Initial Swelling Research Articles

Quantifying the equilibrium swelling responses and swelling-induced snap-through of heterogeneous spherical hydrogels

We employ the finite deformation theory to analyze the inhomogeneous large deformation of a heterogeneous spherical hydrogel subjected to chemo-mechanical loadings. The heterogeneous spherical hydrogel is composed of two concentric spherical hydrogel layers with different material properties. The Gent model is employed for the free energy function of the polymer stretching part in order to tackle the effect of the limiting chain extensibility. The heterogeneous spherical hydrogel is assumed to be perfectly bonded at the interface and is traction free at the external surface. At the internal surface, two boundary conditions are considered: one is internally fixed and the other is internally pressurized. Numerical examples are performed to describe the nonlinear behaviors of a heterogeneous spherical hydrogel when subjected to the swelling and mechanical loadings. For internally fixed case, numerical results show that the limiting chain extensibility and the initial swelling ratio have significant effect on the actuation deformation of a heterogeneous spherical hydrogel. For internally pressurized case, we find that the swelling-induced snap-through instability can be triggered under specified conditions. It is shown that the chemo-mechanical behaviors of the heterogeneous spherical hydrogels can be adjusted by tuning the material properties and the initial swelling ratios.

Recycled Crushed Ceramic Rubble for Improving Highly Expansive Soil

The recycling of waste materials (that polluted the environment) to mitigate and improve the poor geotechnical properties of difficult soils represents one of the sustainable solutions to reduce the negative effects of the waste. The potential for using recycled crushed ceramic rubble (RCCR), from building rubble, as a stabilizer for expansive soil was studied. Five different percentages of two gradations of RCCR were prepared and added to highly expansive soil (HES). The effects of RCCR on geotechnical properties and swelling stages of the soil were investigated. Characterization for the microstructure of natural and stabilized soil was carried out by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). It was found that, regardless of its gradation, RCCR reduces the values of Atterberg limits and optimum water content of the soil. RCCR caused an increase in specific gravity and maximum dry unit weight. The RCCR increased soil strength from 208 to 435 kPa. The curing of HES–RCCR mixtures for 7 days led to significant improvement in strength values. Based on the nonlinear regression, there was a perfect nonlinear relationship found between RCCR and soil strength. On the other hand, RCCR caused 24 to 71% reduction in maximum swelling percent. The magnitude of the total swell decreased by increasing the size of RCCR material or increasing the content of this material, regardless of its size. The mixing of RCCR with HES increased the time required to complete both the initial and primary soil swelling, while the secondary swelling time reduced. However, the maximum RCCR content, to achieve the maximum strength and minimum swell percent, was 30% for both gradations of RCCR. There are compounds with cementation nature formed due to mixing RCCR with HES: such compounds are responsible for the development of strength and mitigation of swell effect. The current results indicate that RCCR is technically practicable in soil stabilization.

Comparison between isolated and associated with codeine acetaminophen in pain control of acute apical abscess: a randomized clinical trial.

The study aimed to compare the acetaminophen administration efficacy or its combination with codeine for pain control in acute apical abscesses cases. Thirty-nine patients who sought emergency treatment in the Faculty of Dentistry of the Federal University of Rio Grande do Sul were included, all of them with acute apical abscess diagnosis. These patients were divided into two groups: acetaminophen group-prescription of acetaminophen (1000mg) and acetaminophen-codeine group-prescription of acetaminophen (1000mg) + codeine (30mg), both with oral intake every 6h for 3days. The pain scores were recorded by the patients on their own at 6, 12, 24, 48, and 72h after finishing clinical assistance, by filling a pain evolution journal, containing a visual analogue scale (VAS). Student t test was conducted to investigate different mean ages between groups 1 and 2. A comparison of weight and means of initial pain scores between groups was carried out using the Mann-Whitney U test. Chi-square test was performed to compare gender, affected tooth, education, initial swelling, and frequency of adverse effect between test and control groups. Mann-Whitney U test was applied to compare groups in the same period. Friedman's test was used to compare results from the same group over time. Both groups showed score reduction over time (P < 0.05). Paracetamol-codeine group showed significant pain score reduction at 48h registers when compared to baseline and at 6h scores (P < 0.05). Further, pain scores at 72h were significantly lower, when compared to the baseline, at 6h, and at 12h scores (P < 0.05). Acetaminophen group showed significant pain score reduction observed at 72h, when compared to the baseline and at 6h scores (P < 0.05). There were no significant differences in pain score reduction over time between groups (P > 0.05). There was no difference between the groups regarding the frequency of adverse reactions (P > 0.05). Both medications were effective for pain control in acute apical abscess cases. The findings might have inferred in pain control of acute apical abscess associated pain in patients who used an antibiotic drug. External validity of the findings for acute apical abscess cases with no need for an antibiotic prescription is uncertain. This paper suggests acetaminophen 1000mg can be used for pain control in the treatment of acute apical abscess associated with systemic manifestation.

