聚丙烯酰胺凝胶的光反应合成及性能研究

以丙烯酰胺为单体,分别以N,N′-亚甲基双丙烯酰胺和过硫酸胺为交联剂、引发剂,利用紫外光引发,分别在聚合物基底(PET,PS薄膜)及硅片上制备了聚丙烯酰胺(PAAm)凝胶.研究表明,凝胶的成胶时间、表面形貌、稳定性、溶胀率等对基底的依赖性很强:在亲水性基底上凝胶成胶时间较疏水性基底短;溶胀率不仅与UV光照时间、交联剂的含量等因素有关,而且还与基底的性质有关,在亲水性基底上形成的凝胶平衡溶胀率小于在疏水性基底上制备的凝胶.     

Influence of Xanthan–Curdlan Hydrogel Complex on Freeze‐Thaw Stability and Rheological Properties of Whey Protein Isolate Gel over Multiple Freeze‐Thaw Cycle

The effect of adding xanthan–curdlan hydrogel complex (XCHC) at 2 concentrations (0.25 and 0.5% w/w) on the freeze‐thaw stability of heat‐induced whey protein isolate (WPI) gel was investigated. Samples were stored at 4 °C for 24 h before subjected to 5 freeze‐thaw cycles alternating between ?16 °C (18 h) and 25 °C (6 h). Adding XCHC to the WPI solution resulted in the reduction of a significant amount of syneresis up to 5 repeated freeze‐thaw cycles. Addition of XCHC decreased the amount of syneresis from 45% in the control sample (pure WPI gel) to 31.82% and 5.44% in the samples containing 0.25% and 0.5% gum, respectively, after the 5th freeze‐thaw cycle. XCHC increased the storage modulus (G′) of the gels and minimized the changes of the G′ values over the 5 freeze‐thaw cycles, indicating improvement of the stability of the system. Furthermore, the minimum protein concentration for gel formation decreased in the presence of the XCHC. Scanning electron microscopy (SEM) images showed that addition of XCHC resulted in the formation of a well‐structured gel with numerous small pores in the network, which consequently improved the water retention ability during the temperature abuses up to 5 freeze‐thaw cycles. These results have important implications for using XCHC in the formulation of the frozen WPI‐based products with improved freeze‐thaw stability and rheological properties.     

大豆蛋白基水凝胶的研究进展

大豆蛋白是一种优质的植物蛋白资源,具有良好的凝胶性、生物相容性和安全性,是制备蛋白基水凝胶材料的主要来源之一。本文概述了基于大豆蛋白的水凝胶最新研究进展;简单介绍了大豆蛋白及其结构后,讨论了当前大豆蛋白水凝胶主要的制备方法以及凝胶机制;总结了大豆蛋白水凝胶在食品领域的应用情况,并提出大豆蛋白水凝胶如今存在的问题及今后的研究方向,为制备具有更高性能的大豆蛋白基水凝胶及推动其在食品领域中的广泛应用提供理论依据。     

黏均分子质量对O-羧甲基壳聚糖/海藻酸钠微球溶胀性能、稳定性及微观结构的影响

O-羧甲基壳聚糖(OCC)与海藻酸钠(SAL)形成的水凝胶微球,在肠道靶向传输过程中具有很大的应用潜力。将不同的OCC与SAL混合后滴入Ca Cl2溶液中制备微球,研究OCC黏均分子质量对OCC/SAL微球在p H 1.2,p H 6.8和p H 7.4溶液中溶胀性的影响。采用扫描电子显微镜分析微球的微观结构。结果表明:OCC黏均分子质量对OCC/SAL微球在p H 1.2溶液中的溶胀性和稳定性无显著影响,而对其在p H 6.8和p H 7.4溶液中的溶胀差异、稳定性和微观结构有重要影响,并且该影响与OCC的取代度有密切关系。当OCC取代度为0.9时,OCC的黏均分子质量对OCC/SAL水凝胶微球在不同p H条件下的溶胀性能均无显著影响,而显著影响水凝胶的稳定性。OCC的黏均分子质量越小,水凝胶在中性及弱碱性条件下的稳定性越差。当OCC取代度为0.83时微球的稳定性也有相似的变化规律,而对其在p H 6.8和p H 7.4溶液中的溶胀性有显著影响,即溶胀率随着黏均分子质量的增加而降低。当取代度为0.53时,OCC/SAL微球在p H 6.8和p H 7.4溶液中的溶胀率随着OCC黏均分子质量的增加而增加,且高黏均分子质量OCC/SAL水凝胶微球在p H 6.8和p H 7.4溶液中均未被观察到裂解,而低分子质量OCC与SAL形成的微球在p H 6.8和p H 7.4溶液中均发生了裂解。扫描电子显微镜分析表明,OCC的黏均分子质量越大,微球表面的凸起越明显,而且聚集很多纳米级的小微球。     

