Initial Swelling Rate Research Articles

Modeling and investigation of swelling kinetics of sodium carboxymethyl cellulose/starch/citric acid superabsorbent polymer

Crosslinked hydrophilic polymers with high water absorption rates are known as superabsorbent polymers (SAPs). Most commercial superabsorbent polymers are made with acrylic acid, which is difficult to biodegrade. So, in this investigation, carboxymethyl cellulose (CMC) was utilized as a significant component in the synthesis of polysaccharide-based SAPs. Citric acid (CA) and starch were chosen as crosslinking agents because they are more eco-friendly, non-toxic, and biodegradable than traditional crosslinking agents. FTIR analysis revealed that the superabsorbent polymer product contains a crosslinked structure of CMC and starch with side chains that carry carboxylate functional groups. Superabsorbent weight loss and grafting data were satisfactorily studied using the TGA approach. Under optimum circumstances, the SAP2 water absorbency capacity in distilled water was 287.37 g.g−1 and SAP1 absorbency capacity in a solution containing 0.9 wt% NaCl was 52.18 g.g−1. Moreover, Schott's pseudo-second-order model was used to determine the kinetic swelling of the superabsorbent. The initial swelling rate of SAPs can be calculated using the Q∞ data acquired in the following order: SAP2 > SAP1 > SAP3 > SAP4 in distilled water and SAP1 > SAP2 > SAP3 > SAP4 in 0.9 wt% NaCl solution, respectively. The findings suggested that a small amount of citric acid introduced into the SAPs matrix could enhance the swelling rate of SAPs. The results of the cytotoxicity tests show that the extraction liquid of composite hydrogel fibers is less cytotoxic than the positive control. As well, SAP underwent in silico docking investigations on the DNA Gyrase enzyme. As the ligand is a monomer of SAP, it was a long chain of carbohydrate molecules with alcoholic groups, esters groups, and keto groups forms a strong binding interaction with DNA gyrase.

A microfluidic-based In-situ investigation of swelling dynamics of superabsorbent polymer microparticles

This paper presents a novel microfluidic-based technique for in-situ time-lapse investigation of the dynamic water absorption (or swelling) of individual superabsorbent polymer (SAP) microparticles (MPs). Most prior studies were restricted to using gravimetric techniques to investigate the equilibrium state of the swelled SAP macroparticles, without considering their swelling dynamics. Time-lapse investigation of the swelling rate is essential for optimizing SAP-MPs' performance to meet the needs of different applications. Moreover, since swelling occurs through the surface of SAP particles, we hypothesize that decreasing their size to microscale (i.e., SAP-MPs) could potentially improve their performance due to the increased surface area-to-volume ratio. In this context, the proposed microfluidic device enabled hydrodynamic trapping of an array of individual SAP-MPs and in-situ investigation of their swelling behaviour under a microscope. The SAP-MPs were initially suspended in ethanol and loaded into the microfluidic device. Once they were trapped, the fluid medium was switched to water to trigger their swelling. Acrylic acid (AA)/acrylamide (Aam)-based SAP-MPs in size range of 250–300 µm were investigated to characterize the device's performance. The SAP-MPs' average trapping time and yield in the device were 9.56 s per SAP-MP and 92%, respectively, at an ethanol loading flow rate of 0.15 mL/min. A minimum water flow rate of 5 mL/min was required to achieve an average ethanol-to-water transition time of 10 s. This was needed to suppress the effect of the solution exchange on the swelling behavior of the SAP-MPs. The equilibrium volumetric swelling ratio (VSReq), swelling rate (SR), and initial SR of AA-Aam-based SAP-MPs were determined to be 5.59 ± 0.13 (m3/m3), 0.039 ± 0.002 (m3/m3.s), and 0.068 ± 0.010 (m3/m3.s), respectively. A significant effect of the neutralization degree (ND) on the swelling behavior of AA-Aam-based SAP-MPs was also observed. At 90% ND, the maximum VSReq of 79.45 ± 2.49 m3/m3 and SR of 1.11 ± 0.047 m3/m3·s were achieved. This microfluidic platform could be used to conduct parametric study and real-time characterization of various SAP-MPs in biological, chemical, medical, and agricultural applications.

