Synthesis and characterization of biodegradable hydrogels based on photopolymerizable acrylate-terminated CL-PEG-CL macromers with supramolecular assemblies of α-cyclodextrins

A series of polypseudorotaxanes were synthesized from α-cyclodextrins (α-CDs) threaded onto photopolymerizable CL-PEG-CL oligomers bearing acrylate terminals. The corresponding supramolecular structured hydrogels were prepared from these polypseudorotaxanes in a mixed solvent of H₂O and DMSO via in situ photopolymerization under UV irradiation. The structure and properties of the gels were characterized by FTIR, TGA-DTG and WAXD. The results show that α-CDs are threaded and immobilized onto the network chains of the hydrogel with crosslinking junctions as stoppers topologically, and the feed molar ratio of α-CDs to the macromers affects the hydrogel structure and the water distribution in the hydrogel. These supramolecular structured hydrogels may be good candidates for biomaterial applications.     

Synthesis and characterization of pH-responsive hydrogels based on chemically modified Arabic gum polysaccharide

This work describes the preparation of a pH-responsive hydrogel from Arabic gum (AG) chemically modified with glycidyl methacrylate (GMA). This report first describes the chemical modification of AG and next the synthesis and characterization of the hydrogel obtained. An appropriate mixture of water and DMSO was used to dissolve AG and GMA. The presence of GMA groups in the modified structure of Arabic gum (AG-MA) was detected by ¹³C NMR, ¹H NMR, and FT-IR techniques. The cross-linking reaction of AG-MA leads to formation of an AG-MA hydrogel, which was characterized by solid-state ¹³C-CP/MAS NMR and FT-IR spectroscopy. Morphology was visualized by scanning electron microscopy. It was observed in water uptake tests that AG-MA hydrogels showed significant pH dependence, which affected the water absorption transport mechanism. In the studied pH range, it was found that the transport mechanism of water into AG-MA hydrogel was controlled by Fickian diffusion and polymer relaxation (anomalous transport). At high pH values, the water transport profile became more dependent on polymer relaxation. This effect was attributed to the increase in the ionized groups of glucuronic acid segments, which contributed to electrostatic repulsion among the groups and led the gel polymer network to expand. AG-MA hydrogels exhibited pH-responsive, demonstrating them to be appropriate materials for further tests as drug carriers.     

Cyclodextrin based hydrogels: Inclusion complex formation and micellization of adamantane and cholesterol grafted polymers

Inclusion complex formation between β-cyclodextrin (β-CD) and suitable guest molecules has frequently been exploited to design self-assembled polymer networks. In this paper, we report on hydrogels composed of eight-armed poly(ethylene glycol) (PEG) grafted with β-CD (8armPEG20k-CD), adamantane (8armPEG20k-ad) or cholesterol (8armPEG20k-chol). Mixtures of 8armPEG20k-CD and 8armPEG20k-ad showed viscous behavior (G″ > G′); 8armPEG20k-CD and 8armPEG20k-chol formed elastic hydrogels (G′ > G″). To study the interaction of adamantane and cholesterol grafted PEG with β-CD, linear model compounds (mPEG5k-ad and mPEG5k-chol) were synthesized. Isothermal titration calorimetry (ITC) experiments showed a higher association constant for inclusion complexes formed with mPEG5k-chol (47,000 ± 1650) than for those formed with mPEG5k-ad (30,000 ± 900). Fluorescence spectroscopy and dynamic light scattering (DLS) measurements further showed the ability of mPEG5k-chol to self-assemble into micelles. Self-assembly of 8armPEG20k-chol further increased the strength of the formed hydrogels. Altogether, this study contributes to a better understanding of cyclodextrin based biomaterials.     

Preparation and properties of hydrogels based on hemicellulose

Xylan with glucuronic acid functionalities, separated from birchwood, was converted into hydrogels by dissolving it together with chitosan in acidic conditions. The hydrogels were formed at certain xylan/chitosan compositions. The mechanism of the gel formation was investigated with FTIR. Complexation between glucuronic acid functionalities of xylan and amino groups of chitosan is suggested to be responsible for network formation. The swelling behavior of these hydrogels was studied at various pH levels and salt concentrations, and the hydrogels responded in a reversible manner to various stimuli. DMA of the films showed separated transitions that may correspond to different phases. Imaging with AFM in TappingMode™ of the surfaces indicated discrete xylan and chitosan phases. A sponge-like microporous structure, as shown with SEM, was formed when a hydrogel was freeze dried. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1661–1667, 1998     

Synthesis and properties of superabsorbent hydrogels based on guar gum and succinic anhydride

