【作者】 冯桂龙；

【导师】 杨亚江；

【作者基本信息】 华中科技大学 ， 高分子化学与物理， 2008， 博士

【摘要】 由小分子凝胶因子通过分子间氢键、π-π堆砌及其它非共价键作用自组装而形成的超分子有机凝胶受到了人们广泛的关注。作为一种主体材料,有机凝胶可以包裹各种客体分子。研究这些客体分子在有机凝胶体系中的传质行为,不仅在主客体分子化学,而且在诸如凝胶电解质、药物控制释放等应用领域,都是一项有重要意义的工作。本文用4,4’-二（硬脂酰胺基）二苯甲烷（BSAPM）在有机溶剂中形成的超分子有机凝胶为主体材料,在研究客体分子对凝胶性能影响的同时,用不同的方法研究了一些客体分子的扩散释放行为和机理。以小分子凝胶因子为凝胶剂制备了一种新型微乳凝胶,研究了水杨酸钠在这种微乳凝胶中的释放行为。另外还考察了受限于多壁碳纳米管内纳米空间内一种二脲型凝胶因子的聚集组装行为。本论文包括以下主要内容:1)采用BSAPM为凝胶因子制备了含有小分子水杨酸和若丹明B的1,1,2-三氯乙烷（TCE）超分子有机凝胶。TEM表征了有机凝胶的微观结构,用落球法考察了水杨酸和若丹明B对超分子有机凝胶的相转变温度(T_GS)影响。用紫外-可见光度法研究了超分子凝胶中两种客体小分子在静态下的扩散释放。结果表明其释放率随凝胶剂浓度的增加而降低。客体小分子的体积大小对其释放有明显的影响,分子体积较大的若丹明B的释放率低于分子体积较小的水杨酸。另外,若丹明B的扩散系数也低于水杨酸,且随凝胶剂浓度的增加,这种趋势更为明显。两种客体分子的累积释放率与时间的平方根成良好的线性关系,符合Higuchi方程,属扩散控制的Fickian释放机理。2)用循环伏安法研究了BSAPM/碳酸丙烯酯超有机凝胶体系中二茂铁的电化学活性和传质行为。结果表明有机凝胶中二茂铁具有氧化还原活性。有机凝胶中二茂铁电化学氧化反应所表现出的伏安曲线与相应的液体电解质的一样。两种不同体系中,二茂铁的氧化还原反应都是一个受扩散控制的单电子转移的准可逆过程。凝胶中二茂铁和二茂铁离子的扩散系数随凝胶因子浓度的增加而下降,随温度的增加而增加。扩散系数与温度的关系符合经典的Arrhenius方程,而且两个不同体系中扩散活化能相同。3)用小分子凝胶因子Bis18-L-Phe使由十四酸异丙酯、Tween 80、1,2-丙二醇和水构成的微乳凝胶化,所得的凝胶微乳具有良好的热可逆性。凝胶微乳的相转变温度(T_GS)与凝胶因子的浓度和微乳的组成有关。用POM和FTIR研究了凝胶微乳的形成机理。偏光显微镜照片表明整个微乳的连续相中形成了相互缠绕的线状聚集体。而FTIR表明分子间的氢键作用是凝胶形成的原因。4)以水溶性的水杨酸钠为模型分子研究了它在凝胶微乳中的释放行为。结果表明水杨酸钠表现出持续释放行为,其释放速率随Bis18-L-Phe含量的增加而降低,随水杨酸钠含量增加而增加,而随IPM的增加而下降。凝胶中水杨酸钠的释放行为符合一级动力学。这些结果表明凝胶微乳可用作于药物释放载体。5)将二脲型凝胶剂MBAU-18通过加热、超声的作用灌注到多壁碳纳米管内,利用DSC研究MBAU-18在受限空间内形成的聚集体的热力学性质,发现其相变温度高于本体空间内形成聚集体的相变温度,利用XRD结合分子模拟软件探讨了在受限空间内凝胶剂可能采取的聚集方式。更多还原