Thermal, Mechanical and Swelling Studies of Semi-Interpenetrating Polymer Network Composed of Natural Rubber and Polyacrylamide

Semi-interpenetrating polymer network (IPN) composed of two polymers, namely natural rubber (NR) and polyacrylamide (PAAm) were prepared by crosslinking with glutaraldehyde. The NR/PAAm semi-IPN films were developed by varying the concentration of crosslinking agents and the polymer blend ratios. The impact of preparation parameters on the mechanical properties was studied. The semi-IPN was characterized by FTIR, DTG, TG and SEM. Swelling studies were done by using toluene as solvent. The kinetics and mechanism of swelling were investigated and the initial rate of swelling, swelling constant, swelling exponent, equilibrium swelling and diffusion coefficient were also determined.

Synthesis and Properties of Rosin-Based Composite Acrylamide Hydrogels

Hydrogels have been widely applied in agricultural drought-resistance, pollution regulation, drug delivery and so on. Acrylamide (AM) is usually used as raw material to synthesize acrylamide hydrogels. However, inherently low mechanical strength greatly limits their applications in some special areas. Therefore, it is necessary to choose suitable functional monomers to optimize acrylamide hydrogels and improve their mechanical performances. In this paper, a novel acrylamide monomer modified by rosin was synthesized, and then polyacrylamide/rosin-based acrylamide (RAM) composite hydrogels were prepared via free radical polymerization using potassium persulfate as initiator, N, N′-methylene-bisacrylamide (MBA) as a crosslinker. The influence of RAM monomer was investigated in detail. The chemical structure, pore structure, swelling properties, thermal performances and mechanical properties of composite hydrogels were characterized by Fourier Transform Infrared spectrometer (FT-IR), thermogravimetric analysis (TG), scanning electron microscope (SEM), and universal testing, respectively. The results showed that the thermal stability and mechanical property of RAM hydrogels were improved significantly. The compressive strength of RAM hydrogels was increased to 3.5 times than that of AM hydrogels, and the tensile strength was 5.1 times compared with AM hydrogels as well. Moreover, RAM hydrogels exhibited a faster initial swelling rate due to the new pore structure formed after introducing the RAM monomer.

Coreflooding Evaluation of Fiber-Assisted Recrosslinkable Preformed Particle Gel Using an Open Fracture Model

Summary Recrosslinkable preformed particle gels (RPPGs) have been used to treat the problem of void space conduits (VSC) and repair the “short-circuited” waterflood in Alaska’s West Sak field. Field results showed a 23% increase in success rates over typical preformed particle gel (PPG) treatments. In this paper, we evaluated whether adding fiber into RPPGs can increase the RPPG plugging efficiency and thus further improve the success rate. We designed open fracture models to represent VSC and investigated the effect of swelling ratio (SR), fracture size, and fiber concentration on gel injection pressure, water breakthrough pressure, and permeability reduction. Results show that fiber can increase RPPG strength and delay its initial swelling rate, but an optimized fiber concentration exists. Beyond that, the fiber entangling problem can result in the recrosslinked bulk gel inhomogeneously and impact gel quality. The injection pressure of fiber-assisted RPPGs increased with the SR and fracture width. During post-injection water process, the breakthrough pressure and residual resistance factor increased when the RPPG SR and fracture width decreased. Fiber-assisted RPPGs can dramatically reduce the permeability of the fractured core up to 1.8×106 times. It is observed that the fiber-assisted RPPGs used in the experiment remain in a bulk form in the fracture when we open the fracture after water injection. Not only does the addition of fiber improve the plugging efficiency, but it also prevents particle precipitation along vertical fractures or conduits.

