基于均苯三甲酸与对羟基吡啶的超分子水凝胶

以均苯三甲酸和对羟基吡啶为原料, 采用简便方法合成了一种新的凝胶因子, 并采用1H NMR、IR和元素分析确认其结构. 红外光谱中2849和1894 cm－1处出峰证明羧基与吡啶基间形成了氢键. 在凝胶化过程中, 凝胶因子可自组装形成纤维状网络结构. 随着凝胶因子浓度的增加, 纤维搭接逐渐致密, 凝胶网络密度逐渐增大, 可冻结水含量逐渐增加. 因此, 通过改变凝胶因子浓度可有效控制凝胶的结构及性能. 该凝胶因子在较低浓度下形成的超分子水凝胶在100 ℃下也能够稳定存在.     

基于均苯三甲酸与4-羟基吡啶的超分子水凝胶

以均苯三甲酸和对羟基吡啶为原料,采用简便方法合成了一种新的凝胶因子,并采用1H NMR、IR和元素分析确认其结构.红外光谱中2849和1894cm-1处出峰证明羧基与吡啶基间形成了氢键.在凝胶化过程中,凝胶因子可自组装形成纤维状网络结构.随着凝胶因子浓度的增加,纤维搭接逐渐致密,凝胶网络密度逐渐增大,可冻结水含量逐渐增加.因此,通过改变凝胶因子浓度可有效控制凝胶的结构及性能.该凝胶因子在较低浓度下形成的超分子水凝胶在100℃下也能够稳定存在.     

超声作用对超分子水凝胶结构及性能的影响

采用一种简便方法,以戊二酸酐和3-羟基2-氨基吡啶合成了一种新的凝胶因子3-羟基-2-[N-(羧丙基羰基)氨基]吡啶(简称SWG),并采用IR、1H-NMR和元素分析确认其结构.红外光谱中2576cm-1和1906cm-1峰的出现证明羧基与吡啶基间形成了氢键.于20°C的超声仪中冷却1.5wt%的SWG水溶液,在1min内形成了超分子水凝胶.基于扫描电子显微镜(SEM)、示差扫描量热仪(DSC)及凝胶-溶液破坏温度(Tgel)分析表明,在凝胶化过程中,SWG自组装形成纤维状网络结构.随着超声功率由200W增加到500W,纤维宽度由8μm逐渐减小到2μm,凝胶网络密度逐渐增大,可冻结水含量逐渐增加,Tgel从60℃增加到70℃.因此,通过改变超声功率可有效控制凝胶的结构及性能.进一步增加SWG的浓度,可使纤维宽度及网络密度均增加,并导致凝胶的Tgel升高.采用多晶X射线衍射仪(XRD)分析表明,在凝胶形成过程中,SWG分子自组装出现明显的择优取向.     

超分子均苯四甲酸/对羟基吡啶水凝胶中纤维状聚集体结构与性能的关系

采用1H-NMR和FT-IR表征了在摩尔比1∶4条件下,由均苯四甲酸和对羟基吡啶合成的一种凝胶因子(G2).通过在室温下冷却G2的水溶液,形成了超分子水凝胶.采用扫描电子显微镜(SEM)、示差扫描量热仪(DSC)和流变仪等多种技术研究了冷却速率对凝胶的组装纤维结构及宏观性能的影响.随着冷却速度的降低,纤维尺寸变大而凝胶的稳定性降低.因此,可以通过环境因素来控制凝胶的性能.采用流变仪分析表明凝胶具有高的机械强度.DSC分析结果表明随着凝胶因子浓度的增加,凝胶中可冻结水的含量降低.相对于在摩尔比1∶2条件下,由均苯四甲酸和对羟基吡啶合成的凝胶因子G1,在相同浓度下,G2在更高的最低凝胶因子浓度(MGC)使水凝胶,并且得到的凝胶具有更低的凝胶-溶胶破坏温度(Tgel).利用环境扫描电镜(ESEM)直接观测了实际含水状态下凝胶的形貌,结果表明采用常规SEM观测到的纤维状网络与ESEM的结果一致,这说明在干燥过程中形貌并未发生太大变化.组装体结构和性能关系有助于认识凝胶形成机理并使凝胶满足不同的应用.     

反应型凝胶剂2,4-二烷脲基甲苯衍生物及有机溶剂的室温凝胶化研究

通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化.该方法限制了某些低沸点溶剂的凝胶化.利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了3种反应型凝胶剂.这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂形成热可逆的有机分子凝胶.场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构.随着烷基胺中的烷基链长度不同,形成的纤维状聚集体的形态也不同.FT-IR和1H NMR研究表明分子间氢键作用是反应型凝胶剂自组装的驱动力.通过XRD和分子模拟推测了其聚集体的结构形态.     