Mechanically Reinforced Localized Structure Design to Stabilize Solid-Electrolyte Interface of the Composited Electrode of Si Nanoparticles and TiO2 Nanotubes.

Silicon anode with extremely high theoretical specific capacity (≈4200 mAh g-1 ), experiences huge volume changes during Li-ion insertion and extraction, causing mechanical fracture of Si particles and the growth of a solid-electrolyte interface (SEI), which results in a rapid capacity fading of Si electrodes. Herein, a mechanically reinforced localized structure is designed for carbon-coated Si nanoparticles (C@Si) via elongated TiO2 nanotubes networks toward stabilizing Si electrode via alleviating mechanical strain and stabilizing the SEI layer. Benefited from the rational localized structure design, the carbon-coated Si nanoparticles/TiO2 nanotubes composited electrode (C@Si/TiNT) exhibits an ideal electrode thickness swelling, which is lower than 1% after the first cycle and increases to about 6.6% even after 1600 cycles. While for traditional C@Si/carbon nanotube composited electrode, the initial swelling ratio is about 16.7% and reaches ≈190% after 1600 cycles. As a result, the C@Si/TiNT electrode exhibits an outstanding capacity of 1510 mAh g-1 at 0.1 A g-1 with high rate capability and long-time cycling performance with 95% capacity retention after 1600 cycles. The rational design on mechanically reinforced localized structure for silicon electrode will provide a versatile platform to solve the current bottlenecks for other alloyed-type electrode materials with large volume expansion toward practical applications.

Effect of Dietary Supplementation of Manganese, Chromium and Cobalt on Semen Qualities in Sahiwal Bulls

The present study was conducted to evaluate the effect of supplemental manganese (Mn), chromium (Cr) and cobalt (Co) on semen qualities in Sahiwal bulls. Twelve Sahiwal bulls divided into three groups T1, T2 and T3 based on their similar semen volume and concentration and were fed with 0, 1.5 and 2.0 times higher Mn, Cr and Co over and above the basal diet (ICAR, 2013) in T1, T2 and T3, respectively, for a period of 120 days. Semen was collected in all the groups twice a week and evaluated for quantitative and qualitative attributes. It was found that additional supplementation of Mn, Cr and Co had no influence on body weight gain, intake and digestibility of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF)]. Seminal mass motility, initial progressive motility, live spermatozoa, normal spermatozoa, intact acrosome and hypo-osmotic swelling test (HOST) positive sperm count was higher (P less than 0.05) in T3 group in comparison to T1 and T2 groups of fresh as well as frozen semen. Blood superoxide dismutase (SOD) activity was higher (P greator than 0.05) in both T2 and T3 than T1. A reduction (P less than 0.05) in lipid peroxidation activity (LPO) in fresh and frozen semen in T3 group was observed. It may be concluded that dietary supplementation of Mn @ 30 ppm, Co @ 0.22 ppm and Cr @ 2 ppm, respectively per day per Sahiwal bull can improve the qualitative and quantitative attributes of semen.

Effect of photoinitiator concentration on hygroscopic stability of UV cured precision replicated composite optics.

