奇偶效应诱导的苯丙氨酸类水凝胶手性反转

为了模拟生物大分子(如DNA和蛋白质等)螺旋手性反转的现象,设计合成了4种酰胺基或脲基共价连接L-苯丙氨酸和苯环,外围为二甘醇胺与3-氨基-1,2-丙二醇的C2对称小分子凝胶因子,利用酰胺基(CONH)与脲基(NHCONH)之间的奇偶效应实现了超分子螺旋手性的反转.通过核磁共振波谱仪(1H-NMR和13C-NMR),高分辨质谱仪(HRMS)对凝胶因子结构和分子量进行了分析表征.并运用圆二色光谱(CD)、扫描电子显微镜(SEM)、紫外可见吸收光谱(UV-Vis)和红外光谱(FTIR)对其组装纤维结构和组装方式进行研究.实验结果表明酰胺基(CONH)与脲基(NHCONH)之间的奇偶效应改变凝胶因子的组装方式,调控了超分子手性特征,实现了超分子水凝胶螺旋手性的反转.     

基于芳香分子-糖类手性超分子组装体及功能

手性超分子组装体广泛存在于自然界中,因其在材料、化学和生物学等领域广阔的应用前景,引起了科学家们极大的兴趣。其中以糖类分子作为手性源,经分子自组装构筑手性超分子组装体的研究已成为超分子化学领域的研究热点之一。本文综述了基于糖类修饰的苝酰亚胺分子、偶氮苯分子、联苯类分子和卟啉类分子等芳香分子化合物经自组装构筑的手性超分子组装体,介绍了其在有机溶剂和水的混合溶剂、水中的凝胶性质,超分子手性特征和功能,糖分子类型与超分子组装体手性间的关系等,并对基于糖类的手性超分子组装体的前景进行了展望。     

超分子凝胶:结构多样性与超分子手性

超分子凝胶作为一种重要的软物质材料,在构建多重刺激响应性、光电功能,以及生物相容材料等功能软物质方面表现出了独特的优越性。超分子凝胶在形成过程中往往得到比较均一的纳米结构,且具有结构多样性;而另一方面,超分子凝胶的构筑单元大部分是手性分子,超分子凝胶也是实现手性在超分子层次/纳米层次表达的重要途径,尤其是手性传递、手性放大、不对称催化方面,同时超分子凝胶也是构筑手性纳米结构的重要手段。本文主要对超分子凝胶形成中的纳米结构以及形貌的多样性和超分子手性进行介绍,并展望该领域未来的发展方向。     

超分子凝胶的手性功能应用:手性分子识别与不对称催化

超分子凝胶通过形成三维空间网络结构将溶剂液体相固定化,是一类重要的软物质材料。由于超分子凝胶能快速形成,自组装形成的纳米结构均一、可调,且可大规模制备,因此成为超分子化学、纳米技术以及材料科学研究的重要研究方向之一,并在诸多领域得到广泛的功能研究和应用拓展,如在材料模板、光电开关、药物释放、分子识别和超分子催化等方面已有大量研究报道。由于超分子凝胶具有固-液相可逆转变、可控组装等特性,成为了超分子手性和分子手性研究的重要载体。近年来超分子凝胶在超分子手性催化、手性分子识别等方面取得了一系列重要突破,为超分子凝胶功能应用开辟了新的空间,为手性科学研究提供了新的手段和方法。     

超分子凝胶中的光化学反应

超分子凝胶中的光化学反应是比较特殊的一类反应,通常是将具有光响应活性的基团或分子引入到超分子凝胶的自组装体系中,因此,能够将超分子凝胶独特的性质与光化学反应的优势有效地结合起来,构筑新型的光功能材料,这使得此类超分子凝胶在光信息存储、光开关及光转换器件等前沿领域具有广阔的应用前景.本文主要总结近年来国内外包括作者课题组对超分子凝胶中光化学反应方面的研究进展,以及其在多重响应凝胶、手性光学开关以及手性合成方面的应用.     

