Swelling Behavior In Water Research Articles

Mechanical, Water-swelling, and Morphological Properties of Water-swellable Thermoplastic Vulcanizates Based on Polyvinyl Chloride/Crosslinked Sodium Polyacrylate/Chlorinated Polyethylene Blends

A novel water-swellable rubber (WSR) was prepared by dynamically vulcanizing polyvinyl chloride (PVC)/chlorinated polyethylene (CPE) blends where a crosslinked poly(sodium acrylate) (CPNaAA) was used as a super water-absorbent resin and dispersed in the CPE rubber. The mechanical, water-swelling, and morphological properties were investigated. The results showed that the dynamically vulcanized PVC/CPNaAA/CPE blends exhibited obvious elastomeric behavior and could be considered as thermoplastic vulcanizates (TPVs). The PVC/CPNaAA/CPE TPVs showed strong water-swelling ability, with the water-swelling ratio of the PVC/CPNaAA/CPE TPV with 30/60/70 weight ratio reaching 2400% at 200 h immersion. Moreover, compared with the first water-swelling behavior, the second and third water-swelling behaviors of the TPVs showed significantly improved water-swelling ratio and a remarkable decrease of weight loss. Morphological study showed that the interface interaction between the CPNaAA and CPE was weak. The CPNaAA particles in the blends could be separated and even be pulled out from the matrix under tensile stress, leading to the formation of suspended CPNaAA particles on the fracture surface of PVC/CPNaAA/CPE TPVs. The surface of the dried TPVs was rough and significant cavities could be found. The dynamic mechanical properties were investigated and the TPVs showed the typical Payne effect.

Synthesis and properties of thermo- and pH-sensitive poly(N-isopropylacrylamide)/polyaspartic acid IPN hydrogels

Abstract Various interpenetrating polymer network (IPN) hydrogels with sensitivity to temperature and pH were prepared by introducing the pH-sensitive polymer polyaspartic acid (PASP) hydrogel, into the poly(N-isopropylacrylamide) (PNIPAAm) hydrogel system for the purpose of improving its response rate to temperature. The morphologies and thermal behavior of the prepared IPN hydrogels were studied by both scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The IPN hydrogels showed a large and uneven porous network structure, without showing the common PNIPAAm hydrogel structure. The paper moreover studied their swelling properties, such as temperature dependence of equilibrium swelling ratio, shrinking kinetics, re-swelling kinetics and oscillatory swelling behavior in water. The swelling experiment results revealed that IPN hydrogels exhibited much faster shrinking and re-swelling in function of the composition ratio of the two network components. These fast responsive hydrogels foster potential applications in biomedical and biotechnology fields.

Thermoresponsive super water absorbent hydrogels prepared by frontal polymerization of N‐isopropyl acrylamide and 3‐sulfopropyl acrylate potassium salt

AbstractSuper water absorbent polymer hydrogels were synthesized by frontal polymerization. These materials were obtained by copolymerizing N‐isopropyl acrylamide (NIPAAm) and 3‐sulfopropyl acrylate potassium salt (SPAK) in the presence of N,N′‐methylene‐bis‐acrylamide as a crosslinker. It was found that their swelling behavior in water can be easily tuned by using either the appropriate monomer ratio or the amount of the crosslinker used. Namely, the swelling ratio was found to range from about 1000% for the NIPAAm homopolymer in the presence of 5.0 mol % of crosslinker, up to 35,000% for the sample containing 87.5 mol % of SPAK and 1.0 mol % of crosslinker. The affinity toward water was also confirmed by contact angle analysis. Moreover, the obtained hydrogels exhibit a thermoresponsive behavior, with a lower critical solution temperature of about 28–30 °C. This value is close to that of poly(NIPAAm) but with a swelling capability that dramatically increases as the amount of SPAK increases. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Thermoresponsive super water absorbent hydrogels prepared by frontal polymerization

