Effect of pH,ionic strength,and temperature on uranyl ion adsorption by poly(N‐vinyl 2‐pyrrolidone‐g‐tartaric acid) hydrogels

Poly‐electrolyte N‐vinyl 2‐pyrrolidone‐g‐tartaric acid (PVP‐g‐TA) hydrogels with varying compositions were prepared in the form of rods from ternary mixtures of N‐vinyl 2‐pyrrolidone/tartaric acid/water. The effect of external stimuli, such as the solution pH, ionic strength, and temperature, on uranyl adsorption by these hydrogels was investigated. Uranyl adsorption capacities of the hydrogels were determined to be 53.2–72.2 (mg UO/g dry gel) at pH 1.8, and 35.3–60.7 (mg UO/g dry gel) at pH 3.8, depending on the amount of TA in the hydrogel. The adsorption studies have shown that the temperature and the ionic strength of the swelling solution also influence uranyl ion adsorption by PVP‐g‐TA hydrogels. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2219–2226, 2000     

Swelling kinetics of poly(N‐vinylimidazole‐co‐sodium styrenesulfonate) hydrogels

Hydrogels of N‐vinylimidazole and sodium styrenesulfonate were synthesized by radical crosslinking copolymerization. Transient swelling measurements in water, at room temperature, reveal an unusual behavior. For some gel compositions, the swelling time dependency is about a δ function: dry hydrogel pellets swell up readily to reach a high degree of swelling and, spontaneously, they deswell to collapse. Such peculiarity was interpreted in terms of several competing events in the swelling mechanism: water diffusion toward the gel, chain disentanglement, sodium–proton interchange through the gel–external bath boundary, approaching of chains to allow interaction of sulfonate groups with neighboring protonated imidazole moieties and diffusion of water outside the gel. The results of cyclic swelling–deswelling following abrupt changes of composition in the external bath, from water to sodium hydroxide solution, support that mechanism. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 191–200, 2002     

The effect of gel composition on the uranyl ions adsorption capacity of poly(N‐vinyl 2‐pyrrolidone‐g‐citric acid) hydrogels prepared by gamma rays

Poly(N‐vinyl 2‐pyrrolidone‐g‐citric acid) (PVP‐g‐CA) hydrogels with varying compositions were prepared from ternary mixtures of N‐vinyl 2‐pyrrolidone–citric acid–water by using ⁶⁰Co γ‐rays. The effect of gel composition on the uranyl ions adsorption capacity of PVP‐g‐CA hydrogels was investigated. Uranyl adsorption capacity of these hydrogels were found to be in the range of 18–144 mg [UO]/g dry gel from the aqueous solution of uranyl nitrate and 22–156 mg [UO]/g dry gel from the aqueous solution of uranyl acetate, depending on the content of citric acid in the hydrogel, while poly(N‐vinyl 2‐pyrrolidone) hydrogel did not sorb any uranyl ion. The swelling of PVP‐g‐CA hydrogel containing 2.7 mol % CA was observed in water (1620%), in uranyl acetate solution (1450%) and in uranyl nitrate solution (1360%), as compared to 700% swelling of pure PVP hydrogels. The diffusion coefficients were varied from 12.57 up to 4.04 • 10⁻⁸ m² s⁻¹. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1037–1043, 2000     

Swelling–deswelling behavior of poly(acrylamide‐co‐maleic acid) hydrogels

In this study the poly(acrylamide‐co‐maleic acid) hydrogels containing small amounts of maleic acid have been synthesized, and the effect of pH, ionic strength, and nature of counterions on the equilibrium water uptake has been investigated. The incorporation of small amount of maleic acid results in the transition of swelling mechanism from Fickian to non‐Fickian. The equilibrium mass swelling has been found to increase with pH of the swelling medium while increase in ionic strength causes a decrease in the swelling. The amount of maleic acid present in the hydrogel affects the swelling behavior in rather an unusual way. With lower acid contents, the equilibrium mass swelling increases while higher concentrations of maleic acid cause a decrease in the degree of swelling. The hydrogels have been found to undergo a number of swelling–deswelling cycles when pH of the swelling medium changes from 8.0 to 2.0. Hydrogels require more time to deswell compared to the time required for swelling, which has been explained on the basis of the fact that gels follow different mechanisms for the two processes. Various swelling parameters such as equilibrium mass swelling, diffusion coefficient, intrinsic diffusion coefficient, swelling exponent, etc., have been evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2782–2789, 2001     