Structural Modifications of Sodium Polyacrylate-Polyacrylamide to Enhance Its Water Absorption Rate

Superabsorbent polymers (SAPs) can absorb a large amount of water and find broad applications in various industries. There are many reports on the synthesis and structural modification techniques to improve the water absorption property of SAPs. However, we see few studies on the comparison and integration of these techniques. In this study, three structurally modified SAPs were synthesized and are evaluated for the effects of surface cross-linking, foaming, and the integration of the two modifications to improve the absorption rate and capacity of a conventional SAP. First, sodium polyacrylate-polyacrylamide was prepared as the base polymer by the aqueous solution polymerization method. Second, the base polymer was modified with surface cross-linking to enhance absorption, and a surface cross-linked SAP was obtained. Third, the base polymer was modified with foaming to obtain a foamed SAP. Lastly, the foamed SAP was modified further with surface cross-linking to obtain a foamed and surface cross-linked SAP. In comparison with the base polymer, the three synthesized SAPs were evaluated for their absorption performance. Results show that their absorption performance could be improved by the three modification processes. Specifically, the surface cross-linked SAP had the best absorption capacity under load, the foamed SAP had the highest absorption capacity of 1954 g/g, and the foamed and surface cross-linked SAP had the fastest absorption rate with an initial swelling rate of Kis = 21.94.

Wood-water interactions of thermally modified, acetylated and melamine formaldehyde resin impregnated beech wood

Abstract The wood-water interactions of modified beech wood (Fagus sylvatica L.) were studied. Specimens were thermally modified at 180 (TM1), 200 (TM2) and 220 °C (TM3), acetylated (Acet), and melamine formaldehyde (MF) resin (Mel) modified. Afterwards, the water vapour characteristics, i.e. water vapour sorption isotherms, equilibrium moisture content (EMC), dimensional stability of specimens conditioned at 30, 65 and 90% RH and liquid water characteristics, i.e. water absorption, maximum moisture content (MC), leachability and swelling kinetics, were determined and the results compared with reference (Ref) specimens. From the results, it is evident that the scale of wood-water interactions was highly dependent on the thermal modification temperature and type of chemical modification. The water vapour isotherms of thermally modified wood decreased, whereas more severe treatment exhibited more distinct reduction. The EMC values of the Mel and TM1 specimens decreased only at high RH, whereas the most significant decrease, within the whole range of observation, was found in the Acet group. The maximum MC reduction was achieved by acetylation. As a consequence of swelling reduction, dimensional stability expressed as anti-swelling efficiency (ASE) was considerably improved. A relatively high initial linear-phase swelling rate was found for the Ref specimens, whereas modified wood exhibited comparatively slow and gradual swelling.

Cellulose-Based Hydrogels as Smart, Green and Controllable Nitrogenous Fertilizers Releasing Agents

Abstract A smart, green, and controllable-release hydrogel based on cellulose was prepared to avoid the problem of soil fertilizer abuse. A field-emission scanning electron microscope (FE-SEM) demonstrated a wrinkled, rough, lamellar structure with long microtubes. The effect of the cross-linker concentration, epichlorohydrin (ECH), on the physical and mechanical properties in addition to swelling and urea-release kinetics was thoroughly studied. A relatively high swelling ratio, urea entrapment, and proper flexibility were obtained for an ECH concentration of 3.33 %. The swelling kinetics of hydrogel was found to be a second-order process. The maximum swelling value and the initial swelling rate were dependent on cross-linker concentration. The hydrogel exhibited a dehydration shrinkage in saline solution. A significantly high urea release of 6.61 % at 3.33 ECH concentrations was estimated. The urea-release mechanism matches well with the Fickian model. Accordingly, the prepared hydrogel is potential as a smart, green, and controllable-release fertilizer for applications in agriculture and horticulture.

