敏感性水凝胶的合成及响应原理

本文综述了敏感性水凝胶的分类,介绍了水凝胶的制备方法:交联共聚,接枝共聚以及互穿网络。论述了水凝胶的体积相转变原理以及pH、温度敏感性水凝胶的响应原理。     

聚丙烯酰胺水凝胶的PH敏感性研究

高分子凝胶是大分子链经交联聚合而成的三维网络或互穿网络与溶剂(通常是水)组成的体系,具有智能响应的能力。研究聚丙烯酰胺水凝胶的pH敏感性对胶体的药物释放控制有积极的指导意义。分析了pH敏感性的变化规律,探讨了离子型水凝胶pH敏感性的溶胀机理。由研究表明,聚丙烯酰胺(PAAM)水凝胶的pH值敏感性变化过程可以分为3个阶段,得到了在pH值影响下的胶体溶胀比的计算公式。     

智能水凝胶的发展现状

综述了智能水凝胶的分类及其合成方法,重点介绍其温敏性、pH敏性、温度和pH双敏性、光敏性和压敏性,另外还讨论了水凝胶敏感性的结构影响因素和敏感机理以及力学性能的改善。     

P(AAm-co-AA)/Ag复合材料制备及表征

以N,N-亚甲基双丙烯酰胺(N,N-MBA)为交联剂,过硫酸钾(KPS)为引发剂,采用交联共聚方法合成了具有pH敏感性的半互穿网络丙烯酰胺-co-丙烯酸水凝胶P(AAm-co-AA),利用水凝胶网络结构作为纳米反应器,自组装制备了纳米复合水凝胶P(AAm-co-AA)/Ag。水凝胶的溶胀行为研究表明,AAm与AA的质量比影响P(AAm-co-AA)/Ag水凝胶平衡溶胀率。     

聚苯胺/碳纳米管杂合水凝胶的合成及膨胀性能研究

合成了一种以甲基丙烯酸-丙烯酰胺共聚网络P(AAm-co-MAA)为基体,以聚苯胺为互穿组分(PANI)的半互穿网络杂合水凝胶。研究表明,当将PANI和MWNTs-COOH被引入到P(AAm-co-MAA)网络中后得到的P(AAm-co-MAA)/PANI/MWCNT-COOH半互穿网络杂合水凝胶则能保持较好的膨胀性,同时发现,依靠调节PA-NI/MWNTs-COOH的含量可以使杂合水凝胶膨胀性增加。这为研究杂合水凝胶的力学性能和pH敏感性提供了一个窗口。     

具有pH及温度敏感性的互穿网络水凝胶的合成及其性能研究

用自由基聚合合成了具有两亲性的N-异丙基丙烯酰胺(NIPAm)与衣康酸(IA)共聚物水凝胶(NIPAm-co-IA),利用互穿网络(IPN)技术合成了壳聚糖(CS)异丙基丙烯酰胺与衣康酸互穿网络水凝胶IPN(CS/NIPAm-co-IA).研究表明, IPN(CS/NIPAm-co-IA)水凝胶具有良好的pH及温度敏感性,研究了其对辅酶A的控制释放,发现其对辅酶A具有良好的控制释放作用.     

粒状聚N-异丙基丙烯酰胺/壳聚糖水凝胶的制备、性能及其应用

用反相悬浮聚合法,合成了具有温度/pH敏感性的聚N-异丙基丙烯酰胺/壳聚糖粒状半互穿网络(PNIPA/CS semi-IPN)水凝胶,研究了该水凝胶在不同温度、不同pH介质以及不同组成下的溶胀率变化.结果表明:该水凝胶的最低临界溶液温度(LCST)与PNIPA水凝胶基本相同,均在33℃左右,pH=3时溶胀率达到最大,具有明显的温度和pH敏感性.壳聚糖(CS)的不同比例也对凝胶的溶胀率产生很大影响.振荡实验表明:凝胶粒子具有温度响应可逆性.同时进行了乳酸吸附与释放的初步研究,当PNIPA/CS质量比为10时,最大吸附达到168.29 mg(g dry gel)-1,释放率为31.74%.     

