Preparation and properties of poly(N‐isopropylacrylamide)/poly(N‐isopropylacrylamide) interpenetrating polymer networks for drug delivery

A novel poly(N‐isopropylacrylamide) (PNIPA)/PNIPA interpenetrating polymer network (IPN) was synthesized and characterized. In comparison with conventional PNIPA hydrogels, the shrinking rate of the IPN hydrogel increased when gels, swollen at 20 °C, were immersed in 50 °C water. The phase‐transition temperature of the IPN gel remained unchangeable because of the same chemical constituent in the PNIPA gel. The reswelling kinetics were slower than those of the PNIPA hydrogel because of the higher crosslinking density of the IPN hydrogel. The IPN hydrogel had better mechanical strength because of its higher crosslinking density and polymer volume fraction. The release behavior of 5‐fluorouracil (5‐Fu) from the IPN hydrogel showed that, at a lower temperature, the release of 5‐Fu was controlled by the diffusion of water molecules in the gel network. At a higher temperature, 5‐Fu inside the gel could not diffuse into the medium after a burst release caused by the release of the drug on the surface of the gel. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1249–1254, 2004     

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     

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     

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.     

Semi‐interpenetrating polymer networks composed of poly(N‐isopropyl acrylamide) and polyacrylamide hydrogels

Three series of semi‐interpenetrating polymer networks, based on crosslinked poly(N‐isopropyl acrylamide) (PNIPA) and 1 wt % nonionic or ionic (cationic and anionic) linear polyacrylamide (PAAm), were synthesized to improve the mechanical properties of PNIPA gels. The effect of the incorporation of linear polymers into responsive networks on the temperature‐induced transition, swelling behavior, and mechanical properties was studied. Polymer networks with four different crosslinking densities were prepared with various molar ratios (25:1 to 100:1) of the monomer (N‐isopropyl acrylamide) to the crosslinker (methylenebisacrylamide). The hydrogels were characterized by the determination of the equilibrium degree of swelling at 25 °C, the compression modulus, and the effective crosslinking density, as well as the ultimate hydrogel properties, such as the tensile strength and elongation at break. The introduction of cationic and anionic linear hydrophilic PAAm into PNIPA networks increased the rate of swelling, whereas the presence of nonionic PAAm diminished it. Transition temperatures were significantly affected by both the crosslinking density and the presence of linear PAAm in the hydrogel networks. Although anionic PAAm had the greatest influence on increasing the transition temperature, the presence of nonionic PAAm caused the highest dimensional change. Semi‐interpenetrating polymer networks reinforced with cationic and nonionic PAAm exhibited higher tensile strengths and elongations at break than PNIPA hydrogels, whereas the presence of anionic PAAm caused a reduction in the mechanical properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3987–3999, 2004     

Positron annihilation lifetime study of continuous volume phase transition of poly(N-isopropylacrylamide) gel induced in methanol–water mixed solvent

The macroscopic volume shrinkage and swelling of poly(N-isopropylacryl-amide) (PNIPA) gel induced by the compositional change in the methanol–water mixed solvent is correlated to the change in the nanoscopic free volume size and numerical concentration formed in the PNIPA gels. The free volume size and numerical concentration are estimated from the longest component appearing in the positron annihilation lifetime curves. The apparent free volume fraction calculated by the free volume size and numerical concentration, and dispersion of the free volume deduced by the size distribution are utilized to analyze the origin and location of the free volumes. The free volume parameters obtained by analysis of the positron annihilation data show various nanoscopic phases occuring within the PNIPA gels during the volume change, implying the variation of the strength of the interactions among the solvent molecules and the polymer chains of the PNIPA. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1141–1151, 1998     

Characterization of well‐defined poly(ethylene glycol) hydrogels prepared by thiol‐ene chemistry

