Synthesis,viscosity behavior,and interactions with a surfactant of some amphiphilic copolymers of diallyldimethylammonium chloride and diallyldodecyl‐ or diallyloctadecyl‐ammonium chloride

The compatibilization of an immiscible polymer system polystyrene/poly(4-vinylpyridine) has been induced by the introduction of carboxylic acid groups within the polystyrene chains. Poly(styrene-co-cinnamic acid), PSCA, copolymers were used to prepare blends and complexes with poly(4-vinylpyridine), P4VP, and in a second time with poly(styrene-co-4-vinylpyridine), PS4VP, copolymer in order to reduce the density of the interacting groups. The miscibility of the systems has been ascertained by DSC, which revealed that both blends and complexes exhibit a single glass transition temperature indicating their single phase nature. The T_gs of the complexes of PS4VP with PSCA15, containing 15 mol % of cinnamic acid content, were higher than those of the corresponding blends indicating that stronger interpolymer interactions were developed in the complexes. Furthermore, the application of the Kwei equation suggested that P4VP interacts more strongly with PSCA15 than does PS4VP. FTIR spectra revealed the development of hydrogen bonding within the PS4VP/PSCA system and both hydrogen bonding and ionic interaction in the P4VP/PSCA blends whereas the same interactions were expected in both systems. This observation confirmed the stronger ability of P4VP to interact with PSCA copolymer. The viscosimetric study showed both positive and negative deviations of the reduced viscosity of the blends from the additivity law confirming the presence of specific interactions within the blend solutions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Intermolecular interaction of supramolecular organic-inorganic hybrid composites of sulfonated polystyrene and oligomeric silsesquioxane possessing pyridyl groups

Supramolecular organic-inorganic hybrid composites of pyridyl groups-possessing oligomeric silsesquioxane (PyOSS) synthesized by the reaction of 2-(2-pyridylethyl)trimethoxysilane and trimethoxyphenylsilane in the molar ratio of 3/5 with 1,3-propanedisulfonic acid (PDS), 1,5-naphthalenedisulfonic acid (NDS), and poly(4-styrenesulfonic acid) (PSS) were prepared by solution casting method at SO₃H/pyridine 1/1. From the FT-IR analysis, the formation of pyridinium cation moiety was confirmed for PDS/PyOSS and NDS/PyOSS, while it could not be elucidated for PSS/PyOSS. As a result of XPS analysis of the newly prepared hybrid composites of PyOSS and sulfonated polystyrenes (SPSx’s) with different degrees of sulfonation (x = 3, 8, 23%), the formation of pyridinium ion structure was confirmed for SPS23/PyOSS, and the ionic interaction gradually changed to hydrogen-bonding interaction with decreasing degree of sulfonation of SPSx. Although the glass transition temperature of SPSx moiety was little affected by the addition of PyOSS, the glass transition itself was gradually weaken and was not detected for SPS23/PyOSS.     

Modification of Nafion membrane using poly(4‐vinyl pyridine) for direct methanol fuel cell

Perfluorinated membrane such as Nafion (from Du‐Pont) has been used as a polymer electrolyte membrane. Nafion 117 membrane, which was usually used as the electrolyte membrane for the polymer electrolyte membrane fuel cell (PEMFC), was modified by using poly(4‐vinyl pyridine) (P4VP) to reduce the methanol crossover, which cause fuel losses and lower power efficiency, by the formation of an ionic crosslink structure (sulfonic acid‐pyridine complex) on the Nafion 117 surface. Nafion film was immersed in P4VP/N‐methyl pyrrolidone (NMP) solution. P4VP weight percent of modified membrane was controlled by changing the concentration of P4VP/NMP solution and the dipping time. P4VP weight percent increased with increasing concentration of dipping solution and dipping time. The thickness of the P4VP layer increased with increasing concentration of dipping solution and dipping time when the concentration of the dipping solution was low. At high P4VP concentration, the thickness of the P4VP layer was almost constant owing to the formation of acid–base complex which interrupted the penetration of P4VP. FTIR results showed that P4VP could penetrate up to 30 µm of Nafion 117 membrane. Proton conductivity and methanol permeability of modified membrane were lower than those of Nafion 117. Both decreased with increasing concentration of dipping solution and dipping time. Methanol permeability was observed to be more dependent on the penetration depth of P4VP. Water uptake of the modified membrane, the important factor in a fuel cell, was lower than that of Nafion 117. Water uptake also decreased with increasing of P4VP weight. On the basis of this study, the thinner the P4VP layer on the Nafion 117 membrane, the higher was the proton conductivity. Methanol permeability decreased exponentially as a function of P4VP weight percent. Copyright © 2006 Society of Chemical Industry     

