Synthesis and characterization of semi‐interpenetrating networks based on poly(dimethylsiloxane) and poly(vinyl alcohol)

Semi‐interpenetrating networks (Semi‐IPNs) with different compositions were prepared from poly(dimethylsiloxane) (PDMS), tetraethylorthosilicate (TEOS), and poly(vinyl alcohol) (PVA) by the sol‐gel process in this study. The characterization of the PDMS/PVA semi‐IPN was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and swelling measurements. The presence of PVA domains dispersed in the PDMS network disrupted the network and allowed PDMS to crystallize, as observed by the crystallization and melting peaks in the DSC analyses. Because of the presence of hydrophilic (? OH) and hydrophobic (Si? (CH₃)₂) domains, there was an appropriate hydrophylic/hydrophobic balance in the semi‐IPNs prepared, which led to a maximum equilibrium water content of ～ 14 wt % without a loss in the ability to swell less polar solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of semi‐interpenetrating polymer network polystyrene cation‐exchange membranes

Polystyrene cation exchange membranes were prepared by a PVC‐based semi‐interpenetrating polymer network (IPN) method. The reaction behaviors during polymerization and sulfonation in the preparation method were investigated. The prepared membranes were characterized in terms of the physical and electrochemical properties. The membranes exhibited reasonable mechanical properties (tensile strength, 13 MPa, and elongation at break, 52%) for an ion‐exchange membrane with the ratio of polystyrene–divinylbenzene (DVB)/poly(vinyl chloride) (PVC) (R_St‐DVB/PVC) of below 0.9. Fourier transform infrared/attenuated total reflectance, differential scanning calorimetry, and scanning electron microscopy studies revealed the formation of a homogeneous membrane. The resulting membrane showed membrane electrical resistance of 2.0 Ω cm² and ion‐exchange capacity of 3.0 meq/g dry membrane. The current–voltage (I–V) curves of the membrane show that the semi‐IPN polystyrene membranes can be properly used at a high current density, and that the distribution of cation‐exchange sites in the membrane was more homogenous than that in commercial membranes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1488–1496, 2003     

Synthesis and swelling properties of pH‐sensitive hydrogels based on chitosan and poly(methacrylic acid) semi‐interpenetrating polymer network

A novel semi‐interpenetrating polymer network (semi‐IPN) hydrogel composed of chitosan and poly(methacrylic acid) was synthesized using formaldehyde as a crosslinker. The amount of crosslinker was searched and optimized. The structure of the hydogel was investigated by Fourier transform infrared (FTIR) spectroscopy. The spectrum shows that a structure of polyelectrolyte complex exists in the hydrogel. The effects of pH, ionic strength, and inorganic salt on the swelling behaviors of the hydrogel were studied. The results indicate the hydrogel has excellent pH sensitivity in the range of pH 1.40 to 4.50, pH reversible response between pH 1.80 and 6.80, and ionic strength reversible response between ionic strength 0.2 and 2.0M. The results also show that the hydrogel has a bit higher swelling capacity in a mix solution of calcium chloride (CaCl₂) and hydrochloric acid (HCl) solution than in a mix solution of sodium chloride (NaCl) and HCl. These results were further confirmed through morphological change measured by scanning electron microscope (SEM). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1720–1726, 2005     

Sulfonated graphene oxide‐doped proton conductive membranes based on polymer blends of highly sulfonated poly(ether ether ketone) and sulfonated polybenzimidazole

Simultaneously improving the proton conductivity and mechanical properties of a polymer electrolyte membrane is a considerable challenge in commercializing proton exchange membrane fuel cells. In response, we prepared a new series of miscible polymer blends and thus the corresponding crosslinked membranes based on highly sulfonated poly(ether ether ketone) and sulfonated polybenzimidazole. The blended membranes showed more compact structures, due to the acid‐base interactions between the two constituents, and improved mechanical and morphological properties. Further efforts by doping sulfonated graphene oxide (s‐GO) forming composite membranes led to not only significantly elevated proton conductivity and electrochemical performance, but also better mechanical properties. Notably, the composite membrane with the filler content of 15 wt % exhibited a proton conductivity of 0.217 S cm^?1 at 80 °C, and its maximum power density tested by the H₂/air single PEMFC cell at room temperature reached 171 mW cm^?2, almost two and half folds compared with that of the native membrane. As a result, these polymeric membranes provided new options as proton exchange membranes for fuel‐cell applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46547.     