pH敏感性P(AAm-co-AA)半互穿网络水凝胶的制备、表征及溶胀动力学研究

以N,N-亚甲基双丙烯酰胺(N,N-MBA)为交联剂、过硫酸钾(KPS)为引发剂,采用自由基交联共聚法合成了具有pH敏感性的半互穿网络水凝胶聚丙烯酰胺-co-丙烯酸[P(AAm-co-AA)],通过傅立叶红外光谱、差热分析研究了水凝胶的结构及热稳定性.水凝胶的溶胀研究表明,随着缓冲溶液pH值的增大平衡溶胀率增大;在不同...     

含聚氨酯型温度和pH双敏性水凝胶的合成及性能研究

合成了两种阴离子型的端烯基聚氨酯（UAA）预聚物，制备了pH值敏感的水凝胶，比较了它们的pH值响应性，将UAA预聚物与N-异内基丙烯酰胺（NIPA）共聚，得到具有温度和pH值双重敏感性的水凝胶，研究发现聚氨酯侧链的引入对NIPA的相转变温度（LCST）几乎无影响，聚合温度和组成比对所合成的水凝胶性能有较大的影响。     

微波辐照合成聚丙烯酸水凝胶及其性能研究

采用微波辐照法合成了聚丙烯酸水凝胶,并对其溶胀性能进行了研究。所制得的凝胶不仅具有pH敏感性和良好的pH反复性,而且在pH<4的酸性溶液中表现出温度敏感性,其溶胀比随温度的升高而上升。     

Thermo‐ and pH‐sensitive poly(vinylmethyl ether)/carboxymethylchitosan hydrogels crosslinked using electron beam irradiation or using glutaraldehyde as a crosslinker

BACKGROUND: Stimuli‐sensitive or intelligent hydrogels have been investigated for many biomedical and pharmaceutical applications. Those hydrogels with dual sensitivity will have more extensive potential applications. The aim of the work presented was to prepare a series of thermo‐ and pH‐sensitive hydrogels based on poly(vinylmethyl ether) (PVME) and carboxymethylchitosan (CMCS). The hydrogels were crosslinked using electron beam irradiation (EB) or using glutaraldehyde (GA) as a crosslinker at room temperature. RESULTS: The structures of the PVME/CMCS hydrogels obtained using the two crosslinking methods are proposed. The effects of component polymer ratio, GA content, irradiation dose, temperature and pH on the swelling behavior of the PVME/CMCS hydrogels were studied. There is a sharp decrease in the swelling ratios when the temperature increases from 25 to 37 °C. At low pH and also at high pH, the hydrogels have a higher swelling ratio; however, deswelling occurs evidently at a pH of around 3. CONCLUSION: The study shows that both EB and GA crosslinked hydrogels are thermo‐ and pH‐ sensitive, simultaneously. Thus, they may be potential candidates for both thermo‐ and pH‐sensitive applications. Copyright © 2009 Society of Chemical Industry     

pH‐ and thermal characteristics of graft hydrogels based on chitosan and poly(dimethylsiloxane)

Graft copolymerization of epoxy‐terminated poly(dimethylsiloxane) (PDMS) onto chitosan was reacted without using a catalyst. pH‐sensitive hydrogels were obtained that are based on two different components: a natural polymer and a synthetic polymer. These PDMS substitutents provide the basis for hydrophobic interactions that contribute to the formation of hydrogels. Various graft hydrogels were prepared from different weight ratios of chitosan and PDMS. Swelling behavior of these hydrogels was studied by immersion of the gels in various buffer solution. Photocrosslinked hydrogels exhibited a high equilibrium water content (EWC). Particularly, the sample CP31 of the highest chitosan–PDMS weight ratio showed the highest EWC in time‐dependent, temperature‐dependent, and pH‐dependent swelling behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2661–2666, 2002     

