Synthesis and properties of electrically‐sensitive poly(acrylic acid‐co‐acetoacetoxy ethyl methacrylate) gels

A series of electric field sensitive copolymer P(AA‐co‐AAEM) gels of acrylic acid (AA) with acetoacetoxy ethyl methacrylate (AAEM) were prepared by free‐radical copolymerization, with N,N′‐methylene bisacrylamide (MBAAm) and ammounium persulfate (APS) as crosslinking agent and initiator, respectively. The structures and properties of the gels were tunable by changing the monomer feed weighty ratio (R) (R = W_AAEM/(W_AAEM + W_AA) of AAEM and AA. The influences of the NaCl concentration and pH buffer solutions on the equilibrium swelling ratios of the gels were studied in detail. It is shown that both NaCl concentration and pH value of the buffer solution affect the swelling properties of the P(AA‐co‐AAEM) gels greatly. Moreover, the gel deswelling behavior induced by a direct current electric field was investigated and an excellent electric‐sensitivity was found. Among all the samples, the gel with monomer feed weighty ratio (R) = 0.1479 showed the best electrical contraction properties. On the basis of the experimental results, the mechanism of the electricity‐induced deswelling behavior was presented. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rapid removal of Cr(VI) ions from aqueous solutions by the macroporous poly(N,N′‐dimethylamino ethyl methacrylate) hydrogels

To improve the adsorption ability of hexavalent chromium [Cr(VI)], the macroporous poly(N, N′‐dimethylamino ethyl methacrylate) [poly(DMAEMA)] hydrogels were successfully fabricated by free‐radical copolymerization in ethanol/water mixture using N, N′‐dimethylamino ethyl methacrylate (DMAEMA) as the monomer, N, N′‐methylenebisacrylamide (MBAA) as the cross‐linker, and Na₂SO₄ solution as the porogen. The effects of various parameters, such as the concentration of Na₂SO₄ solutions, the dosage of MBAA, pH values, adsorption kinetic, and isotherm curves, were all investigated through systematic experiments. Scanning electron microscope (SEM) was employed to characterize the various pore structures. The experimental results showed that the influence of Na₂SO₄ solution to the pore morphology in the matrix was significant. The poly(DMAEMA) hydrogels can effectively adsorb Cr(VI) ions in aqueous media, and the macroporous structures could obvious improve the response rate and adsorption capacity. These results prove that the macroporous poly(DMAEMA) gels can be treated as a potential material for environmental pollution control. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modified carrageenan. 4. Synthesis and swelling behavior of crosslinked κC‐g‐AMPS superabsorbent hydrogel with antisalt and pH‐responsiveness properties

To synthesize a novel biopolymer‐based superabsorbent hydrogel, 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) was grafted onto kappa‐carrageenan (κC) backbones. The graft copolymerization reaction was carried out in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator, N,N,N′,N′‐tetramethyl ethylenediamine (TMEDA) as an accelerator, and N,N′‐methylene bisacrylamide (MBA) as a crosslinker. A proposed mechanism for κC‐g‐AMPS formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The affecting variables on swelling capacity, i.e., the initiator, the crosslinker, and the monomer concentration, as well as reaction temperature, were systematically optimized. The swelling measurements of the hydrogels were conducted in aqueous solutions of LiCl, NaCl, KCl, MgCl₂, CaCl₂, SrCl₂, BaCl₂, and AlCl₃. Due to the high swelling capacity in salt solutions, the hydrogels may be referred to as antisalt superabsorbents. The swelling of superabsorbing hydrogels was measured in solutions with pH ranging 1 to 13. The κC‐g‐AMPS hydrogel exhibited a pH‐responsiveness character so that a swelling–deswelling pulsatile behavior was recorded at pH 2 and 8. The overall activation energy for the graft copolymerization reaction was found to be 14.6 kJ/mol. The swelling kinetics of the hydrogels was preliminarily investigated as well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 255–263, 2005     

Preparation and properties of a form‐stable phase‐change hydrogel for thermal energy storage