基于葫芦[10]脲的超分子水凝胶的制备及其在H2O2检测中的应用研究

以丙烯酰胺(AM)与客体单元二茂铁衍生物(G)在引发剂作用下共聚形成P(AM-G)聚合物.基于客体分子与主体分子葫芦[10]脲之间的动态主-客体相互作用为交联点制备了超分子水凝胶.采用核磁、扫描电镜及流变等测试方法对水凝胶的结构、形貌以及自修复性能等进行研究.结果表明超分子水凝胶为3D多孔结构的弹性体,CB[10]的引入有利于在聚合物网络中提供交联点,并且本研究中的超分子水凝胶可在没有任何外部刺激的情况下进行自修复.在水凝胶制备后,二茂铁的固有催化活性仍然得以保留,其良好的催化活性可应用于H_2O_2的检测,检测限为2.5×10~(-4) mol/L.本研究为超分子水凝胶功能化提供了一种新的方法,在生物技术和环境化学等领域具有潜在应用.     

基于葫芦[10]脲的超分子水凝胶的制备及其在H_2O_2检测中的应用研究

以丙烯酰胺(AM)与客体单元二茂铁衍生物(G)在引发剂作用下共聚形成P(AM-G)聚合物.基于客体分子与主体分子葫芦[10]脲之间的动态主-客体相互作用为交联点制备了超分子水凝胶.采用核磁、扫描电镜及流变等测试方法对水凝胶的结构、形貌以及自修复性能等进行研究.结果表明超分子水凝胶为3D多孔结构的弹性体，CB[10]的引入有利于在聚合物网络中提供交联点，并且本研究中的超分子水凝胶可在没有任何外部刺激的情况下进行自修复.在水凝胶制备后，二茂铁的固有催化活性仍然得以保留，其良好的催化活性可应用于H_2O_2的检测，检测限为2.5×10~(-4) mol/L.本研究为超分子水凝胶功能化提供了一种新的方法，在生物技术和环境化学等领域具有潜在应用.     

基于柱[5]芳烃主客体包结构筑分子响应型超分子水凝胶

主客体相互作用是在水溶液中与大环主体分子形成稳定的包结物的理想驱动力.以功能化的苯并咪唑衍生物为客体(M),水溶性柱[5]芳烃为主体构建了一种分子响应型超分子水凝胶.通过1H NMR, 2D NOESY和扫描电子显微镜(SEM)研究了水凝胶的成凝胶机理.有趣的是,主客体包结作用、柱[5]芳烃间有序的"外腔"π-π相互作用和分层堆积对于获得超分子水凝胶是必不可少的,非共价键相互作用的动态可逆性使凝胶体系对温度变化/化学刺激产生响应.此外,加入竞争性客体己二腈(ADN)/百草枯(PQ)后,柱[5]芳烃基水凝胶可转化为溶胶.因此,该超分子水凝胶可以选择性识别有机分子.     

苯丙氨酸衍生物手性凝胶的制备及其应用

手性超分子凝胶材料在传感器、人工触角、药物缓释、细胞培养等领域表现出潜在的应用前景。本文合成了一种新型的含偶氮苯官能团的D/L苯丙氨酸手性凝胶因子ALP和ADP,具有对称且完全相反的手性信号。该凝胶因子在多种有机溶剂和水混合溶剂中均可形成稳定的淡黄色凝胶,其中在DMSO和水混合溶剂中表现出最优的成凝胶性能,临界成胶浓度可达2.0mg/mL,表明该手性凝胶因子具有良好的成凝胶性能。手性凝胶可对热、光、pH等外界环境刺激产生响应,并伴有宏观上的凝胶-溶胶相互转变。手性凝胶因子自组装形成了不同螺旋纳米纤维结构,并发现L型手性纳米纤维相对于D型手性纳米纤维对细胞具有更好的粘附与增殖效果。     