π-共轭三苯基苯衍生物的合成及其胶凝性能

合成了一系列三单脂肪链具有盘状结构的三苯基苯衍生物并研究了其在有机溶剂中自组装行为. 结果表明, 该系列衍生物在多种低极性有机溶剂中可以形成稳定的凝胶, 利用小角X射线衍射实验和扫描电子显微镜技术观察到干凝胶的分子排列具有层状结构, 形成纤维状和片层状聚集, 紫外-可见吸收光谱和红外光谱结果表明分子间氢键和π-π共轭堆积效应是形成自组装凝胶的主要驱动力. 在形成凝胶过程中, 凝胶剂分子在溶液中通过盘状中心的π-π共轭堆积效应和酰胺键的分子间氢键作用自组装成层状结构, 层状结构进一步组装形成纤维状和片层状聚集体, 最终形成三维网状结构阻碍溶剂流动形成凝胶.     

分子凝胶电解质的电导率研究

凝胶因子4,4'-二(硬脂酰胺基)二苯醚(BSDE)在水和非水介质(如二甲基甲酰胺、二甲基亚砜、碳酸丙烯酯等)中利用非共价键相互作用自组装成有序的三维纤维网络结构,使介质凝胶化.该凝胶被称之为分子凝胶.同样,BSDE也能使锂盐溶液凝胶化,制备一种新型分子凝胶电解质.水分子凝胶锂离子电解质的室温离子电导率达到10^-1～10^-2S·cm^-1,碳酸丙烯酯分子凝胶锂离子电解质的室温离子电导率也能达到10^-2～10^-3S·cm^-1.分子凝胶的离子电导率研究表明,锂盐在凝胶中的行为和其在溶液中的行为相似.在-35℃的低温下,分子凝胶的电导率与其溶液相比约低1～2个数量级.     

反应型二烷基脲凝胶剂及有机溶剂的室温凝胶化研究

通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化。该方法限制了某些低沸点溶剂的凝胶化。利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了三种不同烷基链长的反应型凝胶剂甲苯–2, 4–二（N, N’ –烷基）脲。这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂中形成热可逆的有机分子凝胶。不同烷基链长的亲溶剂作用以及溶剂性质对有机分子凝胶的形成有较大影响。场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构。烷基链长度不同,形成的纤维状聚集体的形态也不同。红外光谱（FT-IR）和核磁共振波谱（1H-NMR）研究表明分子间氢键作用是这种凝胶剂自组装的驱动力。通过X射线衍射（XRD）和分子模拟推测了其聚集体的结构形态。     

一类Fmoc保护二肽醇类凝胶因子的合成与凝胶化研究

合成了一类Fmoc保护二肽凝胶因子(Fmoc-Lys(Fmoc)-Tyr-OR, R=＝Me, Et, Hex),, 并通过加热溶解-冷却静置方法测试了其凝胶性能。. 它们可在多种脂肪醇类溶剂中形成有机凝胶,, 并且具有热可逆性。. 通过透射电镜发现,, R为Me的凝胶因子在正己醇中可自组装成纳米级纤维状结构,, 相互交织使溶剂得以固定形成半透明凝胶,, 而在正丙醇中则倾向自组装成多刺球状,, 形成不透明白色凝胶。. IR及荧光光谱分析结果表明氢键与π-π stacking作用参与了其凝胶化自组装,, 同时氢键在凝胶态的强度较其固态时降低。. 该结果也从XRD数据中得以进一步证实。     

反应型二烷基脲凝胶剂及有机溶剂的室温凝胶化研究

通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化。该方法限制了某些低沸点溶剂的凝胶化。利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了三种不同烷基链长的反应型凝胶剂甲苯–2, 4–二（N, N’ –烷基）脲。这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂中形成热可逆的有机分子凝胶。不同烷基链长的亲溶剂作用以及溶剂性质对有机分子凝胶的形成有较大影响。场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构。烷基链长度不同,形成的纤维状聚集体的形态也不同。红外光谱（FT-IR）和核磁共振波谱（1H-NMR）研究表明分子间氢键作用是这种凝胶剂自组装的驱动力。通过X射线衍射（XRD）和分子模拟推测了其聚集体的结构形态。     

Investigation on the assembled structure-property correlation of supramolecular hydrogel formed from low-molecular-weight gelator

The investigation on structure-property correlation is important for understanding the gelating mechanism of supramolecular hydrogels. In this paper, a low-molecular-weight hydrogelator (termed as gelator 1) prepared from 1,2,4,5-benzene tetracarboxylic acid (BTA) and 4-hydroxy pyridine (PHP) was able to gel water effectively. The influence of environmental stimulation, such as cooling speed and ultrasonic treatment, on the structure of the assembling fibers and the macroscopic properties of the gels was investigated via multiple techniques. The results indicated that the fiber size decreased as increasing the cooling speed and the smallest fibers were obtained under ultrasonic treatment. As the fibers became smaller, the gel with higher T(gel), lower bonded water content and higher dynamic modulus was obtained. Therefore it is possible to control the gel performances via the environmental stimulation. The relationship between the assembled structure and properties is helpful for understanding the gel formation mechanism and makes the gels suitable for different applications.     