Synthesis of novel superabsorbent hydrogels has been investigated with the reaction of guar gum and succinic anhydride (SA), using of 4‐dimethylaminopyridine as esterification promoter and water or dimethylsulfoxide (DMSO) as reaction solvent, followed by NaOH neutralization. Hydrogels prepared in water exhibited somewhat higher water absorbency than those prepared in DMSO; its maximum water absorbency in pure water and aqueous 0.9% NaCl solution was ca. 200 g/g and 80 g/g, respectively. These values were considerably higher than those of hydrogels obtained from starch in a similar way. The products in this study biologically degraded up to 70–80% after 10 days in activated sludge, which shows their excellent biodegradability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Multielectronic redox and electrocatalytic supramolecular films based on a tetraruthenated iron porphyrin

Layer-by-layer electrostatic assembled Fe-3TRPyP/CuTSPc supramolecular films constituted by homogeneously dispersed electrochemically active columnar structures, about 15 nm high, were obtained and characterized. They are redox conductors acting as rectifiers in the presence of redox species in solution, providing an excellent electrocatalyst for both oxidation and reduction of nitrite and sulfite. The spectroelectrochemical characterization of the supermolecular porphyrin in solution (−2.6 to 2.3 V) revealed 11 redox processes involving up to 26 electrons, allowing further applications of the thin films as multi electron-transfer catalysts and active materials for molecular devices.     

Electrochemical study on the selective formation of [Pb(cyclodextrin)]surface inclusion complexes at the carbon paste electrode/ClO4 1 M interphase

The formation constants of surface inclusion complexes were determined using a carbon paste electrode, CPE, and cyclic voltammetry for aqueous-based media containing Pb(II) and α, β and γ cyclodextrins. In order to promote the occupation of the molecular cavities in the cyclodextrins, the medium with the support electrolyte contained ClO₄⁻ ions, which have the capacity to modify the hydrophobic properties of such cavities. The results obtained were: Pb(II)-α_CDK = 883.7 ± 13.6 M⁻¹, Pb(II)-β_CDK = 727.5 ± 20.2 M⁻¹, Pb(II)-γ_CDK = 782 ± 10.7 M⁻¹.     

基于葫芦脲主体超分子水凝胶的研究进展

综述了以葫芦脲为主体的超分子水凝胶的最新研究进展,包括不同客体分子的设计及合成,不同新型超分子水凝胶的自组装,简述了其在材料学、环境学及药物释放等方面的应用。     

Effect of different bases and neutralization steps on porosity and properties of collagen‐based hydrogels

The aim of the work reported was to investigate the effect of bases and neutralization steps on hydrogel microstructures. A series of porous hydrogels with various pore sizes were prepared by neutralizing a conventional hydrogel after gel formation. Scanning electron microscopy was used to characterize the microstructure of the porous hydrogels. The morphology of the samples showed the pores were induced into the hydrogels by water evaporation and gas release resulting from the neutralization process. Experimental results indicated that the hydrogels had an absorbency of 200–220 and 48–50 g g^?1 for distilled water and sodium chloride solutions, respectively. A simple method was used to prepare porous hydrogels. The prepared hydrogels are suitable for horticulture and tissue engineering applications due to their superior salt‐resisting properties. Copyright © 2009 Society of Chemical Industry     

电场敏感性壳聚糖水凝胶制备的研究进展

壳聚糖具有亲水性强、无毒、可降解及生物相容性好等优点,以其为主要原料所制备的电场敏感性水凝胶在传感器、可控药物释放、人工肌肉等领域具有广阔的应用前景。本文就基于壳聚糖的电场敏感性水凝胶的制备方法进行了综述,并对其发展方向进行展望。     

Determination of cyclodextrin inclusion constant for aromatic carbonyl compounds through spectrophotometric and electrochemical methods

α- and β-Cyclodextrins cavity inclusion constants (K_i) were determined for a series of benzaldehydes and acetophenones by using two different methods: Benesi-Hildebrand (BH) UV/vis spectroscopic method and electrochemical current (EC) method, determined by cyclic voltammetry. The values determined in the group of benzaldehydes varied from 322 ± 27 to 5688 ± 317 mol⁻¹ dm³ for UV/vis method, and 342 ± 19 to 7386 ± 142 mol⁻¹ dm³ for EC method. The values determined in the group of acetophenones varied from 2201 ± 88 to 9125 ± 251 mol⁻¹ dm³ for UV/vis method, and 1473 ± 33 to 7555 ± 187 mol⁻¹ dm³ for EC method. The equilibrium time estimated for UV/vis spectroscopic (BH) method was 240 min and for the cyclic voltammetry (EC) method was 310 min. Notably, despite their limitations, both methods were suitable and reliable for inclusion constant measurement, if the equilibrium time of the system is well established.     

