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Porous polymeric materials (poly HIPEs) have attracted considerable attention in many fields focused on biomaterial applications. In this research, co-polymeric hydrogels of poly (HEMA-co-NVP) were synthesized in the emulsion phase. Poly (HEMA-co-NVP) poly HIPE was produced by co-polymerization of 2-Hydroxyethyl methacrylate (HEMA) and N-vinylpyrrolidone (NVP) in the presence of N, N-methylene bisacrylamide (MBA as cross-linker), and initiation of ammonium persulfate (APS) and N, N, N, N-tetramethylene diamine (TEMED). The co-polymerization was based on the free-radical polymerization method by employing two immiscible liquids in the poly HIPE method. The characterization of the poly HIPE-based co-polymer was done by Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The optimization process was done by measuring the water absorption and the best amount was kept stable in each stage. The highest water absorption value of synthetic porous hydrogel synthesized in the HIPEs method was 8.9 g/g with average pores of 2-5 μm, while its synthetic hydrogel with the same values of reactants and without HIPEs method was 1.2 g/g. These results show that the poly HIPE-based polymerization of co-polymers can be intended to raise their water uptake.

Aiming at the complex strata, lost circulation often occurs. and lost circulation control becomes a difficult issue. A drilling fluid loss accident delays the drilling progress and even causes major economic losses. If we take a self-made sodium polyacrylate grafting and modify a starch water absorbent resin, using an amphiphilic compatibilizer as raw material through mechanical blending and chemical compatibilization, we can synthesize a resin–rubber blend swelling lost circulation material. This material presents a good resistance to anti-high-temperature performance, but the quality declines while the temperature is higher than 363 °C, and with the increasing temperature, the water-swelling expansion ratio becomes higher. The range of the water-swelling expansion ratio is 8 to 25 times and the water swelling rate becomes larger along with the reduced diameter of the lost circulation materials and decreases with the increasing salinity. The resin-rubber blend swelling lost circulation material after water swelling has excellent toughness and high elastic deformation capacity, thus, forming a 7 Mpa to 2 mm fracture via expansion, extrusion, deformation, and filling, which presents a good performance for fracture plugging and realizes the purpose of lost circulation control. [ABSTRACT FROM AUTHOR]

CFRP structures are often exposed to humid environment resulting in water absorption and causing property degradation. Water swelling and its effect on tensile, compressive, and flexural properties were investigated according to ASTM standards. Fracture modes were evaluated by analyzing micrographs of fracture areas. The specimens were cut from twill wave CFRP composite plates fabricated using a vacuum infusion technique. Some of them were immersed in water prior to being mechanically tested. It was found that tensile strength, as well as compressive, and flexural strength and moduli decreased due to water swelling, but fracture strain was found to increase due to water swelling. The most severely affected by water swelling is flexural strength (decreased by 25.72%), and the least is compressive modulus (decreased by 1.89%). Tensile specimens underwent fibre breakage followed by matrix cracking, compressive and flexural specimens showed fibre buckling followed by kinking and crushing where flexural specimens failed in their compressive side. In conclusion, water absorption has a bad impact on the composite strength. [ABSTRACT FROM AUTHOR]

Bioelectronics based on organic mixed conductors offers tremendous application potential in biological interfacing, drug delivery systems, and neuromorphic devices. The ion injection and water swelling upon electrochemical switching can significantly change the molecular packing of polymeric mixed conductors and thus influence the device performance. Herein, we quantify ion and water injection, and analyze the change of microscopic molecular packing of typical polymeric mixed conducting materials, namely poly(3,4‑ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) and poly(2‐(3,3′‐bis(2‐(2‐(2‐methoxyethoxy)ethoxy) ethoxy)‐[2,2′‐bithiophen]‐5‐yl)thieno[3,2‐b]thiophene) (p(g2T‐TT)), by integrating electrochemical quartz crystal microbalance with dissipation monitoring, in situ charge accumulation spectroscopy, and electrical current‐voltage measurement. The penetration of ions and water can lead to viscous and disordered microstructures in organic mixed conductors and the water uptake property plays a more dominant role in morphological disruption compared with ion uptake is demonstrated. This study demonstrates the potential application of the combined optical, gravimetric, and electrical operando platform in evaluating the structural kinetics of organic mixed conductors and highlights the importance of concertedly tuning the hydration process, structural integrity, and charge transport properties of organic mixed conductors in order to achieve high performance and stable bioelectronic devices. [ABSTRACT FROM AUTHOR]

