Increasing Polymer Concentration Research Articles

Effect of polymer concentration and cross-linking density on the microstructure and properties of polyimide aerogels

AbstractPolyimide aerogels display excellent mechanical strength, high thermal stability, low thermal conductivity, and outstanding dielectric properties. Typically, the synthesis of polyimide aerogels involves the polycondensation of dianhydride and diamine into poly(amic acid) (PAA) oligomers, which are then cross-linked and chemically imidized into polyimide. The stoichiometry of dianhydride and diamine determines the number of repeat units and length of the PAA oligomers, which in turn determines the cross-linking density. Despite the critical role of polymer concentration and number of repeating units in determining the microstructure and properties of polyimide aerogels, few detailed studies exist on these two parameters. Here, we synthesized and characterized 16 polyimide aerogel formulations from the common monomers biphenyl-3,3′,4,4′-tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA), with different repeat units (n = 5, 15, 30, 45) and total polymer concentrations (4, 7, 10, 13 wt%). An increased polymer concentration accelerated gelation and enhanced the mechanical performance of aerogels, but surprisingly, it also led to higher volumetric shrinkage during aging, solvent exchange, and supercritical drying (SCD). Specific surface areas (SSAs) reached a maximum at intermediate polymer concentrations. A shorter oligomer chain length, i.e., a higher cross-linking density, led to moderately higher SSAs (between 320 and 400 m2/g) and reduced shrinkage, resulting in lower densities for a given polymer concentration. The density dependence of the thermal conductivity exhibits a pronounced U-shaped curve with a minimum in thermal conductivity of 21–23 mW/(m·K) between 0.080 and 0.120 g/cm3, with somewhat lower values for more highly cross-linked aerogels. This systematic study of polyimide aerogels forms the basis for designing polyimide aerogels with tailored properties for targeted applications. Graphical Abstract

Mechanical properties of polymer modified mortars using polymer latexes with varied glass transition temperature and surface charges

Mechanical properties of polymer modified mortar (PMM) were investigated using self-synthesized polymer latexes with varied glass transition temperature (Tg) and colloidal surface charges to build correlations between the mechanical properties of PMMs and the intrinsic properties of the polymers. Generally, compressive strength and elastic modulus of mortar are decreased, but ductility and toughness are enhanced by incorporation of the polymers. Impacts of the lower Tg polymers on the mechanical properties of PMMs are more pronounced. With increasing polymer content, flexural and tensile strength of mortar first increase and then decrease when using low Tg polymers that form continuous film during hardening of the mortars, while steadily decrease in the case of high Tg polymers that exist as individual particles in the hardened PMMs. For the high Tg polymer modified mortars, it is interestingly found that a subsequential heat treatment effectively promotes the film formation of the polymers in the hardened PMMs and thus greatly increases their flexural and tensile strength. This indicates that polymer film formation is essential to the enhancement of the PMMs, because the polymer films play a crack-bridging effect while the individual particles cannot do such job. The high Tg polymers lead to higher tensile strength of PMMs after heat treatment due to the higher inherent strength of the polymer film. Higher colloidal surface charge benefits the mechanical properties of the PMMs by (1) promoting a more homogenous polymer distribution in the hardened PMMs and/or (2) improving the bonding between the polymer phase and cement hydrates.

Development of MWCNTs@PDMS nanocomposites with enhanced hydrophobicity and thermo-oxidative stability

This paper presents the fabrication of hydrophobic polymer nanomaterials with improved thermal characteristics based on MWCNTs and poly(dimethylsiloxane). The samples were synthesized by physical adsorption of poly(dimethylsiloxane) onto P-MWCNTs surfaces in the amount from 5 to 20 wt%. The effect of different content of adsorbed polymer on the structure and properties of the prepared nanocomposites was studied in detail using ATR-FTIR, SEM, TEM, XRD and RS techniques. XPS results showed that with the increase of adsorbed PDMS onto the MWCNTs surfaces, the Si 2p atomic percentage increased from 1.5 to 5.0 at.%. The investigation of thermal properties using TGA/DSC techniques in air atmosphere revealed that polymer adsorption on the MWCNTs surfaces enhances the thermo-oxidative stability of the nanocomposites to a great extent. The WCA of MWCNTs@PDMS-1000(20) nanocomposite reached 138.9° while this value was 81.8° in the case of the P-MWCNTs. The electrical characterization of the examined samples demonstrated a non-linear current–voltage behaviour and the invariance of the electrical current value with the increasing polymer content in the nanocomposites. The results suggest that the obtained nanocomposites have multi-functional surfaces and are promising for integration into a silicon-based polymer matrix for the development of new materials for electronic devices.