Polymer electrolyte membranes composed of an electrospun poly(vinylidene fluoride) fibrous mat in a poly(4‐vinylpyridine) matrix

Newly proposed polymer electrolyte membranes (PEMs) composed of an electrospun poly(vinylidene fluoride) (PVDF) fibrous mat embedded in a poly(4‐vinylpyridine) (P4VP) matrix were successfully fabricated in order to improve the mechanical and dimensional stabilities and ionic conductivity of membranes in lithium rechargeable batteries. Fourier transform infrared spectroscopic analysis showed that as a result of the use of a high voltage during electrospinning the crystalline structure of PVDF changed partially from α‐phase to β‐phase. Energy‐dispersive X‐ray spectroscopy confirmed the existence of crosslinked P4VP in the PVDF fibrous mat. The electrolyte uptakes of PVDF and PVDF/P4VP composite mats were higher than that of PVDF cast film. The tensile properties of PVDF/P4VP composite mat were considerably improved compared to those of the pristine PVDF fibrous mat under both dry and wet (soaked with electrolyte) conditions. In addition, the mechanical and dimensional stabilities of the PVDF/P4VP composite PEM were further enhanced due to crosslinking between the P4VP chains. Furthermore, the PVDF/P4VP composite PEM exhibited an ionic conductivity that was an order of magnitude higher than that of traditional PVDF film. © 2012 Society of Chemical Industry     

Temperature-responsive multilayered micelles formed from the complexation of PNIPAM-b-P4VP block-copolymer and PS-b-PAA core–shell micelles

Multilayered micelles with a polystyrene (PS) core, a swollen poly(acrylic acid) (PAA)/poly(4-vinyl pyridine) (P4VP) complex shell and a poly(4-vinyl pyridine)-block-poly(isopropyl acryl amide) (P4VP-b-PNIPAM) block-copolymer corona was synthesized by complexation between PNIPAM₅₃-b-P4VP₁₀₉ block-copolymers and the PS₁₂₀-b-PAA₄₇ diblock-copolymer core–shell micelles in ethanol due to the hydrogen bonding between the AA units and 4VP units. The surface of the micelle has been modified and a temperature sensitive block PNIPAM was introduced into the corona of the micelles. After being dialyzed against acidic water, PNIPAM corona would collapse onto the PAA/P4VP shell and the excessive P4VP shell would extend into the acidic solution to form the corona reversed micelles when the micelle aqueous solution was heated to 45 °C. The whole process was performed using dynamic light scattering (DLS), static light scattering (SLS), atom force microscope (AFM) and nuclear magnetic resonance (NMR).     

Studies on polybenzimidazole/poly (4‐vinylpyridine) blends and their proton conductivity after doping with acid

In the present work, polybenzimidazole (PBI) and poly(4‐vinylpyridine) (P4VP) were chosen because they form miscible blends and both materials are suitable for acid doping as a matrix, which can eventually be used as proton conductor. The miscibility and inter‐polymer interactions were studied by infrared (IR) spectroscopy and differential scanning calorimetry (DSC). DSC and IR results suggest that PBI blended with P4VP exhibits good miscibility due to the strong hydrogen bonds formed between PBI's NH groups and P4VP's N: groups. The glass transition temperatures of the blends can be fitted to the Fox equation very well. The blends were also studied by thermogravimetry. Their thermal stability is slightly higher than that of P4VP, but is still lower than that of PBI. Temperature‐dependent conductivity of acid‐doped PBI/P4VP blends was studied. As the temperature increases, the conductivity of PBI/P4VP doped with H₃PO₄ increases. The temperature‐dependent conductivity of the blends follows a simple Arrhenius relationship when the P4VP content is low (less than 15%), while a non‐Arrhenius behaviour of the conductivity of the blends becomes more and more significant with increasing P4VP content. This means that the proton transport in the blends is controlled by both a hopping mechanism and the segmental motion of the polymer. The contribution of these two mechanisms depends on the P4VP content. Copyright © 2003 Society of Chemical Industry     