AbstractFrontal polymerization was used as an alternative technique for the preparation of super water absorbent hydrogels obtained from acrylamide and 3‐sulfopropyl acrylate, potassium salt (SPAK) in the presence of N,N′‐methylene‐bisacrylamide as a crosslinker. All samples were synthesized in dimethyl sulfoxide, and their swelling behavior in water was investigated. It was found that their features are dependent on the monomer ratio used, which influenced the porous morphology, and consequently, the swelling capability. The swelling ratio ranges from about 1000% for the acrylamide homopolymer up to 14,000% for the sample containing 87.5 mol % of SPAK, thus indicating that this parameter can be easily tuned by using the appropriate monomer ratio. The affinity towards water was eventually confirmed by contact angle analysis. Polymer hydrogels made from at least 62.5 mol % SPAK exhibit a thermoresponsive behavior, with a lower critical solution temperature of ∼30 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2486–2490, 2010

Primary study on double-layer membranes for direct methanol fuel cell

The double-layer membranes consisting of sulfonated poly(ether ether ketone) (SPEEK) sub-layer and polyvinyl alcohol (PVA) sub-layer were investigated for direct methanol fuel cell (DMFC). The membranes with different prescriptions were prepared by two-step solvent casting. Swelling behavior in water and 2 M methanol solution, ion exchange capacity (IEC) and methanol permeability of the membranes were studied and discussed. In 2 M methanol solution, SP63 provided the planar swelling ratio of 8.16 % and zero at 80 °C and 25 °C, respectively. The low swelling behaviors in planar direction are expected to be useful in maintaining the tight contact between electrolyte membrane and catalyst layer. The double-layer membranes were assembled in DMFC, PVA sub-layer adhered to anode to block methanol crossover. Proton conductivities of the double-layer membranes are restricted by the lower conductivity of PVA sub-layer, which would be improved in our further research. The double-layer membranes are suggested to be ideal candidate proton exchange membrane for DMFC application.

Poly (vinyl alcohol) hydrogels for pH dependent colon targeted drug delivery

Oral drug administration is convenient with pH dependent drug delivery system since the drug has to pass through different pH environments in gastro intestinal (GI) tract. The pH dependent swelling/shrinking behavior of hydrogel drug carrier controls the drug release without affecting the function of drug. pH dependent hydrogels of poly (vinyl alcohol) (PVA) were prepared by cross linking with maleic acid (MA). The hydrogels were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, DSC, porosimetry, SEM, TEM, biocompatibility study and by measuring their swelling behavior in water, simulated gastric fluid (SGF) and intestinal fluid (SIF). Swelling of the hydrogels was found to be highest in SIF (pH: 7.5) and lowest in SGF (pH: 1.2) resembling that required in colon targeted drug delivery systems. Since the swelling behavior of the gel is pH dependent, these hydrogels were studied for colon targeted drug delivery in an in-vitro set-up resembling the condition of GI tract. The ratio of PVA and MA in the hydrogel was varied to study the effect on the drug diffusion rate. For drug delivery study, vitamin B12 and salicylic acid were used as model drugs. The hydrogel, loaded with model drugs vitamin B12 and salicylic acid also demonstrated colon specific drug release with a relatively higher drug release in SIF (pH: 7.5) than that in SGF (pH: 1.2).

Synthesis, Characterization and Study of Metal Ion Sorption Capacity and Water Swelling Behavior of Xanthan Gum‐g‐N,N′‐Dimethylacrylamide

