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.     

基于偏苯三甲酸与对羟基吡啶复合物的超分子水凝胶

基于偏苯三甲酸和对羟基吡啶合成了一种具有支化结构的凝胶因子,采用氢核磁、红外光谱及元素分析确认其结构.该凝胶因子熔体在冷却时可拉出数厘米的长丝,表明分子间形成了强相互作用.将凝胶因子的水溶液分别在25℃和0℃下自然冷却、以及在25℃的超声作用下冷却,凝胶因子自组装成纤维状网络结构并使水凝胶化,纤维网络的密度及凝胶的稳定性均按上述凝胶形成条件顺序增加.通过干凝胶能谱面扫描分析发现氮元素主要处于纤维内部,表明两亲性凝胶因子对分子自组装的影响.通过分析邻苯二甲酸与对羟基吡啶复合物、偏苯三甲酸的单晶结构表明,凝胶因子基于多种氢键识别作用组装成纤维结构.干凝胶的粉末X射线衍射分析表明在凝胶化过程中凝胶因子沿着特定方向进行组装.     

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.     

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.     

基于氢键作用由低分子量凝胶因子形成的超分子水凝胶

利用对羟基吡啶及均苯四甲酸合成的超分子单体, 基于分子间氢键作用, 在水中成功地制备出了具有温度响应性的超分子凝胶, 研究了制备条件对凝胶结构的影响.     

含金刚烷基的N-异丙基丙烯酰胺共聚物水凝胶的制备和性能研究

合成了含金刚烷基的甲基丙烯酸金刚烷酯(AdMA)疏水单体,并通过与N-异丙基丙烯酰胺(NIPAM)共聚,制备了温敏性的(P(NIPAM-co-AdMA))共聚物水凝胶.用傅里叶变换红外光谱仪(FTIR)表征了凝胶的化学结构,用环境扫描电镜(ESEM)对凝胶断层结构的形貌进行了观察,用DSC测试了凝胶的体积相转变温度(LCST),并研究了共聚水凝胶的溶胀性能.结果表明,共聚物水凝胶的LCST能够高效地通过改变疏水单体的含量来调节,在实验所考察的范围内,LCST随AdMA含量的增加而线性降低;疏水单体的含量对凝胶的孔洞结构和溶胀性能存在一最优值,在最优的单体配比下,水凝胶具有均匀规整的大孔结构和超快的响应速率.如疏水单体含量为3%(AdMA∶NIPAM=3%)的共聚物水凝胶具有如渔网般均匀的多孔结构,当发生去溶胀时,在5min内就可以失去92%的水,不到10min的时间就可以完全达到去溶胀平衡,水保留率在4%以下.     

基于功能化聚磷酸酯嵌段共聚物的微凝胶和水凝胶的制备与表征

首先利用聚乙二醇单甲醚(MePEG)作为引发剂前体,对含有炔基的环状磷酸酯单体2-炔丁基-2-氧代-1,3,2-二氧磷杂环戊烷(BYP)进行开环聚合,制备两嵌段共聚物MePEG-b-PBYP.随后,采用巯基-炔(Thiol-yne)点击化学反应对PBYP的炔基进行修饰,分别获得侧链含氨基(—NH2)、羧基(—COOH)和磺酸钠(—SO3Na)的聚磷酸酯嵌段共聚物,在水相中形成聚电解质.通过NMR和GPC对产物的结构和组成进行表征.MTT测试表明,两嵌段共聚物具有较好的生物相容性.进一步将带有不同电荷的聚电解质溶液混合,利用静电作用制备微凝胶.通过DLS、TEM及SEM等测试对聚合物的溶液行为及微凝胶的形貌进行表征.为增强凝胶体系的物理交联作用,将α-环糊精(α-CD)引入体系,诱导形成水凝胶.利用SEM对水凝胶的形貌进行表征,XRD分析水凝胶的包结络合作用,并利用流变仪测试水凝胶的凝胶化时间.该水凝胶以其良好的生物相容性、生物可降解性和一定的机械强度等性能,有望作为可注射型凝胶材料,在药物控释和组织工程等领域具有潜在的应用.     