新型环糊精衍生物的制备及应用

简要介绍了环糊精化学的产生、发展、性能、应用及结构特征。详细介绍了:新型环糊精衍生物的制备及在医药学中的应用;环糊精超分子作用力的自愈合杂化功能材料的制备及应用;环糊精自组装及主客体识别在分析分离科学中的应用。并对环糊精化学的发展进行了展望。     

基于四重氢键的自修复温敏相变凝胶的制备及性能

为提高定型相变材料（SSPCM）的使用寿命，以水和离子液体（IL）为相变材料（PCM），N-异丙基丙烯酰胺（NIPAM）为单体，壳寡糖（COS）为添加剂，引入2-脲基-4[1H]-嘧啶酮（UPy）形成四重氢键二聚体，采用自由基聚合法制备了自修复温敏性相变凝胶（S-EBIL）。通过FTIR、SEM、TEM对相变凝胶的化学结构与微观形貌进行表征，并测定了相变凝胶的自修复性、溶胀性和热性能。结果表明，相变凝胶具有多孔结构，内部孔径为18~38 μm，微凝胶核壳尺寸2~4 μm。相变凝胶具有温度敏感性，当温度升高时，相变凝胶黏弹性增大，不仅能维持相变材料的基本形状，而且能防止相变材料泄漏。相变凝胶相变温度为-10~0 ℃，相变焓值最高为252.9 J/g，导热系数为0.52 W/(m?K)。自修复温敏相变凝胶（S-EBIL3，IL与H2O质量比为3∶10）修复效率可达95.5%（30 s）。     

pH及温度双重敏感水凝胶的制备与性能研究

采用开环聚合的方法制备了Pluronic/寡聚ε-己内酯嵌段共聚物,该共聚物通过酰氯化反应得到了端基结构为丙烯双键的大分子单体;最后以氧化还原引发剂、采用自由基共聚合方法制备了聚（甲基丙烯酸-co-酰氯化大单体）共聚型水凝胶。性能分析表明所制备水凝胶具有良好的pH和温度双重敏感性。     

Antiswelling and robust supramolecular polyurea hydrogels induced by the synergy of hydrogen bond and hydrophobic interaction for constructing durable underwater anti-oil-fouling coatings

Hydrogels are attractive materials for constructing underwater antifouling coatings on solid substrates. However, the application of hydrogel coatings usually faces the obstacles of complex preparation process and poor durability. Herein, we present a facile method to prepare durable hydrogel coatings on metal foils based on rationally designed supramolecular polyurea (PU) hydrogels. PU hydrogels are designed to be cross-linked with hydrogen bonds (H-bonds) and hydrophobic interactions in the hard segment domains by using dihydrazides with different alkyl spacer lengths ( (CH₂)_m ) as chain extender. The synergy of H-bond and hydrophobic interaction can stabilize H-bonds in water, as confirmed by Raman spectroscopy. As a result, PU hydrogels exhibit antiswelling capacity and robustness in both deionized water and seawater. Subsequently, PU hydrogel coatings on Cu/Al foils are prepared by convenient brush coating and subsequent swelling. The resulting hydrogel coatings exhibit excellent underwater anti-oil-adhesion and self-cleaning property, and are durable enough to withstand various static and dynamic damaging tests. The good durability of PU hydrogel coatings should be ascribed to the robust adhesion interface and excellent antiswelling capacity of PU hydrogels. The combination of facile preparation and good durability makes PU hydrogel coatings promising candidates for reliable underwater antifouling.     

磁性半纤维素接枝聚丙烯酰胺水凝胶的制备及其性能研究

以半纤维素和丙烯酰胺为原料,利用自由基聚合法制备了多孔半纤维素接枝聚丙烯酰胺水凝胶,并且通过原位共沉淀法在凝胶上负载Fe3O4粒子,从而得到了磁性水凝胶。分别用FT-IR和SEM对水凝胶的结构和表面形态进行分析;考察了多孔半纤维素接枝聚丙烯酰胺凝胶的溶胀性能并对溶胀动力学进行了数学拟合。研究表明多孔半纤维素接枝聚丙烯酰胺水凝胶的平衡溶胀率随着交联剂量的增大而减小,随着半纤维素/丙烯酰胺比例的增大而增大,随着pH的增大而增大,水凝胶在pH=5.6的溶胀符合Schott溶胀动力学模型。振动样品磁强计(VSM)磁性能测试表明,磁性半纤维素接枝聚丙烯酰胺凝胶具有超顺磁性特征,其饱和磁化强度为10 emu/g。     