In the present paper Xanthan gum‐g‐N,N′‐dimethyl acryl amide was synthesized by free radical polymerization using a bromate/thiourea redox pair in an inert atmosphere. Studies are done to observe the effect of reactants on grafting parameters by varying the reactant concentration and to study some physical‐chemical properties. Grafting ratio, add on and conversion show a decrement on increasing the concentration of Xanthan gum. The grafting parameters increase on increasing the concentration of N,N′‐dimethyl acrylamide from 8.3×10−2 to 20×10−2 mol dm−3, BrO3 − from 1×10−3 to 5×10−3 mol dm−3 and thiourea from 1.2×10−3 to 3.6×10−3 mol dm−3. Optimum temperature and time for grafting of N,N′‐dimethyl acrylamide on Xanthan gum are found to be 35°C and 120 min, respectively. Water swelling behavior, swelling ratio, and metal ion uptake, metal retention capacity are also studied. It was found that the graft copolymer shows a greater enhancement in these properties than the substrate. The graft copolymer is characterized by FTIR and thermal analysis.

Pore structure and water-swelling behavior of porous resins based on methyl acrylate and different divinylbenzene isomers

Porous resins based on divinylbenzene (DVB) and methyl acrylate (MA) were prepared with m-DVB (98.3%) or p-DVB (99.1%) in the presence of toluene as a porogen. The MA/DVB resins thus obtained with a wide range of pore structures were hydrophobic in nature and were swellable by direct contact with water. The behavior of m-DVB and p-DVB as a crosslinker in the MA/DVB monomer system was different from that in the styrene (ST)/DVB system and was influenced by the amount of MA in the MA/DVB monomer system. As a result, a larger specific surface area and pore volume were observed for MA/DVB resins derived from p-DVB than for those derived from m-DVB, which was opposite to that observed for resins based on DVB and ST. The different behaviors of m-DVB and p-DVB in the MA/DVB monomer system also resulted in different swelling abilities of the resins in water. Compared with the MA/DVB resins derived from m-DVB, the p-DVB derived resins swelled faster in water and were water-swellable when the resins had a higher DVB content and, therefore, a stronger hydrophobicity and a larger specific surface area. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2071–2078, 2005

Mechanical properties, water swelling behavior, and morphology of swellable rubber compatibilized by PVA‐g‐PBA

AbstractA novel water swellable rubber (WSR) was prepared by blending chlorohydrin rubber (CHR) with crosslinked polyacrylate (CPA), poly(vinyl alcohol)‐g‐poly(butyl acrylate) (PVA‐g‐PBA), precipitated silica (PSA), and poly(ethylene glycol) (PEG). The amphiphilic graft copolymer PVA‐g‐PBA was incorporated as the compatibilizer between CHR and CPA. Water swellable‐rubber with different grafting percentages and contents of PVA‐g‐PBA was investigated by SEM, mechanical measurement, and water‐swelling tests. The results prove that PVA‐g‐PBA increased interfacial cohesion between CHR and CPA before and after water swelling, decreased percentage loss by weight, and improved water‐swelling behavior. Mechanical properties of WSR were significantly improved by PVA‐g‐PBA, especially for the blends of 5 phr PVA‐g‐PBA with G% = 151.7% before water swelling and that with G% = 340.4% after water swelling.

Water-swellable hydrophobic porous copolymer resins based on divinylbenzene and acrylonitrile. I. Water-swelling behavior

Hydrophobic porous copolymer resins based on divinylbenzene (DVB) and acrylonitrile (AN) could be prepared as directly swellable in water by using purified DVB (98.8%) and technical DVB (79.3%) in the presence of 1,2-dichloroethane as porogen. Compared with the resins based on DVB and methyl acrylate (MA/DVB resins), the AN/DVB resins thus obtained are water-swellable over a wider range of copolymer compositions, and the swelling ability of the AN/DVB resins in water was further confirmed by investigating the water-swelling behavior of the AN/DVB resins undergoing solvent treatment. The copolymer composition (AN and DVB contents) of the resins and the property of the porogen affect the water-swellable behavior of the AN/DVB resins profoundly. The results in this paper provide additional evidence to support the hypothesis that the swelling ability of a hydrophobic porous copolymer in water originates from the existence of the inner stresses in the strained polymer network of the resins and the weak interaction between polymer and water that is negligible in the case of a conventional hydrophobic polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2041–2049, 2004