Self-composite silk fibroin membranes for guided bone regeneration: 1 material 3 architectures with intrinsic integrity

Silk fibroin (SF) takes attention in tissue engineering due to unique features, e.g., excellent biocompatibility/biodegradability with superior mechanical/thermal properties despite its lightweight. Guided bone regeneration (GBR) seeks bilayered GBR membranes to govern bone regeneration, although constituent parts of such membranes may undergo delamination once different biomaterials are combined. Herein, 3-component bilayered SF membranes were prepared for the first time utilizing the same polymer in different forms by eliminating the delamination risk of layers for GBR applications. One side consisted of a non-porous SF film serving as a barrier against penetration of non-osteogenic tissue whereas the other side was porous/fibrous composed of SF sponge and SF fibers for bone regeneration. Proper integration between these layers was confirmed via scanning electron microscopy (SEM). Composites reinforced with high fiber percent (30%) had remarkably enhanced compressive strength and elastic moduli, which were further improved by increasing polymer concentration from 4% to 8%. Non-porous morphology of the barrier side was preserved during 28 days of degradation while pore sizes enlarged on the other surface, which would be beneficial for cell migration into the regenerative side. Saos-2 cells seeded on composites with high fiber percent proliferated more within 14 days; however, alkaline phosphatase (ALP) activity on low-fiber-percent counterparts was elevated more. Osteogenic marker gene expressions were significantly higher than control on day 14. All self-composites were eminent candidates to promote bone regeneration with tailor-made capacity for further improvements. Taken together, 1-material 3-architecture SF fabricated by a green and practical technique holds promise for GBR applications.

Biodegradable maleic–itaconic polymer‐coated phosphatic fertilizer improved phosphorous recovery in calcareous soil

AbstractBackgroundThe poor nutrient recovery of phosphatic (P) fertilizers in calcareous soils is a serious worldwide problem resulting in sub‐optimal P use efficiency. This is mainly attributed to P fixation with calcium (Ca) and magnesium (Mg) ions in the soil solution. As a result, most of the applied P (in the form of fertilizer) becomes insoluble or immobilized in soil due to complex edaphic processes, making it unavailable to plants. Polymer‐coated fertilizers are relatively new approaches to minimizing P‐fixation. However, concerns have been recently raised on the environmental effects of synthetic polymers and microplastic loads in agroecosystems.AimHere we developed and investigated the effectiveness of biodegradable polymer‐coating on commercial diammonium phosphate (DAP) fertilizer to improve P availability in the soil, hence making P more accessible for plant uptake.MethodsThe polymers were coated on DAP fertilizer granules, and two products based on increasing polymer concentration (namely, C‐1 and C‐2, respectively) were achieved. The coated and uncoated DAP granules were characterized for surface properties to confirm the appropriate coating of polymers using scanning electron microscopy (SEM) and crushing strength by a universal telson machine. The biodegradable polymer‐coated C‐1 and C‐2 fertilizers were tested for P availability compared to commercial DAP using spinach as a test plant.ResultsThe SEM micrographs indicated a uniform coating of biodegradable polymers on DAP granules. Application of C‐1 increased the plant's fresh and dry biomass (+10.71% and +18.09%) over commercial DAP, respectively. The C‐1 application increased the N, P, and K uptake by +24.9%, +66.7%, and +11% over commercial DAP. In contrast, C‐2 produced less biomass than C‐1 due to relatively less nutrient uptake and different concentrations of ingredients in C‐2.ConclusionTogether, our results showed that the novel biodegradable polymer approach has demonstrated the potential to improve P recovery and agronomic yield in alkaline soils.

