Thermo‐ and pH‐induced phase transitions and network parameters of poly(N‐isopropylacrylamide‐ co‐2‐acrylamido‐2‐methyl‐propanosulfonic acid) hydrogels

Dual temperature‐ and pH‐sensitive hydrogels composed of N‐isopropylacrylamide (NIPAM) and 2‐acrylamido‐2‐methyl‐propanosulfonic acid (AMPS) were prepared by free‐radical crosslinking copolymerization in aqueous solution at 22 °C. The mole percent of AMPS in the comonomer feed was varied between 0.0 and 7.5, while the crosslinker ratio was fixed at 5.0/100. The effect of AMPS content on thermo‐ and pH‐ induced phase transitions as well as equilibrium swelling/deswelling, interior morphology and network structure was investigated. The volume phase transition temperature (VPT‐T) was determined by both swelling/deswelling measurements and differential scanning calorimetry (DSC) technique. In addition, the volume phase transition pH (VPT‐pH) was detected from the derivative of the curves of the swelling ratio (dQ_v/dpH) versus pH. The polymer‐solvent interaction parameter (χ) and the average molecular mass between crosslinks ( ) of hydrogels were calculated from swelling ratios in buffer solutions at various pHs. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter of hydrogels were also determined by using the modified Flory–Rehner equation. The negative values for ΔH and ΔS indicated that the hydrogels had a negative temperature‐sensitive property in water, that is, swelling at a lower temperature and shrinking at a higher temperature. It was observed that the experimental swelling data of hydrogels at different temperature agreed with the modified Flory‐Rehner approach based on the affine network model. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1713–1724, 2008     

Thermoresponsive properties of porous poly(N‐isopropylacrylamide) hydrogels prepared in the presence of nanosized silica particles and subsequent acid treatment

Porous poly(N‐isopropylacrylamide) hydrogels were prepared by the free‐radical polymerization of its monomer and a suitable crosslinker in the presence of spherical silica particles of different sizes (74 and 1600 nm) and by the subsequent acid extraction of silica. The yields were 81–83%, and the yields were not affected by the silica content. Scanning electron microscopy observations revealed the porous structure of the hydrogels. Porous and nonporous hydrogels showed volume phase transitions from swelling states to deswelling states at approximately 30 °C, as analyzed by the ratio of the diameter of cylinder‐shaped hydrogels to that of the glass tube used for the hydrogel preparation at the corresponding temperature. Deswelling, which was analyzed by rapid changes in the temperature of the aqueous media from 20 to 40 °C, was facilitated by decreased silica particle size and increased silica content. The deswelling rate constant of the hydrogel prepared with 74‐nm silica at 10 v/v % (silica/solvent) was more than 1500 times greater than that of conventional hydrogels. Swelling was similarly analyzed through changes in the temperature from 40 to 20 °C and was independent of the pore structure. The deswelling–swelling cycle was repeatable with reasonable reproducibility. Moreover, the mechanical strength of the porous hydrogels was significantly maintained compared with that of conventional nonporous hydrogels. This method produced thermoresponsive hydrogels of suitable mechanical strength and remarkable deswelling properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4228–4235, 2002     

Poly(N‐isopropylacrylamide) Nanoparticle‐Incorporated PNIPAAm Hydrogels with Fast Shrinking Kinetics

Summary: Novel temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAAm) nanoparticle‐containing PNIPAAm hydrogels were prepared by radical polymerization. In comparison with conventional PNIPAAm hydrogels, the PNIPAAm gels thus prepared exhibit much faster response rates as the temperature is raised above the lower critical solution temperature. The improved properties are a result of the incorporation of PNIPAAm particles, which first shrink and then generate pores for water molecules to be quickly squeezed out of the bulky PNIPAAm gels.

Schematic illustration of the shrinking process: (I) First PNIPAAm particles shrink and generate pores; (II) the bulky gels then shrink further at a rapid rate.     