Replicated composite optics is a promising technique to fabricate high-quality mirrors with reduced weight and processing time compared to conventional glass mirrors; however, the optical layer is organic and susceptible to environmentally-induced dimensional changes, specifically to moisture exposures. Generally, to enhance polymer stability, thermal curing is necessary to maximize the cure state. Because replications are bonded, thermal exposures generate residual stresses that degrade optical quality. In this paper, the cure state of a UV-cured epoxy with RT processing was varied by changing the photoinitiator (PI) concentration, and the replication stability was evaluated in different humidity environments by laser interferometry. Increasing the PI concentration transformed the epoxy microstructure from homogenous to a more phasic network, as evidenced by both DMA and AFM, resulting in significant changes to the Tg, modulus, and moisture absorption. When replications were exposed to moisture, they experienced initial swelling followed by stress relaxation to net-zero regardless of initial processing stress. Reduced PI concentrations exhibited higher moduli and shorter swelling periods, with dimensional changes as small as 35 nm and complete stress relaxation in days. TTS master curves describing stress relaxation behavior correlated well with the observed behavior in replicated mirror samples. Furthermore, it was shown that the relieved stress persisted through multiple humidity cycles between 100% to 0% RH. These results show that high-humidity conditioning treatments can be utilized to eliminate residual stress in as-fabricated replicated mirrors over just a few days, providing a viable manufacturing and processing route for highly precise and stable replicated composite mirrors.

Characterization of blends of virgin nitrile rubber and compounded nitrile rubber latex waste reclaimed with urea. Part 1: Cure characteristics

The objectives of this study were to develop a cost-effective, environmental-friendly, mechanochemical reclaiming process for compounded nitrile rubber (NBR) latex waste generated from the dipping and treatment plants of the glove manufacturing process and evaluate properties of reclaimed NBR and virgin NBR/reclaimed NBR blend compounds. Initially, compounded NBR latex waste containing NBR latex mixed with compounding ingredients was dried and reclaimed mechanically by varying the milling time from 0 min to 12.5 min at 2.5-min time interval. Properties such as initial plasticity, Mooney viscosity, swelling, and cross-link density of the mechanically reclaimed NBR samples were evaluated. Also, a series of mechanochemically reclaimed NBR samples were produced using urea and varying its amount from 0 phr to10 phr at 2 phr intervals and milling according to the selected milling time. The mechanochemically reclaimed NBR samples were also tested for the above properties. Finally, a reclaimed NBR sample was prepared by applying the best urea loading and the optimum milling time. Further, a series of virgin NBR/reclaimed NBR blend compounds was prepared by varying the reclaimed NBR from 0% to 70% at 10% interval. Cure characteristics of the above blend compounds were evaluated and compared with those of the 100% virgin NBR (control) compound. Initial plasticity and Mooney viscosity of mechanochemically reclaimed NBR revealed that urea is effective as a reclaiming agent for dried compounded NBR latex waste. Results in overall indicated that 5 min is the optimum milling time and 6 phr is the optimum loading of urea required to produce the best reclaimed NBR in terms of properties and energy consumption. Minimum torque and cure time of the 50:50 virgin NBR/reclaimed rubber blend compound were higher compared to the control, whereas scorch time, maximum torque, and cure rate index of the former were lower compared to the latter.

Effect of 2-(dimethylamino) Ethyl Methacrylate on Nanostructure and Properties of pH and Temperature Sensitive Cellulose-Based Hydrogels.

The novel double responsive cellulose/poly 2-(dimethylamino) ethyl methacrylate (PDMAEMA) hydrogel was synthesized via in situ free radical polymerization. The results from light transmittance measurements, scanning electron microscopy (SEM), mechanical property testing as well as swelling experiments demonstrated that DMAEMA played a significant impact on in hydrogel's nanostructure.With increasing DMAEMA concentration, the transparency of hydrogels dropped and texture became softer. The incorporation of relatively hard cellulose and increase in crosslink density significantly enhanced 3D network structure of hydrogel. The tensile strength, compression and bending capabilities of the composite responsive hydrogels were fine with the DMAEMA in a certain range. When the DMAEMA concentration increased to 6 g/g(cellulose), the mechanical strength decreased noticeably. An increase in DMAEMA concentration resulted in a faster initial swelling rate and higher equilibrium swelling ratio. Further, three-dimensional structure and increase of DMAEMA concentration can also improve pH and temperature response sensitivity of hydrogels. Thus, the mechanical, swelling and responsive properties of hydrogel could be adjusted by the DMAEMA and polymerization modes.

