Preparation of antibacterial temperature‐sensitive silver‐nanocomposite hydrogels from N‐isopropylacrylamide with green tea

This article reports the temperature‐sensitive, green tea (GT)‐based silver‐nanocomposite hydrogels for bacterial growth inactivation. The temperature‐sensitive hydrogels were prepared via free‐radical polymerization using temperature‐sensitive N‐isopropylacrylamide (NIPAM) monomer with GT as the hydrogel matrix. The nanocomposite hydrogels were encapsulated with silver ions via swelling method, which was later reduced to silver nanoparticles using Azadirachta indica leaf extract. The temperature‐sensitive silver nanocomposite hydrogels were analyzed by using Fourier transforms infrared, UV–visible spectroscopy, differential scanning calorimetry–thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The prepared hydrogels exhibited higher phase volume transition temperature than the NIPAM. The inhibition zone study of the inactivation of bacteria on the developed hydrogels was carried out against Gram negative (Escherichia coli) and Gram positive (Staphylococcus aureus), which revealed that the prepared hydrogels are helpful for the inactivation of these bacteria due to the high stabilization of antibacterial properties of the silver nanoparticles. The developed hydrogels are promising for biomedical applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45739.     

Simultaneous lower and upper critical solution temperature‐type co‐nonsolvency behaviour exhibited in water–dioxane mixtures by linear copolymers and hydrogels containing N‐isopropylacrylamide and N,N‐dimethylacrylamide

The co‐nonsolvency behaviour in water–dioxane mixtures of linear copolymers and hydrogels consisting of N‐isopropylacrylamide (NIPAM) and N,N‐dimethylacrylamide (DMAM) was studied as a function of solvent composition and temperature. The composition of the copolymers, P(NIPAM‐co‐DMAMx), in DMAM units, x, varies from x = 0 up to x = 100%. It is shown that the copolymers combine the lower critical solution temperature (LCST)‐type co‐nonsolvency behaviour of poly‐NIPAM with the upper critical solution temperature (UCST)‐type co‐nonsolvency behaviour of poly‐DMAM. Depending on x, both the LCST‐ and UCST‐type co‐nonsolvency behaviour may be simultaneously observed in water‐rich and dioxane‐rich solvent mixtures, respectively. Due to this complex phase separation behaviour, the variation of the reduced viscosity of the linear copolymers, as well as the swelling–deswelling behaviour of the respective hydrogels, are shown to be temperature‐ and solvent‐sensitive. Copyright © 2006 Society of Chemical Industry     

Synthesis and swelling properties of a pH‐ and temperature‐dual responsive hydrogel by inverse microemulsion polymerization

A novel pH‐ and temperature‐dual responsive hydrogel was synthesized by inverse microemulsion polymerization, using itonic acid (IA) as pH‐responsive monomer, N‐isopropylacrylamide (NPAM) as thermo‐responsive monomer and acrylamide (AM) as the nonionic hydrophilic monomer. Factors affecting water and salt absorption, as well as swellability of the dual responsive hydrogels, such as IA/NPAM mass ratio and crosslinker amount, were investigated. pH‐ and temperature‐sensitivity and dynamic viscoelasticity behaviors of the dual responsive hydrogels were also studied. The dual responsive responsive hydrogels showed suitable water and salt absorbency, remarkable pH‐, and temperature‐sensitivity, adjustable swellability and enhanced viscoelastic behaviors under high stress. Water absorbency and pH‐sensitivity increased while salt absorbency and temperature‐ sensitivity decreased with increasing IA/NIPAM mass ratio. Both water absorbency and salt absorbency increased first with crosslinker amount increased to 0.2 wt %, and then decreased with increasing crosslinker amount. Temperature‐induced shrinkage range of the dual responsive hydrogels was higher and broader than that of the conventional poly(N‐isopropylacrylamide) hydrogel. TEM indicated that the as‐synthesized hydrogel particles were regular and spherical‐like in shape and had the mean particle size of 49nm in the range of 30–78 nm. FTIR indicated the structure of the dual responsive hydrogels. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42139.     