Effect of 1,4‐dioxane on synthesis of macroporous poly(N‐isopropylacrylamide) hydrogels

Thermosensitive Poly(N‐isopropylacrylamide) (PNIPA) hydrogels were synthesized by a free radical solution polymerization in three different ways. Normal hydrogels were prepared at room temperature and normal cryogels were prepared at subzero temperature. A cation surfactant dodecyl dimethyl benzyl ammonium bromide (DDBAB) was used during preparation of novel cryogels in freezing state. The response rates of normal hydrogels were very slow, whereas the rates of both normal and novel cryogels were very fast because of the macroporous structure of the cryogels. Mixed solvents which were composed of pure water and 1,4‐dioxane at various concentrations were used instead of pure water during the polymerization. The effects of the mixed solvent on morphology, swelling ratio, and deswelling/reswelling kinetics of the three kinds of hydrogels were investigated. For normal hydrogels and normal cryogels, there was no remarkable difference no matter the mixed solvent or pure water was used. However, the properties of the resulted novel cryogels were much different with the concentration of dioxane. Finally, the resulted hydrogels were used for concentrating emulsified paraffin. The different separation performance was attributed to the different structure of gel matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6594–6603, 2008     

Novel poly(N‐isopropylacrylamide)/clay/poly(acrylamide) IPN hydrogels with the response rate and drug release controlled by clay content

Novel interpenetrating network (IPN) hydrogels (PNIPAAm/clay/PAAm hydrogels) based on poly(N‐isopropylacrylamide) (PNIPAAm) crosslinked by inorganic clay and poly(acrylamide) (PAAm) crosslinked by organic crosslinker were prepared in situ by ultraviolet (UV) irradiation polymerization. The effects of clay content on temperature dependence of equilibrium swelling ratio, deswelling behavior, thermal behavior, and the interior morphology of resultant IPN hydrogels were investigated with the help of Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), scanning electron microscope (SEM). Study on temperature dependence of equilibrium swelling ratio showed that all IPN hydrogels exhibited temperature‐sensitivity. DSC further revealed that the temperature‐sensitivity was weakened with increasing amount of clay. Study on deswelling behavior revealed that IPN hydrogels had much faster response rate when comparing with PNIPAAm/clay hydrogels, and the response rate of IPN hydrogels could be controlled by clay content. SEM revealed that there existed difference in the interior morphology of IPN hydrogels between 20 [below lower critical solution temperature (LCST)] and 50 °C (above LCST), and this difference would become obvious with a decrease in clay content. For the standpoint of applications, oscillating swelling/deswelling behavior was investigated to determine whether properties of IPN hydrogels would be stable for potential applications. Bovine serum albumin (BSA) was used as model drug for in vitro experiment, the release data suggested that the controlled drug release could be achieved by modulating clay content. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 96–106, 2009     

A novel sodium carboxymethylcellulose/poly(N‐isopropylacrylamide)/Clay semi‐IPN nanocomposite hydrogel with improved response rate and mechanical properties

A novel semi‐IPN nanocomposite hydrogel (CMC/PNIPA/Clay hydrogel) based on linear sodium carboxymethylcellulose (CMC) and poly(N‐isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was prepared. The structure and morphology of these hydrogels were investigated and their swelling and deswelling kinetics were studied in detail. TEM images showed that the clay was substantially exfoliated to form nano‐dimension platelets dispersed homogeneously in the hydrogels and acted as a multifunctional crosslinker. The CMC/PNIPA/Clay hydrogels swell faster than the corresponding PNIPA/Clay hydrogels at pH 7.4, whereas they swell slower than the PNIPA/Clay hydrogels at pH 1.2. The CMC/PNIPA/Clay nanocomposite hydrogels showed much higher deswelling rates, which was ascribed to more passway formed in these hydrogels for water to diffuse in and out. The deswelling process of the hydrogels could be approximately described by the first‐order kinetic equation and the deswelling rate decreased with increasing clay content. The mechanical properties of the CMC/PNIPA/Clay nanocomposite hydrogels were analyzed based on the theory of rubber elasticity. It was found that with increasing clay content, the effective crosslink chain density, v_e, increased whereas the molecular weight of the chains between crosslinks M_c decreased. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1546–1555, 2008     

A novel pH‐ and thermo‐sensitive PVP/CMC semi‐IPN hydrogel: Swelling,phase behavior,and drug release study