Preparation and characterization of semi‐interpenetrating network polystyrene/PVDF cation exchange alloy membranes

The polystyrene‐DVB/PVDF alloy particles were prepared by pulverizing the polymerization product of styrene/DVB/PVDF in DMF, and then sulfonated with concentrated sulfuric acid to gain the cation exchange alloy powder, which was directly thermoformed by a hot‐press machine to form the titled cation exchange alloy membranes with the structure of semi‐interpenetrating polymer network. The effects of the polystyrene‐DVB to PVDF mass ratio and the DVB content in the monomers on the physical and electrochemical properties of the prepared alloy membranes were investigated. While the Fourier transform infrared spectroscopy (FTIR) confirms the components of membranes, the scanning electron microscopy (SEM) reveals that the alloy membranes possess a uniform distribution of functional groups, and a more dense structure with the increases of DVB content and PVDF content. The optimal prepared membranes have the area electrical resistance values within 3.0–6.6 Ω·cm², obviously superior to the commercial heterogeneous cation exchange membrane, as well as the moderate water contents of 35–40% and the desirable permselectivity with a transport number more than 0.95. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1220‐1227, 2013     

A novel pH‐sensitive gelatin–DNA semi‐interpenetrating polymer network hydrogel

Gelatin and DNA were mixed together in various ratios followed by the addition of glutaraldehyde as a cross‐linker. FT‐IR spectroscopy confirmed the formation of a semi‐interpenetrating polymer network (semi‐IPN) between the gelatin and DNA. The gelatin–DNA semi‐IPN hydrogel underwent, reversibly, remarkable changes in swelling degree in response to the variation of pH. In the low‐pH range, the hydrogel showed a lower swelling degree; with an increment in pH, the hydrogel was highly swollen, which is considered to originate from the complexation and de‐complexation between gelatin and DNA, as was verified by turbidity measurements. Higher contents of DNA result in an increase in the swelling degree, which is presumably due to the easy outward expansion of free DNA moieties. The permeability coefficient, P, for a model molecule, cimetidine, through the semi‐IPN hydrogel membranes was determined in pH 1.0 and pH 12.0 buffer solutions. The results show that the permeation of cimetidine is responsive to pH change, and an evident variation in the P values occurs in response to the pH of the media. Copyright © 2004 Society of Chemical Industry     

Swelling behavior of semi‐interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(acrylamide‐co‐sodium methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and poly(acrylamide‐co‐sodium methacrylate) poly(AAm‐co‐SMA) were prepared by the semi IPN method. These IPN hydrogels were prepared by polymerizing aqueous solution of acrylamide and sodium methacrylate, using ammonium persulphate/N,N,N¹,N¹‐tetramethylethylenediamine (APS/TMEDA) initiating system and N,N¹‐methylene‐bisacrylamide (MBA) as a crosslinker in the presence of a host polymer, poly(vinyl alcohol). The influence of reaction conditions, such as the concentration of PVA, sodium methacrylate, crosslinker, initiator, and reaction temperature, on the swelling behavior of these IPNs was investigated in detail. The results showed that the IPN hydrogels exhibited different swelling behavior as the reaction conditions varied. To verify the structural difference in the IPN hydrogels, scanning electron microscopy (SEM) was used to identify the morphological changes in the IPN as the concentration of crosslinker varied. In addition to MBA, two other crosslinkers were also employed in the preparation of IPNs to illustrate the difference in their swelling phenomena. The swelling kinetics, equilibrium water content, and water transport mechanism of all the IPN hydrogels were investigated. IPN hydrogels being ionic in nature, the swelling behavior was significantly affected by environmental conditions, such as temperature, ionic strength, and pH of the swelling medium. Further, their swelling behavior was also examined in different physiological bio‐fluids. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 302–314, 2005     

Radiation synthesis and environmental responsiveness of semi‐interpenetrating polymer networks composed of poly(dimethyl–aminoethyl methacrylate) and poly(ethylene oxide)