Preparation and characterization of poly(N‐tert‐butylacrylamide‐co‐acrylamide) ferrogel

Magnetic‐field‐sensitive gel, called ferrogel, was prepared by a two‐step procedure in which first step requires synthesis of the poly(N‐tert‐butylacrylamide‐co‐acrylamide) [P(NTBA‐co‐AAm)] hydrogel and during second step magnetite (Fe₃O₄) particles were formed in the hydrogel via coprecipitation of Fe(II) and Fe(III) ions in alkaline medium at 70°C. The obtained ferrogel was characterized by attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy combined with energy dispersive spectroscopy, and electron spin resonance measurements. The magnetic responsive of the ferrogel was also investigated by applying magnetic field to the ferrogel. The extent of a bending degree of the ferrogel depends on the applied magnetic field strength. In addition, the magnetic responsive studies also indicated that formed magnetite content in the hydrogel is high enough to achieve considerable magnetic response to external magnetic field. As a result, the P(NTBA‐co‐AAm) ferrogel may be useful for potential applications in magnetically controlled drug release systems, magnetic‐sensitive sensors, and pseudomuscular actuators. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Molecular interactions in poly(methacrylic acid)/poly(N‐isopropyl acrylamide) interpenetrating polymer networks

The molecular interactions between the component networks in poly(methacrylic acid)/poly(N‐isopropyl acrylamide) (PMAA/PNIPAAm) interpenetrating polymer networks (IPNs) were investigated using attenuated total reflectance (ATR)‐Fourier transform IR (FTIR) spectroscopy. Hydrogen‐bond formation was noted between the carboxyl groups of PMAA and the amide groups of PNIPAAm. The ATR‐FTIR results showed shifts in the carboxylic and amide groups, indicating the existence of hydrogen bonding between these two individual networks within the IPNs. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1077–1082, 2001     

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

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

Drug release from electrospun fibers of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) grafted with poly(N‐vinylpyrrolidone)

Poly(N‐vinylpyrrolidone) (PVP) groups were grafted onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. Based on these graft copolymers, electrospun fiber mats and commonly cast films were explored as drug delivery vehicles using tetracycline hydrochloride as a model drug. Toward that end, the fibers were electrospun and the films were cast from chloroform solutions containing a small amount of methanol to solubilize the drug. The Brookfield viscosities of the solution were determined to achieve the optimal electrospinning conditions. The vitro release of the tetracycline hydrochloride from these new drug delivery systems was followed by UV–vis spectroscopy. To probe into the factors affected on the release behavior of these drug delivery systems, their water absorbing abilities in phosphate buffer solution were investigated, together with their surface hydrophilicity, porosity and crystallization properties were characterized by water contact angles, capillary flow porometer, DSC, and WAXD, respectively. The morphological changes of these drug delivery vehicles before and after release were also observed with SEM. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of graft modification with poly(N‐vinylpyrrolidone) on thermal and mechanical properties of poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

Poly(N‐vinylpyrrolidone) (PVP) groups were grafted onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. The effect of graft modification with PVP on the thermal and mechanical properties of PHBV was investigated. The thermal stability of grafted PHBV was remarkably improved while the melting temperature (T_m) was almost not affected by graft modification. The isothermal crystallization behavior of samples was observed by polarized optical microscopy and the results showed that the spherulitic radial growth rates (G) of grafted PHBV at the same crystallization temperature (T_c) decreased with increasing graft yield (graft%) of samples. Analysis of isothermal crystallization kinetics showed that both the surface free energy (σ_e) and the work of chain‐folding per molecular fold (q) of grafted PHBV increased with increasing graft%, implying that the chains of grafted PHBV are less flexible than ungrafted PHBV. This conclusion was in agreement with the mechanical testing results. The Young's modulus of grafted PHBV increased while the elongation decreased with increasing graft%. The hydrophilicity of polymer films was also investigated by the water contact angle measurement and the results revealed that the hydrophilicity of grafted PHBV was enhanced. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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