Phase behavior of binary and ternary blends of poly(styrene‐co‐methacrylic acid), poly(styrene‐co‐4‐vinylpyridine), and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Poly(styrene‐co‐methacrylic acid) (PSMA) and poly(styrene‐co‐4‐vinylpyridine) (PS4VP) of different compositions were prepared and characterized. The phase behavior of these copolymers as binary PSMA/PS4VP mixtures or with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) as PPO/PSMA or PPO/PS4VP and PPO/PSMA/PS4VP ternary blends was investigated by differential scanning calorimetry (DSC). This study showed that PPO was miscible with PS4VP containing up to 15 mol % 4‐vinylpyridine (4VP) but immiscible with PS4VP‐30 (where the number following the hyphen refers to the percentage 4VP in the polymer) and PSMA‐20 (where the number following the hyphen refers to the percentage methacrylic acid in the polymer) over the entire composition range. To examine the morphology of the immiscible blends, scanning electron microscopy was used. Because of the hydrogen‐bonding specific interactions that occurred between the carboxylic groups of PSMA and the pyridine groups of PS4VP, chloroform solutions of PSMA‐20 and PS4VP‐15 formed interpolymer complexes. The obtained glass‐transition temperatures (T_g's) of the PSMA‐20/PS4VP‐15 complexes were found to be higher than those calculated from the additivity rule. Although, depending on the content of 4VP, the shape of the T_g of the PPO/PS4VP blends changed from concave to S‐shaped in the case of the miscible blends, two T_g were observed with each PPO/PS4VP‐30 and PPO/PS4VP‐40 blend. The thermal stability of the PSMA‐20/PS4VP‐15 interpolymer complexes was studied by thermogravimetry. On the basis of the obtained results, the phase behavior of the ternary PPO/PSMA‐20/PS4VP‐15 blends was investigated by DSC. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photoinitiated surface grafting of synthetic fibers,III. Photoinitiated surface grafting of poly(ethylene terephthalate) fibers

Photoinitiated surface grafting of acrylic acid (AA), acrylamide (AM) and 4-vinyl pyridine (VP) onto poly(ethylene terephthalate) (PET) fibers (a commercial textile yarn) has been studied using benzophenone (BP) as photoinitiator. A continuous process as previously described has been applied, which involves presoaking of the PET yarn in a solution of initiator and monomer in acetone and UV irradiation in nitrogen atmosphere. The resulting grafted polymer on the fiber surface has been analyzed by ESCA, titration of carboxy groups (grafted AA), and dye absorption. The relative ESCA intensities (RI) of O1s/C1s and N1s/C1s are used as measure for grafted AA, AM and VP, respectively, after recording the RI-values for ungrafted fibers. For grafting with AA, the RI-values increased from 32.8% (background) to 48.6% after 20 s irradiation time. The amount of carboxy groups measured by titration increased from 0.045 to 0.106 mmol/m². Assuming an even coverage of grafted AA polymer, this means a grafted layer of 4.8 nm thickness. After grafting, the adsorption of the dye Crystal Violet (CV) from aqueous solution increased by about 3 times. With AM as monomer, the RI-values increased from 2.6 (background) to 14.8% and the adsorption of a direct dye Sirius Lichtbordo B-LL increased by about 6 times. With VP as grafted monomer, the RI-values increased from about 2.6 (background) to 5.1% and the adsorption of the direct dye increased by about 4 times.     

Swelling and mechanical properties of superporous hydrogels of poly(acrylamide-co-acrylic acid)/polyethylenimine interpenetrating polymer networks

Swelling and mechanical properties were investigated for superporous hydrogels (SPHs) of poly(acrylamide-co-acrylic acid)/polyethylenimine (P(AM-co-AA)/PEI) interpenetrating polymer networks (IPNs). Gelation kinetics of SPHs changed significantly according to the acidic condition of reactant. The compressive strength of neutralized SPHs decreased monotonically with AA concentration, while the maximum swelling was observed around the AA weight fraction of 0.4 for all PEI concentrations. The SPH samples composed of high concentrations of AA and PEI were easily cracked in water due to the swelling stress developed during water uptake. The swelling kinetics decreased with increasing PEI and PAA concentrations because of the high molecular entanglement and network density associated with ionic interaction between PAA and PEI molecules. For non-neutralized SPHs, the equilibrium water uptake decreased but the compressive strength increased with PEI and PAA concentrations by simple plasticization effect.     