Pseudotumor recurrence in a post-revision total hip arthroplasty with stem neck modularity: A case report

This unique presentation of hip swelling is only the seventh reported case of pseudotumor recurrence in a non-metal-on-metal total hip arthroplasty (THA) construct. The constellation of patient symptoms and laboratory findings contradict the expected elevated serum metal ion levels associated with the formation of pseudotumor. The presentation, lab trends, and imaging findings contribute to the growing base of knowledge surrounding the effects of corrosion in arthroplasty constructs with stem-neck modularity. A 74-year-old man status post primary THA presented with left hip swelling and elevated serum metal ions five years after implantation of a modular stem-neck prosthesis. The swelling was diagnosed as pseudotumor based on laboratory trends and imaging findings and was treated with revision arthroplasty that completely resolved the initial hip swelling. The patient presented with recurrent hip swelling and recurrent pseudotumor findings on imaging in the same hip four months later. Non-operative management with ultrasound-guided hip aspiration resulted in symptom relief and resolution of the recurrent swelling. After one year of follow-up, the patient had no further recurrences of hip swelling. This case of post-revision pseudotumor recurrence elucidates attributable patient, surgical, and implant factors with a discussion of diagnostics, management, and prognosis for patients with pseudotumor in non-metal-on-metal arthroplasty constructs.

Numerical simulation of the evaporation characteristics of a dimethyl ether droplet in supercritical environment

The unsteady spherically symmetrical evaporation of a dimethyl ether droplet in supercritical environment is modelled, considering real gas effects, Soret and Dufour effect, variable thermodynamic properties effects and high- pressure vapor-liquid phase equilibrium. The interface between droplet and environment disappears when it reaches the critical temperature of dimethyl ether-nitrogen system. Subsequently, the evaporation becomes a pure diffusion issue. The calculated results indicate the solubility of the ambient gas in the liquid phase is significant under supercritical conditions, and the temporal evolution of the interface temperature, reduced droplet diameter and dimethyl ether mole fraction are obtained under supercritical conditions as well. The influence of ambient pressure and temperature above critical point on the droplet evaporation characteristics was systematically investigated. Supercritical environment leads to a larger initial swelling of the droplet, when the reduced ambient pressure is 2.0 and temperature is 1.5, the maximum swelling of droplet is 7.7% larger than the initial value. Higher ambient pressure also leads a shorter fuel droplet lifetime in supercritical environment, When the reduced ambient temperature is 1.5, and the reduced pressure is varying from 1.0 to 1.5, the droplet evaporation lifetime of the dimethyl ether is reduced by 11.1%. The ambient temperature affects the droplet evaporation characteristics in a similar manner as the ambient pressure.

Triple La Sota re-vaccinations can protect laying chickens for 3 months against drop in egg production caused by velogenic viscerotropic Newcastle disease virus infection.

One hundred and ten Isa Brown layers were vaccinated with La Sota, once at point of lay at 18 weeks and three times at peak of lay which occurred at 27–29 weeks of age. Thereafter, they were weekly monitored for haemagglutination inhibition (HI) antibody decline. The first batch A of the layers were challenged with velogenic viscerotropic Newcastle disease (vvND) virus (vvNDV) on day 24 post‐vaccination (PV), when the geometric mean titre (GMT) was 84.4, batch B were challenged on day 48 PV at GMT of 42.2, while batch C were challenged on day 97 PV at GMT of 21.1. The individual chicken HI antibody titres of the 10 layers in batch C at the day of challenge were: 7 layers had HI titres of 16, 2 layers had HI titres of 32 and 1 layer had HI titres of 64. Each challenge in the three batches produced no clinical signs including drop in egg production. But there was initial swelling of the spleen followed by atrophy with high antibody responses. The virus was recovered in all the cloacal swabs on days 3–9 post‐challenge (PC) at low titres. On days 145 PV and 48, post‐Batch C challenge the remaining hyperimmunized unchallenged layers demonstrated a drop in total % egg production (p < .05) and changes in egg quality. The HI GMT was 256. The virus was recovered in all the cloacal swabs on days 3–9 following appearance of clinical signs. There was no mortality in the experiment. Based on the above observations, it is concluded that triple La Sota re‐vaccination can protect layers against a drop in egg production in areas where vvNDV infection is enzootic.