Water-Swellable Hydrophobic Porous Copolymers Based on Divinylbenzene and Methyl Acrylate: Preparation and Water-Swelling Behavior

Porous copolymers based on divinylbenzene (DVB) and methyl acrylate (MA) were prepared by suspension polymerization in the presence of toluene as porogen. By using purified DVB (98.8%), the resulting MA/DVB copolymers with a wide range of DVB contents were found to be able to swell in water directly, although both the homopolymers derived from DVB and MA are hydrophobic. The amounts of DVB and MA in the copolymers affect the water-swelling behavior profoundly. However, the direct swelling in water occurs only after the DVB or MA content reaches a critical value, and the effect of the MA content will be significant only when the DVB content is at a high level. The latter observation reflects the combined effect of the cross-linking density and the polymer polarity on the swelling ability of the MA/DVB copolymers in water. The nature of the direct swelling of these hydrophobic porous copolymers in water was discussed by considering both factors: the existence of the inner stresses in the strained polymer n...

Characterization and performance of membranes designed for macroencapsulation/implantation of pancreatic islet cells

Amphiphilic polymer membranes were synthesized for macroencapsulation of cells and characterized by select chemical and biological techniques. The membranes were prepared by crosslinking hydrophilic poly( N, N-dimethyl acrylamide) (PDMAAm) main chains with hydrophobic di-, tri-, and octa-methacrylate telechelic polyisobutylene (PIB) stars. The hydrophilic/hydrophobic composition and the molecular weights between crosslink sites (both M c,hydrophilic and M c,hydrophobic) were controlled by synthesis conditions. Small tubular membranes were made by in situ rotational copolymerization/crosslinking and filled with pancreatic rat islets. The water-swelling behavior, mechanical properties, and oxygen and insulin diffusion were studied. Macroencapsulatory performance of these membranes was investigated in vitro by macroencapsulation of pancreatic rat islets within tubular membranes for up to 1.5 months, and studying the insulin secreting ability of encapsulated islets in culture. The membranes are robust and maintain their integrity for the period of encapsulation. They allow oxygen and insulin diffusion. Macroencapsulated islets maintained their viability and insulin secretion over an extended period (i.e., 45 days).

Elastic Properties of Poly(N-isopropylacrylamide) and Poly(acrylamide) Hydrogels Studied by Scanning Force Microscopy

Poly(N-isopropylacrylamide) (PNIPAAm) and poly(acrylamide) (PAAm) hydrogels of varying cross-linker concentration were characterized for their swelling behavior in water. Local elastic properties of these hydrogels were studied using atomic force microscopy (AFM) in a temperature-controlled liquid cell. Elastic moduli (Young's moduli) of both PNIMAAm and PAAm hydrogels were determined at different temperatures and varying cross-linker concentrations. Spherical probes (micrometer sized) as well as sharp conical probes were used in force vs displacement data acquisition. Young's moduli were determined by evaluating the indentation of the gel surface as a function of the probing load. On PNIPAAm hydrogel surfaces a dramatic increase of the stiffness (up to 10 times) was observed when crossing the phase transition at ∼33 °C. The cross-linker concentration has a strong influence on Young's modulus for temperatures above the critical temperature while only small variations were seen for temperatures below 33 °C. PAAm hydrogels show a different behavior: Young's moduli were found to be just slightly dependent on the temperature though the cross-linker concentration again exerts a strong influence.