智能水凝胶的制备以及在药物缓释方面的研究进展

介绍了温度、pH、电场、磁场、光,葡萄糖敏感型智能水凝胶的制备方法以及智能水凝胶在药物缓释控释领域的应用研究进展,并对未来智能水凝胶的发展方向做了展望。     

温度及pH敏感生物水凝胶的研究

运用互穿网络技术,合成了具有温敏性的聚(N 异丙基丙烯酰胺)(PNIPAm)和生物大分子明胶(gelatin)的互穿网络聚合物(PNIPAm/Gelatinsemi IPN和PNIPAm/GelatinIPN)水凝胶,该水凝胶的最低临界溶液温度(LCST)与PNIPAm水凝胶的LCST基本相同,均为33℃左右,但在LCST以下的平衡溶胀率减小、相变区域略微变宽。在此基础上,通过N 异丙基丙烯酰胺(NIPAm)与丙烯酸(AAc)交联共聚,改变了水凝胶的LCST,在pH=4 0的缓冲溶液中,各水凝胶的溶胀行为基本一致,与AAc含量无关,LCST都为28℃左右;在pH>4 0的缓冲溶液中,LCST随AAc组分含量的增加而增加,但温敏性减小。同时,AAc的加入,使水凝胶具有pH敏感性,敏感点为pH=4 5左右。还考察了该水凝胶降解的特点:戊二醛(GA)交联后的明胶网络,保留了明胶的生物降解性,但互穿网络水凝胶在实验条件下几乎未被胃蛋白酶和胰蛋白酶降解,在pH=9 6的碱性条件下,水凝胶可发生化学降解。     

NVP接枝壳聚糖水凝胶的合成与溶胀性能

合成了N-乙烯基吡咯烷酮（NVP）接枝壳聚糖（CHI）水凝胶,讨论了NVP/CHI、引发剂、交联剂、聚合温度、乙酸浓度等因素对接枝率及凝胶溶胀性能的影响,NVP∶CHI为6时,接枝率达到300%以上. 溶胀温度、pH值、盐浓度等对凝胶溶胀性能的影响实验表明,凝胶表现出温度敏感性,在40 ℃出现最大平衡溶胀率,并观察到一级相转变;在中性或弱酸性介质中溶胀性能较好;与PVP凝胶相比,NVP接枝CHI凝胶表现出反聚电解质效应. 溶胀动力学研究表明,在溶胀前期,CHI含量较高时,凝胶趋向于非Fick溶胀,说明除了溶剂扩散外,凝胶网络链段弛豫、水分子与凝胶网络间及凝胶高分子链段间相互作用对凝胶溶胀性能的影响至关重要;CHI含量较高时则趋向于Fick溶胀.     

Synthetic hydrogels: Synthesis,novel trends,and applications

Hydrogels have been generated and explored for use in various applications. The main objective of this comprehensive review is to collate the fundamental concepts of hydrogels, and elaborate on knowledge gaps, and to provide a perspective on the future directions. This review includes details of constituent molecules (monomers, cross-linkers, composite materials, etc.) and the methods used to prepare polymer networks. Moreover, the review highlights modifications of hydrogels that introduce new properties or enhance the existing features to suit the desired applications and challenges of synthetic polymer hydrogels. The other important topics covered in this review are the synthesis and applications of 3D printed hydrogels, nanocomposite hydrogels, injectable hydrogels, and self-healing hydrogels.     