Swelling characteristics of thermo‐ sensitive poly[(2‐diethylaminoethyl methacrylate)‐co‐(N,N‐dimethylacrylamide)] porous hydrogels

Temperature‐sensitive poly[(2‐diethylaminoethyl methacrylate)‐co‐(N,N‐dimethylacrylamide)] [P(DEAEMA‐co‐DMAAm)] hydrogels with five different DMAAm contents were synthesized with and without the addition of sodium carbonate as porosity generator. The synthesized hydrogels were characterized with dry gel density measurements, scanning electron microscopy observation and the determination of swelling ratio. The influence of the pore‐forming agent and content of DMAAm on swelling ratio and network parameters such as polymer–solvent interaction parameter (χ), average molecular mass between crosslinks (M?_c) and mesh size (ζ) of the cryogels are reported and discussed. The swelling and deswelling rates of the porous hydrogels are much faster than for the same type of hydrogels prepared via conventional methods. At a temperature below the volume phase transition temperature, the macroporous hydrogels also absorbed larger amounts water compared to that of conventional hydrogels and showed obviously higher equilibrated swelling ratios in aqueous medium. In particular, the unique macroporous structure provided numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to the external temperature changes during the deswelling and swelling processes. These properties are attributed to the macroporous and regularly arranged network of the porous hydrogels. Scanning electron micrographs reveal that the macroporous network structure of the hydrogels can be adjusted by applying porosity generation methods during the polymerization reaction. Copyright © 2007 Society of Chemical Industry     

A novel temperature and pH dual‐responsive hybrid hydrogel with polyhedral oligomeric silsesquioxane as crosslinker: synthesis,characterization and drug release properties

Octavinyl polyhedral oligomeric silsesquioxane (OVPS) is used as the crosslinker instead of N,N′‐methylenebisacrylamide (BIS) to copolymerize with 2‐(dimethylamino)ethyl methacrylate (DMAEMA) or DMAEMA and N‐isopropylacrylamide (NIPAM) to prepare hybrid hydrogels: P(OVPS‐co‐DMAEMA) and P(OVPS‐co‐DMAEMA‐co‐NIPAM). The prepared hydrogels are transparent and show dual response to temperature and pH. The hydrogels were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis and tensile tests. Their mechanical properties, swelling ratio, deswelling and reswelling behaviors as well as drug release properties were investigated. The results indicate that OVPS can be incorporated into polymer networks in proportion to feed ratios. The P(OVPS‐co‐DMAEMA) hydrogel exhibits more homogeneous interior structure, higher swelling ratio and faster response than the conventional hydrogel prepared with BIS. Moreover, the incorporation of OVPS enhances the compression and tensile properties of the hydrogels. The feed ratios of OVPS and NIPAM have a great effect on volume phase transition temperature, thermal sensitivity, swelling behavior, mechanical properties and drug release properties of the hybrid hydrogels. The prepared dual‐responsive OVPS‐containing hydrogels are expected to be used as biomedical materials in drug release and tissue engineering. © 2014 Society of Chemical Industry     

Influence of amino group pKa on the properties of stimuli‐responsive piperazine‐based polymers and hydrogels

Linear homopolymers of N‐acryloyl‐N′‐alkyl piperazine (N′‐alkyl: methyl, ethyl, or propyl) and their corresponding crosslinked hydrogels were prepared. The polymers showed good responses to changes in the pH of the medium due to the presence of tertiary amine functions that could be protonated at a low pH. The nature of the N′‐alkyl group attached to the piperazine amino nitrogen greatly affected the pK_a of the amino group. This in turn influenced the solution behavior of the polymers and was studied with light scattering, potentiometry, and viscosity measurements. The basicity of the polymers increased with an increase in the chain length of the N′‐alkyl substituent. The intrinsic viscosity of the polymers in a good polar organic solvent such as dimethylformamide decreased slightly with increasing temperature because of decreased thermodynamic affinity (interaction) at high temperatures. The viscosity behavior of the polymers in sodium chloride solutions was similar to that of classical polyelectrolytes. The swelling property of the hydrogels was studied with water sorption measurements, and the swelling was by anomalous (non‐Fickian) transport. The diffusion coefficient of the gels in solutions of pH 2.6 increased with increasing N′‐alkyl chain length, whereas at neutral pH, the effect was reversed. This behavior was attributed to the increase in both the basicity and hydrophobicity of the gels with an increase in the chain length of the N′‐alkyl groups. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Swelling behavior of thermoreversible poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) hydrogels