Improved Dissolution and Solubility Characteristics of Clopidogrel Bisulphate using Gelucire 44/14

Clopidogrel bisulphate is a poorly aqueous soluble drug belonging to BCS Class II. The drug is widely used to treat blood clotting in patients with peripheral, coronary, and cerebrovascular disorders, but its low bioavailability raises concern. The present study involves an effort for enhancing the solubility and drug release by transforming the drug into solid dispersions. The solid dispersions of clopidogrel bisulphate were prepared with Gelucire 44/14 using solvent evaporation method. The prepared physical mixture and solid dispersions were characterized for drug-carrier interaction, drug content, solubility, and dissolution rate. Results confirmed the increase in drug solubility with increasing polymer concentration. The dissolution profile was found to substantially improve from solid dispersion with maximum drug release in the ratio of 1:5 on comparing it with pure drug and physical mixture. FT‐IR spectra of selected solid dispersion revealed no chemical interaction between drug and polymers while the presence of the drug in the amorphous state was confirmed by DSC thermograms and X-ray diffraction, indicating better dissolution characteristics. The solid dispersions were also found to be stable under accelerated stability conditions. Keywords: Clopidogrel bisulphate, Bioavailability, Solid dispersions, Gelucire 44/14, Solubility Enhancement

STATISTICAL OPTIMIZATION AND EVALUATION OF IN SITU GEL FOR THE OCULAR DELIVERY OF CROMOLYN SODIUM

Objective: The study aimed to develop and optimize cromolyn sodium-based ocular in situ gel to improve the ophthalmic contact period and provide sustained drug release for treating allergic conjunctivitis. Methods: Formulations were prepared using sodium alginate and HPMC K4M (Hydroxypropyl Methylcellulose) polymers and were characterized and evaluated for viscosity, gelling time, in vitro drug release, and optimized using a factorial 32 DOE design (Version 11; Design Expert® software). The resulting cromolyn sodium-based formulation was tested for hyperemia and eye-scratching behavior in Wistar albino rats. Results: Increased polymer concentrations resulted in higher viscosity with decreased gelling time and in vitro drug release. The optimized formulation achieved a viscosity of 15.350 cps, a gelling time of 55.137 s, and sustained drug release of 92.61% over 12 h. The in vivo pharmacodynamic study of the optimized formulation showed a significant decrease in the frequency of eye-scratching behaviour (7.525) at a significance level of (**p<0.01) and hyperemia (1.125) (***p<0.001, *p<0.05) compared to negative and positive control indicating that the developed in situ formulation improved the drug's therapeutic effectiveness by extending its duration within the cul de sac. Conclusion: In light of these findings, this optimized cromolyn sodium in situ gel holds promise as a viable alternative to conventional eye drops

Microwave-assisted synthesis of celecoxib nanocomposites for enhancement of solubility and colon cancer targeting

The purpose of this research was to formulate nanocomposites comprising of celecoxib with shellac and eudragit S100 for solubility enhancement and targeting drug delivery to the colon. Celecoxib belongs to the class NSAIDs and it shows anticancer activity as well, by COX-II dependent and independent mechanisms. The nanocomposites were prepared by the microwave-assisted method. The prepared nanocomposites were evaluated by techniques such as FTIR, DSC, XRD, solubility determination studies, in-vitro dissolution studies, SEM and TEM. The effect of the drug and polymer ratio on the solubility and the release of celecoxib at colonic pH were evaluated. The solubility of the drug increases up to a certain level when the polymer concentration increases, after which it was found to be decreased. The solubility studies revealed that as the concentration of the polymer increases up to the optimum level, the solubility of the drug increases. Enhancement of solubility for optimum batches was found to be 26.22 and 8.58 μg/ml for a 1:3 ratio of celecoxib-shellac nanocomposite (CSNC) and 1:4 for celecoxib-eudragit nanocomposite (CENC), respectively, as compared to pure celecoxib. SEM and TEM analysis showed the surface texture of the composite and the size of nanoparticles embedded in the polymeric matrix. Needle-shaped nanoparticles were observed with a size of about 50 nm in the polymeric matrix. The optimum ratio of drug to polymer showed the release of drug by 92.72 ± 1.7% and 79.66 ± 2.4% for CSNC and CENC, respectively, at the end of 8 h at colonic pH.