Industrial expansion has increased the discharge of contaminated wastewater. Wastewater can be treated by adsorption with petroleum‐based hydrogels but the materials are not biodegradable and therefore cause secondary toxic waste. In this work, hydrogel composites are prepared based on non‐biodegradable polyacrylamide and biodegradable materials of cassava starch (CS) and poly(vinyl alcohol). The effect of CS content on the porous structure is studied. The highest water absorption capacity of 74 g g−1 is obtained from a hydrogel 30 wt% of CS. Within 4 h, the hydrogel effectively adsorbs the cationic dyes methylene blue (MB) and crystal violet, and the anionic dyes congo red and reactive orange. The maximum adsorption capacity toward MB is 993 mg g−1. Experimental data indicate a monolayer adsorption via chemisorption. Silica‐coated ZnO photocatalyst particles are synthesized via a sol–gel method and coated on the outer surface of the hydrogel. Under sunlight, the hydrogel composite degrades almost 90% of adsorbed dye. The hydrogel composite is capable of effective photodegradation for at least three cycles under artificial UV irradiation and four cycles under sunlight, but adsorption capacity remains higher than 80% at the eighth cycle. The hydrogel composite also shows antibacterial activities, indicating an additional beneficial property for industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

Abstract Industrial expansion has increased the discharge of contaminated wastewater. Wastewater can be treated by adsorption with petroleum‐based hydrogels but the materials are not biodegradable and therefore cause secondary toxic waste. In this work, hydrogel composites are prepared based on non‐biodegradable polyacrylamide and biodegradable materials of cassava starch (CS) and poly(vinyl alcohol). The effect of CS content on the porous structure is studied. The highest water absorption capacity of 74 g g−1 is obtained from a hydrogel 30 wt% of CS. Within 4 h, the hydrogel effectively adsorbs the cationic dyes methylene blue (MB) and crystal violet, and the anionic dyes congo red and reactive orange. The maximum adsorption capacity toward MB is 993 mg g−1. Experimental data indicate a monolayer adsorption via chemisorption. Silica‐coated ZnO photocatalyst particles are synthesized via a sol–gel method and coated on the outer surface of the hydrogel. Under sunlight, the hydrogel composite degrades almost 90% of adsorbed dye. The hydrogel composite is capable of effective photodegradation for at least three cycles under artificial UV irradiation and four cycles under sunlight, but adsorption capacity remains higher than 80% at the eighth cycle. The hydrogel composite also shows antibacterial activities, indicating an additional beneficial property for industrial wastewater treatment.

Aiming at the complex strata, lost circulation often occurs. and lost circulation control becomes a difficult issue. A drilling fluid loss accident delays the drilling progress and even causes major economic losses. If we take a self-made sodium polyacrylate grafting and modify a starch water absorbent resin, using an amphiphilic compatibilizer as raw material through mechanical blending and chemical compatibilization, we can synthesize a resin–rubber blend swelling lost circulation material. This material presents a good resistance to anti-high-temperature performance, but the quality declines while the temperature is higher than 363 °C, and with the increasing temperature, the water-swelling expansion ratio becomes higher. The range of the water-swelling expansion ratio is 8 to 25 times and the water swelling rate becomes larger along with the reduced diameter of the lost circulation materials and decreases with the increasing salinity. The resin-rubber blend swelling lost circulation material after water swelling has excellent toughness and high elastic deformation capacity, thus, forming a 7 Mpa to 2 mm fracture via expansion, extrusion, deformation, and filling, which presents a good performance for fracture plugging and realizes the purpose of lost circulation control.

