Volume Swelling Ratio Research Articles

TiO2‐graphene dispersed sulfonated polyphenylenesulfide sulfone nanocomposites for medium temperaturePEMFCs

AbstractSulfonated polyphenylene sulphide sulfone (sPPSS) loaded with titania‐graphene (TiO2‐GNS) was synthesized by the polycondensation method and studied their suitability towards proton exchange membrane fuel cell applications. The structural, morphological, and physic‐chemical properties of sPPSS nanocomposites containing varying amounts of (1%, 2%, 3%, and 5%) TiO2‐GNS was investigated by Fourier transform infrared, H1‐NMR, P‐XRD, FE‐SEM, HR‐TEM, Raman spectrum, swelling ratio (SR), water uptake, thermal analysis, oxidative stability (OS) and proton conductivity. Further, the obtained TiO2‐GNS dispersed polymer membrane exhibits greatly reduced water absorption 4.44% and a less volume SR (15.6%). The 5 wt% TiO2‐GNS dispersed sPPSS nanocomposites exhibited a PC value around 2.03 × 10−2 S/cm at 110°C. The sPPSS nanocomposites membrane confirmed admirable OS with a maximum degradation of 39.15% during immersed in the Fenton reagent for 6 h at 80°C.

Preparation of physically crosslinked polyelectrolyte Gelatin-Tannic acid-κ-Carrageenan (GTC) microparticles as hemostatic agents

In humans, excessive bleeding during civilian accidents, and surgery account for 40% of the mortality worldwide. Hence, the development of biocompatible hemostatic materials useful for rapid hemorrhage control has become a fundamental research problem in the biomedicine community. In this study, we prepared biocompatible gelatin-tannic acid-κ-carrageenan (GTC) microparticles using a facile Tween 80 stabilized water-in-oil (W/O) emulsion method for rapid hemostasis. The formation of GTC microparticles occurs via polyelectrolyte interactions between gelatin and k-carrageenan as well as hydrogen bonding from tannic acid. In addition, the GTC microparticles formulated in our study showed high water adsorption ability with a low volume-swelling ratio for a particle size of 46 μm. In addition, the GTC microparticles displayed >80% biocompatibility in NIH 3T3 cells and <5% hemocompatibility in hemolysis ratio tests. Notably, the GTC microparticles induced rapid blood clotting in 50 s and blood loss of approximately 46 mg in the femoral artery of BALB/c female mice with a 100% survival rate that was significantly better than the control group (blood clot time:250 s; blood loss: 259 mg). Thus, the findings from our study collectively suggest that GTC microparticles may play a promising clinical role in medical applications to tackle hemorrhage control.

Semi-interpenetrating Network Membrane from Polyethyleneimine-Epoxy Resin and Polybenzimidazole for HT-PEM Fuel Cells

In the present work, a semi-interpenetrating network (semi-IPN) high-temperature proton exchange membrane based on polyethyleneimine (PEI), epoxy resin (ER), and polybenzimidazole (PBI) was prepared and characterized, aiming at their future application in fuel cell devices. The physical properties of the semi-IPN membrane are characterized by thermogravimetric analysis (TGA) and tensile strength test. The results indicate that the as-prepared PEI-ER/PBI semi-IPN membranes possess excellent thermal stability and mechanical strength. After phosphoric acid (PA) doping treatment, the semi-IPN membranes show high proton conductivities. PA doping level and volume swelling ratio as well as proton conductivities of the semi-IPN membranes are found to be positively related to the PEI content. High proton conductivities of 3.9 ∽ 7.8 × 10 − 2 S c m − 1 are achieved at 160°C for these PA-doped PEI-ER/PBI series membranes. H2/O2 fuel cell assembled with PA-doped PEI-ER(1 : 2)/PBI membrane delivered a peak power density of 170 mW cm-2 at 160°C under anhydrous conditions.

Changes of water related properties in radiata pine wood due to heat treatment

Wood is a green and renewable building material, however, the hygroscopicity restrict its use in the field of construction and building. To study the effect of heat treatment (HT) on wood hygroscopicity and other water related properties, radiata pine wood was subjected to HT at four temperature levels of 185, 200, 215 and 230 °C, for the duration of 4 h. Overall, the equilibrium moisture content, moisture adsorption, water absorption and volume swelling ratio were all decreased, while hygroscopic hysteresis was enhanced with increasing HT temperature. The surface wettability was clearly weakened after HT, reflected as the increased contact angle and reduced surface free energy.