In this study, we aimed to fabricate a form‐stable phase‐change hydrogel (PCH) with excellent mechanical properties and heat‐storage properties. Sodium alginate (SA) and polyacrylamide (PAAm) composite hydrogels were prepared with ionically crosslinked SA in a PAAm hydrogel network. Glauber's salt [i.e., sodium sulfate decahydrate (Na₂SO₄·10H₂O)] was incorporated within the hydrogel network as a phase‐change material. Scanning electron microscopy micrographs revealed that Na₂SO₄·10H₂O was confined in the micropores of the hydrogel inner spaces, and differential scanning calorimetry curves showed that the composite hydrogel possessed a considerable storage potential. Mechanical properties tests, such as tensile and compressive measurements, presented a decreasing trend with increasing Na₂SO₄·10H₂O dosage. We concluded that the prepared composite PCH could be used to design hydrogel materials with thermal‐energy‐storage applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43836.     

Synthesis,Characterization, and swelling behaviors of acrylic acid/carboxymethyl cellulose superabsorbent hydrogel by glow‐discharge electrolysis plasma

This article exploits a new approach for synthesis of acrylic acid/carboxymethyl cellulose (AA/CMC) superabsorbent hydrogel in aqueous solution by a simple one‐step using glow‐discharge electrolysis plasma, in which N,N′‐methylenebisacrylamide (MBA) was used as a crosslinking agent. The reaction parameters affecting the equilibrium swelling, that is, discharge voltage, discharge time, mass ratio of AA to CMC, content of crosslinker, and degree of neutralization, were systematically optimized to achieve a superabsorbent hydrogel with a maximum equilibrium swelling. The structure, thermal stability, and morphology of AA/CMC superabsorbent hydrogel were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. The swelling kinetics in distilled water and swelling behaviors in various pH solutions and salts solutions (NaCl, KCl, MgCl₂, CaCl₂, AlCl₃, and FeCl₃) were investigated in detail. The effect of six cationic salt solutions on the equilibrium swelling had the following order K⁺ > Na⁺ > Mg²⁺ > Ca²⁺ > Al³⁺ > Fe³⁺. In addition, the pH‐reversibility was preliminarily investigated with alternating pH between 6.5 and 2.0. The results showed that the equilibrium swelling of AA/CMC was achieved in 90 min. The hydrogel was responsive to the pH and salts, and was reversible swelling and deswelling behavior. POLYM. ENG. SCI., 54:2310–2320, 2014. © 2013 Society of Plastics Engineers     

Synthesis and properties of poly(sodium acrylate‐co‐2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid)/attapulgite as a salt‐resistant superabsorbent composite

A novel salt‐resistant superabsorbent composite was prepared by copolymerization of partially neutralized acrylic acid, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid (AMPS) and attapulgite (APT). To enhance the swelling rate (SR) of the copolymer, sodium bicarbonate was used as a foaming agent in the course of copolymerization. Furthermore, for improving the properties of swollen hydrogel, such as strength, resilience and dispersion, the copolymer was surface‐crosslinked with glycerine and sodium silicate, and then the surface‐crosslinked copolymer was blended with aluminum sulfate and sodium carbonate in post treatment process. The influences of some reaction conditions, such as amount of AMPS, APT, and initiator, and neutralization degree of acrylic acid on water absorbency in 0.9 wt% NaCl aqueous solution both under atmospheric pressure (WA) and load (WA_P, P ≈ 2 × 10³ Pa) were investigated. In addition, the effect of them on SR was also studied. The WA and WA_P of the superabsorbent composite prepared under optimal conditions in 0.9 wt% NaCl aqueous solution were 52 g·g^?1 and 8 g·g^?1, respectively. Besides, the SR was fast, and it could reach 0.393 mL·(g·s)^?1. Moreover, the swollen hydrogel possessed excellent salt resistance, hydrogel resilience and dispersion. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Screening and optimization through response surface methodology for synthesis of pH,temperature and salt‐sensitive Aloe vera–acrylic acid‐based biodegradable hydrogel: Its evaluation as dye adsorbent