Thermoresponsive hydrogels based on N‐isopropylacrylamide and N‐vinylimidazole were synthesized, and their swelling–deswelling behavior was studied as a function of the total monomer concentration. For copolymeric structures with better thermoresponsive properties with respect to poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) hydrogels, these hydrogels were protonated with HCl and HNO₃, and the copolymer behaviors were compared with those of the unprotonated hydrogels. The temperature was changed from 4 to 70°C at fixed pHs and total ionic strengths. The equilibrium swelling ratio, dynamic swelling ratio, and dynamic deswelling ratio were evaluated for all the hydrogels. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1619–1624, 2004     

Swelling–deswelling kinetics of poly(N‐isopropylacrylamide) hydrogels formed in PEG solutions

A series of poly(N‐isopropylacrylamide) (PNIPA) hydrogels was prepared by free‐radical crosslinking copolymerization of N‐isopropylacrylamide (NIPA) and N,N′‐methylenebisacrylamide (BAAm) in aqueous solutions of poly(ethylene glycol) of molecular weight 300 g/mol (PEG). The amount of PEG in the polymerization solvent, the crosslinker (BAAm) content, and the gel preparation temperature (T_prep) were varied in the gelation experiments. The hydrogels were characterized by the equilibrium swelling and elasticity tests as well as by the measurements of the deswelling–reswelling kinetics of the hydrogels in response to a temperature change between 25 and 48°C. The rate of deswelling of the swollen gel increases while the rate of reswelling of the collapsed gel decreases as the amount of PEG in the polymerization solvent is increased or as the crosslinker content is decreased. The T_prep effect on the swelling kinetics of the hydrogels was only observed if the PEG content of the polymerization solvent is less than 20%, which is explained with the screening of H‐bonding interactions in concentrated PEG solution. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 37–44, 2006     

Poly(ethylene glycol)‐containing cationic hydrogels with lipophilic character

Not much effort has been focused towards the development of hydrogels that swell in nonpolar solvents. We have synthesized a new set of polyelectrolyte hydrogels and demonstrated their ability to absorb a less‐polar or nonpolar organic solvent, as well as their ability to resist gel‐collapse in a predominantly nonpolar medium. The hydrogels were prepared by free radical polymerization of different molar ratios of poly(ethylene glycol) methyl ether acrylate and (3‐(methacryloylamino)propyl)‐trimethyl ammonium chloride as comonomers in an aqueous medium. Their swelling behavior in organic solvents was studied by varying the dielectric constant of the swelling medium including mixed‐solvent systems. Besides a high degree of swelling (up to 200 times) in polar solvents, some of the hydrogels also exhibited moderate swelling (up to 15 times) in less‐polar organic solvents. Hydrogels samples with high cationic content showed drastic change in swelling extent in some of the mixed‐solvent systems. It was also interesting to note that the retention of significant swelling in dimethyl sulphoxide–toluene mixture with even 90% toluene content for some compositions. These polyelectrolyte hydrogels with improved lipophilicity opens up greater opportunities for the development of even superior soft materials through proper structural optimizations that would successfully function for a wider range of solvents. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39873.     

pH‐ and temperature‐responsive IPN hydrogels based on soy protein and poly(N‐isopropylacrylamide‐co‐sodium acrylate)

pH‐ and temperature‐responsive interpenetrating polymer network (IPN) hydrogels based on soy protein and poly(N‐isopropylacrylamide‐co‐sodium acrylate) were successfully prepared. The structure and properties of the hydrogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analyzer. The equilibrium and dynamic swelling/deswelling behaviors and the drug release properties of the hydrogels responding to pH and/or temperature were also studied in detail. The hydrogels have the porous honeycomb structures, good miscibility and thermal stability, and good pH‐ and temperature‐responsivity. The volume phase transition temperature of the hydrogels is ca. 40°C. Changing the soy protein or crosslinker content could be used to control the swelling behavior and water retention, and the hydrogels have the fastest deswelling rate in pH 1.2 buffer solutions at 45°C. Bovine serum albumin release from the hydrogels has the good pH and temperature dependence. The results show that the proposed IPN hydrogels may have potential applications in the field of biomedical materials such as in drug delivery systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39781.     

