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Random copolymer gels of N -isopropylacrylamide (NIPAM) and N -ethylacrylamide (NEAM) were synthesized in using different monomer compositions in 1:1 methanol-water mixtures and in pure water. The samples were characterized by cononsolvency study in methanol-water mixtures at various temperatures by swelling ratio measurements. It is observed that with the variation of the temperature and monomer compositions in the synthesis reaction mixture, the cononsolvency properties varied significantly. But the variation in the solvents compositions by keeping monomer compositions fixed does not affect the cononsolvency much. All results can be explained on the basis of the differences in thermoresponsive character or difference in the hydrophilicity of PNIPAM and PNEAM in water, preferential adsorption of the solvents by polymer networks, solvent-solvent interactions, heterogeneity of the polymer networks synthesized at different solvent compositions and at different temperatures, difference in their morphological properties, etc.

Random copolymer gels of N-isopropylacrylamide (NIPAM) and N-ethylacrylamide (NEAM) were synthesized using a 1:1 monomer molar ratio in different methanol–water (xm = 0, 0.06, 0.13, 0.21, 0.31 0.43, 0.57, 0.76, where xm = mole fraction of methanol) mixtures. The samples were characterized using different techniques like Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), swelling ratio measurements, deswelling kinetics study, atomic force microscopy (AFM), and rheology. We found that, with the variation of the solvent composition (methanol–water mixtures) the properties of the gels varied significantly. These results can be explained on the basis of the interactions of the two different kinds of monomers with different methanol–water mixtures, their different kinds of thermoresponsiveness and hydrophilicity, and their different cononsolvent properties toward methanol–water mixtures.

Nanocomposite stereoregular hybrid gels of poly(N-isopropylacrylamide) were prepared in 1:1 methanol–water mixture in the presence rare earth yttrium trifluoromethanesulfonate Lewis acid and graphene oxide (GO). The nanocomposite gels were characterized by swelling ratio measurements at different temperatures and different pH, deswelling kinetics, scanning electrone microscopy, FTIR, thermogravimetric analysis, powder XRD, Raman spectroscopy, LCST measurement by DSC etc. Drug release experiments also done by using tramadol hydrochloride as a model drug to check their suitability in application. All results were explained on the basis of porosity, cononsolvency of the synthesis solvents, hydrophilicity, isotacticity, pH effect, interactions between solvents and polymer molecules, interactions between polymer and GO or interactions between GO and solvents etc. © 2016, Springer Science+Business Media New York., KC2014ZDZJ0001A ZDSYS201507141105130 JCYJ20140509172719311 University of Akron 2013-7211-8496-02 National Natural Science Foundation of China: 21574086, We gratefully acknowledge the financial support from TUBITAK, Government of Turkey, through 2216 fellowship program for the foreign citizens and B??lent Ecevit University (#2013-7211-8496-02). The authors also thank the National Science Foundation of China (21574086), Nanshan District Key Lab for Biopolymers and Safety Evaluation (No. KC2014ZDZJ0001A), Shenzhen Sci and Tech research Grant (ZDSYS201507141105130), and Shenzhen City Science and Technology Plan Project (JCYJ20140509172719311) for financial support. We thank Prof. Kevin Cavicchi, University of Akron for comments on this manuscript.

Thermoreversible gelation of three different isotactic linear poly(N-isopropylacrylamide) (PNIPAM)s having meso dyad (m) values 62, 68 and 81% has been observed in benzyl alcohol. All the gels were transparent in nature. SEM image of the dried gels showed fibrillar network morphology. Melting temperature of the gels gradually increased with the increase in the concentration. XRD data of dry polymers and their corresponding dry gels showed shifting in the peak positions. Rheological study showed that stronger gels were formed with increasing isotacticity of PNIPAM while lower isotactic sample exhibited typical polymer melt rheology. The formation of a plunge in the storage modulus as well as in the viscosity plot at the same frequency range indicates the reversible nature of the structure breaking/reformation under frequency sweep. Moreover, the mechanical strength of the gel decreased with increase in temperature. UV-Vis kinetic study also indicated the change in the conformation and aggregation of PNIPAM chains during gelation. Molecular modelling calculation showed that the number of solvent molecules involved in forming gel (polymer-solvent compound) decreased with the increase in the isotacticity of the polymer. Gelation rate of these gels was studied as a function of temperature, concentration and isotacticity using test-tube tilting method. It increased with the increase in the concentration and isoacticity of the polymer, and with the decrease in the temperature. Critical gelation concentration of the gel gradually increased with the decrease in the isotacticity and with the increase in the temperature. All these experimental results indicated that gelation occurs presumably through polymer-solvent compound formation.

