Structure and swelling-release behaviour of poly(vinyl pyrrolidone) (PVP) and acrylic acid (AAc) copolymer hydrogels prepared by gamma irradiation

Copolymer network hydrogels were prepared by gamma irradiation of aqueous solutions of poly(vinyl pyrrolidone) (PVP) and acrylic acid monomer (AAc). The composition of the final hydrogels compared to the composition of the initial preparation solutions of hydrogels was determined. The chemical structure and nature of bonding was characterized by IR spectroscopy analysis, while the thermal durability of the prepared hydrogels was assessed by thermogravimetric analysis (TGA). The kinetic swelling in water and the pH-sensitivity of PVP/AAc copolymer hydrogels was studied. The drug release properties of PVP/AAc hydrogels taking methyl orange indicator as a drug model was investigated. The IR spectra indicate the formation of copolymer networks, whereas the TGA study showed that the PVP/AAc hydrogels possess higher thermal stability than pure PAAc and lower than PVP hydrogels. The kinetic swelling in water showed that all the hydrogels reached equilibrium after 24 h and that the degree of swelling increases with increasing the ratio of AAc in the initial feeding solutions. It was found that the degree of swelling of PVP/AAc hydrogels increases greatly within the pH range 4-7 depending on composition.     

丝素蛋白-聚氨酯复合水凝胶的制备及性能研究

以聚乙二醇(PEG)、聚氧化丙烯二醇(PPG)、异弗尔酮二异氰酸酯(IPDI)为主要原料制备聚氨酯预聚体(PU),与丝素蛋白水溶液(SF)交联制得丝素蛋白-聚氨酯(SF-PU)复合水凝胶.分别利用ATR、SEM对水凝胶组成、结构及微观形貌进行表征;DSC、吸水溶胀测试探讨了丝素蛋白与聚氨酯的质量比(SF/PU)以及聚氨酯中不同软段质量比(PEG/PPG)对SF-PU水凝胶热性能、溶胀性能的影响.结果表明,SF-PU水凝胶具有多孔结构;样品中不同的SF/PU、PEG/PPG均对材料的玻璃化转变温度、结晶度及溶胀性能产生影响,且当水凝胶组分为SF/PU=1/25、PEG/PPG=2/1时,平衡溶胀比(ESR)可达到440%;水凝胶在溶胀初始阶段符合菲克扩散模型,整个溶胀过程遵循溶胀动力学2级方程.     

Synthesis of cationic water‐soluble copolymers and hydrogels based on [2‐(methacryloyloxy)ethyl]trimethylammonium chloride and 2‐hydroxyethylacrylate and their complex formation with poly(acrylic acid)

Water‐soluble cationic copolymers and hydrogels were synthesized by radical copolymerization of [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT) and 2‐hydroxyethylacrylate (HEA). The kinetics of copolymerization has been studied and the reactivity ratios were determined. It was found that MADQUAT exhibits higher reactivity in copolymerization. The complexation between linear MADQUAT‐HEA and linear poly(acrylic acid) (PAA) has been studied in aqueous solutions at different pH. It results in the formation of insoluble polyelectrolyte complexes, whose composition and stability to aggregate depends on MADQUAT content in copolymers and pH. The hydrogels were synthesized by three‐dimensional radical copolymerization of MADQUAT and HEA in the presence of a crosslinker. The effects of the feed mixture composition on yield and swelling properties of the hydrogels were studied. The interactions of these hydrogels with linear PAA result in formation of gel–polyelectrolyte complexes and contraction of the samples. It was found that the contraction depends on copolymer composition, PAA molecular weight, and solution pH. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44:845–853, 2006     

Synthesis and properties of biodegradable thermo- and pH-sensitive poly[(N-isopropylacrylamide)-co-(methacrylic acid)] hydrogels

Thermo- and pH-sensitive hydrogels were synthesized via the copolymerization of N-isopropylacrylamide (NIPAAm) and methacrylic acid (MAA) crosslinked with a biodegradable PEG-co-PCL macromolecular crosslinker under UV irradiation. Swelling measurements showed that temperature and pH sensitivity of the resultant hydrogels were highly dependent on the composition of the hydrogels as well as temperature and pH of the local medium. The pH and temperature dependence of the hydrogels displayed good reversibility. The hydrolytic degradation studies showed that the degradation rate of the hydrogels increased with the increasing content of MAA introduced in the hydrogels in pH 7.4 PBS solutions at 37 °C. The study on the release of BSA indicated that the release rate of BSA was higher at pH 7.4 than at pH 2.0, and increased with the increase of the MAA content in the hydrogels in pH 7.4 PBS solutions at 37 °C. These hydrogel materials are desirable for potential applications as smart drug delivery systems.     