Environmentally sensitive hydrogels: N‐isopropyl acrylamide/Acrylamide/ Mono‐, Di‐, Tricarboxylic acid crosslinked polymers

Environmentally sensitive hydrogels responsive to various stimuli such as temperature, pH, ionic strength of the medium and the solvent were prepared by using N‐isopropyl acrylamide (NIPAM), acrylamide (AAm) and monomers that have various number of carboxylic acid (XA) functionality using N,N′‐methylene bisacrylamide (Bis) as crosslinker. Hydrogels were prepared via free radical polymerization reaction in aqueous solution. P(NIPAAm‐co‐AAm) and p(NIPAAm‐co‐AAm)/XA hydrogels that contain monoprotic crotonic acid (CA) exhibit a lover critical solution temperature (LCST) at 28°C, whereas p(NIPAAm‐co‐AAm)/IA (IA:itaconic acid), and P(NIPAAm‐co‐AAm)/ACA (ACA:acotonic acid) hydrogels exhibit a lover critical solution temperature at 30.7°C and 34.4°C, respectively. Spectroscopic and thermal analyses were performed for the structural and thermal characterizations of the prepared hydrogel. The swelling experiments as equilibrium swelling percentages by gravimetrically were carried out in different solvents, at different solutions temperature, pH, and ionic strengths to determine their effects on swelling characteristic of hydrogels. POLYM. ENG. SCI., 55:843–851, 2015. © 2014 Society of Plastics Engineers     

Smart carboxymethylchitosan hydrogels that have thermo‐ and pH‐responsive properties

Thermo‐responsive poly(N‐isopropylacrylamide) (poly(NIPAAm)) and pH‐responsive poly(N,N′‐diethylaminoethyl methacrylate) (poly(DEAEMA)) polymers were grafted to carboxymethylchitosan (CMC) via radical polymerization to form highly water swellable hydrogels with dual responsive properties. Ratios of CMC, NIPAAm to DEAEMA used in the reactions were finely adjusted such that the thermo and pH responsiveness of the hydrogels was retained. Scanning electron microscopy (SEM) indicated the formation of an internal porous structure for the swollen CMC hydrogels upon incorporation of poly(NIPAAm) and poly(DEAEMA). Effect of temperature and pH changes on water swelling properties of the hydrogels was investigated. It was found that the water swelling of the hydrogels was enhanced when the solution pH was under basic conditions (pH 11) or the temperature was below its lower critical solution temperature (LCST). These responsive properties can be used to regulate releasing rate of an entrapped drug from the hydrogels, a model drug, indomethacin was used to demonstrate the release. These smart and nontoxic CMC‐based hydrogels show great potential for use in controlled drug release applications with controllable on‐off switch properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41505.     

External Stimuli‐Responsive Characteristics of Ionic Poly[(N,N‐diethylaminoethyl methacrylate)‐co‐(N‐vinyl‐2‐pyrrolidone)] Hydrogels

Summary: Polyelectrolyte hydrogels containing diprotic acid moieties sensitive to ionic strength changes of the swelling medium were synthesized from N,N‐diethylaminoethyl methacrylate (DEAEMA), N‐vinyl‐2‐pyrrolidone (VP) and itaconic acid (IA) by using ammonium persulfate (APS) as a free radical initiator in the presence of the cross‐linker, methylenebisacrylamide (MBAAm). The swelling behavior of the ionic poly[(N,N‐diethylaminoethyl methacrylate)‐co‐(N‐vinyl‐2‐pyrrolidone)] [P(DEAEMA/VP)] hydrogels were investigated in pure water; in NaCI solutions with pH 4 and 9; and in water‐acetone mixtures depending on the IA content in the hydrogel. The average molecular mass between cross‐links ( ) and polymer‐solvent interaction parameter (χ) of the hydrogels were determined from equilibrium swelling values. The pulsatile swelling behavior was also observed in response to solvent changes between the solution in water and in acetone. The equilibrium swelling ratio of these hydrogels was basically unaffected with change in temperature. The swelling variations were explained according to the swelling theory based on the hydrogel chemical structure.

Pulsatile swelling behavior of ionic P(DEAEMA/VP) hydrogels in response to solvent changes between water and acetone at 25 °C.     