Preparation and characterization of porous cationic poly[styrene‐co‐(N,N′‐dimethylaminoethyl methacrylate)] nanoparticles and their adsorption of heavy metal ions in water

AbstractUsing styrene (St) and N,N′‐dimethylaminoethyl methacrylate (DMAEMA) as raw materials, monodispersed P(St‐co‐DMAEMA) nanoparticles (NPs) were first prepared via semi‐continuous emulsion polymerization, and using a stepwise acid–alkali post‐treatment, porous P(St‐co‐DMAEMA) NPs were then obtained and used to adsorb heavy metal ions in aqueous phase. Results showed that the post‐treatment conditions including temperature, initial pH and time of acid–alkali treatment had significant effects on the morphology of the porous P(St‐co‐DMAEMA) NPs, with higher temperature, more extreme pH condition and longer treatment time resulting in larger pores and volume swelling ratio. Under the optimized acid–alkali post‐treatment conditions (60 °C, acid treatment at pH = 4.0 for 1 h and then alkali treatment at pH = 10.0 for 1 h), the obtained porous NPs had nearly 15 times the surface area and 1.5 times the amount of surface amino groups than the corresponding solid NPs. An analysis of the mechanism of metal ion adsorption on the porous NPs indicated that the adsorbed amount of metal ions was the result of synergistic effect of physical and chemical adsorption, which was closely related to the porous NP surface area, amount of surface of amino groups and the volume of the ions. © 2018 Society of Chemical Industry

Oral tissue response to soft tissue expanders prior to bone augmentation: in vitro analysis and histological study in dogs.

PurposeTo determine whether the swelling and mechanical properties of osmotic self-inflating expanders allow or not the induction of intraoral soft tissue expansion in dogs.MethodsThree different volumes (0.15, 0.25, and 0.42 mL; referred to respectively as the S, M, and L groups) of soft tissue expanders (STEs) consisting of a hydrogel core coated with a silicone-perforated membrane were investigated in vitro to assess their swelling behavior (volume swelling ratio) and mechanical properties (tensile strength, tensile strain). For in vivo investigations, the STEs were subperiosteally inserted for 4 weeks in dogs (n=5). Soft tissue expansion was clinically monitored. Histological analyses included the examination of alveolar bone underneath the expanders and thickness measurements of the surrounding fibrous capsule.ResultsThe volume swelling ratio of all STEs did not exceed 5.2. In tensile mode, the highest mean strain was registered for the L group (98.03±0.3 g/cm), whereas the lowest mean value was obtained in the S group (81.3±0.1 g/cm), which was a statistically significant difference (P<0.05). In addition, the S and L groups were significantly different in terms of tensile strength (1.5±0.1 g/cm for the S group and 2.2±0.1 g/cm for the L group, P<0.05). Clinical monitoring showed successful dilatation of the soft tissues without signs of inflammation up to 28 days. The STEs remained volumetrically stable, with a mean diameter in vivo of 6.98 mm, close to the in vitro post-expansion findings (6.69 mm). Significant histological effects included highly vascularized collagen-rich fibrous encapsulation of the STEs, with a mean thickness of 0.67±0.12 mm. The bone reaction consisted of resorption underneath the STEs, while apposition was observed at their edges.ConclusionsThe swelling and mechanical properties of the STEs enabled clinically successful soft tissue expansion. A tissue reaction consisting of fibrous capsule formation and bone loss were the main histological events.

Using intra-microgel crosslinking to control the mechanical properties of doubly crosslinked microgels.