基于超分子相互作用的自愈合聚氨酯材料

聚氨酯材料由于其固有的氢键结构被认为是一种理想的自愈合材料。将超分子化学体系引入到聚氨酯中,可以获得性能更加出色的自愈合材料。这些基于超分子相互作用的自愈合聚氨酯材料在受损后能够恢复其大部分物理和化学性质,具有优异的性能。该文首先从不同类型的愈合机理出发,综述了近年来基于超分子相互作用的自愈合聚氨酯材料,包括氢键结合体系、基于芳香基的π-π堆积体系、链段侧链中含有离子基团并彼此形成交联点的离子交联聚合物体系、金属离子与配体进行配位引起材料交联的金属配体相互作用体系、大环分子与特定大小的分子形成包合物的主客互动体系。然后展望了自愈合聚氨酯未来发展优势。     

基于动态硼酸酯键/氢键的自修复水凝胶的制备及性能

通过4-(溴甲基)苯基硼酸(PBA)和1-乙烯基咪唑(IL)的烷基化反应制备了苯硼酸离子液体(PBA-IL)单体。在2,2,6,6-四甲基哌啶-1-氧自由基(TEMPO)氧化纳米纤维素(CNF)的存在下，通过丙烯酰胺(AM)和PBA-IL的一步聚合反应，制备了一种具有半互穿网络结构的自修复导电水凝胶(PAM/PBA-IL/CNF)。通过1HNMR对PBA-IL的化学结构进行表征；通过FTIR、XPS、SEM对水凝胶的化学结构和物理形貌进行表征，并测试了水凝胶的拉伸性能、自修复性能和导电性能。结果表明，PBA-IL单体和水凝胶成功制备，且水凝胶具有典型的多孔结构。PAM/PBA-IL3/CNF水凝胶[3代表PBA-IL含量为30%，以AM、PBA-IL、CNF悬浮液、N,N’-亚甲基双丙烯酰胺(MBA)溶液、过硫酸铵(APS)的总绝干质量为基准]的断裂应力为335.1 kPa、断裂伸长率为1969.5%、断裂能为12.1 kJ/m²、自修复效率为95.43%(150 min)、电导率为6.38 mS/cm。     

纳米银对复合水凝胶性质影响的研究

超声波作用于含有单体AMPS、MMA和交联剂MBA的Ag NO3水溶液,使Ag+还原为纳米级的银粒子,与此同时单体和交联剂形成共聚物,从而在无引发剂和还原剂的条件下制备出纳米银/P(AMPS-MMA)复合水凝胶。TEM表明,制备的纳米银粒径在10~20nm,粒径分布较窄,且均匀地分散在水凝胶聚合物里;通过研究纳米银/P(AMPS-MMA)复合水凝胶和P(AMPS-MMA)水凝胶的溶胀率、溶胀动力学、退溶胀动力学和温敏性质等表明,纳米银增强了复合水凝胶的吸水性能和提高了复合水凝胶的温敏性。     

Preparation and characterization of chitosan based hydrogels containing cyclodextrin inclusion compounds or nanoemulsions of thyme oil

Hydrogels derived from natural polysaccharides are ideal scaffolds for use in biomedical applications. pH‐sensitive polyvinyl alcohol and chitosan hydrogels containing inclusion compounds of thyme oil (TM) with host methyl‐β‐cyclodextrin (MβCD) and hydroxypropyl‐β‐cyclodextrin (HβCD) and TM nanoemulsion (TM‐nano) were prepared via controlled, biocompatible and low cost freeze–thaw method. The structure of the hydrogels was characterized by Fourier transform IR spectroscopy and optical and scanning electron microscopy. The physicochemical properties of the hydrogels such as gel fraction, swelling ratio and tensile properties were measured. The water vapor transmission rate of the hydrogels indicated that they can maintain a moist environment over the wound bed. Encapsulation and release of antibacterial TM from the hydrogels were determined by UV spectroscopy. In all cases, hydrogels with lower amounts of TM evidenced slower and more controlled release. Different kinetic models were applied for evaluating the drug release mechanism. The antibacterial activity of the samples was studied by counting the number of both Gram‐negative and Gram‐positive bacteria surviving in a broth medium and the results proved the antibacterial activity of all prepared hydrogels. The results of an MTT (3‐(4,5‐dimethylthiazol‐2yl)‐2,5‐diphenyltetrazolium bromide) assay indicated more cell viability of TM‐nano hydrogels in comparison with those of TM‐βCD inclusion compounds. Cell attachment observations also showed great biocompatibility of TM‐nano hydrogels. The prepared hydrogels, especially those containing TM‐nano, might be used as potential wound dressings to improve the wound healing process. © 2019 Society of Chemical Industry