Hydrogen-bonding A(LS)2-type low-molecular-mass gelator and its thermotropic mesomorphic behavior

A unique cholesterol-based A(LS)₂-type gelator, which is a hydrogen-bonding complex based on an ALS-type non-gelator molecule 3-cholesteryl 4-(trans-2-(4-pyridinyl)vinyl)phenyl succinate and a counterpart 3-cholesteryloxycarbonylpropanoic acid, shows strong gelation ability in alcohol and aromatic solvents. The formed gel has a high T_g at low gelation concentration, and its xerogel shows fibrillar microstructure revealed by scanning electron microscopy (SEM). FTIR confirms the existence of intermolecular hydrogen bond in the gelator, and X-ray diffraction (XRD) analysis reveals that the gelator possesses a folded conformation in gel and self-assembles into the fibrillar structure mainly by van der Waals interaction between cholesteryl moieties of the gelator. Further more, the thermotropic behavior of the xerogel is studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), which shows typical optical textures of liquid crystals.     

Formation of supramolecular hydrogels with controlled microstructures and stability via molecular assembling in a two-component system

Two isomeric building units, 4-oxo-4-(2-pyridinylamino) butanoic acid (defined as G1) and 4-oxo-4-(3-pyridinylamino) butanoic acid (defined as G2) formed fiber- and tree-like crystals in aqueous solutions, respectively. The crystal formation process of G1 was suggested based on the layered cross section of an individual crystal and the single crystal structure. Through cooling the aqueous solutions of their mixtures under G1/G2 molar ratios ranged from 7/1 to 1/3, a series of supramolecular hydrogels were formed based on hydrogen bonds as the main driving force. As decreasing G1/G2 ratios, the first observed aggregates in solution changed from fiber to particle form, while the gelating time became longer and longer. At the collapsing temperature, the gels formed at G1/G2 ratio 3/1 kept the original gel shape but released water, while at G1/G2 ratio 2/1 they broke into pieces without releasing water. The "dropping ball" experiment indicated that the highest gel-to-sol dissociation temperature (T(gel)) is obtained at G1/G2 ratio of 2/1. As measured by UV-vis spectroscopy, the two building units distributed uniformly within the gel formed at G1/G2 ratio of 1/1, indicating they assembled together in forming hydrogel. The scanning electron microscope (SEM) and infrared spectrometer (FT-IR) analysis of the dried samples indicated that the backbone shape changed from fiber to sheet and the content of free carboxyl groups increased with decreasing G1/G2 ratios, therefore resulting in hydrogels with different stability. The simple gelator structures and the possibility in controlling gel structure and stability make the hydrogels suitable for various uses.     

Microsphere-to-nanotube transition via in situ sonication triggered in a supramolecular self-assembly system based on triphenylamine derivative

A new gelator 1 containing triphenylamine was designed and synthesized, and formed stable gel in ethyl acetate. The self-assembly process of molecule 1 was thoroughly investigated. The solid microsphere structure formed in gel 1 could be turned into nanotube in the transition process of gel to gel via sonication. At the same time, the intermolecular hydrogen bond of self-assembly system was obviously enhanced under sonication. The XRD and water contact angle experiments results of xerogel 1 before and after sonication showed great difference. The hydrophobicity of xerogel 1 film was obviously decreased with the change of contact angle from 142° to 129° after sonication at 100 W for one minute. From the results, it was possible that the solid microsphere was re-dissolved and further reassembled into nanotube. To our knowledge, it was the first example that the solid sphere structure was changed into nanotube in self-assembly system via sonication.     

Controlled self-assembly of chiral gelator molecules into aligned fibers induced by nematic to smectic B phase transitions

Chiral bisoxalamide 1 shows remarkable gelling capacity of the nematic and smectic B liquid-crystalline phases of heptylcyclohexanecarboxylic acid (HCCA). Chiral nematic-containing left-handed helical fiber bundles are formed if the gelator is present in amounts higher than 0.55 wt %. With lower amounts of 1, no nematic gel forms, however, a nematic to smectic B phase transition triggers instantaneous self-assembly of gelator molecules into aligned fibers. The latter liquid crystalline gel system represents an example of controlled self-assembly induced by a liquid crystalline phase transition.     

Biological Glucose Metabolism Regulated Peptide Self‐Assembly as a Simple Visual Biosensor for Glucose Detection

A glucose oxidase (GOx)‐mediated glucose metabolism was in vitro mimicked and employed to regulate the self‐assembly of peptide‐based building blocks. In this new stimuli‐responsive self‐assembly system, two peptide‐based building blocks, respectively, having aspartic acid (gelator 1 ) and lysine (gelator 2 ) residues were designed and prepared. When adding glucose and GOx to the aqueous solution of gelator 1 or the self‐assembled fibrillar hydrogel of gelator 2 to construct glucose metabolism system, the metabolic product (gluconic acid) can trigger the protonation of the peptide molecules and induce the phase transitions of gelators 1 (sol‐gel) and 2 (gel‐sol). Because this glucose metabolism regulated peptide self‐assembly is built on the oxidation of glucose, it can be used as a simple visual biosensor for glucose detection.