Block Sequence Effects on the Self-Assembly Behaviors of Polypeptide-Based Penta-Block Copolymer Hydrogels.

Peptide-based hydrogels have great potential for applications in tissue engineering, drug delivery, and so on. We systematically synthesize, characterize, and investigate the self-assembly behaviors of a series of polypeptide-based penta-block copolymers by varying block sequences and lengths. The copolymers contain hydrophobic blocks of poly(γ-benzyl-l-glutamate) (PBG, Bx) and two kinds of hydrophilic blocks, poly(l-lysine) (PLL, Ky) and poly(ethylene glycol) (PEG, EG34), where x and y are the number of repeating units of each block, where PBG and PLL blocks have unique functions for nerve regeneration and cell adhesion. It shows that a sufficient length of the middle hydrophilic segment capped with hydrophobic end PBG blocks is required. They first self-assemble into flower-like micelles and sequentially form transparent hydrogels (as low as 2.3 wt %) with increased polymer concentration. The hydrogels contain a microscale porous structure, a desired property for tissue engineering to facilitate the access of nutrient flow for cell growth and drug delivery systems with high efficiency of drug storage. We hypothesize that the structure of Bx-Ky-EG34-Ky-Bx agglomerates is beyond micron size (transparent), while that of Ky-Bx-EG34-Bx-Ky is on the submicron scale (opaque). We establish a working strategy to synthesize a polypeptide-based block copolymer with a wide window of sol-gel transition. The study offers insight into rational polypeptide hydrogel design with specific morphology, exploring the novel materials as potential candidates for neural tissue engineering.

Transition in solution dynamics of polyacrylic acid: An interplay between nonergodicity and triple mode relaxation

AbstractDynamic light scattering (DLS) measurements have been performed on the polyacrylic acid (PAA) to investigate the polyelectrolyte effect on its solution dynamics. Viscosity measurements confirm the solution to be in the nondilute regime. The polyelectrolyte impacts are contrasted by using two solution pHs, five electrolyte concentrations, and in each with four different polymer concentrations. An interesting ergodic nonergodic ergodic transitions are being observed with variation in solution pH and electrolyte concentrations, which is directly coupled to a similar transition between bi‐modal and triple mode relaxation. The partial heterodyne method is used to analyze the DLS data exhibiting nonergodicity; otherwise, the standard Siegert relation is being employed. For the new third mode of relaxation, in addition to the conventional fast and slow mode, a novel term of nonergodic mode being coined because of a direct association between its presence with the sample becoming nonergodic. The fast relaxation time being analyzed through Rouse model and both the nonergodic and slow relaxation time show a monotonous increase with rise in polymer concentration. The stretched exponent , a measure of inhomogeneity, decreases with increase in solution pH and polymer concentration while increases with the addition of salt to the solution.

Hydrogen bonding regulation on phase change in stimuli responsive copolymer aqueous solution

Hydrogen bonding (HB) is vital for the phase transition and physical properties of stimuli responsive copolymers. However, the governing mechanism remains unclear. Herein, we investigated the HB dynamics in a representative thermo-responsive copolymer (PNIPAM-AM) aqueous solution. Three types of HB were identified: polymer-polymer chain (CO:H–N), polymer chain-water molecule (CO:H–O) and water-water molecules (H–O:H–O) by vibrational spectroscopy. Increasing polymer concentration, the H–O:H–O softened and CO:H–O stiffened, leading to the destruction of HB network in water-water clusters. Upon increasing solution temperature, CO:H–O softened while CO:H–N stiffened, resolving the dehydration and cross-linking of polymer chains. Confinement of water molecules in the “cages” (∼ tens to hundreds of micrometers) after sol-gel phase transition was visualized, disclosing the mechanism of water holding capacity of PNIPAM-AM. The correlation of molecule vibration and copolymer microscopic structure was established, contributing to the fundamental understanding of phase behavior and physical properties regulations in stimuli responsive copolymer aqueous solution.

Unidirectional Freezing of Polymer Solution Droplets.