Lactam–amide graft copolymers as novel support for enzyme immobilization

AbstractA graft random copolymer of N‐vinyl‐2‐pyrrolidone and N,N′‐dimethylacrylamide onto polypropylene was synthesized using a simultaneous gamma radiation technique from a 60Co source, so that the hydrogel poly(propylene‐g‐vinylpyrrolidone‐co‐N,N′‐dimethylacrylamide) [PP‐g‐(VP‐co‐DMAM)], thus produced by grafting, could be used as a support for enzyme immobilization. The grafted spheres showed very good swelling behavior in water due to the incorporation of hydrophilicity in the PP spheres. The influence of pH and temperature on as well as the determination of the kinetic parameters, KM and Vmax, for both immobilized and soluble invertase were determined. PP‐g‐(VP‐co‐DMAM) grafting onto the PP spheres caused a significant change in the water content of the support and was more pronounced for the spheres with a high degree of grafting. A porous structure of the polymeric spheres was observed by scanning electron microscopy (SEM). The porous structure contributed to the reaction rate decrease due to diffusional effects, as shown by the larger KM value observed for immobilized invertase relative to the free enzyme. The enzyme affinity for the substrate (KM/Vmax) remains quite good after immobilization. The thermal stability of immobilized invertase was significatively higher than that of the free enzyme and a displacement of 20°C was observed for the immobilized enzyme. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 767–777, 2002; DOI 10.1002/app.10326

A novel thermosensitive soluble polypyrrole composite

Electrically conducting PPy/DBSA/poly(NiPAAm-co-AMPS) composites were synthesized by chemical oxidation of pyrrole using ammonium persulfate (APS) as the oxidant in an aqueous solution. Dodecylbenzene sulfonic acid (DBSA) and a copolymer, poly(NiPAAm-co-AMPS), of N-isopropyl acrylamide (NiPAAm) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) were used as a primary dopant and a co-dopant, respectively. We figured out poly(NiPAAm-co-AMPS) was incorporated into the PPy composite as the co-dopant through sulfate anion of AMPS. When more poly(NiPAAm-co-AMPS) was fed into the polymerization solution, more poly(NiPAAm-co-AMPS) existed in the resulting composite. Most of the composites showed good solubility in chloroform with extra DBSA. From the composite solutions, we cast free-standing films with excellent quality whose electrical conductivities were in the range of 10−2 to 5S/cm.We found the PPy composites exhibited moisture-dependent electrical conduction behavior. Electrical conductivity of the PPy composite increased with increase of moisture concentration in air, which resulted from the moisture absorbed by hydrophilic NiPAAm moiety in the composite. Moisture absorption by NiPAAm was confirmed by higher swelling ratio in water of the composites containing more NiPAAm moiety. We also found PPy/DBSA/poly(NiPAAm-co-AMPS) composites showed thermosensitive swelling behavior in water. The swelling ratios of PPy composites gradually decreased with temperature until 35°C, which is known as the lower critical solution temperature (LCST) of poly(NiPAAm). We, therefore, concluded the decrease of swelling ratio with temperature was caused by release of water from the composite by coagulation of the thermally sensitive NiPAAm moiety in the composite. We expect the moisture-dependent electrical conductivity and thermosensitive swelling behvior of the composite synthesized in this study may be useful for diverse attractive applications.

Synthesis and swelling properties of 2‐hydroxyethyl methacrylate‐co‐1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine hydrogels

AbstractA series of 2‐hydroxyethyl methacrylate/1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine (HEMA/VSIB) copolymeric gels were prepared from various molar ratios of HEMA and the zwitterionic monomer VSIB. The influence of the amount of VSIB in copolymeric gels on their swelling behavior in water and various saline solutions at different temperatures and the drug‐release behavior, compression strength, and crosslinking density were investigated. Experimental results indicated that the PHEMA hydrogel and the lower VSIB content (3%) in the HEMA/VSIB gel exhibited an overshooting phenomenon in their dynamic swelling behavior, and the overshooting ratio decreased with increase of the temperature. In the equilibrium water content, the value increased with increase of the VSIB content in HEMA/VSIB hydrogels. In the saline solution, the water content for these gels was not affected by the ion concentration when the salt concentration was lower than the minimum salt concentration (MSC) of poly(VSIB). When the salt concentration was higher than the MSC of poly(VSIB), the deswelling behavior of the copolymeric gel was more effectively suppressed as more VSIB was added to the copolymeric gels. However, the swelling behavior of gels in KI, KBr, NaClO4, and NaNO3 solutions at a higher concentration would cause an antipolyelectrolyte phenomenon. Besides, the anion effects were larger than were the cation effects in the presence of a common anion (Cl−) with different cations and a common cation (K+) with different anions for the hydrogel. In drug‐release behavior, the addition of VSIB increased the drug‐release ratio and the release rate. Finally, the addition of VSIB in the hydrogel improved the gel strength and crosslinking density of the gel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2888–2900, 2001