Poly(N‐vinyl‐pyrrolidone) (PVP) hydrogel has been considered as a very interesting and promising thermosensitive material. The most vital shortcoming of PVP hydrogel as thermosensitive material is that it does not exhibit thermosensitivity under usual conditions. In this work, semi‐interpenetrating polymer network (semi‐IPN) hydrogels based on PVP and carboxymethylcellulose (CMC) were prepared. The volume phase transition temperature (VPTT) of the hydrogels was determined by swelling behavior and differential scanning calorimetry (DSC). The results showed that the VPTT was significantly dependent on CMC content and the pH of the swelling medium. The amount of CMC in the semi‐IPN hydrogels was 0.050, 0.075, and 0.100 g, the VPTT in buffer solution of pH 1.2 was 29.9 °C, 27.5 °C and 24.5 °C, respectively. In addition, the VPTT occurred in buffer solution of pH 1.2, but did not appear in alkaline medium. Bovine serum albumin (BSA) as a model drug was loaded and the in vitro release studies were carried out in different buffer solutions and at different temperatures. The results of this study suggest that PVP/CMC semi‐IPN hydrogels could serve as potential candidates for protein drug delivery in the intestine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1749–1756, 2010     

β‐Cyclodextrin hydrogel incorporating hydrophobically modified poly(N‐isopropylacrylamide) for a temperature‐dependent release

Hydrogels exhibiting a temperature‐dependent release were prepared by incorporating hydrophobically modified poly(N‐isopropylacrylamide) (HmPNIPAM) into β‐cyclodextrin hydrogels (β‐CD hydrogels). The specific loading of HmPNIPAM was about 0.0069 g HmPNIPAM/g β‐CD hydrogels. The incorporation of the polymer was qualitatively conformed by FT‐IR spectroscopy and SEM. The percent release of blue dextran in 24 hr at 20°C (about 77%) was markedly higher than those obtained at 35°C and 45°C (about 53 and 55%, respectively). At the higher temperatures, the volume of the hydrogel could decrease upon the thermal contraction of HmPNIPAM, leading to a smaller mesh and a suppressed release. In fact, the swelling ratio in 24 hr at 35°C and 45°C (about 396% and 405%, respectively) was obviously lower than that obtained at 20°C (about 465%). Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and characterization of κ‐carrageenan/poly(N,N‐diethylacrylamide) semi‐interpenetrating polymer network hydrogels with rapid response to temperature

In this study, a novel classical thermo‐ and salt‐sensitive semi‐interpenetrating polymer network (semi‐IPN) hydrogel composed of poly(N,N‐diethylacrylamide) (PDEAm) and κ‐carrageenan (KC) was synthesized by free radical polymerization. The structure of the hydrogels was studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR and SEM revealed that the semi‐IPN hydrogels possessed the structure of H‐bonds and larger number of pores in the network. Compared to the PDEAm hydrogel, the prepared semi‐IPN hydrogels exhibited a much faster response rate to temperature changes and had larger equilibrium swelling ratios at temperatures below the lower critical solution temperature (LCST). The salt‐sensitive behavior of the semi‐IPN hydrogels was dependent on the content of KC. In addition, during the reswelling process, semi‐IPN hydrogels showed a non‐sigmoidal swelling pattern. Copyright © 2008 John Wiley & Sons, Ltd.     

Structure and properties of cellulose/poly(N‐isopropylacrylamide) hydrogels prepared by IPN strategy

Interpenetrating polymer network (IPN) strategy was developed to fabricate novel hydrogels composed of cellulose and poly(N‐isopropylacrylamide) (PNIPAAm) with high mechanical strength and adjustable thermosensitivity. Cellulose hydrogels were prepared by chemically cross‐linking cellulose in NaOH/urea aqueous solution, which were employed as the first network. The second network was subsequently obtained by in situ polymerization/cross‐linking of N‐isopropylacrylamide in the cellulose hydrogels. The results from FTIR and solid ¹³C NMR indicated that the two networks co‐existed in the IPN hydrogels, which exhibited uniform porous structure, as a result of good compatibility. The mechanical and swelling properties of IPN hydrogels were strongly dependent on the weight ratio of two networks. Their temperature‐sensitive behaviors and deswelling kinetics were also discussed. This work created double network hydrogels, which combined the advantages of natural polymer and synthesized PNIPAAm collectively in one system, leading to the controllable temperature response and improvement in the physical properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of polyhedral oligomeric silsesquioxane hybrid co‐crosslinked poly(N‐isopropylacrylamide‐co‐dimethylaminoethyl methacrylate) hydrogels