A pH‐, temperature‐, and salt‐sensitive hydrogel was synthesized using acrylic acid (AA) as monomer, natural polysaccharide Aloe vera as backbone, ammonium persulfate–N,N‐methylene‐bis‐acrylamide as an initiator–crosslinker system via free‐radical grafting method. Different parameters such as treatment time, temperature, amount of solvent, pH, concentration of initiator, crosslinker and monomer were screened using Plackett–Burman design (PBD). The PBD showed that pH, monomer, and crosslinker were taken as the most important variables, which highly impact the swelling behavior of the synthesized hydrogel as compared to the rest of the variables. The half normality plot was used to find the significant parameters regarding the swelling capacity of the hydrogel. The center composite design was used for further optimizing the important variables like pH, monomer, and crosslinker. The pH and monomer interaction on percentage swelling (Ps) was studied through the analysis of variance model. Synthesized hydrogel Av‐cl‐poly(AA) was characterized by different techniques such as Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction, and scanning electron microscopy (SEM). The effect of different chloride salt solutions like KCl, NaCl, BaCl₂, FeCl₃, and CoCl₃·6H₂O on Ps of synthesized Av‐cl‐poly(AA)‐based hydrogel was also studied. Biodegradation studies of the synthesized polymer were also carried out using soil burial and vermicompositing methods. Biodegradation of semi interpenetrating polymer network (SIPN) was confirmed by SEM and FTIR techniques. Synthesized SIPN was also used as a device for the removal of dye and was found very effective as an adsorbent. POLYM. ENG. SCI., 59:2323–2334, 2019. © 2019 Society of Plastics Engineers     

Preparation and characteristic of electric stimuli responsive hydrogel composed of polyvinyl alcohol/poly (sodium maleate‐co‐sodium acrylate)

Maleic anhydride was used to preparare polyvinyl alcohol/poly (sodium maleate‐co‐sodium acrylate) hydrogels (PVA/poly(SMA‐SAA)) by a repeated frost‐defrost process because of its higher charge density and potential electric stimuli sensitivity. The bending angle was measured in a noncontact electric field using carbon as plate electrodes. It was found that the bending angle was dependent on various factors, including composition of hydrogel, concentration of NaCl solution, types of electrolyte solution, and electric voltage. It exhibited that the bending angle increased when the concentration of NaCl solutions and the electric voltages increased. An abnormal bending direction was observed, and it was affected not only by the kinds of hydrogels, but also by the exterior variations. The hydrogel showed good reversibility in on‐off electric field and could be a candidate for practical application. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The swelling behaviors and network parameters of cationic starch‐g‐acrylic acid/poly(dimethyldiallylammonium chloride) semi‐interpenetrating polymer networks hydrogels

Amphiphilic semi‐interpenetrating polymer networks (semi‐IPN) hydrogels were prepared by a sequential‐IPN method by acrylic acid graft copolymerization into cationic starch in mild aqueous media of poly(dimethyldiallylammonium chloride). Some main factors were investigated to evaluate the swelling of hydrogels, and the network parameters M_c were given accordingly to elaborate the interaction between polymers. The chemical structure of the resulting hydrogel was confirmed using Fourier transform infrared spectroscopy. The cationic starch‐based semi‐IPN hydrogels achieved a high swelling capacity of 1070 g/g in deionized water and 94 g/g in 0.9 wt % NaCl solution, respectively) and high compressive stress in a high water content. Besides, a different pH‐dependent behavior was found for this semi‐IPN hydrogel. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and properties of a salt‐resistant superabsorbent polymer

Crosslinked sodium polyacrylate was prepared by solution polymerization with N,N‐methylene‐bisacrylamide (bisAM) as crosslinking agent; it was subsequently surface‐crosslinked by ethylene glycol diglycidyl ether (EGDE) and then was modified with inorganic salt to obtain a superabsorbent with water absorbency in 0.9 wt % NaCl aqueous solution at atmosphere and applied pressure (P ≈ 2 × 10³ Pa) of 55 and 20 g.g^?1, respectively. Moreover, it also had excellent hydrogel strength. The effects of reaction temperature, reaction time, neutralization degree (ND) of acrylic acid, amount of initiator, crosslinking agent, and surface‐crosslinking agent, mass ratio of inorganic salt to initial superabsorbent, molar ratio of sodium aluminate (NaAlO₂) to potassium dihydrogen hyphosphate (KH₂PO₄) on water absorbency (WA) in 0.9 wt % NaCl aqueous, and the hydrogel modulus were investigated and optimized. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2532–2541, 2004     