Poly(N-isopropylacrylamide)s (PNIPAM) with low polydispersity and different isotacticity have been synthesized successfully in different compositions of environment-friendly and less toxic methanol-water mixtures by RAFT polymerization in the presence of 0.1 M Yttrium trifluoromethanesulfonate [Y(OTf) 3]. The reactions were successful with high yield in the solvent compositions having mole-fraction of methanol (x m) at or above 0.31. Molecular weights were found to be in between 2.78 × 10 4 – 5.7 × 10 4 and polydispersity index (M w/ M n= 1.11 – 1.37) was close to unity. Isotacticity [meso diad (m), %] of the polymers increased from 55 to 86% with the increase in the x m value from 0.31 to 1.0. The lower critical solution temperature (LCST) of the formed PNIPAMs in water decreased with the increase in their isotacticity.

The synthesis of amphiphilic block-copolymers of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-acryloyl- l -phenylalanine methyl ester) (PNALPA) by RAFT polymerization is reported. The polymers were characterized by proton NMR (1H NMR), gel permeation chromatography (GPC), powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) to understand their structure-property relationships. All synthesized polymers show pH triggered release at acidic (pH 5) and biological pH (pH 7.4). Critical micellar concentration also varied systematically depending on the amphiphilic nature of the polymers. Biocompatibilities of the polymers are also determined to check their suitability for biomedical applications.

Some physical properties of high molecular weight linear poly(N-isopropylacrylamide)s (PNIPAM) having different isotacticities (m, meso dyad = 47, 62, 68, 81, and 88 %) have been studied. The solubility of these polymers in different solvents varied with their isotacticity. Thermal degradation of higher isotactic polymer started slightly earlier. Cloud point of these polymers in water gradually decreased with increase in m up to 68 %. Surface tension of these polymers in N,N-dimethylformamide (DMF) was slightly lower than DMF and almost independent of their isotacticity in the temperature range of 20–60 °C. But it decreased linearly with the increase in temperature. Moreover, for all polymers, it decreased very slightly with the increase in their concentrations in the range of 0.001–0.01 % (w/v). Viscosity of these polymers in DMF increased with (i) the increase in the concentration range of 1–5 % (w/v), (ii) the increase in their m values, and (iii) the decrease in the temperature in the range of 20–60 oC.

Well-defined linear dihydrophilic amphiphilic ABA-type triblock copolymers of e-caprolactone (CL) and N-isopropylacrylamide (NIPAAm) have successfully been synthesized with a high yield by combining the ring opening polymerization (ROP) and xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization methods. The resulted block copolymer shows the formation of micelles in water as supported by light scattering. The critical micelle concentration (cmc) value of the micelle increases with the increase in the chain length of the poly (N-isopropylacrylamide) (PNIPAAm) block. Cloud point of the block copolymers decreases with the decrease in the PNIPAAm chain length. The TGA analysis shows a one-step degradation and a lower thermal stability of the triblock copolymer than the PNIPAAm. The DSC analysis of the triblock copolymer shows the lowering of glass transition temperature (T g), and melting temperature (T m) peaks possibly due to the partial miscibility of the poly (e-caprolactone) (PCL) block with the amorphous PNIPAAm block through the interaction of ester groups of PCL with the amide groups of PNIPAAm. The XRD pattern of the triblock copolymer shows a broad peak due to the suppression of the crystallization of PCL block owing to the mixing of PNIPAAm block with the PCL block.