pH快速响应PNIPAAm-co-PAAc水凝胶的制备及溶胀动力学

pH快速响应PNIPAAm-co-PAAc水凝胶的制备及溶胀动力学;N-异丙基丙烯酰胺;pH敏感性;溶胀历史     

Autonomously-triggered microfluidic cooling using thermo-responsive hydrogels

We present autonomously-triggered on-chip microfluidic cooling devices that utilize thermo-responsive hydrogels to adapt to local environmental temperatures. An external rotating magnetic stirrer couples with an in situ fabricated nickel impeller in these centrifugal-based microfluidic cooling devices to recirculate cooler water. Temperature-responsive hydrogels, which exhibit volumetric expansion and contraction, are integrated at the axle of the impeller. In this design, the hydrogels behave similar to an automotive clutch, to autonomously control the impeller's rotation as a function of the local environmental temperature. Therefore, the hydrogels act as both sensors and actuators and help take away the necessity for additional temperature sensing, feedback, and/or control units here. Cooling devices capable of on-chip thermal management at multiple predetermined onset operation points are realized by changes to the composition of hydrogel to alter its lowest critical solution temperature (LCST). Furthermore, the effect of magnetic stirrer frequency on the fluid cooling and flowrates for different two-blade nickel impeller designs are presented.     

Electrical response characterisation of poly(ethylene glycol) macromer (PEGM)/chitosan hydrogels in NaCl solution

Interpenetrating polymer network hydrogels composed of poly(ethylene glycol) macromer (PEGM) and chitosan were synthesised by UV irradiation of solutions in a mild aqueous media. The IPN hydrogels exhibited the equilibrium water content (EWC) in the range of 86-94%. The hydrogels were characterised using FT-IR, FT-Raman spectroscopy and differential scanning calorimetry (DSC). The results from DSC measurements indicate that the melting endotherms of PEGM, within the hydrogels, decreased in intensities and shifted to lower temperatures comparing with a linear PEGM. This was due to the decrease of the crystallinity in the IPN hydrogels with higher contents of PEGM. The electrical response of the IPN hydrogels was also investigated by applying electrical current to the hydrogels immersed in a NaCl solution. The extent of a bending degree of the IPN hydrogel depends on the IPN hydrogel composition and applied electric field strength.     

几类甲基丙烯酸pH—敏感水凝胶的溶胀行为研究

本文合成了以甲基丙烯酸为基础的各类ｐＨ敏感型水凝胶,并研究它们的溶胀行为。初步探索了水凝胶的组成与其ｐＨ敏感的关系,比较了阴离子型水凝胶、阳离子型水凝胶和两性水凝胶的溶胀热力学动力学行为,得出了两性水凝胶在整个ｐＨ范围内都有一定的溶胀比,且在ｐＨ中性时,其溶胀速率要高于相应的阴离子型和阳离子型水凝胶。     

Synthesis of poly (acrylamide-co-aconitic acid) adsorbents by gamma-irradiation,characterization, adsorption studies and application for cationic dyes removal

In this study, acrylamide (AAm)/aconitic acid (ACA) copolymers were prepared with two different mol% of aconitic acid 4%, 17% and were irradiated with gamma irradiation at different irradiation doses (4 - 25kGy). The percent yield was assigned by gravimetrical method. The effect of irradiation dose, pH and involved amounts of monomers (AAm/ACA) in hydrogels on swelling properties were investigated. The conversion of monomers to hydrogels was 100% at 25kGy. Poly(acrylamide-co-aconitic acid) P(AAm/ACA) hydrogels have been used for the adsorption of some aqueous solutions of dyes such as Methylene Blue (MB) and Safranine-O (S). The hydrogels were swollen in distilled water at pH 3, 5, 7, 8 and in aqueous solutions of dyes. The initial swelling rates of hydrogels are increased by increasing of pH. The effects of concentration of the aqueous solutions of dye and hydrogel composition on the adsorption were investigated. The adsorption is increased and changed depending on the structure of dye and composition of hydrogel.     

Preparation and characterization of biodegradable gelatin-PAAm-based IPN hydrogels for controlled release of maleic acid to improve the solubility of phosphate fertilizers

In this study, interpenetrating polymer network (IPN) hydrogel systems including maleic acid (MA) were constituted to improve the solubility of phosphate fertilizers. A series of full and semi-IPN hydrogels were prepared from various gelatin/polyacrylamide mixtures by using two different cross-linkers. The effects of polymer composition on the morphological structures and swelling behaviors of the hydrogels were investigated. The swelling values of all hydrogels were found to be in between 435% and 830%. MA release from load0ed hydrogels was followed and it was determined that MA-loaded hydrogels efficiently decreased pH and improved the solubility of Ca₃(PO₄)₂ in releasing medium.     