Thermal properties of poly(maleic anhydride‐alt‐acrylic acid) in the presence of certain metal chlorides

Polychelates were synthesized by the addition of aqueous solutions of copper(II), cadmium(II), and nickel(II) chlorides to aqueous solutions of poly(maleic anhydride‐alt‐acrylic acid) [poly(MA‐alt‐AA)] in different pH media. The thermal properties of poly(MA‐alt‐AA) and its metal complexes were investigated with thermogravimetry and differential scanning calorimetry (DSC) measurements. The polychelates showed higher thermal stability than poly(MA‐alt‐AA). The thermogravimetry of the polymer–metal complexes revealed variations of the thermal stability by complexation with metal ions. The relative thermal stabilities of the systems under investigation were as follows: poly(MA‐alt‐AA)–Cd(II) > poly(MA‐alt‐AA)–Cu(II) > poly(MA‐alt‐AA)–Ni(II) > poly(MA‐alt‐AA). The effects of pH on the complexation and gravimetric analysis of the polychelates were also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3926–3930, 2006     

Polyelectrolyte complex–surfactant interactions: effect of neutralization degree on viscometric behaviour in aqueous solution

The interaction between polyelectrolytes and ionic surfactants has attracted significant interest in recent years in different areas of research. In this study, the effect of the neutralization degree α on the viscosimetric behaviour of (hydrolyzed polyacrylamide, AD37–poly(4-vinylpyridine), P4VP) complex in aqueous solution and in the presence of sodium dodecyl sulphate (SDS) at T = 25 °C was studied. Physicochemical results show that neutralization degree has an important effect on reduced viscosities values of (AD37–P4VP–SDS) system that reveals the electrostatic and hydrophobic interactions. Indeed, these values increase with α, and this influence is even greater for low P4VP—high AD37 concentrations systems.     

The synthesis of a physically crosslinked NVP based hydrogel

Complexes of polyvinyl pyrrolidinone–polyacrylic acid (PVP–PAA) were prepared by photopolymerisation from a mixture of the monomers NVP and AA. The complexes were characterised by means of differential scanning calorimetry, Fourier transform infrared spectroscopy (Ftir), potentiometric titration, swelling studies and gel permeation chromatography. The Ftir spectra of PVP–PAA copolymer complexes indicates hydrogen bonding between the carbonyl group in the PVP and the carboxylic acid group in the PAA moiety. As the percentage of AA increases in the copolymer there is evidence of increased intermolecular hydrogen bonding between the carboxylic acid groups of the AA segments. Swelling of the PVP–PAA complex in a higher pH medium is significantly different from results in low pH solutions. The critical pH range was found to be between 4.07 and 4.49. Above a pH of 4.49, there is a progressive break up of the polymer chain due to a reduction in the amount of intermolecular hydrogen bonding. There is also a significant increase in the solubility of the copolymer complex at higher pHs. The low solubility of the copolymer at low pH may make the complex suitable for gastric drug delivery systems.     

Removal of 2,4-D, MCPA and Metalaxyl from water using Lewatit VP OC 1163 as sorbent

The objective of this study was to investigate the use of organic polymer resin Lewatit VP OC 1163 to remove the pesticides MCPA, 2,4-D, and Metalaxyl. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data obtained from three measurements (SAC₂₅₄, COD, and KMnO₄ Demand) of pesticide adsorption. The adsorption capacities of the pesticides studied followed the order: Metalaxyl > 2,4-D > MCPA. S-type isotherms were obtained, which indicates a moderate interaction between adsorbate molecules and adsorbent. A series of column tests were performed to determine the breakthrough curves using organic polymer resin Lewatit VP OC 1163. The good adsorbability of Metalaxyl on Lewatit VP OC 1163 could be confirmed by the column experiments. The ionic characters of MCPA and 2,4-D are responsible for the short breakthrough times in the Lewatit VP OC 1163 column. It has been concluded that lower the pK_a value, the greater is the adsorption for the uncharged (neutral) organic polymer resin. The key parameters that can be derived from this overview are thus, in order of relative influence: pK_a, solubility, and hydrophobicity.     