Ice templating provides a means of generating textures with a well-defined topography. Recent applications involve the freezing of water droplets, with or without colloids, on flat or textured surfaces. An interesting feature of water droplets freezing on a substrate is the formation of a pointy tip at a constant angle, regardless of the substrate temperature, surface energy, or droplet volume. Here, by adding the polymer to water, we demonstrate how to manipulate and even prevent the formation of such an icy tip. We find that the sharpness of the tip decreases with increasing polymer concentration until completely disappearing above the overlap concentration, while the total freezing time increases concomitantly. Building on these observations, we combined simple geometrical arguments with heat flux measurements to model and connect the spatial and temporal evolution of polymer droplets under unidirectional freezing. Together our results provide new ways to control the shape of frozen droplets for ice templating or microstructure fabrication, with applications in tissue engineering, separation membranes, and soft robotics.

Hexavalent chromium removal from aqueous solution by polymer-enhanced ultrafiltration

This study compares the effects of two different polymers using polymer-enhanced ultrafiltration (PEUF) to remove hexavalent chromium ions from an aqueous solution with a polyacrylonitrile (PAN) membrane. Two water-soluble polymers were examined: starch and polyethylene glycol (PEG). The analysis explored the impacts of solution pH, pressure, and polymer concentration on hexavalent chromium rejection and permeate flux. The results show that the hexavalent chromium rejection increased with increasing polymer concentration and solution pH. The rejection reached 90% and 96% with starch and PEG, respectively. At pH 10, it reached 100% with starch and 91% with PEG. Increasing the transmembrane pressure doesn’t affect the rejection of hexavalent chromium.

Limiting molar conductivity behaviour of ENR-50 electrolyte in mixed solvent system at ambient temperature

The present research investigates the behaviour of the limiting molar conductivity (Λo) of ENR-50/LiClO4 in a mixed solvent systemcomprising tetrahydrofuran (THF) and acetonitrile (ACN) at ambient temperature. The study uses the power law, to determine the Λovalue of ENR-50/LiClO4/THF:ACN at a specific reference salt concentration. The ENR-50/LiClO4 electrolyte system was prepared witha fixed THF:ACN ratio of 8:2, at different ENR-50 concentration of range between 0.001-0.003 g/cm3. The correlation values obtainedfor the three polymer concentrations ranged from 0.9959 to 0.9966. Regression analysis revealed that as the polymer concentrationincreases, the Λo decreases, indicating an inverse relationship which suggesting an enhanced ion dissociation due to an increase in total free-moving ions within the liquid polymer electrolyte system. The characterization of ENR-50/LiClO4/THF:ACN was verified through ATR-FTIR spectroscopy, confirming the ion dipole interaction between the C-O-C group of ENR-50 and Li ions.

Effect of dopants addition on the displacing phase properties in a polymer flooding process using computed tomography scanning

This study evaluated the impact of the four most used dopants in core-flooding tests, supported by computed tomography, on the behavior of polymer viscosity. Initially, the minimum concentration of each dopant required to achieve an adequate contrast between phases was estimated by varying the amount of dopant in solution and comparing the CT number of polymer solution and oil to guarantee a differential highest than 300 CT. Afterward, the effect of adding the different dopants on the polymer solution viscosity was determined through Brookfield viscosimeter. Subsequently, the polymer concentration to counteract the viscosity reduction was quantified by adding different polymer amounts. The results showed that sodium iodide achieved the highest attenuating effect between phases with the lowest dopant concentration. Moreover, this dopant caused the lowest polymer viscosity diminution and required the smallest increase in polymer concentration to reach the base case viscosity, making this dopant the most suitable agent to be used in polymer injection experiments at the conditions evaluated. Finally, the impact of crude oil density on the lowest amount of dopant required to achieve sufficient differentiation between phases was analyzed, and as a result, a correlation was found that could be used in future experiments at similar conditions to evaluate polymer flooding in a porous medium by means computed tomography scan as a visual and non-intrusive technique, reaching the best contrast between crude oil and HPAM.

Colloidal and Thermal Stability of Three-Component Hybrid Materials Containing Clay Mineral, Polysaccharide and Surfactant.