Properties of biodegradable hydrogels prepared by γ irradiation of microbial poly(ϵ-lysine) aqueous solutions

Poly(?-lysine) (PL) hydrogels have been prepared by means of γ irradiation of PL produced by Streptomyces albulus in aqueous solutions. When the dosage of γ irradiation was 70 kGy or more and the concentration of PL in water was 1–7 wt %, transparent hydrogels (opaque hydrogels for 1–3 wt % PL concentration) could be produced. In the case of 70 kGy of γ irradiation and 5 wt % PL concentration, the specific water content (wt of absorbed water/wt of dry hydrogel) of the PL hydrogel was approximately 160. Specific water contents of PL hydrogels decreased markedly with an increase in the dosage of γ irradiation. The specific water contents were increased with an increase in PL concentration in the irradiated solution. This result indicates the presence of a radical scavenger in the PL solution. Swelling equilibria of PL hydrogels were measured in water or in aqueous solutions of various pHs or concentrations of NaCl, Na₂SO₄, and CaCl₂. Under acid conditions, the PL hydrogel swelled due to the ionic repulsion of the protonated amino groups in the PL molecules. The degree of deswelling in electrolyte solution was smaller than that of other ionic hydrogels [poly(γ-glutamic acid), poly(acrylic acid) etc.]. In addition, the enzymatic degradations of PL hydrogel were studied at 40°C and pH 7.0 in an aqueous solution of the neutral protease [Protease A (Amano)] produced from Aspergillus oryzae. The rate of enzymatic degradation of the respective PL hydrogels was much faster than the rate of simple hydrolytic degradation. The rate of enzymatic degradation decreased with the increase in γ-irradiation dose during preparation of the PL hydrogel. © 1995 John Wiley & Sons, Inc.     

Characteristics of poly(AAc5‐co‐HPMA3‐cl‐EGDMA15) hydrogel‐immobilized lipase of Pseudomonas aeruginosa MTCC‐4713

Four series of noble networks were synthesized with acrylic acid (AAc) copolymerized with varying amount of 2‐hydroxy propyl methacrylate or dodecyl methacrylate (AAc/HPMA or AAc/DMA; 5:1 to 5:5, w/w) in the presence of ethylene glycol dimethacrylate (EGDMA; 1, 5, 10, 15, and 20%, w/w) as a crosslinker and ammonium per sulfate (APS) as an initiator. Each of the networks was used to immobilize a purified lipase from Pseudomonas aeruginosa MTCC‐4713. The lipase was purified by successive salting out with (NH₄)₂SO₄, dialysis, and DEAE anion exchange chromatography. Two of the matrices, E_15a, i.e. [poly (AAc₅‐co‐DMA₁‐cl‐EGDMA₁₅)] and I_15c, i.e. [poly (AAc₅‐co‐HPMA₃‐cl‐EGDMA₁₅)], that showed relatively higher binding efficiency for lipase were selected for further studies. I_15c‐hydrogel retained 58.3% of its initial activity after 10th cycle of repetitive hydrolysis of p‐NPP, and I_15c was thus catalytically more stable and efficient than the other matrix. The I_15c‐hydrogel‐immobilized enzyme showed maximum activity at 65°C and pH 9.5. The hydrolytic activity of free and I_15c‐hydrogel‐immobilized enzyme increased profoundly in the presence of 5 mM chloride salts of Hg²⁺, NH₄⁺, Al³⁺, K⁺, and Fe³⁺. The immobilized lipase was preferentially active on medium chain length p‐nitrophenyl acyl ester (C:8, p‐nitrophenyl caprylate). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4636–4644, 2006     

pH–temperature responsive poly(HPA‐Co‐AMHS) hydrogel as a potential drug‐release carrier