In this work, a novel natural pozzolan-incorporated super-absorbent polymer composites (SAPCs), a potential soil-additive to increase water holding capacity and water use efficiency of soil, was synthesized and characterized. Consequently, barley plants have been grown on the produced SAPCs under (1) well-watered and (2) water-deficient conditions. Results showed that SAPCs could reach the highest theoretical equilibrium swelling capacities of 20,000% and 3260% (wt/wt) in pure water and saltwater. Natural pozzolan (NP) incorporation with super-absorbent polymer improves water absorption capacity and thermal stability. Under the water-deficit condition, the amendment of soil with %1 SAPCs and %1 NP suppressed the reduction of relative water content as 4–8%, while it was recorded as 14% in control plants. These results confirmed that SAPC-amended soil could hold significant amounts of water and release it to plant roots gradually as needed. In conclusion, poly(AA-co-AM)/NP SAPCs can be used as a soil additive to reduce water loss, especially in arid/semi-arid regions. [ABSTRACT FROM AUTHOR]

Flexible and stretchable conductors are crucial components for next‐generation flexible devices. Wrinkled structures often have been created on such conductors by depositing conductive materials on the pre‐stretched or organic solvent swollen samples. Herein, water swelling is first proposed to generate the wrinkled structures on silicone elastomers. By immersing silicone/sugar hybrid in water, a significant amount of swelling occurs as a result of osmosis and capillary interactions with the sugar and silicone matrix. Considering the drastic swelling effect and controllable swelling ratio, water swelling is used to replace the conventional pre‐stretching and organic solvent swelling to fabricate stretchable conductors. In situ growing of silver nanoparticles (AgNPs) is carried out on the swollen silicone elastomers. Wrinkled conductive silicone elastomers are successfully constructed after removing the residual water. The conductive elastomer has a sheet resistance of less than 1 Ω sq‐1 at zero strain and also shows high sensitivity when subjected to external deformation up to 100% strain. The silicone/sugar composite also possesses good 3D printability with the desired shear‐thinning property. Human motion detection is demonstrated using the 3D printed sensors. This work provides a facile and environment‐friendly strategy to fabricate superior flexible and stretchable sensing devices. [ABSTRACT FROM AUTHOR]

The use of degradable polymer materials as controlling additives to the working fluid during hydraulic fracturing is an area of interest in developing stimulation technologies. A temporary plugging agent with high compressive strength is used to block pre-fracturing or natural cracking and to initiate new fracture joints in order to increase the oil and gas passages, thereby realizing a stable production of oil and gas reservoirs. The temporary plugging agent prevents the fluid from entering the existing cracks, allowing the fracturing fluid to create new cracks and a more complex network of fractures within the reservoir. Considering the technological requirements, the temporary plugging agent must have a strong pressure resistance, good water solubility, and good returning performance, which can make new and old cracks simultaneously effective. In this paper, a new type of internal temporary plugging agent is developed, and the temporary plugging mechanism is evaluated through experiments, including plugging material microstructure, particle size, water absorption, water absorption speed, temporary plugging effect, and conductivity after dissolution. Our study shows that the temporary plugging agent provides a good temporary plugging effect, causes no pollution to the oil well, and can play a good protective role on the reservoir in repeated fracturing. [ABSTRACT FROM AUTHOR]

One of the main problems in cardiovascular surgery is the lack of functionally reliable small-diameter (no more than 4 mm) vascular grafts required for coronary artery bypass grafting and peripheral artery and vein bypass grafting. The purpose of this work is the development of a composite biopolymer porous tubular matrix (CPTB matrix) 2 and 4 mm in diameter with adjustable resorption time and physicomechanical properties close to native blood vessels of the same diameter. The specimens of CPTB matrices with a diameter of 2 and 4 mm were produced by means of electrospinning from poly(hydroxybutyrate-co-hydroxyvalerate) and gelatin solution in hexafluoroisopropanol. The matrix structure was stabilized by treatment with glutaraldehyde (HA) vapor. It was demonstrated that the best specimen in terms of structure, physicomechanical properties, and resorption rate is the matrix obtained with the ratio of poly(hydroxybutyrate-co-hydroxyvalerate) : gelatin equal to 1 : 2 v/v in the solution and additionally crosslinked in HA vapor for 48 h. The detected slight cytotoxicity of the CBPT matrices developed is easily eliminated by treatment with an aqueous solution containing a set of amino acids. Decreasing the diameter of the substrate rod from 4 to 2 mm is accompanied by small changes in the surface structure and the physicomechanical properties of the CPTB matrix. [ABSTRACT FROM AUTHOR]