Congenital urethral dilatation in cattle calves: Diagnosis and surgical intervention.

Background and Aim:Congenital anomalies of the urinary system are common affections in ruminants. Dilatation of the pelvic urethra is one of these affections in which the pelvic urethra dilated than normal diameter. This study aimed to explain the diagnosis and surgical treatment of urethral dilatation in cattle calves.Materials and Methods:Twenty-three bull calves (2-7 months old) were presented with a history of stranguria, tenesmus, and straining. Diagnosis of urethral dilatation was relied on the case history and clinical examination and was confirmed using survey and contrast radiography, ultrasonography, and biochemical tests. Treatment was done by urethrostomy under the effect of local infiltration analgesia.Results:Physical examination revealed the presence of an oval, firm, and painless swelling at the perineal region, starting just below the anus and extended to the base of the scrotum. The owners reported that the initial swelling size and severity of symptoms increased with the progress of animal age. Biochemical findings revealed non-significant changes in blood urea nitrogen and creatinine levels. Radiographic findings showed an oval radiopaque mass. However, a well-demarcated structure with acoustic enhancement was detected on ultrasonographic examination. Urethrostomy resulted in a successful outcome of all cases.Conclusion:Depending on these findings, ultrasonography is the most reliable diagnostic tool and urethrostomy is the intervention of choice with acceptable results for diagnosis and treatment of urethral dilatation in cattle calves, respectively.

Effect of DMAEMA content and polymerization mode on morphologies and properties of pH and temperature double-sensitive cellulose-based hydrogels

Double responsive cellulose/ poly 2-(dimethylamino) ethyl methacrylate (PDMAEMA) hydrogels were prepared through in situ radical polymerization. The results from Fourier transform infrared spectroscopy, scanning electron microscopy, mechanical property testing, swelling experiments as well as thermogravimetric analysis demonstrated that 2-(dimethylamino) ethyl methacrylate (DMAEMA) content and polymerization modes played a decisive role in hydrogel’s structure. Firstly, with increasing DMAEMA content, the texture of hydrogel became softer. The incorporation of relatively hard cellulose and the increase in crosslink density markedly strengthened the three-dimensional network structure of hydrogels, and the tensile strength, compression and bending properties of the composite’s hydrogels were fine with the content of DMAEMA in a certain range. When the DMAEMA content increased to 6 g/g(cellulose), the mechanical strength decreased obviously. An increase in the DMAEMA content resulted in a faster initial swelling rate and higher equilibrium swelling ratio (ESR). Secondly, freezing in hydrogel formation was beneficial to formation of interpenetrating network structure, which can raise its initial swelling rate and higher ESR. Freeze–thaw had a certain destructive effect on the micropore structure. Thirdly, three-dimensional structure and the increase of DMAEMA content can also improve the pH and temperature response sensitivity of hydrogels. Thus, the mechanical, swelling and responsive properties of this hydrogel could be adjusted by the DMAEMA content and polymerization modes.

EFFECTS OF VISCOELASTIC PROPERTIES AND HYDRATION KINETIC ON DRUG RELEASE FROM THE TABLET OF DICLOFENAC SODIUM BASED ON POLY (SODIUM ACRYLATE)-GRAFTED-GELLAN MATRIX

Investigation of the effects of viscoelasticity and hydration kinetic on the drug release behavior from the poly (sodium acrylate)-grafted-gellan matrix (PSAc-g-GG) was the main objective of this study. At first, poly (acrylic acid)-grafted-gellan was treated with 0.05M NaOH to obtain poly (sodium acrylate)-grafted-gellan followed by its purification and subsequent lyophilicity study and viscoelastic study on PSAc-g-GG with different degree of grafting. The study revealed that the degree of grafting greatly affects the viscoelastic and rheologic characteristics of the copolymer, which further affect the drug release profile from the polymeric matrix. The copolymer with highest grafting (626.3%) exhibited much higher starting % strain (17.79%), stress (53.7 Pa) for structural breakdown at Gꞌ = Gꞌꞌ (214.4 Pa), higher storage modulus (G’), much greater values of complex viscosity (11.5 Pa.s) and cross-over point (Gꞌ = Gꞌꞌ =271.65 Pa) compared to that of the batch of copolymer with lower grafting. The water uptake index (%WE) was found to be directly proportional to the percentage grafting (%G), whereas the batches with higher grafting revealed lower initial swelling rate representing its inversely proportional relation to %grafting in case of 0.1N HCl acid. Equilibrium swelling and hydration were also found to be proportional to % grafting. The similar effect was observed in phosphate buffer solution (pH 6.8) with an exception that the degree of the swelling parameters obtained from phosphate buffer was very much greater compared to that found in 0.1N HCl. PSAc-g-GG exhibited extended drug release over a period of 10 hours with the drug release mechanism based on Case-1 Fickian diffusion or square root of time kinetic. The study also exhibited the usefulness of viscoelastic and swelling study in order to identify the effects of the degree of grafting on the drug release.