吡啶基聚合离子液体的制备及其对油中噻吩硫的吸附性能

以4-乙烯基吡啶（VP）和1,4-对二氯苄（PXDC）为原料,通过自由基聚合和季铵化交联反应,制得了一种高度交联的离子液体聚合物--PVP-PXDC。采用凝胶渗透色谱法、元素分析法、红外光谱分析法、扫描电镜、热重分析及比表面积分析等分析方法对离子聚合物的组成、结构、形貌、热稳定性及比表面积、孔结构参数等进行了表征,并考察了吸附剂的脱硫性能。结果表明,先通过聚合得到重均分子量16万以上的PVP线性聚合物,再在DMF溶剂中按VP与PXDC摩尔比2：1加入交联剂,可得到平均孔径为17.8 nm聚合离子液体介孔材料,其热分解温度在250℃以上,比表面积为56.9 m²·g^-1。在油/剂质量比50：1和30℃条件下,其对1000 mg·kg^-1模型油中二苯并噻吩（DBT）、苯并噻吩（BT）和噻吩（T）的吸附量分别为5.65、5.48和4.53 mg S·g^-1,远高于常规吡啶基离子液体,吸附等温线符合Freundlich方程。     

External Stimuli‐Responsive Characteristics of Ionic Poly[(N,N‐diethylaminoethyl methacrylate)‐co‐(N‐vinyl‐2‐pyrrolidone)] Hydrogels

Summary: Polyelectrolyte hydrogels containing diprotic acid moieties sensitive to ionic strength changes of the swelling medium were synthesized from N,N‐diethylaminoethyl methacrylate (DEAEMA), N‐vinyl‐2‐pyrrolidone (VP) and itaconic acid (IA) by using ammonium persulfate (APS) as a free radical initiator in the presence of the cross‐linker, methylenebisacrylamide (MBAAm). The swelling behavior of the ionic poly[(N,N‐diethylaminoethyl methacrylate)‐co‐(N‐vinyl‐2‐pyrrolidone)] [P(DEAEMA/VP)] hydrogels were investigated in pure water; in NaCI solutions with pH 4 and 9; and in water‐acetone mixtures depending on the IA content in the hydrogel. The average molecular mass between cross‐links ( ) and polymer‐solvent interaction parameter (χ) of the hydrogels were determined from equilibrium swelling values. The pulsatile swelling behavior was also observed in response to solvent changes between the solution in water and in acetone. The equilibrium swelling ratio of these hydrogels was basically unaffected with change in temperature. The swelling variations were explained according to the swelling theory based on the hydrogel chemical structure.

Pulsatile swelling behavior of ionic P(DEAEMA/VP) hydrogels in response to solvent changes between water and acetone at 25 °C.     

Investigations on pyridinium salts as a solid‐state ionics

The object of this work is to prepare polymer poly(2vinylpyridine), P‐2VP, and its salts like P‐2VP‐HI, P‐2VP‐HIO₃, and P‐2VP‐HIO₄. The formation of P‐2VP salts was confirmed by IR and ¹H NMR techniques. Conductivities of these were determined in solid state at various temperatures from 30 to 90°C. Observations indicated that the addition of I^? or IO₃^? or IO₄^? ions affect the ionic conductivity of P‐2VP. Molecular mass determination and analytical results indicated that 94, 92.5, and 95% of the pyridine molecules in the P‐2VP chain were hydroiodated, iodated, and periodated, respectively, with the corresponding acids of iodine. The total ionic transport number and activation energy of the polymers were also determined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Homogeneous complex solution formed through interactions of poly(acrylamide‐co‐acrylic acid)/poly(acrylamide‐co‐dimethyldiallylammonium chloride) complex with M n+ hydration metal ions in aqueous media

A homogeneous complex solution, formed through inter‐polyelectrolyte complexation of poly(acrylamide‐co‐acrylic acid) (P(AM‐AA)) with poly(acrylamide‐co‐dimethyldiallylammonium chloride) (P(AM‐DMDAAC)) and interaction of the P(AM‐AA)/P(AM‐DMDAAC) complex with M ⁿ⁺ hydrated metal ion, was prepared and the structure and properties of the P(AM‐AA)/P(AM‐DMDAAC)/M ⁿ⁺ homogeneous complex solution were studied by UV spectrometry, dynamic light scattering and viscometry. The experimental results show that the homogeneous complex solution can be obtained by controlling the composition of the P(AM‐AA)/P(AM‐DMDAAC) complex and the M ⁿ⁺ metal ion content. Compared to the constituents, ie the P(AM‐AA) solution, the P(AM‐DMDAAC) solution and the P(AM‐AA)/P(AM‐DMDAAC) complex solution, the P(AM‐AA)/P(AM‐DMDAAC)/M ⁿ⁺ complex solution has a new peak at 270 nm in its UV spectrum, a larger hydrodynamic radius, and hence a higher solution viscosity, all of which indicate that there exist specific interactions between polymers and M ⁿ⁺ metal ions. These interactions lead to the formation of a network structure and hence an obvious increase not only in solution viscosity but also in resistance of the polymer solution to simple salts, to temperature changes and to shearing. © 2001 Society of Chemical Industry     