Semi‐interpenetrating polymer networks (semi‐IPNs) composed of poly(dimethyl–aminoethyl methacrylate) (PDMAEMA) and poly(ethylene oxide) (PEO) were synthesized by γ‐radiation; three semi‐IPNs with 80 : 20, 90 : 10, and 95 : 5 weight ratios of DMAEMA/PEO were obtained by use of this technique. The gel–dose curves showed that the hydrogels were characterized by a structure typical of semi‐IPNs and the results of elemental analysis supported this point. The temperature‐induced phase transition of semi‐IPNs with the composition of 95 : 5 was still retained, with the lower critical solution temperature of PDMAEMA shifting from 40 to 27°C. The temperature sensitivity of the other two semi‐IPNs gradually disappeared. The pH sensitivity of three semi‐IPNs was still retained but the pH shifted slightly to lower values with increasing PEO content in the semi‐IPNs. The effect of PEO content in semi‐IPNs on their environmental responsiveness was discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2995–3001, 2004     

PDMS/PVDF microporous membrane with semi‐interpenetrating polymer networks for vacuum membrane distillation

In this article, using the non‐solvent induced phase separation process, a new microporous membrane with the semi‐interpenetrating polymer network (semi‐IPN) structure was produced. For this membrane, polydimethylsiloxane (PDMS) polymer is crosslinking and poly(vinylidene fluoride) (PVDF) polymer is linear, by changing the mass ratio of PDMS/PVDF, the structure and the performance of the prepared membranes were studied. The membranes were also investigated by attenuated total reflection‐Fourier transform infrared (ATR‐FTIR), scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, thermogravimetric analysis, and water contact angle, etc. ATR‐FTIR spectroscopy confirmed the formation of semi‐IPN; compared with the PDMS/PVDF polymer without semi‐IPNs structure, the viscosity of the semi‐IPNs structured casting solution increased, membrane mechanical property increased but its hydrophobicity decreased. Using the resulting membranes for the vacuum membrane distillation desalt of the NaCl solution (30 g/L), 99.9% salt rejection and reasonable flux were obtained. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45792.     

Sulfonated polyimide and poly (ethylene glycol) diacrylate based semi‐interpenetrating polymer network membranes for fuel cells

Semi‐interpenetrating polymer network (semi‐IPN) membranes based on novel sulfonated polyimide (SPI) and poly (ethylene glycol) diacrylate (PEGDA) have been prepared for the fuel cell applications. SPI was synthesized from 1,4,5,8‐naphthalenetetracarboxylic dianhydride, 4,4′‐diaminobiphenyl 2,2′‐disulfonic acid, and 2‐bis [4‐(4‐aminophenoxy) phenyl] hexafluoropropane. PEGDA was polymerized in the presence of SPI to synthesize semi‐IPN membranes of different ionic contents. These membranes were characterized by determining, ion exchange capacity, water uptake, water stability, proton conductivity, and thermal stability. The proton conductivity of the membranes increased with increasing PEGDA content in the order of 10^?1 S cm^?1 at 90°C. These interpenetrating network membranes showed higher water stability than the pure acid polyimide membrane. This study shows that semi‐IPN SPI membranes based on PEGDA which gives hydrophilic group and structural stability can be available candidates comparable to Nafion® 117 over 70°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermal properties of poly(vinyl alcohol)/poly(diallyldi‐methylammonium chloride) interpenetrating polymer networks

Interpenetrating polymer networks (IPNs) constructed with poly(vinyl alcohol) (PVA) and poly(diallyldimethyl ammonium chloride) (PDADMAC) using a sequential IPN method were prepared. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), dielectric analysis (DEA), and thermogravimtric analysis (TGA). Decreases in the melting temperature of PVA segments in IPNs were observed with increasing PDADMAC content using DSC. DEA was employed to ascertain glass transition temperature of IPNs. The thermal decomposition of IPNs was investigated using TGA, and thermal decomposition of IPNs could be decelerated by changing PVA content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1346–1349, 2003     

Synthesis and characterization of konjac glucomannan/poly(vinyl alcohol) interpenetrating polymer networks

Novel interpenetrating polymer networks (IPNs) coded as KP were synthesized successfully from poly(vinyl alcohol) (PVA) and konjac glucomannan (KGM) in the presence of glutaraldehyde as a crosslink agent. The transparent IPN films that were 40 μm thick were prepared by means of conventional solvent‐casting technique and dried at room temperature for 2 days. The structure and miscibility of the KP films were studied by Fourier transformed infrared spectra, scanning electron microscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, and ultraviolet visible spectroscopy (UV–Vis). The results indicated that strong intermolecular interaction caused by crosslink bonding between PVA and KGM occurred in the IPN films, resulting in wonderful miscibility when the reaction time is 4 h. The tensile strength, elongation at break, and moisture uptake was much higher than that of the pure PVA film, KGM film, and uncrosslinked blend films. In other words, the structure of IPN endowed the films with excellent performance, so the new material has promising applications to food package film and agricultural film because of its biodegradability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2775–2780, 2004     