吡嗪二羧酸-三聚氰胺双组分水凝胶的制备及性能

以3,6-二甲基-2,5-吡嗪二羧酸(P)和三聚氰胺(M)为组分,采用不同的摩尔比(1∶1,1∶2,1∶3)混合配制了3个样品PM11,PM12和PM13,并对其凝胶性能进行了测试.实验结果表明,PM能在水中及部分含水有机溶剂中形成稳定的凝胶,这些凝胶对酸碱具有良好的响应性能.采用扫描电子显微镜分析了3种水凝胶的微观形貌,均为纤维状的网络结构;红外光谱及紫外光谱测试结果表明氢键是形成凝胶的关键驱动力;XRD测试结果显示凝胶为层状结构.对PM12在不同pH值的水中的凝胶性能测试结果表明,在pH=3~11的范围内PM12均能形成凝胶.测试了PM12在混合溶剂中的凝胶性能,并将测试结果与混合溶剂的Hansen溶解度参数关联,以便用于分析溶剂与凝胶因子间的相互作用,所得结果亦表明氢键在凝胶形成的过程中起重要作用.     

一种有机酰腙类配体及其金属凝胶的结构及性能

设计合成了一种带有长链烷基和配位基团的新型有机配体2-吡啶甲醛-4'-十二烷氧基苯甲酰腙(简称L),并采用核磁(1H-NMR)、红外(FTIR)、电喷雾质谱(ESI-MS)和元素分析确认其结构.在乙醇和水的混合溶剂中,配体L可使溶剂凝胶化,并可与多种金属离子(Co(Ⅱ),Ni(Ⅱ),Zn(Ⅱ)和Cu(Ⅱ)作用,形成金属凝胶.采用扫描电镜分析表明,L自身形成的凝胶及金属凝胶的微观形貌均为相互搭接的纤维状结构.采用紫外光谱分析表明在乙醇溶液中L分子形成了聚集体.采用平板流变仪分析表明引入金属离子可提高凝胶的强度.进一步合成了L与Cu(Ⅱ)的配合物,通过对比配合物与金属凝胶的红外光谱和紫外光谱,证明金属凝胶中配体L与金属离子间形成了配位作用.     

有机锆交联魔芋葡甘聚糖凝胶的制备及性能

以正丁醇锆为中心离子试剂,分别以3-氨基-1,2-丙二醇(APG)和N-甲基二乙醇胺(MDEA)为有机配体制备两种正丁醇锆交联剂,用魔芋葡甘聚糖(KGM)溶液与正丁醇锆交联剂制备了一系列水基压裂液。通过傅里叶变换红外光谱仪(FT-IR)、核磁共振波谱(NMR)、高分辨质谱(HRMS)、流变仪、扫描电子显微镜(SEM)和差示扫描量热仪(DSC)系统地表征了压裂液的结构、形貌以及性能。讨论了锆酸盐与植物胶发生交联的反应途径,并运用Winter-Chambon公式准确确定溶胶-凝胶转变点。研究了反应物浓度、配体种类对储能模量(G′)、损耗模量(G″)和溶胶-凝胶转变时间(tcr)的影响。结果表明,相较于APG配体,以MDEA为配体的有机锆/KGM凝胶体系的延迟交联性能、耐温耐剪切性能更好,其tcr随KGM质量浓度的增大呈先减小后增大的趋势,并且随配体浓度和交联剂质量分数的增加呈减小趋势,KGM质量浓度控制在4.0 g/L时,凝胶体系的常温延时交联时间在7～45 min内可调节,溶胶-凝胶转变温度(T_sol-gel)为71.4℃,其耐温性能高达120℃,在170 s-1剪...     

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.     

Investigation on the Crystal Structure of Substituted Pyridine Based Organic Salt as the Low Molecular Weight Gelator

In order to define the chemical conformation of gelator,para-hydroxy pyridinium salt of 1,2,4,5-benzene tetracarboxylic acid(defined as G1),four model compounds were prepared from para-,meta-,ortho-phthalic acid with 4-hydroxy pyridine(PHP),and 1,2,4,5-benzene tetracarboxylic acid(BTA) with 4-pyridylcarbinol(PCB),and their 1H NMR spectra were investigated.The single crystal of G1 obtained directly from gelling solvent was measured,which displayed complicated hydrogen-bonded networks arising from the supramolecular synthons and other weak interactions between H2O and the components.The powder X-ray diffraction(XRPD) experiments were also carried out to understand the relationship between molecular packing of the bulk crystal and the gelation behavior.     