Swelling kinetics of thermally modified wood

The swelling kinetics of native and thermally modified wood was studied. Norway spruce, Scots pine, European beech, and English oak specimens of dimensions 20 × 20 × 10 mm were modified at 180, 200, and 220 °C. The swelling kinetics of the specimens was monitored during 24 h of water immersion. The results are presented as relative swelling rate, and values for maximal radial and tangential swelling, and anti-swelling efficiency. A relatively high initial linear-phase swelling rate was found for spruce, pine, and beech wood, while oak wood exhibited more gradual swelling. Thermal modification improved dimensional stability, depending on the wood species, anatomical direction, and intensity of treatment.

Effect of Swelling of N-Vinylpyrrolidone-Based Polymers on Sorption of Nitrophenols

Swelling of synthesized N-vinylpyrrolidone-based polymer sorbents in aqueous solutions with different pH has been studied. The initial rate and degree of swelling, their dependence on the ratio of functional monomer and cross-linking agents in the polymer samples synthesized in various solvents have been found. It has been shown that the sorption of nitrophenols depends on the swelling of the polymers and increases with increasing amount of a cross-linking agent, but is not directly related to the specific surface of the sorbent.

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.

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.

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.

Design and molecular dynamics of multifunctional sulfonated poly(dimethylaminoethyl methacrylate)/mica hybrid cryogels through freezing-induced gelation.

This article addresses various strategies that have been explored to design sulfonated poly(dimethylaminoethyl methacrylate)/mica hybrid-gels with optimized network parameters and mechanical/swelling properties. A series of hybrid cryogels and hydrogels containing amino and sulfonic acid groups were prepared from N,N-dimethylaminoethyl methacrylate (DMAEMA) and 2-acrylamido-2-methyl-1-propane sulfonic acid in the presence of inorganic additive mica via a cryogelation process and conventional in situ copolymerization. Cryogelation was used to fine-tune the mechanical properties of the PDMAEMA-based hybrid gels. The effects of pH, temperature and mica content on the network parameters, mechanical properties and swelling behavior were discussed. X-ray diffractometry and Fourier transform infrared spectroscopy confirmed that mica particles had participated in (cryo)polymerization, and the thermal stability and surface morphologies were improved by the addition of mica. The profile of water loss, decomposition of amine groups and breakdown of PDMAEMA chains of the resulting hybrid gels were determined by thermogravimetric analysis. A critical mica concentration was found for the hybrid hydrogels where the degree of swelling attains a maximum value. Below 0.50% (w/v) of mica, the ionic nature of mica dominates its crosslinker effect. The hybrid cryogels were tough and able to recover at room temperature after compression testing. The prepared hybrid-gels showed an enhanced swelling response and on-off switching swelling characteristics in water and in aqueous NaCl solutions. The parameters of equilibrium swelling, the initial swelling rate, the diffusional exponent, and the diffusion coefficient were evaluated and the swelling kinetics of the hybrid hydrogels and cryogels in water followed the pseudo second order model. All the prepared hybrid hydrogel and cryogel materials with tunable mechanical stability and elasticity can be excellent candidates for designing smart materials.

Synthesis of poly (acrylamide-co-aconitic acid) adsorbents by gamma-irradiation, characterization, adsorption studies and application for cationic dyes removal

In this study, acrylamide (AAm)/aconitic acid (ACA) copolymers were prepared with two different mol% of aconitic acid 4%, 17% and were irradiated with gamma irradiation at different irradiation doses (4 - 25kGy). The percent yield was assigned by gravimetrical method. The effect of irradiation dose, pH and involved amounts of monomers (AAm/ACA) in hydrogels on swelling properties were investigated. The conversion of monomers to hydrogels was 100% at 25kGy. Poly(acrylamide-co-aconitic acid) P(AAm/ACA) hydrogels have been used for the adsorption of some aqueous solutions of dyes such as Methylene Blue (MB) and Safranine-O (S). The hydrogels were swollen in distilled water at pH 3, 5, 7, 8 and in aqueous solutions of dyes. The initial swelling rates of hydrogels are increased by increasing of pH. The effects of concentration of the aqueous solutions of dye and hydrogel composition on the adsorption were investigated. The adsorption is increased and changed depending on the structure of dye and composition of hydrogel.