Swelling behaviors of ionic poly(N,N‐dimethylacrylamide‐co‐acrylamide) hydrogels in various media

Polyelectrolyte hydrogels were synthesized from N,N‐dimethylacrylamide, acrylamide, and itaconic acid with ammonium persulfate as a free‐radical initiator in the presence of methylene(bis)acrylamide as a crosslinker. The swelling behavior of the ionic poly(N,N‐dimethylacrylamide‐co‐acrylamide) hydrogels was investigated in pure water, in KSCN solutions with pHs 4 and 9, and in water–acetone mixtures according to the itaconic acid content in the hydrogel. The pulsatile swelling behavior of these hydrogels was studied both in water–acetone and in pH 2–9 buffer solutions. Although the equilibrium swelling ratio of the hydrogels with low concentrations of itaconic acid was almost not affected by changes in the temperature, the equilibrium swelling ratio of the hydrogels with high concentrations of itaconic acid increased in the temperature range of 20–50°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2140–2145, 2007     

Preparation and swelling behavior of macroporous poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels

Macroporous superabsorbent hydrogels (SAHs) composed of acrylamide (AAm) and sodium methacrylate (NMA) were prepared by aqueous solution polymerization in the presence of a glucose solution. Their swelling capacity was investigated as a function of the concentrations of the glucose solution, sodium methacrylate, crosslinker, initiator, and activator. The porosity of the poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels was confirmed using scanning electron microscopy. The SAHs were characterized by IR spectroscopy. To estimate the effect on the swelling behavior, three types of crosslinkers were employed: N,N′‐methylenebisacrylamide, 1,4‐butanediol diacrylate, and diallyl phthalate. Network structural parameters such as initial swelling rate, swelling rate constant, and maximum equilibrium swelling were evaluated by water absorption measurement. The equilibrium water content (EWC%) of the AAm–NMA macroporous SAHs was found to be in the range of 93.31–99.68, indicating that these SAHs may have applications as biomaterials in the medicinal, pharmaceutical, and veterinary fields. Most of the SAHs prepared in this investigation followed non‐Fickian‐type diffusion, and few followed a case II– or super–case II‐type diffusion. The diffusion coefficients of these macroporous SAHs were investigated. Further, the swelling behavior of these SAHs also was investigated at different pHs and in different salt solutions and simulated biological fluids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3202–3214, 2006     

Temperature‐responsive characteristics of poly(N‐isopropylacrylamide) hydrogels with macroporous structure

Macroporous poly(N‐isopropylacrylamide) (PNIPA) hydrogels were synthesized by free‐radical crosslinking polymerization in aqueous solution from N‐isopropylacrylamide monomer and N,N‐methylenebis (acrylamide) crosslinker using poly(ethylene glycol) (PEG) with three different number‐average molecular weights of 300, 600 and 1000 g mol^?1 as the pore‐forming agent. The influence of the molecular weight and amount of PEG pore‐forming agent on the swelling ratio and network parameters such as polymer–solvent interaction parameter (χ) and crosslinking density (ν_E) of the hydrogels is reported and discussed. Scanning electron micrographs reveal that the macroporous network structure of the hydrogels can be adjusted by applying different molecular weights and compositions of PEG during polymerization. At a temperature below the volume phase transition temperature, the macroporous hydrogels absorbed larger amounts of water compared to that of conventional PNIPA hydrogels, and showed higher equilibrated swelling ratios in aqueous medium. Particularly, the unique macroporous structure provides numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to external temperature changes during the swelling and deswelling process. These macroporous PNIPA hydrogels may be useful for potential applications in controlled release of macromolecular active agents. Copyright © 2006 Society of Chemical Industry     

Synthesis and network parameters of hydrophobic poly(N‐[3‐(dimethylaminopropyl)]methacrylamide‐co‐lauryl acrylate) hydrogels

Hydrophobic poly(N‐[3‐(dimethylaminopropyl)]methacrylamide‐co‐lauryl acrylate) [P(DMAPMA‐co‐LA)] hydrogels with different LA content were synthesized by free‐radical crosslinking copolymerization of corresponding monomers in water by using N,N‐methylenebis(acrylamide) as the crosslinker, ammonium persulfate as the initiator, and N,N,N′,N′‐tetramethylethylenediamine as the activator. The swelling equilibrium of the hydrogels was investigated as a function of temperature and hydrophobic comonomer content in pure water. An interesting feature of the swelling behavior of the P(DMAPMA‐co‐LA) hydrogels with low LA content was the reshrinking phase transition where the hydrogels swell once and collapse as temperature was varied in the range of 30–40°C. The average molecular mass between crosslinks (M?_c) and polymer–solvent interaction parameter (χ) of the hydrogels were calculated from equilibrium swelling values. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter for the hydrogels were determined by using the Flory–Rehner theory based on the phantom network model of swelling equilibrium. The positive values for ΔH and ΔS indicated that the hydrogels had a positive temperature‐sensitive property in water, that is, swelling at a higher temperature and shrinking at a lower temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4159–4166, 2006     