Microgels (MGs) are crosslinked polymer particles that swell when the pH approaches the pKa of the constituent polymer. Our earlier work showed that concentrated MG dispersions can be covalently interlinked to form macroscopic hydrogels, which are termed doubly crosslinked microgels (DX MGs). Here, we study for the first time the effects of intra-MG crosslinking on the swelling of the MGs and the mechanical properties of the DX MGs. The MGs were synthesised by emulsion copolymerisation of ethyl acrylate (EA) or methacrylic acid (MAA) and divinylbenzene (DVB). The latter was a crosslinking monomer. For comparison, MGs were prepared where DVB was replaced by either 1,4-butanediol diacrylate (BDDA) or a 1 : 1 mixture of both DVB and BDDA. The MG swelling behaviours were studied by dynamic light scattering; whereas, the DX MG mechanical properties were studied by dynamic rheology and uniaxial compression measurements. Inclusion of DVB within the MGs resulted in both highly swelling MGs and highly ductile DX MGs. The average strain-at-break value for the DVB-containing DX MGs was 76% which represents the highest value yet reported for a DX MG prepared using commercially available monomers. It was also shown that good tuneability of the DX MG properties could be obtained simply by controlling the DVB and BDDA contents within the MG particles. Analysis of the swelling and compression data enabled relationships between the volume-swelling ratio of the MGs and either the modulus or strain-at-break values for the DX MGs. These relationships also applied to a DVB-free system prepared with a low BDDA content. An interesting conclusion from this study is that the DX MGs can be thought of mechanically as macroscopic MG particles. The results of this study provide design tools for improving DX MG ductility and hence increasing the range of potential applications for this new class of hydrogel.

A novel phosphoric acid doped poly(ethersulphone)-poly(vinyl pyrrolidone) blend membrane for high-temperature proton exchange membrane fuel cells

A high-temperature proton exchange membrane, poly(ethersulphone)-poly(vinyl pyrrolidone) (PES-PVP) blend membrane is successfully prepared by scalable polymer blending method. The physical properties of blend membrane are characterized by DSC, TG and tensile strength test. The DSC and TG results indicate PES-PVP blend membranes possess excellent thermal stability. After phosphoric acid (PA) doping treatment, the blend membrane shows enhanced proton conductivity. PA doping level and volume swelling ratio of the blend membrane are found to be positively related to the PVP content. A high proton conductivity of 0.21 S/cm is achieved at 180 °C for PA doped PES-PVP 80% with a PA doping level of 9.1. PEM fuel cell based on PA doped PES-PVP 80% membrane shows a high power density of 850 mW/cm2 and outstanding stability at 180 °C without extra humidification.

Preparation and characterization of cationic pH-sensitive SiO2/polymer core-shell nanoparticles with amino groups in the shell

Silica/poly(styrene-N,N′-dimethylaminoethyl methacrylate) (SiO2/P(St-DMAEMA)) cationic pH-responsive core-shell particles with a narrow size distribution and diameter of less than 200 nm were synthesized by emulsion polymerization. The effects of the St/DMAEMA molar ratio, SiO2 core size, monomer amount, and cross-linking degree on the morphology and pH-responsiveness of the core-shell particles were investigated by transmission electron microscopy, dynamic light scattering, and conductometric titration. The results showed that core-shell particles with only one SiO2 core could be obtained when the cross-linker divinyl benzene (DVB) was used, and the diameter of the core-shell particles increased with the size of the SiO2 core and the total amount of monomer. It was observed that the amount of surface amino groups, zeta potential, and volume swelling ratio of the core-shell particles were significantly affected by the St/DMAEMA molar ratio, and a high volume swelling ratio was achieved at pH 4 and a DVB content of 3 mol%. The zeta potential was observed to be a function of pH, and the particles were positively charged when the pH value was below approximately 7.2.

Baclofen novel gastroretentive extended release gellan gum superporous hydrogel hybrid system: in vitro and in vivo evaluation

Baclofen is a centrally acting skeletal muscle relaxant with a short elimination half-life, which results in frequent daily dosing and subsequent poor patient compliance. The narrow absorption window of baclofen in the upper gastrointestinal tract limits its formulation as extended release dosage forms. In this study, baclofen extended release superporous hydrogel (SPH) systems, including conventional SPH, SPH composite and SPH hybrid (SPHH), were prepared aiming to increase the residence of baclofen at its absorption window. The applicability of different polymers, namely, gellan gum, guar gum, polyvinyl alcohol and gelatin, was investigated in preparation of SPHH systems. The prepared SPH systems were evaluated regarding weight and volume swelling ratio, porosity, mechanical properties, incorporation efficiency, degree of erosion and drug release. In vivo assessment was performed in dogs to evaluate gastric residence time by X-ray studies. In addition, the oral bioavailability of baclofen relative to commercially available Lioresal® immediate release tablets was also investigated. The novel baclofen gellan SPHH cross linked with calcium chloride was characterized by optimum mechanical properties, acceptable swelling properties as well as extended drug release. It also exhibited a prolonged plasma profile when compared to twice daily administered Lioresal®.