Although controlled-release fertilizer (CRF) is a safer and more efficient strategy to administer nutrients for plant growth, it is still a daunting task to reduce the cost and improve the degradability of the synthetic resin coatings. In this paper, an inorganic/organic composite coating for urea fertilizer was prepared from a biodegradable castor oil-based polyurethane (PU) filled with the layered Na-bentonite (Na-BT), which was ultrasonically treated by a series of green PEG surfactants. Synergistically influenced by various intercalation ability, cation-hosting ability and hydrophilicity of the PEGs, the porous structures of the modified Na-BT (MBT) fillers were simply tuned by varying the Mn molecular weights of the PEGs, resulting in the adjustable water swelling and mechanical properties of the MBT/PU composites. Moreover, it was confirmed that the water swelling property played a critical role in controlling the early stage of nutrient release, and the mechanical properties were important for the longevity of nutrient release from the CRFs. The best MBT/PU composite supported a CRF with a long-term release of 75 % in 38 days, which was much longer than the one based on pure PU (20 days). The porous structures of the modified Na-BT (MBT) samples were tuned under the synergistic effects of PEG-intercalation interaction, particle surface charge and water replacement, which promoted the intrusion of the mixture precursor of TDI and castor oil into the internal pores of the MBT filler. After coating on the urea granules, the comprehensive performance of the coating fertilizer can be enhanced due to the improved interfacial interactions. [Display omitted] • Green modification, structure control and investigation of Na-bentonite via PEGs • The effects of PEG-intercalation, particle surface charge and water replacement • Improving water absorbency and mechanical properties of composite film • Optimizing controlled-release performance of coated fertilizer [ABSTRACT FROM AUTHOR]

When nitrile rubber contacting with water under the external force during the service life, swelling and sliding wear occur. Since nitrile has similar polarity to water, the interaction between water and nitrile rubber and its influence on mechanical and tribological behaviors of the nitrile rubber play an important role in rubber performance, which is extremely necessary to be studied systematically. In this study, immersion experiments were conducted on three nitrile rubber samples which contained different acrylonitrile weight percentages of 18%, 26% and 41% (i.e. N18, N26, and N41) respectively. The hardness, tensile, dry and wet unidirectional sliding wear tests were further conducted. To reveal the mechanisms, the nuclear magnetic resonance (NMR) analysis and scanning electron microscopy (SEM) analysis were performed and interpreted accordingly. The results showed that cross-linking break based structural damage, substance dissolution and surface layer defects occurred after swelling, resulting in decreases in hardness and tensile strength and increases in permanent deformation fracture rates of the nitrile rubbers. The friction coefficient value of the un-swollen NBRs was positively related to the wear loss and decreased with the increase of the acrylonitrile content. During the wear process under dry conditions, the un-swollen rubbers presented hardening in aging while the swollen samples softened along with the deterioration of adhesive wear with higher steady-state friction coefficient value and wear loss. Under wet friction conditions, the susceptible wear behavior of the swollen rubbers induced reductions in friction coefficient and increases in wear loss. The swelling degree and its effects on mechanical and tribological behavior decreased with the increase of the acrylonitrile content. The swelling influences on the tribological behavior of nitrile rubber affected and acted on the entire wear process.