Well-defined amphiphilic poly( d , l -lactide)- b -poly( N -vinylpyrrolidone) (PDLLA- b -PNVP) block copolymers were successfully prepared using ring-opening polymerization (ROP) and xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization. Synthesized PDLLA- b -PNVP block copolymers were characterized by 1 H NMR spectroscopy and GPC. Spherical micelles of ∼30.2 nm diameter were formed from the aqueous solution of amphiphilic diblock copolymer PDLLA 42 - b -PNVP 63 as revealed by TEM and supported by 1 H NMR and light scattering. The critical micelle concentration value of the block copolymers, determined by fluorescence spectroscopy using pyrene as probe, increased with the increase in the chain length of PNVP block. The average hydrodynamic radius ( R h ) of the micelles remained almost constant above the cmc value over the angles of scattering measurement. Thermal properties of these block copolymers were studied by TGA, DTA and DSC. Crystalline properties of these block copolymers were studied by WXRD.

Two new alkyne-terminated xanthate reversible addition-fragmentation chain-transfer (RAFT) agents: (S)-2-(Propynyl propionate)-(O-ethyl xanthate) (X3) and (S)-2-(Propynyl isobutyrate)-(O-ethyl xanthate) (X4) were synthesized and characterized and used for the controlled radical polymerization of N-vinylpyrrolidone (NVP). X3 showed better chain transfer ability in the polymerization at 60°C. Molecular weight of the resulted polymer increased linearly with the increase in monomer loading. Kinetics study with X3 showed the pseudo-first order kinetics up to 67% monomer conversion. Molecular weight (Mn) of the resulting polymer increased linearly with the increase in the monomer conversion up to around 67%. With the increase in the monomer conversion, polydispersity of the corresponding poly(NVP)s initially decreased from 1.34 to 1.32 and then increased gradually to 1.58. Chain-end analysis of the resulting polymer by 1H-NMR and FTIR showed clearly that polymerization started with radical forming out of xanthate RAFT agent. Living nature of the polymerization was also confirmed from the successful homo-chain extension experiment and the hetero-chain extension experiment involving synthesis of poly(NVP)-b-polystyrene amphiphilic diblock copolymer. Formed alkyne-terminated poly(NVP) also allowed easy conjugation to azide-terminated polystyrene by click chemistry to prepare well-defined poly(NVP)-b-polystyrene block copolymers. Resulting polymers were characterized by GPC, 1H-NMR, FTIR, and thermal study. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels and the corresponding linear homopolymers were synthesized in different methanol-water mixtures (x(m) = 0, 0.13, 0.21, 0.31, 0.43, 0.57, and 0.76, where x(m) is the mole fraction of methanol) in the presence of 0.1 M Y(OTf)(3) Lewis acid. The isotacticity (meso dyad (m), %) and cloud-point temperature of these homopolymers were gradually increased and decreased, respectively, with the increase in the x(m) values of the synthesis solvent mixtures. Moreover, the corresponding linear PNIPAM homopolymers prepared in the absence of Y(OTf)(3) showed an almost constant isotacticity of m = 45% and a cloud-point temperature of 33.0 °C. A SEM study revealed that the resulting hydrogels were highly porous except for the gels prepared at x(m) = 0 and 0.76. The swelling ratios of these hydrogels in water at different temperatures and in different methanol-water mixtures at 20 °C and the deswelling rate and the reswelling rate of these hydrogels were studied. All of these swelling results were compared with that of the corresponding gels prepared in the absence of a Lewis acid (Biswas, C. S.; Patel, V. K.; Vishwakarma, N. K.; Mishra, A. K.; Bhimireddi, R.; Rai, R.; Ray, B. J. Appl. Polym. Sci.2012, DOI: 10.1002/app.36318) and explained on the basis of the porosity of the gel, the state of aggregation and isotacticity of the PNIPAM chain segment, and the cononsolvency of the methanol-water mixture toward the PNIPAM chain segment.