Synthesis and application of cinnamate-functionalized rubber for the preparation of UV-curable films

A butyl rubber derivative that can be cured upon exposure to UV light in the absence of additional chemical additives was developed. This polymer was prepared by the reaction of hydroxyl-functionalized butyl rubber with cinnamoyl chloride to provide a cinnamate functionalized rubber. The cinnamate content was varied by starting with derivatives prepared from butyl rubber containing either 2 or 7mol% isoprene. The kinetics of the cross-linking was studied by UV–visible spectroscopy and it was found to vary according to the film thickness. The changes in gel content and volume swelling ratio with irradiation time were dependent on the cinnamate content. Toxicity studies suggested that the cross-linked materials do not leach toxic molecules. The approach was also applied to obtain cross-linked films of butyl rubber-poly(ethylene oxide) graft copolymers, leading to surfaces that resisted the adhesion and growth of cells. Thus the approach is versatile and is of particular interest when non-leaching coatings of cross-linked butyl rubber are desired for biomedical or other applications.

Hydrophilic and flexible polyurethane foams using sodium alginate as polyol: Effects of PEG molecular weight and cross-linking agent content on water absorbency

Hydrophilic and flexible polyurethane foams were prepared using sodium alginate as a polyol, and characterized by optical microscopy, FT-IR spectroscopy, density measurements, volume swelling, and water absorbency. Optical microscopy revealed that the resulting cells were closed with round and elongated shapes. FT-IR confirmed that the urethane linkages were formed between the isocyanate and sodium-alginate. As an indirect measurement of porosity, the apparent density indicated an initial decrease followed by an increase with increasing glycerin content. The volume-swelling ratio was initially constant, followed by a gradual decrease with glycerin content. The volume swelling ratio increased with PEG molecular weight. The water absorbency initially increased, followed by a decrease with increasing glycerin content. The correlation-ships between water absorbency, density, and volume-swelling ratio indicated that the absorbency was predominantly influenced by density when the PEG molecular weight was low and was greatly affected by the volume-swelling ratio when the PEG molecular weight was relatively high.

Novel beaded polymers from telechelic methacrylic ether esters

A series of telechelic dimethacrylic ether-esters (MEE) were prepared by solventless reaction of α,ω-dihydroxy poly(oxytetramethylene) (polytetrahydrofuran, PTHF) with phthalic anhydride and glycidyl methacrylate (GMA). MEE was polymerized with GMA as well as GMA–ethylene dimethacrylate (EGDM) to form porous beads. The terpolymer beads were observed using optical microscopy and SEM and characterized for internal pore volume, equilibrium volume–swelling ratio and dimethyl formamide and aqueous buffer regain. The morphology of the beads was dictated by the mole fraction and molecular weight of MEE in the feed. Porosity was found to increase with increase in molecular weight of MEE. Thus, porosity as high as 49%, 50% and 55% was observed with MEE of molecular weights 1580, 2580 and 3480, respectively. At a specific terpolymerization feed ratio of monomers, the terpolymers formed transform from gel like structure into a macroporous one, with increase in molecular weight of MEE.

Surface modification on poly (EGDMA- co-HEMA) synthetic matrices to be used as specific adsorbents

The preparation and modification of ethylene glycol dimethacrylate/2-hydroxyethyl methacrylate copolymers [poly (EGDMA- co-HEMA)] were carried out to study their properties on Immobilized Metal Ion Affinity Chromatography (IMAC). For that purpose, the adsorption–desorption assays of a phosphoprotein, ovalbumin (OVA) on different ion-containing adsorbents were investigated. The metal ion-complexing agent used was iminodiacetic acid (IDA) and the metal ions chelated were Al 3+ or Fe 3+. The efficiency on both modification reactions and OVA retention was analysed taking into account the pore volumes ( V p) and specific surface area ( S s) values in macropores zones and equilibrium volume-swelling ratio ( q v) from base matrices and final ion-containing supports. In general, Fe 3+-containing products resulted more efficient adsorbents in the OVA retention and although the adsorption assays on Fe 3+ or Al 3+-containing supports were fast, the complete and faster OVA desorption was reached when Al 3+-containing matrix was used.