Anion exchange membranes prepared from imidazolium cations still need to overcome the drawbacks of water solubility and chemical stability in strong base. Here, we use density functional theory (DFT) to focus on alkaline stability of imidazolium-based monomers with different C4/C5-position substituents and analyze their degradation mechanism when treated with 10 M NaOH. On the basis, we select methyl-substituted imidazolium (MeIM) cationic compound to construct ether-free main-chain type polymers via superacid-catalytic reaction, together with the introduction of branched monomer to inhibit water swelling of membrane. The optimized branched structure maintains stable dimension performance under 80 °C compared to linear polymer dissolved in water. Meanwhile, the alkaline-resisted membrane with branched structure expands the operating temperature range of fuel cell to 90 °C and maintains long-term durability. [Display omitted] • The main-chain type imidazolium-based AEM is prepared by superacid-catalytic polymerization. • Excellent alkaline stability of methyl-substituted imidazolium on C4 and C5 position when treated 10 M KOH. • The branched polymer structure is designed to suppress water swelling of imidazolium-based AEM. • The operating temperature of fuel cell is expanded to 90 °C for AEM's long-term stability. [ABSTRACT FROM AUTHOR]

Acrylamide/maleic acid hydrogel, a superabsorbent polymer, was prepared by free radical polymerization in aqueous solution of acrylamide (AAm) and maleic acid (MA) : monomer and comonomer, respectively. Potassium persulfate and N,N,N’,N’-tetramethylethylenediamine were used as an initiator system. Also, ethylene glycol dimethacrylate (EGDMA) and N,N’-methylenebisacrylamide (MBA) were used as crosslinkers. Different compositions of acrylamide, maleic acid and crosslinkers were employed. Water swelling, equilibrium water content and swelling power of the hydrogel formed were determined. The result showed that the swelling in water at equilibrium of hydrogels was in the range of 8,420-10,300% and 3,160- 3,560%, equilibrium water content was in the range of 0.9880-0.9902 and 0.9630-0.9727 and swelling power was in the range of 84-103 and 31-36 using 1%EGDMA and 1%MBA as crosslinkers, respectively. The diffusion of water into hydrogel followed non-Fickian character based on swelling power.

Copolymers of N(-1,1-dimethyl-3-oxobutyl)acrylamide (DOBA) and Methyl methacrylate (MMA) were prepared in dimethylformamide using benzoylperoxide as the initiator at 70 °C. They were characterized by IR,1H NMR, and13C NMR. Copolymer compositions were determined by the analysis of1H NMR spectra. The weight and number average molecular weights of the polymers were determined by size exclusion chromatography. Monomer reactivity ratios were found to be 1.52 for MMA and 0.43 for DOBA according to Kelen–Tüdos method. Glass transition temperatures of the copolymers were determined by differential scanning calorimetry. The initial decomposition temperatures of the polymers were about 215 °C as measured by thermogravimetric analysis under nitrogen atmosphere. Swelling properties of the polymers were measured in distilled water. Maximum water uptake of about 70% was observed for poly(DOBA). In case of copolymers, water uptake decreases with the increase of MMA content in the polymer chain. [ABSTRACT FROM PUBLISHER]