S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and the newly syn- thesized (S)-2-(ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the revers- ible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of N-vinylpyrrolidone (NVP). The former showed the better chain transfer ability in the polymerization at 60 C. Kinetics study with X1 shows the psuedo-first order kinetics upto 45% monomer conversion. Molecular weight (Mn) of the resulted polymer increases linearly with increase in the monomer conversion upto around 45%. Polydispersity of the corresponding poly(NVP)s increase grad- ually from 1.2 to 1.9 with increase in the monomer conversion. Chain-end analysis of the resulted polymer by 1 H NMR shows clearly that polymerization started with radical forming out of xanthate mediator. Living nature of the polymerization was confirmed from the successful homo chain extension experiment and also the het- ero-chain extension experiment involving synthesis of poly(NVP)-b-polystyrene amphiphilic diblock copolymer.

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels were simply prepared by free radical polymerization in different methanol–water mixture. A scanning electron microscopy study revealed that the freeze-dried hydrogels were macroporous. The swelling ratios in water at 20°C of the resulting hydrogels followed the order: X0.43>X0.21>X0.76 ≈ X0.57>X0.31>X0.13>X0.06>X0, where Xm denotes a gel prepared in a methanol–water mixture with m mole fraction of methanol (xm). Below the lower critical solution temperature, the swelling ratio values of all of the hydrogels gradually decreased with the increase in the temperature. The complete collapse of the PNIPAM chain of all the gels occurred at about 38°C, whereas the same was observed at about 35°C for the conventional gel prepared in water. The swelling ratio values of all the PNIPAM gels in the methanol–water mixtures with different xm values at 20°C passed through a minimum in the cononsolvency zone. The deswelling rates of the hydrogels decreased in the following order: X0.43> X0.31> X0.21> X0.57> X0.76 ≈ X0.13> X0.06> X0. The reswelling rates of these hydrogels decreased in the following order: X0> X0.31> X0.06 ≈ X0.13 > X0.76> X0.57> X0.21> X0.43. The release rates of the Tramadol Hydrochloride drug at 37°C from the drug-loaded hydrogels were almost same for all of the hydrogels. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Well-defined amphiphilic poly(e-caprolactone)-b-poly(N-vinylpyrrolidone) (PCL-b-PNVP) block copolymers were successfully prepared via the combination of ring-opening polymerization (ROP) and xanthate-mediated reversible addition−fragmentation chain transfer (RAFT) polymerization. Well-defined poly(e-caprolactone) (PCL−OH) was synthesized by ROP in bulk at 110 °C using benzyl alcohol as initiator and stannous octate [Sn(Oct)2] as catalyst . The −OH end group was then converted into its corresponding xanthate (PCL−X) via the conversion to its corresponding bromide (PCL−Br). These are verified by 1H NMR spectroscopy. PCL-b-PNVP block copolymers were synthesized via RAFT polymerization in tetrahydrofuran (THF) at 80 °C using PCL−X as macro-chain transfer agent and characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The amphiphilic diblock copolymer PCL63-b-PNVP90 forms spherical micelles of ∼34 nm diameter in water as shown by transmission electron microscopy (TEM), supported by 1H N...

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels were prepared by free-radical polymerization in different ethanol–water mixtures. A scanning electron microscopy study revealed that the resulting hydrogels were macroporous. The swelling ratios of the resultant hydrogels in water at 20°C followed this order: X0.34 ≈ X0.68 > X0.48 > X0.09 > X0.04 > X0, where Xa denotes a gel prepared in an ethanol–water solvent mixture with an ethanol molar fraction of a. Below the lower critical solution temperature, the swelling ratio values of all of the hydrogels gradually decreased with increasing temperature. The complete collapse of the PNIPAM chain of all of these gels occurred at about 38°C, whereas the same was observed at about 35°C for the conventional gel prepared in water. The swelling ratio values of all of the PNIPAM gels with different molar fractions of ethanol at 20°C passed through a minimum in the cononsolvency zone. The deswelling rates of the hydrogels decreased in the following order: X0.34 > X0.48 > X0.68 > X 0.09 > X0.04 > X0. The reswelling rates of these hydrogels decreased in the following order: X0 > X0.04 ≈ X0.48 > X0.09 ≈ X0.68 > X 0.34. The freeze-drying process decreased the swelling ratios but increased the deswelling and reswelling properties of the PNIPAM gels. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and the newly synthesized (S)-2-(ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the reversible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of N-vinylpyrrolidone (NVP). The former showed the better chain transfer ability in the polymerization at 60 °C. Kinetics study with X1 shows the psuedo-first order kinetics upto 45% monomer conversion. Molecular weight (M n) of the resulted polymer increases linearly with increase in the monomer conversion upto around 45%. Polydispersity of the corresponding poly(NVP)s increase gradually from 1.2 to 1.9 with increase in the monomer conversion. Chain-end analysis of the resulted polymer by 1H NMR shows clearly that polymerization started with radical forming out of xanthate mediator. Living nature of the polymerization was confirmed from the successful homo chain extension experiment and also the hetero-chain extension experiment involving synthesis of poly(NVP)-b-polystyrene amphiphilic diblock copolymer.