Humic acid embedded chitosan/poly (vinyl alcohol) pH-sensitive hydrogel: Synthesis, characterization, swelling kinetic and diffusion coefficient

In the present research, humic acid (HA) embedded chitosan (CHT)-poly (vinyl alcohol) (PVA) pH-sensitive hydrogels have been synthesized using glutaraldehyde as a crosslinker. The hydrogels were characterized by Fourier-transform infrared (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) analysis. The effect of HA content, pH, and temperature on the equilibrium solvent uptake has been investigated. With higher HA contents, the equilibrium swelling capacity increases while lower concentrations of acid cause a decrease in the degree of the swelling. The hydrogels have been found to undergo a number of swelling/deswelling cycles when pH of the swelling medium changes from 1.5 to 11.0. Fick’s law, first-order, and second-order kinetic models were applied to the swelling ratio of hydrogels to explain the mass transfer mechanism and specify swelling kinetic parameters. The swelling parameters such as equilibrium swelling capacity, swelling rate constant, swelling exponent, initial swelling rate, diffusion coefficient, etc., have been evaluated.

EFFECTS OF FORMULATION PARAMETERS ON PROPERTIES OF GASTRIC FLOATING TABLETS CONTAINING POORLY SOLUBLE DRUG: DICLOFENAC SODIUM

Objective: The objective of this study was to prepare and investigate the effects of formulation parameters on the properties of gastric floating tablets containing diclofenac sodium (DICL) as a model of poorly soluble acidic drug, sodium bicarbonate (NaHCO3) or calcium carbonate (CaCO3) as gas-forming agent, hydroxypropyl methylcellulose (HPMC) K100M or K15M as swelling polymer and sodium lauryl sulfate (SLS) as wetting agent.Methods: DICL floating tablets were prepared using direct compression method. The compressed tablets were evaluated for tablet properties, swelling index, and in vitro buoyancy. The in vitro release under non-sink condition was determined. Molecular interaction was studied using differential scanning calorimetry and fourier transform infrared spectroscopy.Results: The tablet properties of all DICL floating tablets were within the acceptance criteria. The molecular interaction between DICL and excipients in the formulation was excluded. Depends on the formulation compositions, the swelling index at 3 h (SI) ranged from 44±11 to 1158±33 %, whereas the buoyancy properties namely floating lag time (FLT) and total floating time (TFT) were 0.33±0.03 to 10.04±0.04 min and 10.0±0.0 to>12 h, respectively. NaHCO3 showed higher swelling, buoyancy and release properties compared to those of CaCO3. NaHCO3 at 20% gave sufficient swelling (SI of 1074±16 %), buoyancy (FLT of 0.39±0.03 min, TFT of>12 h) and release properties (cumulative release of 5.83±0.02 %). HPMC K100M showed better swelling property of which its initial swelling rate was 1412±25 %/h compared to HPMC K15M (1042±31 %/h). HPMC K100M at 20% showed better buoyancy and release properties compared to those obtained from HPMC K100M at 30%. The release testing under non-sink conditions was able to distinguish the effect of formulation parameters on the DICL release profiles. Incorporation of SLS at 0.25% could enhance both release rate and cumulative release of DICL from the floating tablets. Nevertheless, it showed the unacceptable adverse effect on swelling and buoyancy properties of DICL floating tablets. The TFT of DICL floating tablets containing 0.25% SLS was only 0.5±0.0 h.Conclusion: DICL floating tablets were successfully prepared. Tablets possessing suitable swelling and buoyancy properties were obtained using NaHCO3 at 20% as a gas-forming agent, with HPMC K100M at 10 and 20% as floating matrix and swelling polymer. Addition of SLS as wetting and solubilizing agent showed the unacceptable adverse effect on the swelling and buoyancy properties of DICL floating tablets. The release under sink conditions and/or in vivo pharmacokinetic studies shall be further performed.