超分子水凝胶的制备与应用

水凝胶在日常生产与生活中发挥着重要作用,但传统水凝胶由于缺乏刺激响应性等动态性,无法满足日益增长的生产与生活需求。因此,制备并应用具有优异自修复性、刺激响应性以及可适应性等动态性的超分子水凝胶（SHGs）备受关注。综述了SHGs的制备与应用研究进展,系统归纳了高分子类SHGs（如聚丙烯酸SHGs、聚丙烯酰胺SHGs等）和天然高分子类SHGs（如壳聚糖SHGs、透明质酸SHGs等）的合成方法,阐述了SHGs在生物医药、柔性传感、防污材料等领域中的应用情况,最后展望了SHGs存在问题及发展趋势。     

Hydrogels as a Potential Chromatographic System: Absorption,Speciation, and Separation of Chromium Species from Aqueous Media

Hydrogels with highly charged forms and amphiphilic character, based on an anionic monomer 2-acrylamido-2-methyl-1-propansulfonic acid sodium salt (AMPSNa) and a cationic monomer 3-acrylamidopropyltrimethylammoniumchloride (APTMACl), were synthesized via a photo-polymerization technique and investigated for potential use in the separation of chromium species with different oxidation states. They were used for three main purposes. First, a single chromium species was successfully removed from an aqueous medium in the presence of other forms using the appropriate design and synthesis of the hydrogels. Secondly, the copolymerized p(AMPSNa-co-APTMACl) hydrogels were used to remove two chromium species simultaneously from an aqueous medium. Lastly, in addition to speciation of the chromium species, their separation and removal by an externally applied magnetic field using magnetically responsive hydrogels was demonstrated.     

Thermosensitive fibres of lyocell/poly(N‐isopropylacrylamide): multiparametric analysis for studying the graft copolymerization

The thermosensitive properties of the hydrogel poly(N‐isopropylacrylamide) (pNIPAAm) together with the good mechanical properties of lyocell fibres make a combination of the two to be thought of as a smart textile. In the present study the optimal values of various parameters that control the grafting process of pNIPAAm onto lyocell fibres were determined considering the influence of the interaction between them. The copolymerization of pNIPAAm hydrogel onto lyocell fibres was performed in aqueous acidic medium using cerium(IV) as initiator. An experimental design was planned in order to study the effect of the interactions between some variables that affect the kinetics of the graft copolymerization: the cerium(IV) initiator concentration, the N‐isopropylacrylamide (NIPAAm) monomer concentration and the liquor fibre‐to‐bath ratio. The results show that the interaction between the concentrations of NIPAAm and the initiator significantly affects the degree of grafting (DG), the optimum values being 1250 and 12.25 mmol L^?1, respectively. In contrast, the liquor ratio parameter shows no significant interaction with the other two variables studied, meaning that it acts independently but showing a proportional relationship with respect to the DG obtained. In addition, the presence of pNIPAAm in the copolymer obtained was confirmed by Fourier transform infrared spectral analysis. Moreover, the water sorption capacity, depending on the temperature, of the lyocell/pNIPAAm copolymer was studied, with an increase being observed when the DG is higher than 60% and also increasing with the temperature.© 2012 Society of Chemical Industry     