Two series of macroporous poly(N-ethylacrylamide) (PNEAM) gels are synthesized in different composition of methanol-water mixtures (x(m)=0, 0.06, 0.13, 0.21, 0.31, and 0.43; where x(m)=mole fraction of methanol) in presence as well as in the absence of 0.1M Y(OTf)(3) Lewis acid as additive. The gels synthesized in the absence of Lewis acid are atactic and in the presence of the same are isotactic. Synthesis of the corresponding linear PNEAM homopolymers shows that, the isotacticity (meso dyad, %) of the resulted polymers increases for the gels prepared in the presence of Lewis acid (LA) and remains constant for the gel prepared in the absence of LA, respectively, with the increase in the concentration of the synthesis solvent methanol. SEM micrographs reveal that, the hydrogels synthesized in the presence of LA are more porous than the gels prepared in the absence of LA. Swelling ratio of all the hydrogels decreases with the increase in the temperature and LA gels show higher swelling ratio values than non LA gels (NLA). Deswelling rate of the hydrogels prepared in methanol-water mixture in presence of LA is faster than the hydrogels prepared in absence of LA. Moreover, reswelling rate increases with increase in the isotacticity of the PNEAM segment in the gel. All these results have been explained on the basis of the formation of highly porous hydrogels with higher isotactic PNEAM chain segment in the presence of LA in methanol-water mixtures. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41668.

Random copolymer hydrogels of N-isopropylacrylamide and N-ethylacrylamide (NEAM) were prepared using different monomer compositions in 1:1 methanol–water mixtures. The samples were characterized by cononsolvency study in methanol-water mixtures at various temperatures, swelling properties measurements, scanning electron microscopy. With changing ratio of the monomers in the reaction mixture, the thermal, morphological and swelling properties, varied significantly. The change in the properties with monomer composition variation are interpreted based on the different thermoresponsive characteristics and interactions of gels of N-isopropylacrylamide and NEAM (homo- and copolymer gels) in water and different methanol-water mixtures, their variable compositions in the synthesis mixtures, and their morphologies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45176.

A series of high molecular weight poly(N-isopropylacrylamide) (PNIPAM)s with low polydispersity (Mn = 7.0 × 104 to 10.2× 104 g mol–1, PDI = 1.23–1.35) having different isotacticity [meso diad (m) =...