Considering the large number of applications for hydrogels, a better understanding of the relation between molecular structure and mechanical properties for well‐defined hydrogel is essential. A new library has been compiled of poly(ethylene glycol) polymers (PEG) of different length end functionalized with diallyl, dithiol, and dimethacrylate, and crosslinked with complementary trifunctional crosslinkers. In this study, the hydrogels were initially analyzed by FT‐Raman and NMR to study the conversion ratio of the functional groups. The effects of solvent type, solid content concentration, curing time and length of the PEG chains on the final leaching, swelling and tensile properties of the hydrogels were studied. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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     

Saccharide‐structure effects on poly N‐isopropylacrylamide phase transition in aqueous media; Reflections on protein stability

Protein stability in aqueous solutions is important in numerous fields, particularly biotechnology and food‐science. To shed new light on the protective effect of carbohydrates on proteins, we studied saccharide‐structure effects in aqueous solutions on the coil‐to‐globule transition occurring at the lower critical solution temperature (LCST) of poly‐N‐isopropylacrylamide (PNIPA), an isomer of polyleucine, as a simple model representing certain key behaviors of proteins (e.g., denaturation/renaturation). We systematically selected sugars and polyols to relate structural and physical characteristics of these carbohydrates to their effect on PNIPA solutions. Using isothermal titration‐microcalorimetry, we showed that no significant binding of saccharides to the polymer occurs. Using micro‐DSC, we studied the decreasing polymer LCST temperature with rising carbohydrate concentration. Beyond the expected observation that steric exclusion is important, we observed previously‐unreported significant differences among the effects of isomeric aldohexoses and also among the effects of isomeric diglucoses on PNIPA LCST. We found good correlation between the sugar hydration number and its effect on LCST. We conclude that the larger and denser the hydrated cluster a carbohydrate forms, the worse a cosolvent is for the polymer, and the stronger it's lowering effect of the coil‐to‐globule transition. Such favoring of the compact globule state provides a protective effect against denaturation of globular proteins. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2307–2318, 2008     

Electric‐field‐controlled synthesis of HPMA hydrogels containing self‐organized arrays of micro‐channels

We report the synthesis of poly N‐(2‐hydroxypropyl)methacrylamide ordered arrays of fluid filled channels. The polymerization and crosslinking reactions are carried out under the influence of a constant electric field (60 V/cm). A charged comonomer, immobiline (pK 3.6), and porogen, polyethylene glycol (PEG) are added to the pregel solutions. Scanning electron microscopy reveals that the channels have a typical diameter of 2–25 μm and are oriented parallel to the electric field employed during synthesis. The self‐organization of channels occurs around an optimal PEG concentration of 8.6 wt/vol %, whereas significantly higher or lower concentrations yield random, isotropic pore structures. Moreover, tensile strength measurements show that the mechanical stability increases with decreasing concentration of PEG. Rheology experiments reveal that the swelling degree of these superabsorbant hydrogels increases with increasing PEG. Possible applications of these microstructured hydrogels as bidirectional scaffolds for regenerating neurons in the injured spinal cord are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2593–2600, 2007     

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     

Purification and Characterization of Three Lectins Extracted from Cassia Fistula Seeds and Effect of Various Physical and Chemical Agents on Their Stability

Three lectins designated as CSL‐1, CSL‐2 and CSL‐3 were purified from Cassia fistula seeds by gel filtration on Sephadex G‐50 followed by ion‐exchange chromatography on DEAE cellulose and finally by affinity chromatography on Sepharose 4B. The molecular weights of the lectins CSL‐1, CSL‐2 and CSL‐3, determined by gel filtration on Sephadex G‐75 column were 37,000, 42,400 and 46,000, and by SDS gel electrophoresis were 37500, 42000 and 46500, respectively. All three lectins agglutinated rat red blood cells and the agglutination was inhibited specifically by galactose and galactose containing saccharide. The neutral sugar contents of the lectins, CSL‐1, CSL‐2 and CSL‐3 were estimated to be 3.5, 3.1 and 2.0%, respectively. The sugar composition of the lectins was found to be galactose in CSL‐1, galactose and glucose in CSL‐2, and galactose and mannose in CSL‐3. The lectins exhibited maximum hemagglutinating activities around pH 7.2 to 7.5 and at a temperature range of 20° to 35 °C. Biological activities of the lectins were abolished sequentially with the increase in concentration of acetic acid and denaturant solutions such as urea and guanidine‐HCl.     

