【作者】 李媛媛；

【导师】 郝爱友；

【作者基本信息】 山东大学 ， 有机化学， 2010， 硕士

【摘要】 十几年来,小分子凝胶剂及其物理凝胶的研究引起了人们越来越多的重视。随着研究工作的不断深入,取得了许多引人注目的成就。刺激响应性凝胶作为小分子凝胶(物理凝胶)的一重要分支,由于其在智能材料和药物运输方面存在巨大的潜在应用价值,受到更多的关注。热致有机凝胶不但是刺激响应性凝胶的一个重要凝胶类型,并且由于其明显不同于常规有机凝胶低温下成凝胶而是在高温下形成凝胶,这一特点使得热致有机凝胶受到越来越多地关注和研究。热致凝胶包含两种类型：一种是不可逆的热致凝胶,这种凝胶通常是由聚合物形成的,特别是蛋白质。另一种是可逆的热致凝胶,这种凝胶通常就是由小分子凝胶因子形成的。本论文主要介绍了两种新型热致可逆凝胶体系以及对其进行的初步改性研究。首先介绍的是一种基于环糊精超分子作用的、热致可逆的新型有机凝胶体系。该凝胶体系是由p-环糊精(β-CD)、二苯胺(DPA)以及氯化锂(LiCl)在N,N-二甲基甲酰胺(DMF)中形成的,属于典型的小分子凝胶体系。随着温度的升高,DPA可以在DMF中凝胶化而不是溶解性增大,而随着温度降低,DPA又可以溶解到DMF中,这个现象是可逆的、可重复的。这个现象与一般的有机小分子在有机溶剂中,随着温度升高溶解性增大的一般规律相反。例如β-CD、DPA或其他有机小分子在DMF中的溶解性是比较大的,特别是当温度升高的时候，溶解度会更大。该凝胶体系是首例基于环糊精超分子作用而形成的热致有机小分子凝胶。针对该凝胶体系,我们做了以下的表征和研究：光学显微镜(Optical microscopy, OM)、扫描电子显微镜(Scanning electron microscopy, SEM)、差示扫描量热法(Differential scanning calorimetry, DSC)、X射线衍射(X-ray diffraction, XRD)和傅里叶红外光谱测试(FTIR measurements, FT-IR)。该新型凝胶体系的特点如下：(1)该体系是多组分凝胶体系,并且每一个组分对凝胶的形成都起到重要的作用。(2)该凝胶体系的凝胶因子是由一些简单的、尺寸较小并且廉价的有机小分子组成的。(3)该有机凝胶体系是一个热响应的有机小分子凝胶体系。他不同于常规的凝胶体系升温溶解的一般特性,反而是升温形成凝胶。凝胶样品在室温下呈澄清的溶液态,而当加热到凝胶化温度(Tgel)附近时,体系变成凝胶态。(4)通过DSC测试比较准确地证明该凝胶体系是对温度可逆的。当温度低于凝胶化温度后,凝胶态会恢复到溶液态。(5)该凝胶体系对氯化锂的量还有响应性。当体系中没有氯化锂的时候,该体系是不能形成凝胶的。(6)该体系对客体分子也有响应性。当加入其他客体分子后,该凝胶体系的凝胶化温度大多是降低的。但是也有一些尺寸与环糊精的空腔匹配性较好的客体分子会破坏凝胶的形成。并且利用分子动力学模拟了该凝胶体系形成的可能性机理。其次我们介绍的是首例异于常规凝胶的、新型三重响应性(gel-sol-gel)凝胶体系,它是由一定比例的β-环糊精(p-CD)、二苯胺(DPA)和氯化锂(LiCl)在N,N-二甲基乙酰胺(DMAC)中基于超分子作用形成的多组分、热响应的有机凝胶体系。常规的热可逆凝胶体系是两重响应的(sol-gel),它有两种热可逆方式：一种是先加热体系至澄清状态,然后冷却到凝胶化温度(Tgel)形成凝胶；另一种是体系在室温下呈溶胶态,加热该体系至Tgel后形成凝胶。本文介绍的是一定比例的β-CD,DPA和LiCl在DMAC中,通过室温搅拌即可形成凝胶(gel A),然后将gel A置于油浴中加热,gel A会坍塌融化成澄清溶液态,然后继续加热至一定温度(凝胶化温度,Tgel),该体系转而又形成一种凝胶态(gel B)。该凝胶体系经过了以下表征：光学显微镜(Optical microscopy, OM)、扫描电子显微镜(Scanning electron microscopy, SEM)、傅里叶红外光谱测试(FTIR measurements, FT-IR)和流变学测试(Rheology)。我们发现该体系有很多突出的特点,具体如下：(1)该凝胶体系是一个多组分的凝胶体系,体系中的四个凝胶因子组分对凝胶的形成都是不可或缺的；(2)该凝胶体系属于热响应性的小分子有机凝胶,并且它不同于常规两重响应的凝胶体系,属于三重响应体系；(3)通过SEM,得知两个凝胶态的微观结构是不一样的。由于该三重响应性凝胶体系具有显著地自组装特点,所以它很有可能有更广阔的应用前景。最后,我们针对这两个新型热致有机凝胶体系的进行了简单改性。通过对凝胶因子的改性和更换来探讨凝胶体系的形成机理以及寻找更优异的凝胶体系。更多还原