In this study, a novel pH–temperature‐responsive copolymer was first synthesized by the radical copolymerization between HPA (2‐hydroxypropyl acrylate and 2‐hydroxyisopropyl acrylate) and AMHS (aminoethyl methacrylate hydrochloric salt). The molecular structure of the corresponding copolymer has been confirmed by ¹H‐NMR and FTIR. The lower critical solution temperature of the resulting copolymer exhibited a considerable dependence upon the ratio of monomers and pH value in the medium. On the basis of the copolymer, a hydrogel as drug release carrier was prepared via the introduction of a crosslinker, N,N′‐methylenebisacrylamide. The swelling behaviors of hydrogel in the different pH value, temperature, and NaCl concentration have indicated that the hydrogel showed a remarkable phase transition at 31.5°C. The swelling ratio was increased with an increasing of pH value, especially in the greater pH values. By the use of caffeine as a model drug, we investigated the caffeine‐controlled release from hydrogel systematically as a function of pH value, temperature, and crosslinker content. The caffeine release was sensitive to the temperature. Only 55% caffeine was released from the hydrogel at room temperature, whereas ～ 92% caffeine diffused into the medium at 37°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of silk sericin-<Emphasis Type="Italic">g</Emphasis>-poly(acrylic acid-co-acrylamide) superabsorbent hydrogel

A novel superabsorbent hydrogel has been synthesized with the crosslinking graft copolymerization of acrylic acid (AA) and acrylamide onto the chain of silk sericin. Potassium persulfate (KPS)–sodium sulfite (NaHSO₃) as redox initiation system and N,N′-methylenebisacrylamide (MBA) as crosslinker were used. The structure of the product characterized by Fourier transform infrared absorption spectroscopy and the surface morphology of the hydrogel were observed by scanning electron microscopy. The certain parameters of the graft copolymerization including the monomer, the initiator, the crosslinker concentration, neutralization degree of AA, reaction temperature, and time were systematically optimized to achieve a hydrogel with maximum swelling capacity (2150 g/g). The optimal conditions were initiator 8 mmol/L, MBA 2.5 mmol/L, neutralization degree of AA 75%, reaction temperature 55 °C, and time 6 h. The swelling ratio in salt solutions was also determined (in 0.9% NaCl aqueous solution: 98 g/g). In addition, the swelling capability of the hydrogel was measured in solutions with pH ranged from 1 to 13. The synthesized hydrogel exhibited a pH-dependent character. Water absorbency of the product in aqueous chloride salt solutions has the Na⁺ > Ca²⁺ > Mg²⁺ > Al³⁺ order in the investigated concentration.     

Novel poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers through atom transfer radical polymerization

Poly(methyl methacrylate)‐block‐polyurethane‐block‐poly(methyl methacrylate) tri‐block copolymers have been synthesized successfully through atom transfer radical polymerization of methyl methacrylate using telechelic bromo‐terminated polyurethane/CuBr/N,N,N,N″,N″‐pentamethyldiethylenetriamine initiating system. As the time increases, the number‐average molecular weight increases linearly from 6400 to 37,000. This shows that the poly methyl methacrylate blocks were attached to polyurethane block. As the polymerization time increases, both conversion and molecular weight increased and the molecular weight increases linearly with increasing conversion. These results indicate that the formation of the tri‐block copolymers was through atom transfer radical polymerization mechanism. Proton nuclear magnetic resonance spectral results of the triblock copolymers show that the molar ratio between polyurethane and poly (methyl methacrylate) blocks is in the range of 1 : 16.3 to 1 : 449.4. Differential scanning calorimetry results show T_g of the soft segment at ?35°C and T_g of the hard segment at 75°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electric‐field‐induced aggregation of polymeric micelles to construct secondary assembly films

A new amphiphilic quaternary random ionomer (PIDHES) was used to construct self‐assembly films. PIDHES was prepared by a selective ionization of quaternary random copolymer, poly(N,N‐domethyl amimethyl methartylate‐co‐2‐hydroxypropyl methacrylate‐co‐2‐ethylhexyl acrylate‐co‐styrene) precursor, which was synthesized by free radical copolymerization of commercial hydrophilic monomers N, N‐domethyl amimethyl methartylate and 2‐hydroxypropyl methacrylate and hydrophobic monomers 2‐ethylhexyl acrylate and styrene PIDHES could self‐assemble into polymer micelles in water, which underwent orientated deposition in the electric field and ultimately produced secondary assembly films. Scanning electron microscopy studies showed that the resultant PIDHES secondary assembly film was smooth and compact. Moreover, it was found that PIDHES micelles concentration and electric‐field‐induced time had a strong influence on the morphologies of the resultant secondary assembly film. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An EPR investigation of conductive polyaniline–poly(methyl methacrylate‐co‐acrylic acid) blends