Thermo and pH-responsive methylcellulose and hydroxypropyl methylcellulose hydrogels containing K2SO4 for water retention and a controlled-release water-soluble fertilizer

Hydrogel as commercial soil conditioner has the potential to improve soil properties and reduce water scarcity in growing plants. However, use of polyacrylamide-based hydrogel in agriculture pose potential human health hazards. Hydrogel systems were prepared from temperature-responsive methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) blended with potassium sulfate (K2SO4, K-containing fertilizer). Blended K2SO4 in hydrogels affects the hydrophobic interaction of MC and HPMC, and hydrogels prepared in 0.25 M K2SO4 decrease the gelation temperatures of MC and HPMC from 55.6 and 67.4 °C to 27.8 and 35.1 °C, respectively. The equilibrium swelling ratio (St) of MC and HPMC hydrogels was increased 15 times and hydrogels maintained a steady appearance. The swelling kinetics of the MC and HPMC hydrogels followed Schott's second-order model and kinetic parameters indicated that adding K2SO4 can improve the initial swelling rate. K2SO4 decreases the pore size of the MC and HPMC hydrogel from 26.8 and 21.5 μm to 14.7 and 14.2 μm. A plant growth assessment indicated inhibition in plant growth occurred without the application of the hydrogels. Adding K2SO4 increases mechanical properties of the hydrogels. Treatment with 0.5% hydrogel considerably improves the water-holding and water-retention capacities of sandy soil. The 20-20-20 fertilizer release results revealed at that at 35 °C and a pH below 7, the hydrogel systems reduce the release rate of the fertilizer. The best result was observed with the Korsmeyer–Peppas model, indicating that the fertilizer transport mechanism involves Fickian diffusion and swelling-controlled release. This study discovered that environmentally responsive cellulose-based hydrogels have potential for use as soil conditioners and as controlled release devices in horticulture and agriculture.

Physical nanocomposite hydrogels filled with low concentrations of TiO2 nanoparticles: Swelling, networks parameters and cell retention studies

Physical nanocomposite hydrogels composed of poly(2-hydroxyethylmethacrylate) and titanium oxide nanoparticles at low concentrations (<1.0 wt%) were synthesized. The effect of the nanoparticle content on the water swelling and mechanical properties of the hydrogels was investigated. Additionally, to study the influence of the polymer-nanoparticle interactions, a second type of nanocomposite was synthesized using surface functionalized nanoparticles with 3-methacryloxypropyltrimethoxysilane as the filler. The pristine nanoparticles increased the swelling capacity, especially at short time scales, and greater solvent diffusion coefficients and initial swelling rates were achieved. In contrast, the nanocomposite filled with functionalized nanoparticles exhibited a diminished swelling capacity, a constant diffusion coefficient and a significant decrease in the initial swelling rate. The mechanical properties were studied by dynamic mechanical analyses using stress-relaxation tests. Two Maxwell models in parallel agreed well with the curves of the relaxation modulus as a function of time and indicated that at short relaxation times, the nanoparticles did not cause an effect, but that at longer times, the nanoparticles decreased the relaxation time. Finally, hydrogel network parameters determined by swelling measurements and mechanical experiments indicated that the hydrogel with well distributed nanoparticles decreases the molar mass between crosslink point and the mesh size, while poorly distributed nanoparticles lead to larger mesh size. Our functional studies show that the addition of titanium oxide nanoparticles improves the ability of nanocomposite hydrogels to retain aggregates of skeletal muscle cells, revealing their potential use as suitable scaffolds for tissue repair strategies.