均苯四甲酸与对羟基吡啶超分子聚合物的制备

超分子聚合物(supramolecular polymer)是指单体单元间依靠可逆和高度取向的非共价作用力结合的、在溶液或本体中表现出聚合物特性的一类特殊聚合物[1].其中,氢键结合超分子聚合物因氢键的高度取向性及丰富的结合形式而具有特殊结构与性能,已成为近期关注的热点[2~4].文献中报道的氢键结合超分子聚合物主要有多重氢键结合和基于羧基与吡啶基的氢键结合(其键能可达45kJ·mol-1[5])两类,它们均可表现出和传统聚合物诸多类似的性质,诸如高的溶液粘度、形成凝胶、具有弹性等,同时其结构和性能又随温度等环境条件的变化而发生可逆变化,使得这类…     

Influence of gelator structures on formation and stability of supramolecular hydrogels

A supramolecular hydrogel(defined as G1) formed from 1,2,4,5-benzene tetracarboxylic acid (BTCA) and 2-amino-3- hydroxypyridine possessed higher T_(gel) than that of another hydrogel(defined as G2) formed from BTCA and 3-hydroxypyridine. Based on the analysis of their xerogels by ~1H NMR,IR and XRD,the higher stability of G1 was attributed to the formation of stronger hydrogen binding enhanced by the ortho amino group of 2-amino-3-hydroxypyridine.     

Hydrogen-bonded Supramolecular Hydrogels Derived from 3,3',4,4'-Benzophenonetetracarboxylic Acid and Hydroxylpyridines

In this paper, four gelators (defined as G1 – G4 ) were prepared from 3,3′,4,4′‐benzophenonetetracarboxylic acid (BPTA) and para‐hydroxylpyridine or meta‐hydroxylpyridine at molar ratios 1:2 and 1:4 respectively, and characterized by ¹H NMR, IR, UV‐Vis spectra and elemental analysis. Due to the amphiphilic features, all the gelators were able to gel water via cooling their aqueous solution under different stimulations. The structure of the assembling fibers and the macroscopic properties of the gels were investigated by multiple techniques. The results indicated that the minimum gelator concentration (MGC) increased by the order of G1 , G2 , G3 and G4 , while the gel‐to‐sol dissociation temperature (T_gel) decreased by the same order, which were explained from the assembling structures of the gels.     

Self-assembled thermoreversible gels of nonpolar liquids by racemic propargylic alcohols with fluorinated and nonfluorinated aromatic rings

The synthesis and colloidal study of a new class of low molecular weight organogelators is reported. Racemic propargylic alcohols with perfluoroaryl and nonfluorinated aryl rings are capable of forming gels in alkane liquids and/or silicone oil. A full colloidal characterization of alkane gels prepared from (R/S)-1-pentafluorophenyl-3-phenylprop-2-yn-1-ol [(R/S)- 1] was conducted, including both structural [optical microscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), attenuated total reflectance infrared spectroscopy (ATR-IR)] and thermal stability [differential scanning calorimetry (DSC)] studies. A model of the organization of gelator molecules within gel fibers has been proposed primarily based on the correlation of diffraction data for the powder XRD pattern of a gel and a simulated powder pattern from a sublimed crystal of the gelator. Furthermore, structural requirements for propargylic alcohol gelators were investigated by subjecting derivatives with modified structures to gelation tests. An enantiomerically enriched sample [(R)- 1, 83% ee] fails to entrap the solvent under conditions where the racemate successfully forms a gel. The remaining racemic derivatives (with p-alkoxy or p-alkyl substituents on the nonfluorinated arene) form gels or partial gels in silicone oil and in some alkane preparations.     

Thermal Behavior of Syndiotactic Polystyrene/1,2‐Dichloroethane Gels and Stoichiometry of Polymer‐Solvent Compounds

Abstract

The phase behavior of syndiotactic polystyrene (sPS)/1,2‐dichloroethane (DCE) gels has been investigated by differential scanning calorimetry (DSC) and wide angle x‐ray diffraction (WAXD) for different gel formation conditions. DSC data show that the gel melting temperatures are independent of the cooling conditions leading to gel formation, whereas the melting enthalpies of the gels depend on the cooling history. WAXD measurements show that for low concentration gels the sPS/DCE clathrate structure is obtained, whereas for high concentration gels both the clathrate structure and the solvent‐free β phase can be obtained. Furthermore, the onset of formation of the β phase is dependent on the cooling rate. In light of combined DSC and WAXD data, the reliability of the DSC in evaluating the absolute stoichiometry of polymer‐solvent compounds formed in sPS/DCE gels is discussed.