WOS: 000347696100012, Macroporous poly(N-ethylacrylamide) (PNEAM) hydrogels have been prepared in a methanol-water (1:1, v/v) mixture in the presence of 0, 0.05, 0.1, 0.15, and 0.2 M yttrium trifluoromethanesulfonate [Y(OTf)(3)] Lewis acid (LA) concentrations. SEM micrographs show that the resulted hydrogels are highly porous. Swelling ratios of all the hydrogels in water decrease with the increase in the temperature, and the hydrogels show lower critical solution temperature (LCST) volume phase transition at around 75 A degrees C. LCST of PNEAM homopolymers gradually increases with the increase in the isotacticity of the polymers. Moreover, the hydrogels show cononsolvency in different methanol-water mixtures at 50 A degrees C. Deswelling rate of the hydrogels prepared in the presence of LA is higher than the gel prepared in the absence of LA and this rate increases with increase in the LA concentration. The reswelling rate of the hydrogels also follows the same order, that is reswelling rate also increases with the increase in the LA loading in the gels. All these results are explained on the basis of the formation of the highly porous hydrogels with a higher isotactic PNEAM chain segment in a methanol-water mixture in the presence of LA., TUBITAK, Government of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK); TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [211T016]; Bulent Ecevit University Research FundBulent Ecevit University [BEU-2012-10-03-13], We gratefully acknowledge the financial support from TUBITAK, Government of Turkey, through 2216 fellowship program for the foreign citizens (CSB). This work was also supported by both TUBITAK (grant no. 211T016) and the Bulent Ecevit University Research Fund (#BEU-2012-10-03-13). We personally thank Elvan Sulu for her technical assistance.

Novel amphiphilic ABA-type poly(D-gluconamidoethyl methacrylate)-b-polyurethane-b-poly(D-gluconamidoethyl methacrylate) (PGAMA-b-PU-b-PGAMA) tri-block copolymers were successfully synthesized via the combination of the step-growth and copper-catalyzed atom transfer radical polymerization (ATRP). Dihydroxy polyurethane (HO-PU-OH) was synthesized by the step-growth polymerization of hexamethylene diisocyanate with poly(tetramethylene glycol). PGAMA-b-PU-b-PGAMA block copolymers were synthesized via copper-catalyzed ATRP of GAMA in N, N-dimethyl formamide at 20°C in the presence of 2, 2′-bipyridyl using Br-PU-Br as macroinitiator and characterized by 1H-NMR spectroscopy and GPC. The resulting block copolymer forms spherical micelles in water as observed in TEM study, and also supported by 1H NMR spectroscopy and light scattering. Miceller size increases with increase in hydrophilic PGAMA chain length as revealed by DLS study. The critical micellar concentration values of the resulting block copolymers increased with the increase of the chain length of the PGAMA block. Thermal properties of these block copolymers were studied by thermo-gravimetric analysis, and differential scanning calorimetric study. Spherical Ag-nanoparticles were successfully synthesized using these block copolymers as stabilizer. The dimension of Ag nanoparticle was tailored by altering the chain length of the hydrophilic block of the copolymer. A mechanism has been proposed for the formation of stable and regulated Ag nanoparticle using various chain length of hydrophilic PGAMA block of the tri-block copolymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Macroporous poly(N-isopropylacrylamide) (PNIPAM) hydrogels have been prepared in methanol-water (1:1, v/v) mixture in the presence of 0, 0.05, 0.1, 0.15, and 0.2 M Y(OTf)(3) Lewis acid concentrations. Synthesis of the corresponding linear PNIPAM homopolymers in the absence of a cross-linker keeping all other conditions the same shows that the isotacticity (meso dyad, %) and the cloud point temperature of the resulted in polymers increases and decreases, respectively, with the increase in the concentration of the Lewis acid. SEM micrographs reveal that the resulted hydrogels are highly porous. Swelling ratios of all the hydrogels in water decrease with the increase in the temperature. Moreover, swelling ratios of all the hydrogels in different methanol-water mixtures pass through a minimum in the co-nonsolvency zone, and the co-nonsolvency zone shifts toward the lower methanol-content solvent mixture with gradual increase in the Lewis acid concentration. Deswelling rate of the hydrogel prepared in methanol-water (1:1, v/v) mixture is much faster than that of the conventional hydrogel prepared in water. Moreover, the deswelling rate slightly increases with the hydrogels prepared with the increasing concentrations of Lewis acid. But, the reswelling rate of the hydrogels follows almost the reverse order. All these results have been explained on the basis of the formation of highly porous hydrogels with higher isotactic PNIPAM chain segment owing to the faster polymerization rate in the methanol-water mixture in the presence of Lewis acid and the co-nonsolvency behavior of the methanol-water (1:1, v/v) mixture toward PNIPAM chain segment in the PNIPAM hydrogel.