Effect of low temperature on the regulation of cell volume after hypotonic shock in gastric cancer cells.

Although peritoneal lavage with distilled water performed after surgery prevents peritoneal seeding, cancer cells may avoid rupture under mild hypotonicity through regulatory volume decrease(RVD), which is the homeostatic regulation of ion and water transport. The aim of the present study was to investigate the effect of low temperature on cell volume and cell death under hypoosmolal conditions and determine the underlying molecular mechanisms in gastric cancer (GC). Three human GC cell lines (NUGC4, KATO‑III and MKN45) were exposed to hypotonic solutions, and the effects of low temperature on cell volume and viability were examined. Low temperature‑induced changes in membrane transporters were evaluated, and knockdown and overexpression experiments were conducted to determine their effects on cell volume during hypotonic stimulation. Low temperature (24˚C) during hypotonic stimulation inhibited RVD and enhanced the cytocidal effects on GC cells. The expression of leucine‑rich repeat containing proteinA (LRRC8A), a component of a Cl‑ channel, was decreased, and aquaporin5 (AQP5) expression was increased at low temperatures. LRRC8A knockdown markedly slowed the decrease in cell volume following cell swelling by hypotonic shock. AQP5 overexpression enhanced initial cell swelling after hypotonic shock and increased the final cell volume. These results suggest that a hypotonic solution at low temperature increased initial water influx via activation of AQP5 and decreased Cl‑ efflux via inhibition of LRRC8A. Therefore, low temperature enhanced the hypotonicity‑induced cytocidal effects on GC cells, and these results may contribute to the development of a novel lavage method effective in reducing peritoneal recurrence in GC.

Effect of wetting–drying–freezing–thawing cycles on the swelling behaviour of the Yanji mudstone

One of the most important characteristics of mudstones is their susceptibility to swelling upon absorption of water, which is influenced by climatic processes. This study investigated the swelling pressure and strain of the Yanji mudstone subjected to wetting–drying (W–D), freezing–thawing (F–T) and wetting–drying–freezing–thawing (W–D–F–T) cycles. The swelling curves were analysed using a simulation of the logistic function, and the coefficient of initial swelling (Cis), coefficient of primary swelling (Cps), coefficient of secondary swelling (Css), and ultimate swell were derived from the mathematical simulation. The results show that the cyclic treatments can significantly influence the swelling kinetics and ultimate swell. As the number of treatment cycles increases, Cis increases and then decreases due to the competition between the increasing permeability and the decreasing swelling potential induced by the propagation of cracks and large voids, while Cps and Css decrease because of the compaction and contraction of the aggregates after cyclic treatments. The ultimate swelling pressure and ultimate swelling strain decrease with increasing treatment cycles and the relationships among these parameters were also established, allowing the ultimate swelling pressure and strain of the Yanji mudstone under the full range of seasonal variation to be predicted.

Fluid‐dynamic gauging for studying the initial swelling of soft solid layers

AbstractAn innovative fluid‐dynamic gauging (FDG) device to study the initial as well as long‐term swelling or removal of soft solid layers immersed in a liquid environment in real time and in situ is presented. This sideways FDG (SiDG) device was developed for soft solid layers whose properties change significantly on contact with liquid. Calibration tests indicated a resolution of ±10 μm. The open source computational fluid dynamics (CFD) code OpenFOAM was used to model the flow in the SiDG nozzle. Good agreement was obtained between experimental and CFD results at different nozzle clearances, so that the shear stress exerted by the gauging flow can be computed accurately. A series of demonstration studies are presented, on layers of petroleum jelly, polyvinyl acetate, gelatin and a complex model soil. Initial swelling dynamics are captured and the influence of pH on initial swelling behavior, previously inaccessible, is reported.