基于柱[5]芳烃主客体包结构筑分子响应型超分子水凝胶（英文）

主客体相互作用是在水溶液中与大环主体分子形成稳定的包结物的理想驱动力.以功能化的苯并咪唑衍生物为客体(M),水溶性柱[5]芳烃为主体构建了一种分子响应型超分子水凝胶.通过1H NMR, 2D NOESY和扫描电子显微镜(SEM)研究了水凝胶的成凝胶机理.有趣的是,主客体包结作用、柱[5]芳烃间有序的"外腔"π-π相互作用和分层堆积对于获得超分子水凝胶是必不可少的,非共价键相互作用的动态可逆性使凝胶体系对温度变化/化学刺激产生响应.此外,加入竞争性客体己二腈(ADN)/百草枯(PQ)后,柱[5]芳烃基水凝胶可转化为溶胶.因此,该超分子水凝胶可以选择性识别有机分子.     

骨及生物材料中的纳米磷酸钙

纳米磷酸钙在自然界骨组织的形成过程中起到了关键作用。尽管骨的类型有所不同,但在其初级结构中的无机成分都是纳米磷酸钙。纳米磷酸钙结构能够给予骨良好的机械性能和生物学活性。在生物体中,无机纳米磷酸钙在有机基质的调控下能定向自组装成特定的生物矿物。体外细胞实验显示小尺寸纳米羟基磷灰石更能促进骨髓基质干细胞的增殖,而同尺寸的结晶型纳米磷酸钙则比无定形磷酸钙更能利于干细胞分化。鉴于纳米磷酸钙具有很好的生物相容性和骨诱导性,可以发展成为理想的生物材料常用于骨组织工程和生物医学。     

骨及生物材料中的纳米磷酸钙

纳米磷酸钙在自然界骨组织的形成过程中起到了关键作用。尽管骨的类型有所不同,但在其初级结构中的无机成分都是纳米磷酸钙。纳米磷酸钙结构能够给予骨良好的机械性能和生物学活性。在生物体中,无机纳米磷酸钙在有机基质的调控下能定向自组装成特定的生物矿物。体外细胞实验显示小尺寸纳米羟基磷灰石更能促进骨髓基质干细胞的增殖,而同尺寸的结晶型纳米磷酸钙则比无定形磷酸钙更能利于干细胞分化。鉴于纳米磷酸钙具有很好的生物相容性和骨诱导性,可以发展成为理想的生物材料常用于骨组织工程和生物医学。     

Performance evaluation of a new nanocomposite polymer gel for water shutoff in petroleum reservoirs

Abstract

A new polymer gel nanocomposite is fabricated for excess water production control (water shut off) in petroleum reservoirs and its rheological behavior is evaluated in the presence of sea water and formation water at the temperature of 100?°C. It is shown that at a high salinity without using SiO₂ nanoparticles, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water are 12.5?Pa and 9.8?Pa respectively. However by incorporation of SiO₂ nanoparticles in the polymer gel matrix, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water can be improved to 13.56?Pa and 11.57?Pa respectively, which is quite interesting from reservoir engineering viewpoint. Equilibrium Swelling Ratio (ESR) of the nanocomposite polymer gel in sea water and formation water decreases as the concentration of the SiO₂ increases. Thermal stability of the polymer gel is investigated by differential scanning calorimetry (DSC) measurements. The inflexion temperature of the polymer gel is improved by incorporation of 2000?ppm SiO₂ nanoparticles. The fabricated polymer gel nanocomposite in this work can have potential application in reduction of excess water production during enhanced oil recovery (EOR) operations in petroleum industry.     

Regulating the Mechanical and Optical Properties of Polymer-based Nanocomposites by Sub-Nanowires

Sub-nanowires (SNWs) exhibit great potential applications in nanocomposites owing to their high specific surface area, high flexibility, and similarity to polymer chains in dimension, which are a good entry point to bridge inorganic materials and polymer materials. Herein, we synthesized hydroxyapatite sub-nanowires (HAP SNWs) and engineered hydroxyapatite sub-nanowires/polyimide (HSP) gels and films by simple mixing of HAP SNWs and polyimide (PI). Benefiting from the interactions between HAP SNWs and PI, these nanocomposites were a continuous hybrid network. As the increase of HAP SNWs contents, the viscosity and modulus of HSP gels were greatly improved by one or two orders of magnitude compared with PI gel. HSP films not only maintained high transparency but also gained high haze, as well as exhibited enhanced Young's modulus. Thus, both HSP gels and films developed in this work are promising for various applications in coatings and high-performance films.     