Withcrystalline polycaprolactone diols (PCL) used as soft segments, and 1,4-butanediol (BDO), dimethylolpropionic acid (DMPA), and N-methyldiethanolamine (MDEA), respectively, used as differentpH-sensitive components,three types of thermal and pH-sensitive polyurethanes (PUs) were prepared by using the block copolymerization technique and are referred to as PU(a), PU(b), and PU(c), correspondingly. Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetry (DSC) were used to study the distinct functional groups of the PUs and their segmented structures. Their thermal and pH stimuli sensitivity were measured by water permeability (WP) and water swelling (WS) tests. Fourier transform infrared analysis demonstrated that the ‒COOH and ‒N(CH3)‒ groups were successfully introduced into the PU(b) and PU(c), respectively, and these acid–base groups did not change the basic structure of their main chains. X-ray photoelectron spectroscopy analysis showed that the O and N concentration increased on the surface of PU(b) and PU(c), respectively. Differential scanning calorimetry analysis indicated that all three PUs showed phase-separated structures and similar phase-transition temperatures of the soft segments (defined as the switch temperature, Ts), which showed that the introduction of the acid–base functional groups did not much affect the phase-separated structures and crystallization of the soft segments. The WP study indicated that all PUs showed thermal intelligent responses, i.e., the WPs were correspondingly changeable with change of the temperature. In particular, when the temperature varied near the Ts, e.g., from Ts−10°C to Ts + 10°C, the WPs changed markedly. In addition, due to PU(b) and PU(c) containing ‒COOH and ‒N(CH3)‒ groups, respectively, they both showed a pH response in their WP and WS. When the pH changed from 4.0 to 5.5, the WP and WS of PU(b) were obviously changed. The same change also occurred for PU(c) in the pH range from 8.5 to 10.0. We thus conclude that the method utilized is an efficient way to prepare PUs that are dually responsive to both thermal and pH stimuli. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to investigate the effect of molecular weight (MW) on the drug release from poly(ethylene carbonate) (PEC) based surface-eroding in situ forming depots (ISFD). In phosphate buffered saline (PBS) pH 7.4, 63.7% of bovine serum albumin BSA was released from high MW PEC of 200kDa (PEC200) in DMSO (15%, w/w) in 2days, while during the same time period, the release of BSA from PEC41 samples was only 22.5%. At higher concentrations of PEC41 (25%, w/w), the initial burst was further reduced, and even after 6days, only 16.3% was released. Compared to depots based on PEC200, there was lower rate of solvent release, slower phase inversion, and a denser surface in PEC41 samples. An expansion in size of PEC41 depots suggested that the polymer barrier of PEC41 impeded the diffusion of solvent out of the samples effectively. In conclusion, the initial burst of protein from ISFD of PEC41 was significantly reduced, which would be a promising candidate as polymeric carrier. [Copyright &y& Elsevier]

Flexible composite films were produced by impregnating aqueous phenol formaldehyde (PF) resin into water-swollen cellulose nanofibril (CNF) films. CNF films were prepared using a pressurized filtration method in combination with freeze drying. The freeze-dried films were swollen with water then impregnated with PF resin by soaking in aqueous resin solutions of varying concentrations. Small amounts of PF slightly enhanced the tensile properties of CNF films. The formulation with the best mechanical properties was CNF/PF films with 8 wt % resin exhibiting tensile stress and toughness of 248 MPa and 26 MJ/m, respectively. Resin concentrations higher than about 8 % resulted in composites with decreased tensile properties as compared to neat CNF films. The wet strength of the composite films was significantly higher than that of the neat CNF films. The resulting composites showed greater resistance to moisture absorption accompanied by reduced thickness swelling when soaked in water as compared to neat CNF films. The composites also showed decreased oxygen permeability at low humidity compared to neat films, but the composites did not show improved barrier properties at high humidity. [ABSTRACT FROM AUTHOR]

This paper presents the results from a laboratory research project about water flow through and around coniferous and deciduous shrubs. These are the only two types of shrubs that were considered in this research project. The shrub obstruction consisted of natural branches fixed in the bed of the flume, transversly to the direction of the flow. Besides hydrodynamic parameters, shrub density, water swelling over them, and local drag coefficients of the shrubs was measured and calculated. The final measurement was influenced by the density of both shrub types mentioned above and the spatial orientation of their branches in specified shrub zones in the path of the flowing water. These were analyzed both quantitatively and qualitatively and the appropriate computational formulae were proposed. [ABSTRACT FROM AUTHOR]

Abstract: To provide the relationship between the freeze-thaw resistance of concrete and addition of crumb rubber, the effect of particles size, volume of crumb rubber on the freeze-thaw resistance of concrete was experimentally studied. The results show that the effect of particles size and the volume of crumb rubber on the freeze-thaw resistance of concrete are significant, apart from the air content of concrete. Excessively thick or excessively fine crumb rubber is not favorable for the freeze-thaw resistance of concrete. In addition, the excessive dosage of crumb rubber is also bad for the freeze-thaw resistance of concrete. Water swelling is one of the reasons for freezing and thawing failure of crumb rubber concrete in comparison to normal concrete. [Copyright &y& Elsevier]