【Abstract】 During the last decade, physical gels prepared by small molecular gelators have attracted more and more attention. As an important branch of physical gel, stimuli-responsive gels, which inculde hydrogels and organogels, have been extensively investigated and have potential applications in smart biomaterials and drug-delivery systems. As one of the special gels, the heat-set organogels which are formed at high temperature in organic solvents have received increasing attention for their great potential applications in materials, medicines and other fields. The heat-set organogels inculde two types. One is irreversible gels, which is usually prepared by polymers, particularly proteins. The other is reversible gels, which is usually prepared by small organic molecules.This paper mainly introduced two new thermally reversible gel systems and preliminary research on their modification. Firstly, we introduced a new reversible, heat-set organogel based onβ-CD. The gel system is a thermal responsive organogel of small organic molecules formed by a system of DPA withβ-CD and LiCl in DMF. DPA could be gelated in DMF particularly as the temperature increasing, while be dissolved again with the temperature decreasing whenβ-CD and LiCl are introduced into the system. This is very interesting and unusual for that DPA,β-CD and other organic molecules dissolve respectively very well in DMF, particularly as the temperature increases. The gel system as the first heat-set small organic molecules organogel based onβ-CD was characterized by OM, SEM, DSC, XRD, FT-IR. The appealing features of this new kind of gel are described as follows. (1) It is a multicomponent system where each of the four components is required for the organogelation property. (2) The gel system is formed by simple, small, and commercially available chemicals. (3) It is a thermo-responsible organogel of small organic molecules, which is different from the conventional gels dissolved upon heating. The sample is a transparent solution at room temperature, but a gel can be formed when it heated to a Tgel(the temperature of gelation). (4) It could be reversible to temperature, which was confirmed by DSC. When the temperature is lower than the Tgel, the gel could turn to a solution again. (5) It is responsive to the amount of LiCl. There’s no gel could be formed without the presence of LiCl. (6) It is responsive to the guest molecules. Generally, the Tgel decreased by adding the guest molecules into the gel system, but some guest molecules, whose structure is exactly fitted to the cavity of CDs, could destroy the gel formation of the gel system.Secondly, we introduced a triple-transforming gel system (gel-sol-gel) for the first time, which is a thermo-responsive organogel with multi-components prepared byβ-CD, DPA and LiCl in DMAC in a suitable proportion based on the supramolecular interactions. The conventional thermo-responsive gels is duplicate-transforming (sol-gel), which could be thermo-reversible by one way of heating or cooling around the gelation temperature (Tgel), or the other way of heating upon Tgel and cooling down. The first gel (gel A) could be formed byβ-CD, DPA and LiCl in DMAC at room temperature based on stirring, then the gel could transform into a clear solution based on heating, and then the other gel (gel B) can be formed at a relatively high temperature (Tgel, the gelation temperature by heating). This gel system was characterized by OM, SEM, FT-IR and Rheology. Some significant features of the gel system were found as follows:(1) the system has multi-components, where each of the four components is required for the organogelation; (2) the system is a thermo-responsive organogel of small organic molecules such as DPA and DMAC, which is different from the conventional gels with a duplicate-transforming (sol-gel) process; (3) the two gel states have different micro-structures observed by SEM. The striking self-assembly properties of the thermo-responsive triple-transforming system may bring in much broad prospects for applications.Finally, we have modified the two gel systems simply by modifying the gelators or replacing the gelators. Based on the modifications, we could indicate the possible mechanism for gel formation and explore for more excellent gel system.更多还原