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

DNA adsorption on poly(N,N‐dimethylacrylamide)‐grafted chitosan hydrogels

In this study, poly(N,N‐dimethylacrylamide) grafted chitosan (PDMAAm‐g‐CT) hydrogels were prepared for deoxyribonucleic acid (DNA) adsorption. Instead of directly grafting the N,N‐dimethylacrylamide (DMAAm) monomer onto the chitosan (CT) chains, poly(N,N‐dimethylacrylamide) with carboxylic acid end group (PDMAAm‐COOH) was firstly synthesized by free‐radical polymerization using mercaptoacetic acid (MAAc) as the chain‐transfer agent and then grafted onto the CT having amino groups. The synthesis of PDMAAm‐COOH and its grafting onto the CT chains were confirmed by attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy. From gel permeation chromatography measurements, the number‐average molecular weight (M _n) and polydispersity index of PDMAAm‐COOH were found as 2400 g/mol and 2.3, respectively. The PDMAAm‐g‐CT hydrogels were utilized as the adsorbents in DNA adsorption experiments conducted at +4°C in a trisEDTA solution of pH 7.4. The hydrogels produced with higher PDMAAm‐COOH content exhibited higher DNA adsorption capacity. The DNA adsorption capacity up to 4620 μg DNA/g dry gel could be achieved with the PDMAAm‐g‐CT hydrogels prepared in 80.0 wt % PDMAAm‐COOH feed concentration. This value is approximately seven times higher than that of CT alone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Characterization of degraded hydrogels based on poly(vinyl alcohol) grafted with poly(lactide‐co‐glycolide)

Poly(vinyl alcohol) (PVA) grafted with poly(lactide‐co‐glycolide) and cross‐linked as a material of increased hydrophobicity relative to PVA was produced. The properties were examined with respect to the mass loss, water uptake, hydrophilicity, and mechanical characteristics upon hydrolytical degradation. The hydrogels investigated display water uptake increasing with degradation time because of increasing hydrophilicity. The mass loss amounts up to 15% after eight weeks of degradation. The mechanical properties of the hydrogels are within the range of those of natural tissue, the E modulus is 18 MPa, or even 100–200 MPa, depending on the structure of material. The mechanical characteristic and their dependence degradation show the most recognizable correlation with the chemical structure. Studies of the topography of degraded samples (scanning electron microscopy) and IR measurements demonstrate the degradation to occur at slow rate due to the high degree of grafting. The mass loss is rather low and a bulk degradation mechanism takes place. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adsorption of surfactant by hydrophobically modified poly[2‐(diethylamino)ethylmethacrylate‐co‐N‐vinyl‐2‐pyrrolidone/octadecyl acrylate)] hydrogels and effect of surfactant adsorption on the volume phase transition

Hydrophobically modified poly[2‐(diethylamino)ethylmethacrylate‐co‐N‐vinyl‐2‐pyrrolidone/octadecyl acrylate) [P(DEAEMA‐co‐NVP/OA)] hydrogels were synthesized by free‐radical crosslinking copolymerization of 2‐(diethylamino)ethylmethacrylate (DEAEMA), N‐vinyl‐2‐pyrrolidone (NVP) with different amounts of hydrophobic comonomer octadecyl acrylate (OA) in tert‐butanol with ethylene glycole dimethacrylate (EGDMA) as a crosslinker. The swelling equilibrium of the hydrogels was investigated as a function of temperature and hydrophobic comonomer content in aqueous solutions of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant dodecyltrimethylammonium bromide (DTAB). The results indicated that the swelling behavior and temperature sensitivity of the hydrogels were affected by the type and concentration of surfactant solutions. Additionally, the amount of the adsorbed SDS and DTAB molecules onto the hydrogels was determined by fluorescence measurements. An increase of OA content in the hydrogel caused an increase in the amount of adsorbed surfactant molecules in both media. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3771–3775, 2007     

Interpolymer‐specific interactions and miscibility in poly(styrene‐co‐acrylic acid)/poly(styrene‐co‐N,N‐dimethylacrylamide) blends