【Abstract】 Supramolecular organogels formed by the self-assembly of gelator through intermolecular hydrogen bonding,π-πstacking and other non-covalent bond interations have been receiving considerable attention.As a stable host matrix,some guest molecules such as organic dyes and drugs can be entrapped in organogels by simply adding them to the sol prior to its gelation.Therefore,a better understanding of the mass transfer behavior of guest molecules in organogel is required not only for the development of fundamental research on host/guest interaction,but also for potential applications such as drug delivery and gel electrolytes.In this dissertation,when supramolecular organogels of a bis-（4-stearoylaminophenyl） methane（BSAPM） in some solvents or electrolyte solution in propylene carbonate were used as host,the diffusional release or the electrooxidation reaction of guests was investigated by different methods.A novel organogel based on the gelation of aqueous microemulsion was prepared by using low molecular weight gelator N-stearine-N’-stearyl-L-phenylalanine（Bis18-L-Phe）.Sodium salicylate was entrapped within the gelled microemulsion and used as model drug.The in vitro sodium salicylate release behavior in gelled microemulsion was investigated by using UV-Vis spectroscopy. In addition,we reported herein self-assembly of supramolecular organogel when confined within the multiwalled carbon nanotubes,the thermodynamic properties and the possible mechanism of self-assembly were studied.This paper are consisted of several sections as the following:1) BSAPM as a gelator was used for preparation of 1,1,2-trichloroethane（TCE） supramolecular organogels.The existence of salicylic acid and Rhodamine B as the guest molecules slightly led to the decrease of gel-sol phase transition temperatures(T_GS) of the organogels.The diffusion and release of the guest molecules in the organogels were investigated by using UV-Vis spectroscopy.The results indicated that release ratios of the guest molecules decreased with the increase of the gelator concentration.Wherein,the release ratios of Rhodamine B were less than that of salicylic acid,which could be attributed to the larger molecular size of Rhodamine B.In addition,the diffusion coefficients of Rhodamine B were also less than that of salicylic acid.This trend was more clearly with the increase of BSAPM concentration.The investigation indicated that the diffusion and release behavior of the guest molecules in the self-assembled organogel followed the Higuchi equation and diffusion-controlled mechanism of Fickian model.2) Supramolecular organogel was formed by self-assembly of BSAPM in propylene carbonate containing LiClO₄.The electrochemical behavior and diffusion of ferrocene （Fc） and ferricenium（Fc⁺） entrapped within the organogel was investigated by cyclic voltammetry.The Fc molecules still show redox activity within the organogels in comparison with corresponding solutions of propylene carbonate containing LiClO₄.The shape of the cyclic voltammograms of the Fc electrooxidation in organogel was similar to that in corresponding solutions.The results indicated that redox reactions of Fc/Fc⁺ were a quasi-reversible process of diffusion-controlled single electron transfer in organogels.The diffusion coefficients of Fc and Fc⁺ in organogels decreased with an increase of the concentration of gelator BSAPM,but increased with an increase of temperature.The temperature dependence of the diffusion coefficient in organogels followed classical Arrhenius equation.The activation energy in organogels was found of no difference from that in corresponding solutions.3) Low molecular weight organogelator,N-stearine-N’-stearyl-L-phenylalanine （Bis18-L-Phe） is able to gelatinize the microemulsion consist of isopropyl myristate （IPM）,Tween 80,propylene glycol（PG） and water in a very low concentration.The resulting gelled microemulsions showed good thermo-reversibility.The phase transition temperature(T_GS) of gelled microemulsion increased with an increase of Bis18-L-Phe and the ratio of SC to IPM.The mechanism of formation of the gelled microemulsions was studied by POM and FTIR.POM image showed elongated and strandlike aggregates dispersed throughout the continuous phase to form a coherent network.FTIR spectroscopy indicated that intermolecular hydrogen bonding may be responsible for the gel formation.4) Water-soluble sodium salicylate was used as a model drug and its release from the gelled microemulsions was studied.The results showed that the release of drug exhibited a sustained release behavior and the release rate reduced with increasing the proportion of Bis18-L-Phe.Moreover,the release rate of drug increased as the content of drug increased and decreased with an increase in the proportion of IPM.The release behavior of drug followed first-order release kinetics.These results indicated that the gelled microemulsion was potentially useful in drug delivery systems5) A bisurea gelators 1-methyl-2,4-bis（N’-octadecylureido）benzene（MBUB-18） was affused into the the multiwalled carbon nanotubes（MWCNTs） by heating and ultrasonication to investigate the gelation of chlorobenzene confined within the MWCNTs.Based on an analysis of the DSC and XRD data for the gels confined within the MWCNTs and formed in the bulk space,we argued that the self-assembled of supramolecular organogel in an unusual manner when confined within MWCNTs in comparison with that in bulk space.The results not only provide a good addition to the development of new types of CNT-based composites,but they also are helpful for the understanding of the mechanism of natural self-assembling processes and the related phenomena within nano-scale environments.更多还原