Radiation synthesis and characterization of polyDMAEMA hydrogel

Poly N, N-dimethylaminoethyl methacrylate (polyDMAEMA) hydrogels were synthesized by γ-irradiation technology, and the conditions of synthesis, such as total dose, dose rate, concentration of monomer and crosslinker in aqueous solution, were investigated. The property measurements of the hydrogels showed that they exhibited temperature sensitivity in a temperature range of 38–40°C and pH sensitivity at pH=2.5. They also had electric responsive behavior although it was not typical. The hydrogels synthesized were transparent and elastic and displayed good swelling behavior in water, therefore, they can be used as a kind of carrying material in drug delivery systems.

Chlorohydrin water-swellable rubber compatibilized by an amphiphilic graft copolymer. III. Effects of PEG and PSA on water-swelling behavior

Chlorohydrin water-swellable rubber—composed of chlorohydrin rubber (CHR), crosslinked polyacrylate (CPA), the amphiphilic compatibilizer poly(vinyl alcohol)-g-poly(butyl acrylate) (PVA-g-PBA), precipitated silica (PSA), and poly(ethylene glycol) (PEG)—was prepared. The dispersion of PEG in the blend was characterized by wide-angle X-ray diffraction (WAXD). The dependence of the water absorbing ratio by weight, the water-swelling ratio by volume, and the percentage loss by weight on PEG and PSA contents were investigated. The effects of PEG and PSA on the second water-swelling behaviors and long-term water-retention behaviors were also studied. Optimums for the water-absorbing and water-swelling abilities within the range of the experiment were obtained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2509–2516, 2001

Preparation and characterization of water-swellable natural rubbers

Water-swellable rubbers were prepared by dispersing the superabsorbent polymer particles, sodium polyacrylate particles, in natural rubber, and their water absorption properties were investigated. Sodium polyacrylate particles were synthesized using the inverse suspension polymerization technique, and their thermal and water absorption properties were characterized. The equilibrium water uptake in sodium polyacrylate particles was strongly dependent on both the salt concentration of aqueous media and crosslinking density of polymer. The dynamic and equilibrium water-swelling behavior of the prepared rubbers were significantly affected by addition of carbon black, hydrophilic polymer, and coupling agent. Those effects were well explained by microphotographic morphologies obtained using a scanning electron microscope. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 115–121, 2001

The effect of preparation temperature on the swelling behavior of poly (N-isopropylacrylamide) gels

The role of the preparation temperature of poly(N-isopropylacrylamide) (PNIPA) gels on their swelling behavior in water and in aqueous solutions of sodium dodecylbenzenesulfonate was investigated. PNIPA gels were prepared by free-radical crosslinking copolymerization of N-isopropylacrylamide and N,N'-methylene(bis) acrylamide in water at fixed monomer and crosslinker concentrations. The equilibrium swelling ratio of the gels increases first slightly up to about 20°C then rapidly with increasing gel preparation temperature. Magnitude of the collapse transition in water at 34°C becomes larger as the gel preparation temperature increases. Calculations indicate a decrease in the effective crosslink density of PNIPA gels with increasing preparation temperature. The gels prepared at temperatures higher then 20°C were heterogeneous consisting of highly crosslinked regions interconnected by the PNIPA chains.