Novel proton conducting membranes based on copolymers containing hydroxylated poly(ether ether ketone) and sulfonated polystyrenes

A novel series of hydrocarbon‐based copolymers containing flexible alkylsulfonated groups and hydroxylated poly(ether ether ketone) backbones was designed and prepared as proton conducting membranes. Among the membranes, the membrane SPO₃–(PMS–PSBOS)₂ with the ion exchange capacity 1.70 showed good proton conductivity at 0.137 S/cm at 80 °C, which was two times as much as that of the control membrane SPO. Further, incorporating the sulfonated graphene oxide (s‐GO) into SPO₃–(PMS‐PSBOS)₂ leads to the composite membrane SPO₃–(PMS–PSBOS)₂–SGO, which exhibited higher proton conductivity compared to Nation 117 and the native membrane SPO₃–(PMS–PSBOS)₂. In addition, the composite membrane SPO₃–(PMS–PSBOS)₂–SGO showed well‐defined phase separated structures and high selectivity (1.40 × 10⁵ Ss/cm³), which were about three times as that of Nafion 117 (0.52 × 10⁵ Ss/cm³). These results suggested that these membranes are promising materials for direct methanol fuel cell (DMFC) applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45205.     

Spin probe study of semi‐interpenetrating polymer networks based on polyurethane and polymethacrylate functional prepolymers

The motional transition and heterogeneity of semi‐interpenetrating networks (SIPNs) based on polyurethane (PU) with carboxylic groups and methacrylic copolymer (PM) with tertiary amine groups were studied by the electron spin resonance (ESR) spin probe method. The concentration of functional groups in both prepolymers varied from 0 to 0.45 mmol g^?1. Spin‐probed SIPNs show that the temperature‐dependent spectra are sensitive to polymer interactions imposed by functional groups. These interactions determine the free volume distribution in the matrix and temperature at which motional transition takes place. The fraction of free volume increases with functional group concentration and reaches its maximum at 0.25 mmol g^?1. Further increases in the functional group concentration reduce the free volume. The results of the networks with strong interactions are discussed in terms of the interference of the plasticizing effect of the PU component and the formation of possible cluster cross‐links, which restricts segmental motions. Copyright © 2003 Society of Chemical Industry     

Proton exchange membranes based on poly(vinylidene fluoride) and sulfonated poly(ether ether ketone)

Blend membranes were obtained by solution casting from poly(vinylidene fluoride) (PVDF) and sulfonated poly(ether ether ketone) (SPEEK) in N,N-dimethylacetamide (DMAc). DSC and XRD were used to characterize the structure of the blend membranes. The effect of PVDF content on the membrane properties was investigated. The methanol permeability, water uptake and the swelling ratio of blend membranes decreased with the increase of PVDF content. Though the proton conductivity decreased upon the addition of PVDF, they were still comparable to that of Nafion^® 117 membrane. Higher selectivities were also found for most blend membranes in comparison with Nafion^® 117 membrane. The effect of methanol concentration on solution uptake, swelling ratio and methanol permeability of the blend membranes was also studied.     

Electroactive characteristics of interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(N‐isopropylacrylamide)

An interpenetrating polymer network (IPN) composed of poly(vinyl alcohol) (PVA) and poly(N‐isopropylacrylamide) (PNIPAAm) was prepared by the sequential IPN method. The equilibrium swelling ratio and bending behavior under electric fields of the IPN hydrogel were measured in an aqueous NaCl solution. The IPN exhibited a high equilibrium swelling ratio, in the range 280–380%. When the IPN in aqueous NaCl solution was subjected to an electric field, the IPN showed significant and quick bending toward the cathode. The IPN hydrogel also showed stepwise bending behavior, depending on the electric stimulus. In addition, the ionic conductivity of the IPN hydrogel was measured using dielectric analysis, and its conductive behavior followed the Arrhenius equation. The conductivity of the IPN hydrogel and the activation energy for the form of the IPN were 1.68 × 10^?5 S/cm at 36°C and 61.0 kJ/mol, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 890–894, 2003     