Swelling behavior of amphiphilic hydrogels of copolymers of the vinyl ether of ethylene glycol and vinyl isobutyl ether,and their interaction with cationic surfactant

Amphiphilic hydrogels of copolymers of the vinyl ether of ethylene glycol and vinyl isobutyl ether were synthesized by -radiation-induced free radical polymerization. Hydrogels with certain copolymer compositions showed thermo-sensitive behavior in aqueous solutions. The swelling behavior of the hydrogels in cetylpyridinium bromide aqueous solution was studied. Increased swelling of the hydrogels was observed in the surfactant solutions. The increased swelling was more prominent for the hydrogels with a higher content of hydrophobic moiety in the copolymer composition, and with higher surfactant concentration. The reason for this phenomenon is discussed. Treatment of some hydrogels in the surfactant solutions resulted in higher swelling ability in distilled water with distinct thermo-induced contraction over a narrow temperature interval.     

γ-irradiated chitosan-polyvinyl pyrrolidone hydrogels as pH-sensitive protein delivery system

The effects of pH of the buffer solution and the composition of the hydrogel system on the bovine serum albumin (BSA) adsorption capacity of chitosan (CS)–polyvinyl pyrrolidone (PVP) (CSPVP) hydrogels and release of BSA were investigated. Poly-electrolyte CSPVP hydrogels with different compositions were prepared by irradiating CS/PVP/water mixtures with γ-rays at ambient temperature. The adsorption capacity of hydrogels was found to increase from 0 to 350 mg BSA/g dry gel, by changing external stimuli and hydrogel composition. The adsorption of BSA within CSPVP hydrogels increased with increase in CS content in the hydrogels. When the irradiation doses of hydrogel increased, the adsorption of BSA decreased. The maximum adsorption of BSA was observed at pH 5. A significant amount of the adsorbed BSA (up to 95%) was eluted in the phosphate medium containing 0.1 M NaCl at pH 7.4.     

Synthesis and characterization of biodegradable network hydrogels having both hydrophobic and hydrophilic components with controlled swelling behavior

A new class of biodegradable hydrogels, consisting of hydrophobic poly(D ,L )lactic acid (PDLLA) and hydrophilic dextran segments with a polymer network structure, was synthesized with UV photopolymerization. Unsaturated vinyl groups first were introduced onto the PDLLA and dextran polymer backbones, then followed by a crosslinking reaction of diacrylate-terminated PDLLA and dextran acrylate. The chemical crosslinking forced the hydrophobic PDLLA and hydrophilic dextran segments to mix with each other in the network hydrogels. The new polymers were characterized by standard polymer characterization methods such as NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. The effects of reaction time, temperature, and molar ratio of the reactants on the incorporation of acrylate onto the polymer backbone were examined. A series of hydrogels with different dextran/PDLLA composition ratios was prepared, and their swelling behaviors were studied. These new bicomponent network hydrogels had a wide range of hydrophilicity to hydrophobicity that was difficult to achieve in totally hydrophilic hydrogels. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4554–4569, 1999     

Superabsorbant hydrogels based on xanthan and poly(vinyl alcohol): 1. The study of the swelling properties

The swelling properties of some superabsorbant composite hydrogels, based on xanthan and poly(vinyl alcohol) and crosslinked with epichlorohydrin, were studied. The maximum swelling degree of the hydrogels and the swelling rate constant were determined as a function of the hydrogel's composition (the % of poly(vinyl alcohol) in the polymer mixture and the amount of crosslinking agent), the crosslinking reaction conditions (the time and the temperature of the crosslinking reaction), and the composition of the swelling solutions (the glycerin/water ratio and the concentration of the electrolyte).     

Cross‐linking induced thermoresponsive hydrogel with light emitting and self‐healing property

Development of self‐healing hydrogels with thermoresponse is very important for artificial smart materials. In this article, the self‐healing hydrogels with reversible thermoresponses were designed through across‐linking‐induced thermoresponse (CIT) mechanism. The hydrogels were prepared from ketone group containing copolymer bearing tetraphenyl ethylene (TPE) and cross‐linked by naphthalene containing acylhydrazide cross‐linker. The mechanical property, light emission, self‐healing, and thermo‐response of the hydrogels were investigated intensively. With regulation of the copolymer composition, the hydrogels showed thermoresponse with the LCST varied from above to below body temperature. At the same time, the hydrogels showed self‐healing property based on the reversible characteristic of the acylhydrazone bond. The hydrogel also showed temperature‐regulated light emission behavior based on AIE property of the TPE unit. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 869–877     

温度与pH快速响应性P(NIPAM-co-AAc)水凝胶的制备及其性能

以氯化钠水溶液作为反应介质,成功制备了温度与pH快速响应性聚(N-异丙基丙烯酰胺-co-丙烯酸)[P(NIPAM-co-AAc)]水凝胶,研究了氯化钠水溶液的浓度对凝胶性能的影响.通过红外光谱(FT-IR)、扫描电镜(SEM)、测溶胀比对凝胶性能进行了表征.结果表明:凝胶具有相同的化学组成与结构,但具有不同的微观形态;随着反应介质中氯化钠浓度的增加,凝胶在20℃蒸馏水中的平衡溶胀比增大,并表现出较强的温度与pH敏感性以及较快的去溶胀速率.     