Abstract: The permeation of helium, oxygen and nitrogen in perfluorosulphonic acid ionomeric (PFSI) membranes with short and long side chains, namely Aquivion® and Nafion® 117, was studied in the relative humidity range between 0 and 90%, and at temperatures between 35 °C and 65 °C. The presence of humidity enhances, up to a factor of 100, the gas permeability in the membranes, due to the permeation of gas molecules in the hydrophilic domains: the enhancement is rather pronounced for O2 and N2, and less marked for He permeability. The relative permeability increase, Pgas/Pgas,0, shows a complex dependence on the relative humidity, as the water content in the membrane is itself a non linear function of this parameter. The water volume fraction in the membrane at each activity was accurately estimated from measurements of vapor-induced swelling, which indicate that the partial molar volume of water is smaller than its pure liquid value, in both membranes at 35 °C. When plotted against water volume fraction, the gas permeability increases exponentially in the range between 2% and 20%; the slope of the curve is higher for Nafion® than for Aquivion®, as it is reasonable due to their different microstructures. The ideal selectivity of the two membranes for He over N2, O2 over N2 and He over O2, decreases markedly with increasing water content in the membrane. [Copyright &y& Elsevier]

[Display omitted] • Micro- and nanoscale wrinkled structures were enabled by water-induced swelling. • Swelling is governed by osmotic pressure and constraining stress of polymer chains. • Water transport to elastomer involves Fickion diffusion and non-Fickion interaction. • Conductive materials of gold and graphene were deposited on the swollen elastomers. • The wrinkled conductors exhibited good electrical performance in strain sensing. Polymer blend system has been commonly applied in a wide variety of applications. Herein, we propose to introduce sugar particles to polymer matrix, which results in a controllable polymer swelling under the action of osmotic pressure upon soaking in water. Taking advantage of this economic and environment-friendly, water-induced polymer swelling process, we have fabricated wrinkled conductive films and 3D structures by depositing conductive materials on the swollen polymer substrates for stretchable strain sensing devices. Several commercial silicone elastomers were utilized in the study. Key processing factors affecting the polymer swelling were investigated, including film thickness, sugar concentration, and temperature of soaking medium. The swelling ratio can be regulated by changing these parameters and the soaking duration. By sputtering gold (Au) on the swollen films (through vapor deposition) or depositing graphene on 3D complex structures companied by polymer swelling (in aqueous dispersion), wrinkled conductive elastomer films and 3D structures have been fabricated. These conductors not only demonstrated high sensitivity in electrical response when subjected to external deformations from 5% up to 100%, but also possessed good stability after long-term stretching/releasing cycles. The excellent electrical properties of these elastomer conductors implied a great potential in applications of flexible and stretchable sensors. [ABSTRACT FROM AUTHOR]

Abstract: Properties of CMV cation exchange membranes used for electrodialysis of sulfuric acid solutions were investigated. Membrane characterization has led to determine the ion-exchange capacity and the hydrogen ion transport number in sulphuric acid media. The membrane electrical conductivities were measured as a function of the acid concentration. These data were used to check the applicability of the micro-heterogeneous model which describes the inner membrane microstructure as consisting of a joint gel phase and an interstitial phase. The derived value of the interstitial phase volume fraction is large (20%). This value has been correlated to the membrane water content in terms of a model taking into consideration the molecular conformation of polyvalent (polystyrene sulfonate) macro-ions located in the joint gel phase. The behaviour of membranes placed respectively in their acid and salt forms have been studied and discussed. In the interpretation of membrane swelling and acid absorption, emphasis has been put on the role of polyelectrolyte morphological modifications as a function of the concentration in the equilibrating solutions. The overall membrane homogeneity has been tested by using chronopotentiometric measurements at different current densities. [Copyright &y& Elsevier]