Polymer electrolyte membranes prepared by EB‐crosslinking of sulfonated poly(ether ether ketone) with 1,4‐butanediol

Crosslinked sulfonated poly(ether ether ketone) (SPEEK) membranes were prepared through the electron beam (EB)‐irradiation crosslinking of SPEEK/1,4‐butanediol under various irradiation conditions and used as a proton exchange membrane (PEM) for fuel cell applications. The crosslinked membranes were characterized by gel fraction, a universal testing machine (UTM), dynamic mechanical analysis (DMA), and small‐angle X‐ray scattering (SAXS). The gel fraction of the crosslinked membranes was used to estimate the degree of crosslinking, and the gel fraction was found to be increased with an increase of the crosslinker content and EB‐absorbed dose. The UTM results indicate that a brittle EB‐crosslinked membrane becomes more flexible with an increase in the crosslinker content. The DMA results show that the EB‐crosslinked membranes have well‐developed ionic aggregation regions and the cluster T_g of membranes decrease with an increase in the 1,4‐butanediol crosslinker content. The SAXS results show that the Bragg and persistence distance of crosslinked membranes increase with an increase in the crosslinker content. The proton conductivities of the EB‐crosslinked membranes were more than 9 × 10^?2 S/cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41760.     

Curing and mechanical properties of dicyanate/poly(ether sulfone) semi‐interpenetrating polymer networks

Semi‐interpenetrating polymer networks (semi‐IPNs) composed of a dicyanate resin and a poly(ether sulfone) (PES) were prepared, and their curing behavior and mechanical properties were investigated. The curing behavior of the dicyanate/PES semi‐IPN systems catalyzed by an organic metal salt was analyzed. Differential scanning calorimetry was used to study the curing behavior of the semi‐IPN systems. The curing rate of the semi‐IPN systems decreased as the PES content increased. An autocatalytic reaction mechanism was used to analyze the curing reaction of the semi‐IPN systems. The glass‐transition temperature of the semi‐IPNs decreased with increasing PES content. The thermal decomposition behavior of the semi‐IPNs was investigated. The morphology of the semi‐IPNs was investigated with scanning electron microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1079–1084, 2003     

Proton exchange composite membranes from blends of brominated and sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide)

New composite proton exchange membrane was prepared by mixing a 1‐methyl‐2‐pyrrolidone (NMP) solution of sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) in sodium form and brominated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (BPPO) for hydrophilic‐hydrophobic balance, then casting the solution as a thin film, evaporating the solvent, and treating the membrane with aqueous hydrochloric acid. The resulting membranes were subsequently characterized using FTIR‐ATR, SEM‐EDXA, and TGA instrumentation as well as measurements of basic properties such as ion exchange capacity (IEC), water uptake, proton conductivity, methanol permeability, and single cell performance. Water uptake, IEC, proton conductivity, and methanol permeability all increased with a corresponding increase of SPPO content. By properly compromising the conductivity and methanol permeability, membranes with 60–80 wt % SPPO content exhibited comparable proton conductivity to that of Nafion^® 117, with only half the methanol permeability, thereby demonstrating higher single cell performance. The membranes developed in this study could thus be a suitable candidate electrolyte for proton exchange membrane fuel cells (PEMFCs). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Engineering properties of poly(vinyl chloride)–poly(butyl methacrylate) semi‐1 and semi‐2 interpenetrating polymer networks

Semi‐1 and semi‐2 interpenetrating polymer networks (IPNs) of poly(vinyl chloride) (PVC) and in situ formed poly(butyl methacrylate) (PBMA) have been synthesized using diallyl phthalate and ethylene glycol dimethacrylate as the crosslinkers of PVC and PBMA, respectively. These were then characterized with reference to their mechanical, thermal, and morphological properties. The mechanical and thermal characteristics revealed modification over the unmodified polymeric systems in relation to their phase morphologies. The semi‐1 IPNs displayed a decrease in their mechanical parameters of modulus and UTS while semi‐2 IPNs exhibited a marginal increase in these two values. The semi‐1 IPNs, however, also revealed a decrease in the elongation and toughness values away from the normal behavior. The thermomechanical behavior of both the systems is in conformity with their mechanicals in displaying the softening characteristics of the system and stabilization over unmodified PVC. The DSC thermograms are also correlated to these observations along with the heterogeneous phase morphology which is displayed by both the systems especially at higher concentration of PBMA incorporation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008