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     

Swelling behavior and network structure of hydrogels synthesized using controlled UV‐initiated free radical polymerization

N‐vinyl‐2‐pyrrolidone (VP) and 2‐hydroxyethyl methacrylate (HEMA) copolymeric gels have been synthesized using UV‐initiated photopolymerization to understand their characteristic behavior for development as a bioengineering material, specifically for tissue expansion. The properties of the gels have been investigated by systematic variation of the monomer feed composition and initiator and crosslinker concentrations as well as UV irradiation intensity, which was controlled by various photomasks. The swelling kinetics and network characteristics for the various hydrogels were investigated through the observation of gel swelling behavior in saline solutions and compression modulus determination of the fully swollen hydrogels. The equilibrium swelling ratio (q_e) of the gels increased as expected with increasing VP content and decreasing crosslinker concentration. However, it was found that as the amount of initiator or UV intensity increased, unexpectedly q_e also increased, which indicates a network structure with decreasing effective crosslink density (ν_e) (or increasing average molecular weight between crosslinks (M_c)). Based on this anomalous swelling behavior and thermal analysis of the gels, a molecular structure is proposed consisting of increasing number of dangling chain ends within the polymer network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1450–1462, 2008     

Modeling the swelling pressure of degrading hydroxyethylmethacrylate‐grafted dextran hydrogels

Degrading hydroxyethylmethacrylate‐grafted dextran (dex‐HEMA) hydrogels generate a relatively sudden increase in osmotic pressure upon degradation into dextran solutions. This phenomenon is currently being examined as a possible means of developing a pulsatile drug‐delivery system. Here a mathematical model based on scaling concepts is presented to describe this sudden increase in swelling pressure and to provide a framework for the rational design of pulsatile delivery systems based on this phenomena. The model provides a good fit to the swelling pressures measured for dex‐HEMA gel/free dextran mixtures that simulate degrading dex‐HEMA gels. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3397–3404, 2004     

Dynamic mechanical properties and swelling of UV‐photopolymerized anionic hydrogels

The tensile dynamic mechanical properties and weight degree of swelling for anionic 2‐hydroxyethyl methacrylate‐co‐acrylic acid hydrogels were observed. Fabrication parameters examined were UV‐photopolymerization exposure time, UV‐photopolymerization intensity, and weight percentage crosslinker. The environmental conditions tested were electrolyte compositions of 0.5 and 0.05 M potassium hydroxide under applied frequencies of 0.1, 1, or 10 Hz. The overall maximum and minimum storage modulus was 1.83 ± 0.18 MPa and 68.5 ± 7.2 kPa, respectively, loss modulus was 432 ± 63 and 7.67 ± 3.22 kPa, respectively, and weight degree of swelling was 14.27 ± 1.27 and 1.95 ± 0.33, respectively. The morphology of fabricated hydrogels was examined using scanning electron microscopy showing a range of porous structures over the fabrication and environmental conditions examined, accounting for the variation in mechanical properties. The properties examined are of interest to researchers fabricating, designing, or modeling active hydrogel‐based microfluidic components. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Preparation and characterization of pH- and temperature-responsive semi-IPN hydrogels of carboxymethyl chitosan with poly (<Emphasis Type="Italic">N</Emphasis>-isopropyl acrylamide) crosslinked by clay

A new kind of pH- and temperature-responsive semi-interpenetrating polymer network hydrogel based on linear carboxymethylchitosan (CMCS) and poly (N-isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was prepared. The pH-and temperature-responsive behaviors, the deswelling kinetics, and the mechanical properties of the hydrogel were investigated. The hydrogels exhibited a volume phase transition temperature around 33 °C with no significant deviation from the conventional PNIPA hydrogels. The results of the influence of pH value on the swelling behaviors showed that the minimum swelling ratios of the hydrogels appeared near the isoelectric point (IEP) of CMCS, and when pH deviated from the IEP, the hydrogels behaved as polycations or polyanions. The novel hydrogels had much higher response rate than the conventional CMCS/PNIPA hydrogels. Moreover, the semi-IPN hydrogels crosslinked by clay could be elongated to more than 800% and the elongation could be recovered almost completely and instantaneously.     