Swelling kinetics and release characteristic of crosslinked chitosan: Polyether polymer network (semi-IPN) hydrogels

The aqueous swelling kinetics of a series of crosslinked chitosan (cr-CS) with glutaraldehyde (GA) interpenetrating polyether hydrogels have been studied as functions of pH, the N-deacetylation degree of chitosan, the amount of crosslinking agent, the electrolyte composition in solution, temperature, and gel composition. Based on these results, the swelling mechanism of the hydrogels was discussed. The release profiles of chlorhexidini acetas from the semi-IPN were also investigated. © 1994 John Wiley & Sons, Inc.     

Sorption properties of freshly precipitated alumogels

The influence of the pH of precipitation and the ionic medium nature on the composition, surface charge, and kinetic sorption characteristics of aluminum oxyhydroxides formed by alkaline hydrolysis of an aqueous solution of aluminum nitrate was studied. The methods of drop titration with alkali, argentometric titration, point of zero charge, and indicator reactions of heterogeneous hydrolysis were used. The composition of the freshly precipitated hydrogels of aluminum(iii) oxyhydroxide, rate constants of heterogeneous hydrolysis of the IrCl₆ ^2– ions as indicator reactions, and the pH of the point of zero charge were determined. The rate of indicator reactions (as for other oxyhydroxide hydrogels) depends strongly on the pH of precipitation. However, it is lower than the rates characteristics of iron(iii) and chromium(iii) oxyhydroxides obtained under similar conditions. The pH of the point of zero charge for the alumogels in a chloride medium is 8.3 and that in a sulfate medium is 9.5.     

Frontal polymerization synthesis and characterization of temperature- and pH-sensitive hydrogels

The temperature- and pH-sensitive hydrogels, poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AAc)), were synthesized via frontal polymerization (FP). The reaction components have been varied in order to find their influences on frontal parameters and copolymer features. The results showed that front velocity and front temperature were dependent on the initiator concentration, reactant dilution, and NIPMA/AAc molar ratio. In addition, the morphology and sensitive behavior of the FP hydrogels were mainly affected by monomers’ ratio. Namely, the pore size, swelling abilities, LCST, and response kinetics of copolymer hydrogels obviously increased with the increasing acrylic acid concentration; however, they slightly changed with varying of amounts of initiator and solvent. Finally, in comparison with the hydrogels prepared by conventional batch polymerization, the ones synthesized by frontal polymerization exhibited more homogeneous chain composition and improved microstructure and response ability.     

羧甲基纤维素与丙烯酸接枝共聚凝胶的溶胀动力学及过溶胀平衡特性的研究

采用接枝共聚合成了羧甲基纤维素钠、丙烯酸与N,N′-亚甲基双丙烯酰胺的交联凝胶, 研究了这类凝胶在不同pH值的缓冲溶液中的溶胀行为, 发现在酸性介质中凝胶的溶胀动力学行为表现出过溶胀平衡特性(overshooting effect), 即凝胶先发生溶胀到最大值, 然后再逐渐消溶胀到平衡. 这种现象可归因于凝胶溶胀过程中羧基之间通过氢键所产生的协同物理交联. 较之凝胶的组成, 缓冲溶液的pH值对过溶胀平衡现象的影响更为显著. 前者是因为凝胶羧基的总摩尔分数并不随两组分结构单元摩尔数的改变而改变, 羧基之间通过氢键形成的物理交联程度在交联剂摩尔分数接近的条件下变化不大; 后者是由于溶液的pH值显著影响凝胶羧基的质子化程度, 进而影响羧基之间通过氢键形成的物理交联程度. 凝胶在酸性介质中的溶胀过程符合E. Díez-Peña等提出的溶胀动力学定量模型, 理论曲线与实验数据有较好的相关性. 凝胶在pH≥5.0的缓冲溶液中的溶胀不产生过溶胀平衡现象, 这一现象归因于完全离子化的羧基之间不能形成物理交联. 凝胶的溶胀过程遵循Schott二级溶胀动力学.