Photo-Polymerization Damage Protection by Hydrogen Sulfide Donors for 3D-Cell Culture Systems Optimization

Photo-polymerized hydrogels are ideally suited for stem-cell based tissue regeneration and three dimensional (3D) bioprinting because they can be highly biocompatible, injectable, easy to use, and their mechanical and physical properties can be controlled. However, photo-polymerization involves the use of potentially toxic photo-initiators, exposure to ultraviolet light radiation, formation of free radicals that trigger the cross-linking reaction, and other events whose effects on cells are not yet fully understood. The purpose of this study was to examine the effects of hydrogen sulfide (H₂S) in mitigating cellular toxicity of photo-polymerization caused to resident cells during the process of hydrogel formation. H₂S, which is the latest discovered member of the gasotransmitter family of gaseous signalling molecules, has a number of established beneficial properties, including cell protection from oxidative damage both directly (by acting as a scavenger molecule) and indirectly (by inducing the expression of anti-oxidant proteins in the cell). Cells were exposed to slow release H₂S treatment using pre-conditioning with glutathione-conjugated-garlic extract in order to mitigate toxicity during the photo-polymerization process of hydrogel formation. The protective effects of the H₂S treatment were evaluated in both an enzymatic model and a 3D cell culture system using cell viability as a quantitative indicator. The protective effect of H₂S treatment of cells is a promising approach to enhance cell survival in tissue engineering applications requiring photo-polymerized hydrogel scaffolds.     

Thermodynamic investigation of thermoresponsive xanthan‐poly (N‐isopropylacrylamide) hydrogels

Polysaccharide‐based hydrogels, such as xanthan maleate/poly(N‐isopropylacrylamide) (PNIPAAm) interpenetrated polymer networks, are thermostimulable materials of interest for the controlled release of biologically active components due to conformation changes at the low critical‐solution temperature (LCST) PNIPAAm phase transition. The phase transition of these interpenetrated polymer network hydrogels, where PNIPAAm is in a ‘confined’ environment, was examined by high resolution magic angle spinning nuclear magnetic resonance and differential scanning calorimetry. High resolution magic angle spinning nuclear magnetic resonance spectroscopy allows the accurate determination of LCST and an evaluation of the corresponding thermodynamic data. More particularly, the evolution of these data as a function of the composition of the hydrogel, and of the external parameters such as pH and ionic strength, was considered. LCST shows a minimal value with increasing xanthan content. Moreover, it was possible to calculate, as a function of temperature, the fraction of NIPAAm which remains uncollapsed. The data obtained for pure PNIPAAm hydrogels are in good agreement with recently published results. The phase transition of PNIPAAm in a diphasic hydrogel is broader when PNIPAAm is ‘confined’ within an interpenetrated polymer network than in a pure PNIPAAm crosslinked network. The widening of the transition with increasing xanthan content indicates a reduction of the PNIPAAm interchain aggregation in a network structure. Copyright © 2011 Society of Chemical Industry     

Adsorption of nile red by poly(N‐isopropylacrylamide) gels in binary water/tetrahydrofuran mixtures

The adsorption of Nile Red by poly(N‐isopropylacrylamide) (PNIPAM) gels in binary water/tetrahydrofuran solutions was investigated using absorption spectrophotometry as a function of the volume fraction of THF, φ. Due to the cononsolvency abilities of such binary solvent mixtures, deswelling of the PNIPAM gels is observed in water‐rich mixtures, 0 ≤ φ ≤ 0.6, while the gels reswell for φ > 0.6. The position of the absorption band of Nile Red before and after equilibration with the PNIPAM gels indicates that the composition of the external solvent mixture is not practically influenced by the swelling process. On the other hand, it is found that the gels can effectively adsorb Nile Red in water‐rich mixtures (φ < 0.6), whereas no significant adsorption was observed in tetrahydrofuran‐rich mixtures. In fact, about 80% of the dye is adsorbed by the PNIPAM gels, at φ = 0.2. Under these conditions, the rather shrunk PNIPAM gel offers a more convenient less polar environment for Nile Red than the water‐rich bulk solvent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010