The miscibility or complexation of poly(styrene‐co‐acrylic acid) containing 27 mol % of acrylic acid (SAA‐27) and poly(styrene‐co‐N,N‐dimethylacrylamide) containing 17 or 32 mol % of N,N‐dimethylacrylamide (SAD‐17, SAD‐32) or poly(N,N‐dimethylacrylamide) (PDMA) were investigated by different techniques. The differential scanning calorimetry (DSC) analysis showed that a single glass‐transition temperature was observed for all the mixtures prepared from tetrahydrofuran (THF) or butan‐2‐one. This is an evidence of their miscibility or complexation over the entire composition range. As the content of the basic constituent increases as within SAA‐27/SAD‐32 and SAA‐27/PDMA, higher number of specific interpolymer interactins occurred and led to the formation of interpolymer complexes in butan‐2‐one. The qualitative Fourier transform infrared (FTIR) spectroscopy study carried out for SAA‐27/SAD‐17 blends revealed that hydrogen bonding occurred between the hydroxyl groups of SAA‐27 and the carbonyl amide of SAD‐17. Quantitative analysis carried out in the 160–210°C temperature range for the SAA‐27 copolymer and its blends of different ratios using the Painter–Coleman association model led to the estimation of the equilibrium constants K₂, K_A and the enthalpies of hydrogen bond formation. These blends are miscible even at 180°C as confirmed from the negative values of the total free energy of mixing ΔG_M over the entire blend composition. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1011–1024, 2007     

Synthesis and characterization of fast responsive thermo‐ and pH‐sensitive poly[(N,N‐diethylacrylamide)‐co‐(acrylic acid)] hydrogels

BACKGROUND: A considerable amount of research has been focused on smart hydrogels that can respond to external environmental stimuli, especially temperature and pH. In this study, fast responsive thermo‐ and pH‐sensitive poly[(N,N‐diethylacrylamide)‐co‐(acrylic acid)] hydrogels were prepared by free radical copolymerization in aqueous solution using poly(ethylene glycol) (PEG) as a pore‐forming agent. RESULTS: Swelling studies showed that the hydrogels produced had both temperature and pH sensitivity. The deswelling kinetics at high temperature demonstrated that the shrinking rates were influenced by the addition of the pore‐forming agent and the amount of acrylic acid in the initial total monomers. The deswelling curves in low‐buffer solutions had two stages. Pulsatile swelling studies indicated that the PEG‐modified hydrogels were superior to the normal ones. These different swelling properties were further confirmed by the results of scanning electron microscopy. CONCLUSION: Such fast responsive thermo‐ and pH‐sensitive hydrogels are expected to be useful in biomedical fields for stimuli‐responsive drug delivery systems. Copyright © 2008 Society of Chemical Industry     

Specific interactions in poly(styrene‐co‐2‐hydroxyethyl acrylate)/poly(styrene‐co‐N,N‐dimethylacrylamide) systems

Amphiphilic copolymers of poly(styrene‐co‐2‐hydroxyethyl acrylate) (SHEA) and poly(styrene‐co‐N, N‐dimethylacrylamide) (SAD) of different compositions were prepared by free radical copolymerization and characterized by different techniques. Depending on the nature of the solvent and the densities of interacting species incorporated within the polystyrene matrices, novel materials as blends or interpolymer complexes with properties different from those of their constituents were elaborated when these copolymers are mixed together. The specific interpolymer interactions of hydrogen bonding type and the phase behavior of the elaborated materials were investigated by differential scanning calorimetry (DSC) and Fourier transform infra red spectroscopy (FTIR). The specific interactions of hydrogen bonding type that occurred within the SHEA and within their blends with the SAD were evidenced by FTIR qualitatively by the appearance of a new band at 1626 cm^?1 and quantitatively using appropriate spectral curve fitting in the carbonyl and amide regions. The variation of the glass transition temperature with the blend composition behaved differently with the densities of interacting species. The thermal degradation behavior of the materials was studied by thermogravimetry. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Absorbency and adsorption of poly(acrylic acid‐co‐acrylamide) hydrogel