Hydrogels as smart biomaterials

Hydrogels were the first biomaterials rationally designed for human use. Beginning with the pioneering work of Wichterle and Lím on three‐dimensional polymers that swell in water, we review the design, synthesis, properties, and applications of hydrogels. The field of hydrogels has moved forward at a dramatic pace. The development of suitable synthetic methods encompassing traditional chemistry to molecular biology has been used in the design of hydrogels mimicking basic processes of living systems. Stimuli‐sensitive hydrogels, hydrogels with controlled degradability, genetically engineered poly(amino acid) polymers reversibly self‐assembling in precisely defined three‐dimensional structures, and hybrid polymers composed of two distinct classes of molecules are just some examples of these exciting novel biomaterials. The biocompatibility of hydrogels and their applications from implants to nanomaterials are also reviewed. Copyright © 2007 Society of Chemical Industry     

Investigation of mechanical and thermodynamic properties of pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels prepared with different crosslinking agents

pH‐sensitive poly(N,N‐dimethylaminoethyl methacrylate) hydrogels were synthesized by free‐radical crosslinking polymerization using two different crosslinking agents; tetraethylene glycol dimethacrylate (TEGMA) and N,N′‐methylenebis(acrylamide) (BAAm). The influence of the polymerization factors such as the type of the crosslinking agent and the gel preparation concentration on the swelling behavior, the gel strength, the effective crosslinking density and the average chain length between the crosslink points for the resulting hydrogels was investigated. The results of the equilibrium swelling measurements in water showed that the linear swelling ratio of the resulting hydrogels increases with increasing gel preparation concentration. The swelling ratio of PDMAEMA hydrogels crosslinked with BAAm is larger than those for hydrogels crosslinked with TEGMA over the entire range of the polymer network concentration. The hydrogels exhibit very sharp pH‐sensitive phase transition in a very narrow range of pH between 7.7 and 8.0. From the mechanical measurements, it was also found that the linear swelling ratio of resulting hydrogels depends on the crosslinking density and also the type of the crosslinker used in the preparation. The resulting hydrogels are thought to be good candidates for pH‐sensitive drug delivery systems. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Dual stimuli responsive neutral/cationic polymers/clay nanocomposite hydrogels

In this work, a thermodynamic-based equilibrium-swelling model was proposed to predict the swelling process of neutral/cationic polymers-clay nanocomposite hydrogels sensitive to dual stimuli temperature and pH. Indeed, the new swelling model can estimate the effect of the rigid clay nanoparticles component on swelling behavior of blend nanocomposite hydrogels. The mixing term in model was developed based on lattice theory by considering the effects of solvent-polymers, solvent-clay, and polymer-clay interaction parameters. The influence of the ionic groups of the clay layers and cationic polymer on the swelling was also taken into account in the proposed model. The model was verified by preparation of polyvinyl alcohol/chitosan/montmorillonite intelligent nanocomposite hydrogel by tripolyphosphate crosslinking method followed by freezing–thawing process. It was found that it could give good prediction for the equilibrium swelling of polymer-clay nanocomposite hydrogels in the case of phantom network, especially where the swelling temperature and clay loading level are high and the pH of swelling medium is low. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48797.     

Novel polyketones with pendant imidazolium groups as nanodispersants of hydrophobic antibiotics

In this work, we present a new method to nanodisperse the pH‐sensitive antibiotics oxolinic acid and flumequine by the use of a pH‐sensitive synthetic polyketone derivative with amphiphilic characteristics. The pH‐sensitive polymer bears imidazolium residues on pendant groups as weak acids, and its solvophobic properties can be tuned by changing the pH. While the antibiotics are soluble in water at pHs higher than 7.0 for flumequine and 8.4 for oxolinic acid, and the polymer is soluble in water at pHs lower than 5.5, nanoprecipitates presenting hydrodynamic radius of 35–100 nm and positive zeta potential containing both the polymer and any of the antibiotics are formed at pH 6.8 by mixing stock solutions whose pH has been adjusted to 5.4 for the polymer and higher than 10 for the antibiotics. The out‐of‐equilibrium process occurring upon mixing both solutions produces pH changing, molecular arrangement, and a controlled collapse of the system in the form of nano‐ and submicron particles. The driving forces for the arrangements are found among hydrophobic forces, long‐range electrostatic interactions, and short range aromatic–aromatic interactions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42363.