Degradation of phospholipid polymer hydrogel by hydrogen peroxide aiming at insulin release device

The purpose of this study is to ascertain the applicable possibility of H 2O 2 degradable hydrogel for fabrication of insulin release system synchronized with the change in the glucose concentration in the medium. The hydrogel was prepared by using 2-methacryloyloxyethyl phosphorylcholine (MPC) and crosslinker. The favorable characteristic of the hydrogel was H 2O 2 concentration responsive degradation. The H 2O 2 was utilized and produced by enzymatic reaction between glucose oxidase and glucose. Poly(MPC) (PMPC) was easily degraded in H 2O 2 aqueous solution, and the PMPC hydrogel was also degraded in H 2O 2 aqueous solution. The degradation mechanism was considered to be main chain scission of PMPC. The degradation profile was evaluated by using weight swelling ratio and volume swelling ratio. The weight swelling ratio of PMPC hydrogel firstly increased due to the reduction of crosslink density, then the ratio decreased to zero (complete degradation). The degradation profile was proportional to the H 2O 2 concentration. Furthermore, volume swelling ratio also increased, and complex elastic modulus decreased with degradation in H 2O 2 aqueous solution. These results indicated that the hydrogel was degraded by hydroxy and/or hydroperoxy radicals which was produced by H 2O 2, the crosslink density and mechanical property decreased. The release profile from the hydrogel was estimated by using lipid microsphere (LM) as an insulin model. The LM was released with the degradation of PMPC hydrogel. Taking these results into account, the PMPC hydrogel was available for H 2O 2 degradable hydrogel for synchronization with glucose concentration by using enzymatic reaction.

Network structure of cellulose ethers used in pharmaceutical applications during swelling and at equilibrium.

The purpose of this work was to investigate the swelling behavior of four cellulose ethers that differ in their type and degree of substitution and to elucidate the network structure of the swollen matrices under dynamic and equilibrium conditions. Dynamic vapor sorption was performed to assess the ability of polymer chains and water molecules to interact. Dynamic and equilibrium swelling studies were performed to calculate molecular parameters of swollen polymers using the Flory-Rehner theory. We determined the volume-swelling ratio of the polymer matrices and observed that it was dependent on their hydrophilicity. We determined molecular parameters that characterize the swollen hydrogels of cellulose derivatives, such as the polymer volume fraction in the swollen state, u2,S, the effective molecular weight of the polymer chain between physical entanglements, Me, the number of repeating units between two entanglements, u, and the number of entanglements per chain, e. The Me of the cellulose derivatives studied varied significantly depending on the type of cellulose ether and on the swelling time. The order of mesh size, an important parameter for predicting drug diffusion and release, taking into account all determined parameters, is: hydroxypropyl cellulose < hydroxyethyl cellulose < hydroxypropyl methyl cellulose K100M < hydroxypropyl methyl cellulose K4M.

Release Behavior of High Molecular Weight Solutes from Poly(ethylene glycol)-Based Degradable Networks

Water-soluble PEG-based macromers containing oligomeric blocks of a hydrolyzable α-hydroxy acid were synthesized and photopolymerized to form degradable hydrogels to control the release of high molecular weight, hydrophilic solutes. First, network mesh size and volume swelling ratio during the degradation process were characterized to understand fundamentally the effect of hydrogel degradation kinetics and subsequent changes in network structure on solute release. Second, the release behavior was examined and related to the swelling and structural properties of the hydrogels; experimental results show that solute transport can be diffusion controlled or degradation controlled depending on the relative size of the hydrogel mesh size to the solute. Finally, the ability to tailor the release from multilaminated biodegradable hydrogels to obtain an approximate zero-order release profile was studied theoretically.