Development of a novel method utilising dissolution imaging for the measurement of swelling behaviour in hydrophilic matrices

A variety of imaging techniques are currently used within the field of pharmaceutics to help understand and determine a wide range of phenomena associated with drug release from hydrophilic matrix tablets. This work for the first time aims at developing an appropriate testing imaging methodology using a surface dissolution imaging instrument (SDI2) for determining the swelling of whole compacts using hypromellose as a model hydrophilic matrix former. The influence of particle morphology (CR and DC grades) and two compressional forces (5 and 15 kN) on the initial swelling behaviour of hypromellose were investigated. The results showed that a lower absorbance of 50 mAu with a wider measurement zone proved successful in determining the edge of the gel layer and growth measurements in real-time with high level of details under flow. Despite the differences in the morphology of the grades of hypromellose tested, it was however discovered that gel growth was statistically similar between them which may be attributed to their similar chemistry. This novel method also highlighted differences in the hydrated polymer’s appearance which may have been as a result of differences in porosity and solid fraction. This information is of great importance to a formulator as gel growth plays a crucial role in determining drug release from polymer compacts.

Insight into (alkyl)methacrylate-based copolymer/sepiolite nanocomposite cryogels containing amino and sulfonic acid groups: Optimization of network properties and elasticity via cryogelation process

(Alkyl)methacrylate-based copolymer/sepiolite nanocomposite gels containing amino and sulfonic acid groups have been prepared via (cryo) gelation of N,N-dimethylaminoethyl methacrylate (DMAEMA) and 2-acrylamido-2-methyl-propanosulfonic acid (AMPS) in the presence of fibrous clay mineral sepiolite (SEP). The morphology, thermal stability, compression performance, and swelling behavior of nanocomposite gels were systematically studied with various SEP contents. X-ray diffractometry results indicated that SEP had been participated in (cryo)gelation, and the resulting thermal stability and surface morphology were improved by the addition of inorganic clay SEP. Owing to dispersion of SEP, the prepared nanocomposite cryogels exhibited dramatic improvements on their elasticity while low water absorption capacity was maintained. The presence of low amount of SEP significantly enhanced the mechanical strength and the cross-link density of DMAEMA-based nanocomposite gels due to its fibrous morphology and crystalline structure acting as cross-links. Addition of 0.4% (w/v) SEP led to five-fold increase in the compressive modulus of nanocomposite cryogels. As SEP concentration in the feed was increased from 0 to 2.40% (w/v), the effective cross-link density in the nanocomposite matrix increased continuously from 2.84 to 22.9 × 103 mol/m3. The prepared nanocomposite gels showed enhanced swelling response and on-off switching characteristics in aqueous KBr solutions. The parameters of equilibrium swelling, initial swelling rate, diffusional exponent, and diffusion coefficient were evaluated and the swelling kinetics of the nanocomposite gels in aqueous KBr solution followed the pseudo second order model. Since DMAEMA and inorganic clay SEP were effectively combined in a nanocomposite network, the obtained results would expand the range of responsive properties and related industrial applications available to DMAEMA and SEP individually.

A phase-field model for fracture in water-containing soft solids

In this paper, a phase field model with energy decomposition previously developed for rubber is extended for hydrogel. Predications of the extended model are qualitatively and quantitatively compared with our experimental results. To be consistent with the phase field model for rubber, we first reformulate the free energy of hydrogels with initial swelling that takes into account the initial volume fraction of water. The free energy (for intact hydrogels) is then modified to be suited for phase field modeling by splitting the deformation into isochoric and volumetric parts. The model parameters are calibrated by experimental tests performed under uniform compression without the phase field damage. A typical water-containing soft solid, hydrogel, is fabricated. Compression and three-point bending experiments on hydrogel blocks are carried out under plane strain conditions. The phase field model can capture the experimentally observed sequence of deformation and fracture at finite strains. It is also found that the energy decomposition is a key for the robust modeling of experimental fracture involving the compression. The role of the water played in the toughness of the gel is also revealed.