Polyhedral oligomeric silsesquioxane hybrid temperature and pH double‐responsive hydrogels with organic–inorganic co‐crosslinked networks are synthesized by in situ, free‐radical polymerization of N‐isopropylacrylamide and dimethylaminoethyl methacrylate in the presence of both organic crosslinker N,N′‐methylenebis(acrylamide) (BIS) and inorganic crosslinker octavinyl polyhedral oligomeric silsesquioxane (OvPOSS) in tetrahydrofuran media. The resulting hydrogels (OR‐OvP gels) display obvious temperature and pH double responsiveness, OvPOSS particles dispersed in polymer make a dominant effect on the properties of gels. With the increase of OvPOSS, the aggregation of particles on nano‐ or microscale happens and causes a considerable change on the properties of gels, such as the lower critical solution temperature and better compression strength. Specially, the interconnected microporous structure of gels ascribed to the microphase separation results in faster deswelling rate, which makes the gel become attractive. Besides, the crosslink by BIS intensifies the heterogeneity of gels significantly, which could also be used to adjust the properties of gels. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1494–1504     

Preparation and separation function of N‐isopropylacrylamide copolymer hydrogels

In this paper, N‐isopropylacrylamide (NIPA) was synthesized by acrylonitrile and isopropanol. Poly(N‐isopropylacrylamide) (PNIPA) was prepared by a chemical method. The dependence of its swelling behavior on temperature was studied. Results showed that PNIPA hydrogel was a temperature‐sensitive gel. Its LCST (lower critical solution temperature) was about 32 °C, and its swelling ratio (at 20 °C) was about 17–18. Sodium acrylate (SA) and sodium methylacrylate (SMA) were copolymerized with NIPA respectively. Equilibrium swelling ratios of the copolymer hydrogels at lower temperature were two to three times that of PNIPA. The LCST of the copolymer hydrogels could be controlled between 32 and 45 °C by adjusting the content of SA or SMA. Kinetics of P(NIPA‐co‐SA) hydrogels, whether swelling or shrinking processes, were in good agreement with apparent second order kinetic equations. Several experiments were designed to separate aqueous bovine serum albumin solution using the hydrogels prepared above. The separation efficiency was about 80%. Copyright © 2000 John Wiley & Sons, Ltd.     

Dextran Hydrogels Containing Poly(N‐isopropylacrylamide) as Grafts and Cross‐Linkers Exhibiting Enzymatic Regulation in a Specific Temperature Range

Summary: Specific temperature‐responsive biodegradable hydrogels were synthesized and characterized in terms of their regulation of enzymatic accessibility based on the physical properties of the temperature‐responsive polymers. The hydrogels consist of glycidyl methacrylate‐modified dextran grafted with the poly(N‐isopropylacrylamide) (PNIPAAm) homopolymer, and cross‐linked by co‐polymerization with NIPAAm and N,N‐dimethylacrylamide (DMAAm). The coil‐globule change in the grafted poly(NIPAAm) chains and only a slight dehydration of the poly(NIPAAm‐co‐DMAAm) cross‐linkers are effective in controlling the enzymatic degradation over a specific temperature range.

The thermo‐responses of the graft chains (steric hindrance) and the crosslinkers (slight deswelling of the hydrogel networks) control the enzymatic degradation of the hydrogel.     