pH‐responsive ionic poly(N,N‐diethylaminoethyl methacrylate‐co‐N‐vinyl‐2‐pyrrolidone) hydrogels: Synthesis and swelling properties

A series of an ionic hydrogels composed of N,N‐diethylaminoethyl methacrylamide (DEAEMA), N‐vinyl‐2‐pyrrolidone (VP), and itaconic acid were synthesized by free‐radical cross‐linking copolymerization in water–ethanol mixture by using N,N‐methylenebis(acrylamide) as the cross‐linker, ammonium persulfate as the initiator, and N,N,N′,N′‐tetramethylenediamine as the activator. The swelling behaviors of these hydrogels were analyzed in buffer solutions at various pH. It was observed that the swelling behavior of cross‐linked ionic poly(N,N‐diethylaminoethyl methacrylamide‐co‐N‐vinyl‐2‐pyrrolidone) [P(DEAEMA/VP)] hydrogels at different pH agreed with the modified Flory–Rehner equation based on the affine network model and the ideal Donnan theory. The swelling process in buffer solutions at various pH was found to be Fickian‐type diffusion. The pH‐reversibility and on–off switching properties of the P(DEAEMA/VP) hydrogels may be considered as good candidate to design novel drug‐delivery system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2819–2828, 2005     

Biodegradable thermo‐ and pH‐responsive hydrogels for oral drug delivery

In this article, novel smart hydrogels based on biodegradable pH sensitive poly(L ‐glutamic acid‐g‐2‐hydroxylethyl methacrylate) (PGH) chains and temperature‐sensitive hydroxypropylcellulose‐g‐acrylic acid (HPC‐g‐AA) segments were designed and synthesized. The influence of pH and temperature on the equilibrium swelling ratios of the hydrogels was discussed. The optical transmittance of the hydrogels was also changed as a function of temperature, which reflecting that the HPC‐g‐AA part of the hydrogels became hydrophobic at the temperature above the lower critical solution temperature (LCST). At the same time, the LCST of the hydrogels had a visible pH‐dependent behavior. Scanning electron microscopic analysis revealed the morphology of the hydrogels before and after enzymatic degradation. The biodegradation rate of the hydrogels was directly related to the PGH content and the pH value. The in vitro release of bovine serum albumin from the hydrogels were investigated. The release profiles indicated that both the HPC‐g‐AA and PGH contents played important roles in the drug release behaviors. These results show that the smart hydrogels seem to be of great promise in pH–temperature oral drug delivery systems. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A facile pathway for the fast synthesis of colloidal crystal‐loaded hydrogels via frontal polymerization

In this work, a dually sensitive colloidal crystal (CC)‐loaded hydrogel has been synthesized via frontal polymerization (FP) in a facile and rapid way. First, a polystyrene CC film was fabricated by vertical deposition on the inner wall of a test tube. Then, a mixture of acrylic acid (AAc), 2‐hydroxyethyl methacrylate (HEMA), and glycerol along with the initiator and crosslinker was added to this test tube to carry out FP, resulting in the formation of CC‐loaded hydrogel. The influence of the mass ratios of HEMA/AAc on front velocity and temperatures were studied. The swelling behavior, the morphology, and the stimuli‐responsive behavior of the CC‐loaded hydrogels prepared via FP were thoroughly investigated on the basis of swelling measurement, scanning electron microscopy, and reflection spectra. Results show that the as‐prepared CC‐loaded hydrogels exhibit excellent dual sensitivity to both methanol concentrations and pH values with very short response time, which can be observed visually without the aid of instruments. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011