A conductive blend of polyaniline (PANI) with sodium form poly(methyl methacrylate‐co‐acrylic acid) copolymer (PMMAA) was prepared by in situ dispersion polymerization. The PANI‐PMMAA blends were characterized with UV–vis, FTIR, and electron paramagnetic resonance (EPR) spectra. The effects of PANI and temperature on the electronic properties of the PANI‐PMMAA blends were studied with EPR technique. The PANI and temperature affect the intermolecular interaction between PANI and PMMAA and then determines the EPR parameters (A/B ratio, g factor, T₂, ΔH_pp, N_s, and lineshape). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Synthesis of poly(N,N‐diethylacrylamide‐co‐acrylic acid) hydrogels with fast response rate in NaCl medium

A series of thermo‐ and pH‐sensitive poly (N,N‐diethylacrylamide‐co‐acrylic acid) (P(DEA‐co‐AA)) hydrogels were prepared in NaCl aqueous solutions with different concentrations. Swelling and deswelling studies showed that in comparison with conventional P(DEA‐co‐AA) hydrogels (prepared in distilled water), the P(DEA‐co‐AA) hydrogels thus prepared had almost the same volume phase transition temperature (VPTT), but exhibited much faster response rates as the temperature was raised above their VPTT. Besides, the hydrogels prepared by this method had faster response rates in low pH buffer solutions, and the response rates increased with the increased concentration of the NaCl solutions used during the polymerization. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of charged linear and crosslinked maleic diester polymers with electron‐beam irradiation

Series of maleic mono‐ and diester monomers have been prepared by esterification of maleic anhydride with poly(ethylene glycol) having different molecular weights, and with n‐dodecyl alcohol. These monomers were copolymerized with 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) using different dose rates of electron‐beam irradiation ranging from 40 to 150 kGy. The synthesized copolymers were characterized by IR and ¹H NMR analysis. Their aggregation behaviour and viscometric properties in aqueous solutions were investigated. The crosslinked copolymers were prepared in aqueous acidic solutions at pH 1 or in the presence of 1% of N,N‐methylene bisacrylamide (MBA) as crosslinking agent. The final equilibrium water content and swelling capacities for the prepared hydrogels were determined in aqueous solutions at pH = 1, 6.8 and 12 at 298 K. Swelling equilibria for the prepared hydrogels were carried out in aqueous solutions of NaCl, KCl, CaCl₂, Na₂SO₄, K₂SO₄ and CaSO₄ at concentrations ranging from 1 × 10^?6 to 2 M at 298 K. © 2003 Society of Chemical Industry     

An autonomous self‐healing hydrogel based on surfactant‐free hydrophobic association

Self‐healing hydrogels are attractive for a variety of applications including wound dressings and coatings. This paper describes the facile preparation and characterization of an autonomous self‐healing hydrogel system comprising surfactant‐free hydrophobic associations. The hydrogel comprised a copolymer of benzyl methacrylate (B), octadecyl methacrylate (O), and methacrylic acid (MA). The hydrogels were prepared via a controlled dehydration procedure to achieve the formation of strong intermolecular hydrophobic associations of the octadecyl groups above a critical polymer concentration. Fractured hydrogels healed within 30 min without any external intervention. Increasing hydrogel polymer content from 31 wt % to 39 wt % resulted in a threefold increase in the shear modulus and 50% reduction of the relaxation time. Addition of 4 mM NaCl to a hydrogel of 31 wt % polymer content resulted in 2.5 times longer relaxation time and 24% decrease in shear modulus. The hydrogels swelled up water by up to four times its weight, which corroborates the robustness of the hydrophobic association crosslinks. The bulk properties of the hydrogels are discussed in terms of the hydrophobic associations of the O‐groups and the electrostatic interaction of the MA‐groups in the polymer chains. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44800.