Multilayer composite surfaces prepared by an electrostatic self‐assembly technique with quaternary ammonium salt and poly(acrylic acid) on poly(acrylonitrile‐co‐acrylic acid) membranes

An electrostatic self‐assembly technique was applied to prepare ion complex polymer layers on polyacrylonitrile with acrylic acid segments {poly(acrylonitrile‐co‐acrylic acid) [P(AN‐co‐AA)]}. For the ionic complex layers, quaternary ammonium salts, such as cetyl trimethyl ammonium chloride (CTAC) and tetramethyl ammonium chloride (TMAC), were used as cationic species, and also, poly(acrylic acid) (PAA) was used as an anionic species. These cationic and anionic species were self‐assembled alternately on the surface of the P(AN‐co‐AA) membrane. Fourier transform infrared spectroscopy, AFM, and water contact angle measurements of the membrane surface were used to confirm the formation of the multilayer composites on the P(AN‐co‐AA). The permeabilities of water and macromolecules of different molecular weights were evaluated by a membrane filtration technique. The values of permeability strongly depended on the formation layer by layer of these ion composites on the base P(AN‐co‐AA). Through the measurement of the values of the contact angle of water, it was clear that surface nature of the base membrane treated by CTAC or TMAC and PAA dramatically changed. We concluded that such an electrostatic self‐assembly technique is useful for the preparation of multicomposite layers to modify the surface of base P(AN‐co‐AA) membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characterization of poly(methyl methacrylate) from radiation-induced polymerization in the presence of a kaolin clay substrate

Two types of polymer are formed in the radiation-initiated polymerization of methyl methacrylate (MMA)–kaolin clay complexes. Homopolymer can be extracted from the complex by the use of organic solvents. Inserted polymer must be removed by dissolution of the polymer–clay complex with hydrofluoric acid. The polymers formed show no differences in structure (as determined by infrared analysis), had high molecular weights (1–5 × 10⁶), and had similar molecular weight distributions (as determined by GPC). The molecular weights of the homopolymer increased as temperature increased (25°–75°C), and dose rate decreased (24.9–7.35 rads/sec). The isotacticity of the polymers when compared to irradiated bulk polymer decreased as follows: inserted > homo > bulk. The compressive properties of the irradiated composite compared well with those of commercial bulk polymers. Degradation temperatures were 20° to 30°C higher for the composite than for the commercial chemically initiated bulk polymer.     

Drug complexation and physicochemical properties of vinylpyrrolidone‐N,N′‐dimethylacrylamide copolymers

Solid dispersions of the nonsteriodal antiinflammatory drug (NSAID) 2′,4′‐difluoro‐4‐hydroxy‐(1,1′‐biphenyl)‐3‐carboxylic acid (DIF) with the water‐soluble random copolymer poly(N‐vinyl‐2‐pyrrolidone‐co‐N,N′‐dimethylacrylamide) (VP‐co‐DMAm) were prepared by the solvent method (coevaporates) and melting DIF/VP‐co‐DMAm (cofused) physical mixtures. Differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and X‐ray diffraction (XRD) were used to elucidate the possible interaction between the NSAID drug and VP‐co‐DMAm in cofused and coevaporated polymer–drug solid dispersions. The XRD and FTIR studies suggest the presence of physical interactions with formation of a charge transfer complex between DIF and the VP‐co‐DMAm copolymers as a consequence of the coevaporation or cofusion processes. In solution, dynamic and equilibrium solubility studies were determined to elucidate the mechanism of interaction between DIF and VP‐co‐DMAm copolymers. Thermodynamics data about the DIF: VP‐co‐DMAm dissolution process indicate that the coevaporated systems are more stable that the cofused systems. The dissolution of the cofused and coevaporated systems was diffusion controlled and the dissolution kinetics followed the Noyes–Whitney and the Levich equations. Molecular simulations using semiempirical quantum chemical calculations reinforce the experimental results, suggesting that the improvement in the DIF solubility could be attributed to the charge transfer complex formation between the drug and VP‐co‐DMAm copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1337–1347, 2004