Synthesis and characterization of a nano‐hydroxyapatite/chitosan/polyethylene glycol nanocomposite for bone tissue engineering

A novel nanocomposite involving nano‐hydroxyapatite/chitosan/polyethylene glycol (n‐HAP/CS/PEG) has been successfully synthesized via co‐precipitation approach at room temperature. The purpose to synthesize such nanocomposite is to search for an ideal analogue which may mimick the composition of natural bone for bone tissue engineering with respect to suitable biocompatibility, cytotoxicity and mechanical properties. The FTIR spectra of n‐HAP/CS and n‐HAP/CS/PEG scaffolds indicated significant intermolecular interaction between the various components of both the nanocomposites. The results of XRD, TEM and TGA/DTA suggested that the crystallinity and thermal stability of the n‐HAP/CS/PEG scaffold have decreased and increased respectively, relative to n‐HAP/CS scaffold. The comparison of SEM images of both the scaffolds indicated that the incorporation of PEG influenced the surface morphology while a better in‐vitro bioactivity has been observed in n‐HAP/CS/PEG than in n‐HAP/CS based on SBF study, referring a greater possibility for making direct bond to living bone if implanted. Furthermore, MTT assay revealed superior non‐toxic nature of n‐HAP/CS/PEG to murine fibroblast L929 cells as compared to n‐HAP/CS. The comparative swelling studies of n‐HAP/CS/PEG and n‐HAP/CS scaffolds revealed a better swelling rate for n‐HAP/CS/PEG. Also n‐HAP/CS/PEG showed higher mechanical strength relative to n‐HAP/CS supportive of bone tissue ingrowths. Copyright © 2014 John Wiley & Sons, Ltd.     

Viscoelastic and fractal characteristics of a supramolecular hydrogel hybridized with clay nanoparticles

The supramolecular hydrogels derived from low-molecular-mass gelators represent a unique class of soft matters and have important potential applications in biomedical fields, separation technology and cosmetic science. However, they suffer usually from weak mechanical and viscoelastic properties. In this work, we carry out the in situ hybridization of clay nanoparticles (Laponite RD) into the supramolecular hydrogel formed from a low-molecular-mass hydrogelator, 2,6-di[N-(carboxyethyl carbonyl)amino]pyridine (DAP), and investigate the viscoelastic and structural characteristics of resultant hybrid hydrogel. It was found that a small concentration of Laponite RD could lead to a significant increase in the storage modulus, loss modulus or complex viscosity. Compared with neat DAP hydrogel, the hybrid hydrogel has a greater hydrogel strength and a lower relaxation exponent. In particular, the enhancement of the clay nanoparticles to the viscoelastic properties of the DAP hydrogel is more effective in the case of higher DAP concentration. By relating its macroscopic elastic properties to a scaling fractal model, such a hybrid hydrogel was confirmed to be in the strong-link regime and to have a more complex network structure with a higher fractal dimension when compared with neat DAP hydrogel.     