Effect of the anionic‐group/cationic‐group ratio on the swelling behavior and controlled release of agrochemicals of the amphoteric,superabsorbent polymer poly(acrylic acid‐co‐diallyldimethylammonium chloride)

A series of amphoteric, superabsorbent polymers [poly(acrylic acid‐co‐diallyldimethylammonium chloride)] with different molar ratios of anionic groups to cationic groups were prepared by solution polymerization to investigate their swelling behaviors and the controlled release of agrochemicals. Various factors, including the solution pH, the concentrations of different salt solutions, and the temperature, were studied. The dynamic parameters of hydrogels at different temperatures suggested that diffusion was Fickian at lower temperatures, whereas non‐Fickian diffusion prevailed at higher temperatures. A copolymer hydrogel with a low anionic‐group/cationic‐group ratio showed a higher swelling capacity in water and higher salt tolerance. Also, the anionic‐group/cationic‐group ratio was not the dominant factor in determining the water retention. A poly(acrylic acid‐co‐diallyldimethylammonium chloride) hydrogel could control the release of agrochemicals effectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 986–991, 2006     

Temperature‐sensitive poly(N‐tert‐butylacrylamide‐co‐acrylamide) hydrogels bonded on cotton fabrics by coating technique

Different from the conventional method of developing stimuli‐sensitive textiles by graft copolymerization of environmental responsive polymers onto the fabric, the coating technique was applied to bond temperature‐sensitive hydrogels with cotton fabric through chemical covalent in our work. A temperature‐sensitive linear copolymer of N‐tert‐butylacrylamide (NTBA) and acrylamide (AAm) was prepared in methanol. Then, the cotton fabrics were coated using an aqueous solution of this copolymer containing 1,2,3,4‐butanetertracarboxylic acid as a crosslinker and sodium hypophosphite (SHP) as a catalyst, followed by drying and curing. The surface of the cotton fabrics was bonded on more or less coatings of poly (NTBA‐co‐AAm) hydrogels, as verified by Fourier transform infrared spectroscopy and scanning electron microscopy images. The poly(NTBA‐co‐AAm) hydrogels‐coated fabrics exhibited temperature sensitive, and the temperature interval of the deswelling transition was higher than lower critical solution temperature of linear copolymer solution. The coated fabrics presented good water‐impermeable ability because of the swelling of hydrogels bonded, especially when the add‐on was as high as 14.14%. Environmental scanning electron microscopy images revealed that coating hydrogels swelled and covered on the surface as a barrier to prevent water from penetrating once the coated fabric came into contact with water. The findings demonstrate that the temperature‐sensitive hydrogels can be covalently bonded on the cotton fabrics by coating technique and the coated fabrics have potential on immersion fabrics. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Swelling and diffusion characteristics of novel semi‐interpenetrating network hydrogels composed of poly[(acrylamide)‐ co‐(sodium acrylate)] and poly[(vinylsulfonic acid), sodium salt]

A series of novel semi‐interpenetrating polymer networks (IPNs) composed of poly[(acrylamide)‐co‐(sodium acrylate)] with varying amounts (5, 10, and 15 wt%) of poly[(vinylsulfonic acid), sodium salt] was synthesized. The semi‐IPN hydrogels were characterized by infrared spectroscopy. The swelling behavior of these IPNs was studied in distilled water/physiological solutions/buffer solutions/salt solutions. As the amount of poly[(vinylsulfonic acid), sodium salt] increased in the network, the swelling capacity of the semi‐IPNs increased considerably. The swelling and diffusion characteristics such as water penetration velocity (v), diffusion exponent (n), and diffusion coefficient (D) were calculated in distilled water, as well as in other physiological solutions. The highest swelling capacity was noted in urea and glucose solutions. The semi‐IPN hydrogels followed non‐Fickian diffusion behavior in water and physiological fluids, whereas Fickian behavior was observed in buffer solutions. The stimuli‐responsive characteristics towards physiological fluids, salt concentration, and temperature of these semi‐IPN hydrogels were also investigated. The swelling behavior of the semi‐IPNs decreased markedly with an increase of the concentration of the salt solutions. Copyright © 2006 Society of Chemical Industry