Dual thermo‐ and pH‐sensitive network‐grafted hydrogels formed by macrocrosslinker as drug delivery system

Dual thermo‐ and pH‐sensitive network‐grafted hydrogels made of poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) network and poly(N‐isopropylacrylamide) (PNIPAM) grafting chains were successfully synthesized by the combination of atom transfer radical polymerization (ATRP), reversible addition‐fragmentation chain transfer (RAFT) polymerization, and click chemistry. PNIPAM having two azide groups at one chain end [PNIPAM‐(N₃)₂] was prepared with an azide‐capped ATRP initiator of N,N‐di(β‐azidoethyl) 2‐chloropropionylamide. Alkyne‐pending poly(N,N‐dimethylaminoethyl methacrylate‐co‐propargyl acrylate) [P(DMAEMA‐co‐ProA)] was obtained through RAFT copolymerization using dibenzyltrithiocarbonate as chain transfer agent. The subsequent click reaction led to the formation of the network‐grafted hydrogels. The influences of the chemical composition of P(DMAEMA‐co‐ProA) on the properties of the hydrogels were investigated in terms of morphology and swelling/deswelling kinetics. The dual stimulus‐sensitive hydrogels exhibited fast response, high swelling ratio, and reproducible swelling/deswelling cycles under different temperatures and pH values. The uptake and release of ceftriaxone sodium by these hydrogels showed both thermal and pH dependence, suggesting the feasibility of these hydrogels as thermo‐ and pH‐dependent drug release devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Introduction of pH‐sensitivity into mechanically strong nanoclay composite hydrogels based on N‐isopropylacrylamide

pH‐sensitive nanoclay composite hydrogels based on N‐isopropylacrylamide (NIPA) were synthesized by copolymerization with cationic and anionic comonomers. Laponite nanoclay particles served as multifunctional crosslinkers, producing hydrogels with exceptionally high mechanical strengths, as measured by elongation at break. Cationic copolymer gels based on NIPA and dimethylaminoethylmethacrylate were prepared by aqueous free radical polymerization, adopting a procedure reported by Haraguchi (Adv Mater 2002, 14, 1120–1124). Without modification, this technique failed to produce anionic copolymer gels of NIPA and methacrylic acid (MAA), due to flocculation of clay particles. Three methods were conceived to incorporate acidic MAA into nanoclay hydrogels. First, NIPA was copolymerized with sodium methacrylate under dilute conditions, producing hydrogels with good pH‐sensitivity but weak mechanical characteristics. Second, NIPA was copolymerized with methyl methacrylate, which was then hydrolyzed to generate acid sidegroups, yielding hydrogels that were much stronger but less pH sensitive. Third, NIPA was copolymerized with MAA following modification of the nanoclay surface with pyrophosphate ions. The resulting hydrogels exhibited both strong pH‐sensitivities at 37 °C and excellent tensile properties. Optical transparency changed during polymerization, depending on hydrophobicity of the components. This work increases the diversity and functionality of nanoclay hydrogels, which display certain mechanical advantages over conventionally crosslinked hydrogels. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6630–6640, 2008     

Synthesis,characterization, and drug release behaviors of a novel thermo‐sensitive poly(N‐acryloylglycinates)

In this study, a novel thermo‐sensitive poly(N‐acryloylglycinates) was prepared in order to get a potential drug release carrier. The corresponding monomers and the polymers were characterized with Fourier‐transform infrared (FTIR) and ¹H NMR. The thermo‐sensitivity of the poly(N‐acryloylglycinates) was evaluated by measuring their lower critical solution temperatures (LCST) in water, inorganic salt solution, and different pH solutions. The results indicated that poly(N‐acryloylglycine methyl ester) (NAGME) and poly(N‐acryloylglycine ethyl ester) (NAGEE) exhibit a reversible thermo‐sensibility in their aqueous solutions at 61.5 and 12.5°C, respectively. However, no thermo‐sensitive behavior of poly(N‐acryloylglycine propyl ester) (NAGPE) was found due to its over hydrophobicity. The swelling studies on hydrogels were carried out at different temperatures, in different pH, and inorganic salt solutions. The hydrogels showed a remarkable phase transition at about 35°C with changing temperature. The release rate of caffeine from the thermo‐sensitive hydrogel was apparently decreased as the crosslinker content increased and temperature decreased. Seventy five percent caffeine from the polymeric hydrogel with 5% NMBA (N, N‐methylenebis(acrylamide)) was released at room temperature within 240 min, whereas 95.4% caffeine diffused into the medium at 37°C. Copyright © 2009 John Wiley & Sons, Ltd.     