Triterpenoid‐Based Self‐Healing Supramolecular Polymer Hydrogels Formed by Host–Guest Interactions

Pentacyclic triterpenoids, a class of naturally bioactive products having multiple functional groups, unique chiral centers, rigid skeletons, and good biocompatibility, are ideal building blocks for fabricating versatile supramolecular structures. In this research, the natural pentacyclic triterpenoid glycyrrhetinic acid (GA) was used as a guest molecule for β‐cyclodextrin (β‐CD) to form a GA/β‐CD (1:1) inclusion complex. By means of GA and β‐CD pendant groups in N,N′‐dimethylacrylamide copolymers, a supramolecular polymer hydrogel can be physically cross‐linked by host–guest interactions between GA and β‐CD moieties. Moreover, self‐healing of this hydrogel was observed and confirmed by step‐strain rheological measurements, whereby the maximum storage modulus occurred at a [GA]/[β‐CD] molar ratio of 1:1. Additionally, these polymers displayed outstanding biocompatibility. The introduction of a natural pentacyclic triterpenoid into a hydrogel system not only provides a biocompatible guest–host complementary GA/β‐CD pair, but also makes this hydrogel an attractive candidate for tissue engineering.     

Preparation and characterization of a novel stimuli-responsive nanocomposite hydrogel with improved mechanical properties

A novel stimuli-responsive organic/inorganic nanocomposite hydrogel (NC hydrogel) with excellent mechanical properties was synthesized by in situ polymerization of 2-(2-methoxyethoxy) ethyl methacrylate (MEO(2)MA), oligo (ethylene glycol) methacrylate (OEGMA) and acrylic acid (AAc), as the polymeric matrix (PMOA), and fibrillar attpulgite (AT), as the reinforcer and cross-linker. The effect of the AT content on the mechanical properties for the swollen and dried NC hydrogels was determined by tensile testing and dynamic mechanical analysis (DMA), respectively. The tensile testing results showed that the incorporation of AT nanoparticles significantly enhanced the mechanical properties of NC hydrogels. As the content of AT increased, the tensile strength, tensile modulus and effective cross-linked chain density increased. The DMA results showed that the storage modulus of AT/PMOA NC hydrogels was increased and the glass transition temperatures shifted to higher temperature compared to the pure PMOA hydrogel, which further indicated that the enhancement of mechanical property depended upon the presence and content of AT. In addition, the faster swelling rates of the NC hydrogels were observed in comparison with the corresponding physically cross-linked PMOA hydrogel, except for 1% AT/PMOA sample. However, the deswelling kinetics of NC hydrogels was obviously retarded.     

Self‐Sorting Double‐Network Hydrogels with Tunable Supramolecular Handedness and Mechanical Properties

Self‐sorting, simultaneous, and orthogonal operations during the self‐assembly of complex mixtures are commonly observed for biological species but rare in artificial systems. In this study, we designed two gelators (LPF and LPFEG) containing the same chiral phenylalanine core but different achiral peripheral substituents to give hydrogels with opposite supramolecular handedness. When the two hydrogels were mixed, double‐network nanofibers with opposite handedness were formed by spontaneous high‐order organization and self‐sorting of the two gelators. The chiroptical activity of the double‐network hydrogels could be tuned by varying the molar ratio of LPF and LPFEG in the mixture, thus showing that the two gelators were highly independent of each other. Enhanced mechanical properties were observed for the interpenetrating networks when the LPF/LPFEG molar ratio was 3:7, with a more than fourfold increase in both the storage (G′) and loss modulus (G′′) relative to those of the individual hydrogels.     

The Construction and Transition of Supramolecular Hydrogels Induced by Cyclodextrin Inclusion

Soft hydrogel nano‐ and micro‐structures have great potential applications in the field of tissue engineering and chemical sensors. In this paper, a supramolecular hydrogel was constructed by combining a triblock copolymer poly(ethylene oxide)₁₀₀‐(propyleneoxide)₇₀‐(ethyleneoxide)₁₀₀ (PEO₁₀₀‐PPO₇₀‐PEO₁₀₀ ) (Pluronic F127), mono‐6‐thio‐β‐cyclodextrins (SH‐β‐CDs), and silver nanoparticles. Here, SH‐β‐CDs couple to the silver nanoparticles via thio groups and include PPO blocks of F127 using the hydrophobic cavity to form pseudo‐polyrotaxanes. Moreover, the hydrogel can be transformed to a homogenous solution by the addition of hydrochloride powder. These results are important for research related to the construction of soft hydrogel materials and control their mechanical properties.