A water-swelling rubber was prepared by in situ formed sodium acrylate (NaAA) in chlorinated polyethylene (CPE). The water-swelling properties of the CPE/NaAA vulcanizates were investigated, and the kinetics of the water-swelling processes and the state of water absorbed in the CPE/NaAA vulcanizates were explored. The results showed that the water-swelling properties depended on the formulation of the vulcanizates such as the dicumyl peroxide (DCP) content, NaAA content and the molar ratio of sodium hydroxide (NaOH) and acrylic acid (AA). Moreover, the environmental conditions, such as aqueous medium component and temperature, had great effects on the water-swelling properties. The mechanism of the water-swelling process was not purely Fickian diffusion, and relates to the relaxation effect of the sodium polyacrylate (PNaAA) and CPE chain. The diffusion coefficient (D) and the relaxation rate constant (kr) increase with increasing temperature, decrease with increasing DCP content and increase with increasing NaAA content. The differential scanning calorimetry (DSC) measurements indicated that the water absorbed in the vulcanizate existed in PNaAA and CPE networks in three different physical states, namely, free water, freezable bound water and non-freezable bound water. [Copyright &y& Elsevier]

Ultrathin hydrogels were prepared by sequential formation of amide linkages between commercially available poly(acrylic acid-co-acrylamide) with an acrylic acid content of 10mol%, plus poly(vinylamine) using a water-soluble carbodiimide on a solid substrate. Assembly processes and physicochemical properties of the resulting ultrathin hydrogels were characterized in detail. [ABSTRACT FROM AUTHOR]

The effect of temperature on the swelling kinetics of glassy gelatin matrices exposed to water was studied. The movement of two distinct and characteristic swelling boundaries was measured directly using an optical microscope. Swelling rate constants associated with these moving boundaries demonstrated Arrhenius behavior over the temperature range of 15 to 40°C. The apparent activation energy for non-Fickian water transport into the gelatin glassy core was determined to be 8.1 kcal/mol, and 3.5 kcal/mol was found for the outer expansion of the swelling gelatin network due to water sorption. These findings are compared with activation energies for other solvent-glassy polymer systems, and possible reasons for the unexpectedly low value for non-Fickian water transport in the glassy gelatin solid are considered. [ABSTRACT FROM AUTHOR]

To ameliorate the trade-off effect between ionic conductivity and water swelling of anion exchange membranes (AEMs), a crosslinked, hyperbranched membrane (C-HBM) combining the advantages of densely functionalization architecture and crosslinking structure was fabricated by the quaternization of the hyperbranched poly(4-vinylbenzyl chloride) (HB-PVBC) with a multiamine oligomer poly(N,N-Dimethylbenzylamine). The membrane displayed well-developed microphase separation morphology, as confirmed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Moreover, the corresponding high ionic conductivity, strongly depressed water swelling, high thermal stability, and acceptable alkaline stability were achieved. Of special note is the much higher ratio of hydroxide conductivity to water swelling (33.0) than that of most published side-chain type, block, and densely functionalized AEMs, implying its higher potential for application in fuel cells. [ABSTRACT FROM AUTHOR]

Multiblock poly(arylene ether sulfone) copolymers are attractive for polyelectrolyte membrane fuel cell applications due to their reportedly improved proton conductivity under partially hydrated conditions and better mechanical/thermal stability compared to Nafion. However, the long hydrophilic sequences required to achieve high conductivity usually lead to excessive water uptake and swelling, which degrade membrane dimensional stability. Herein, we report a fundamentally new approach to address this grand challenge by introducing shape-persistent triptycene units into the hydrophobic sequences of multiblock copolymers, which induce strong supramolecular chain-threading and interlocking interactions that effectively suppress water swelling. Consequently, unlike previously reported multiblock copolymer systems, the water swelling of the triptycene-containing multiblock copolymers did not increase proportionally with water uptake. This combination of high water uptake and low swelling behavior of these copolymers resulted in excellent proton conductivity and membrane dimensional stability under fully hydrated conditions. In particular, the triptycene-containing multiblock copolymer film with the longest hydrophilic block length (i.e., BPSH100-TRP0-15k-15k) had a water uptake of 105%, an excellent proton conductivity of 0.150 S/cm, and a volume swelling ratio of just 29% (more than 42% reduction compared to Nafion 212).