Facile synthesis of N‐vinylimidazole‐based hydrogels via frontal polymerization and investigation of their performance on adsorption of copper ions

We report a new facile strategy for quickly synthesizing pH sensitive poly(VI‐co‐HEA) hydrogels (VI = N‐vinylimidazole; HEA = 2‐hydroxyethyl acrylate) by frontal polymerization. The appropriate amounts of VI, HEA, and ammonium persulfate (APS)/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) couple redox initiator were mixed together at ambient temperature in the presence of glycerol as the solvent medium. Frontal polymerization (FP) was initiated by heating the upper side of the mixture with a soldering iron. Once initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the VI/HEA weight ratios were investigated. The pH sensitive behavior, morphology, and heavy metal removal study of poly(VI‐co‐HEA) hydrogels prepared via FP were comparatively investigated on the basis of swelling measurements, scanning electron microscopy, and inductively coupling plasma spectrometer. Results show that the poly(VI‐co‐HEA) hydrogels prepared via FP exhibit good pH sensitivity and adsorption capacity. The FP can be exploited as an alternative means for synthesis of pH sensitive hydrogels in a fast and efficient way. The as‐prepared hydrogels can be applied to remove heavy metals. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4005–4012, 2010     

pH/temperature double responsive behaviors and mechanical strength of laponite‐crosslinked poly(DEA‐co‐DMAEMA) nanocomposite hydrogels

A nanocomposite (NC) hydrogel crosslinked by inorganic Laponite XLG was successfully synthesized via in situ free radical polymerization of monomers N,N‐diethylacrylamide and (2‐dimethylamino) ethyl methacrylate (DMAEMA). Polymerization was carried out at room temperature due to the accelerating effect of DMAEMA. The as‐prepared hydrogels displayed controlled transformation in optical transmittance and volume in response to small diversification of environmental factors, such as temperature and pH. The compressive strength of swollen D_6:1G₆ hydrogels was as high as 2219 kPa while compressive strain was 95%. Cyclic compression measurement exhibited good elastic properties of NC hydrogels. This work provides a facile method for fabricating stimuli‐responsive hydrogels with superior mechanical property. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 876–884     

Temperature‐Sensitive Poly(N‐isopropylacrylamide) Hydrogels with Macroporous Structure and Fast Response Rate

Macroporous temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPA) hydrogels were prepared by a novel phase‐separation technique to improve the response properties. In comparison with a conventional PNIPA hydrogel prepared in water, these macroporous hydrogels, prepared by polymerization in aqueous sucrose solutions, have higher swelling ratios at temperatures below the lower critical solution temperature and exhibit much faster response rates to temperature changes.

Scanning electron microscopy image of the surface of a PNIPA hydrogel, prepared in 1.50 M aqueous sucrose solution.     

Conducting hydrogels based on semi‐interpenetrating networks of polyaniline in poly(acrylamide‐co‐itaconic acid) matrix: synthesis and characterization

In this work, acrylamide/itaconic acid copolymeric hydrogels are prepared by free radical polymerization initiated by redox initiators of potassium persulfate and N ,N ,N ′,N ′‐tetramethyl ethylene diamine; N ,N ′methylene bisacrylamide was employed as a crosslinking agent. Aniline monomer was absorbed in the network of poly(acrylamide‐co‐itaconic acid) P(AAm‐co‐IA) hydrogel and followed by gamma radiation induced polymerization at room temperature. The novel semi‐interpenetrating network was comprised of linear polyaniline immersed in P(AAm‐co‐IA) matrix. Electrical conductivity of the hydrogels was measured using four‐probe technique. The conductivities for the prepared hydrogels are found to increase from 5.5 × 10^?7 S cm^?1 for P(AAm‐co‐IA) alone to 4.4 × 10^?3 S cm^?1 for semi‐interpenetrating polymer network P(AAm‐co‐IA)/polyaniline. Thus, a new composite hydrogel with good conductive properties also displaying enhanced mechanical strength and pH sensitivity was prepared. Copyright © 2017 John Wiley & Sons, Ltd.