤立的球晶結(jié)構(gòu),從而得到模量較低的凝膠。加入成核劑后可以顯著的提高PLA結(jié)晶的成核密度,構(gòu)成網(wǎng)絡(luò)結(jié)構(gòu),使得凝膠的模量提高了三個數(shù)量級,電導(dǎo)率的大小與成核劑的加入無關(guān),只與離子遷移數(shù)有關(guān)。這項研究為通過PLA結(jié)晶來提高離子凝膠的模量找到了一種簡單易行的方法。(3)在多孔材料中聚乳酸常常是作為被除去的一相,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舉足輕重的作用,因此開發(fā)出聚乳酸納孔膜材料仍是一個挑戰(zhàn)。通過調(diào)控離子凝膠膜中聚乳酸和離子液體的相分離程度,并選擇性地除去離子液體,得到了不同孔結(jié)構(gòu)的聚乳酸納孔膜。實驗證明結(jié)晶溫度和離子液體的濃度可有效調(diào)節(jié)相分離程度,低溫有利于形成小孔,高濃度有利于形成大而連通的孔,但是結(jié)晶溫度過低或離子液體含量過少并不利于具有雙連續(xù)多孔聚乳酸膜的形成,結(jié)果證明結(jié)晶溫度為4℃時,離子液體含量為70wt%,所制備聚乳酸納孔膜對蛋白的截留率可達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，

本文編號：1367003