Poly(acrylic acid‐co‐acrylamide) (PAAAM) hydrogels have been prepared from partly neutralized acrylic acid (AA) and acrylamide (AM) by solution polymerization, and their absorbency and adsorption in both CuCl₂ and FeCl₃ solutions have been investigated. PAAAM hydrogels and their complexes with Cu²⁺ or Fe³⁺ have been characterized by FTIR. The absorbency of PAAAM in both CuCl₂ and FeCl₃ solutions increases initially and then decreases as the absorbing time increases. The adsorption of PAAAM in both CuCl₂ and FeCl₃ solutions can be described by the pseudo‐second order chemisorption kinetics proposed by Ho and McKay, and the equilibrium uptake of Cu²⁺ on PAAAM can well be fit with the Langmuir adsorption isotherm. However, the equilibrium uptake of Fe³⁺ on PAAAM increases as the initial Fe³⁺ concentration increases for Fe³⁺ concentration smaller than 5.625 × 10^?3 mol/L, and then decreases with Fe³⁺ concentration. The largest uptakes for Cu²⁺ and Fe³⁺ are 247 and 173 mg/g, respectively. The results also show that the uptake of Cu²⁺ and Fe³⁺ on PAAAM increases remarkably when pH of the solution is changed from 2.3 to 4.2 and from 1.0 and 2.1, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Morphology and thermal behavior of organo‐bentonite clay/poly(styrene‐co‐methacrylic acid)/poly(isobutyl methacrylate‐co‐4‐vinylpyridine) nanocomposites

Poly(styrene‐co‐methacrylic acid) containing 29 mol % of methacrylic acid (SMA‐29) and poly(isobutyl methacrylate‐co‐4‐vinylpyridine) containing 20 mol % of 4‐vinylpyridine (IBM4VP‐20) were synthesized, characterized, and used to elaborate binary and ternary nanocomposites of different ratios with a 3% by weight hexadecylammonium‐modified bentonite from Maghnia (Algeria) by casting method from tetrahydrofuran (THF) solutions. The morphology and the thermal behavior of these binary and ternary elaborated nanocomposites were investigated by X‐ray diffraction, scanning electron microscopy, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetry. Polymer nanocomposites and nanoblends of different morphologies were obtained. The effect of the organoclay and its dispersion within the blend matrix on the phase behavior of the miscible SMA29/IBM4VP20 blends is discussed. The obtained results showed that increasing the amount of SMA29 in the IBM4VP20/SMA29 blend leads to near exfoliated nanostructure with significantly improved thermal stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of cononsolvency on preferential adsorption phenomenon in poly(N‐isopropylacrylamide) ternary solutions

In this work, the effect of cononsolvency on the phase transition and preferential adsorption phenomenon behaviors of poly(N‐isopropylacrylamide)/methanol/water ternary solutions was studied. In this cononsolvent system, the , , and χ₁₂ values show a nonlinear behavior and the minimum values of and , while the maximum value of χ₁₂ at ϕ₂ is around 0.7. These facts indicated that one water molecule could directly bond with one methanol molecule to form the H₂O MeOH complex. The H₂O MeOH complex structure was found to remarkably affect the phase transition of poly(N‐isopropylacrylamide) (PNIPAM) in ternary solution. However, at the composition of mixed cononsolvent, ϕ₂ < 0.2, the PNIPAM molecules may preferentially adsorbed pure water molecules; therefore, the LCST decreases slightly with composition of mixed cosolvent and this may be because of the small amount of H₂O MeOH complexes in the mixed cononsolvent. While, at ϕ₂ > 0.7, the PNIPAM molecules may preferentially adsorbed pure methanol molecules. PNIPAM ternary solutions were transparent and no transition occurred in this region. This indicates that the PNIPAM coils exhibited a much‐extended conformation in solutions. In contrast, at 0.2 < ϕ₂ < 0.4 and 0.4 < ϕ₂ < 0.7, PNIPAM molecules preferentially adsorbed water and methanol molecules, respectively, and also adsorbed large amount of H₂O MeOH complexes. In these regions, the clathrate‐like structure around the side chain of PNIPAM molecule became more defected with adsorbing H₂O MeOH complex. Therefore, we considered that the various thermodynamic behaviors between PNIPAM and mixture solvents must be related different preferential adsorption phenomena, which were mainly related to different degrees of polymer–solvent interaction and structures of solvent used. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008