The paper presents the colloidal and thermal stability of the three-component hybrid materials containing halloysite, polysaccharides (alginic acid, cationic cellulose and hydroxyethyl cellulose) and Tritons. TX-100, TX-165 and TX-405 were used as non-ionic surfactants. Stability and other properties of the hybrid materials were tested by the following methods: UV-Vis, TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry), CHN (elemental analysis), SEM-EDX (scanning electron microscopy with energy dispersive X-ray spectroscopy) and tensiometry. According to the results with the increasing polymer concentration the colloidal stability of the tested systems also increases. Moreover, the addition of the surfactants causes the increase of polysaccharide adsorption but the colloidal stability of the tested systems decreases due to large weights of formed aggregates. As follows from the thermal analysis, the comparison of the TG/DTG-DSC curves obtained for the investigated polymers confirms that their thermal decomposition courses have some common features. The obtained results have the application potential in the formation of the materials for the pollutants removal from water and sewages.

Numerical Investigation of Mechanical Performance and Micro-Structure Failure of Polymer-Fiber Reinforced Sand.

Natural sand has a loose and porous structure with low strength, and is prone to many geoengineering problems that cause huge losses. In this study, an organic polymer-polymer-fiber blend was used to improve the strength of sand. Using a series of laboratory and numerical simulation tests, researchers have investigated the microdamage behavior of an organic polymer and fiber-treated sand in various types of mechanical tests and explored the improvement mechanism. The results showed that the polymer- and fiber-treated sand enhanced the integrity and exhibited differential damage responses under different test conditions. The increase in polymer content induced uniform force transfer, leading to a wider range of particle motion and crack initiation, whereas the fibers adhered and confined the surrounding particles, inducing an arching force chain and dispersive/buckling cracking. Polymer- and fiber-treated sands increased their energy-carrying capacity and improved their energy release, which affected the damage characteristics. Organic polymers, fibers, and sand particles were wrapped around each other to form an effective interlocking structure, which enhances the integrity and mechanical properties of sand. This study provides novel ideas and methods in the polymer-fiber composite treatment of sand in the microscopic field.

Effect of solvent-free membranes-forming processes on HT-PEM properties of highly soluble polybenzimidazole

The cost-effective sol-gel process for the preparation of phosphoric acid (PA) doped P-PBI membranes using PPA as both condensation reagent and solvent could avoid the use of hazardous organic solvents. However, optimizing the trade-off effect between mechanical properties and proton conductivity of sol-gel membranes by increasing polymer content is ineffective due to the limited solubility of P-PBI in PPA. Herein, we successfully fabricated a series of sol-gel membranes with tunable properties using a highly soluble polybenzimidazole (N-PBI). In addition, the sol-gel (5 wt%) N-PBI membrane was further specially dried and post-doped with PA to obtain a re-doped sol-gel N-PBI membrane. Therefore, the properties of PA-doped N-PBI membranes fabricated using three different processes-conv, sol-gel, and re-doped sol-gel-were thoroughly characterized. The sol-gel N-PBI membranes demonstrated a dependence of mechanical properties and proton conductivity on polymer content, with a maximum tensile strength of 7.0 MPa at 7 wt% polymer content and a maximum proton conductivity of 205 mS/cm (200 °C) at 2 wt% polymer content. The ADL-controlled re-doped sol-gel N-PBI membrane achieved higher saturated ADL than the sol-gel N-PBI membrane, resulting in higher proton conductivity and fuel cell performance. The sol-gel (2 wt%) N-PBI membrane exhibited an ultra-high H2/O2 peak power density of 1058 mW/cm2 under an optimized operating condition, and the sol-gel (7 wt%) N-PBI membrane achieved stable operation without apparent degradation for over 2000 h at 160 °C with 0.3 A/cm2 current density.

Polyelectrolyte complex gels used for CO2 absorption

AbstractPolymer gels have shown application potential in minimizing gas channeling during CO2 enhanced oil recovery and storage processes, but the pumping pressure of preformed gels was too high, and the in‐situ cross‐linking in reservoirs was uncontrollable. Here we developed polyelectrolyte complex gels through the columbic attraction between sodium carboxymethyl cellulose (NaCMC) and protonated polyethyleneimine (PEI+) by CO2 in the presence of water. Without CO2, the viscosity of polymer complex solution is relatively low; after streaming CO2, the viscosity of the NaCMC‐PEI+ mixture aqueous solution increases significantly, forming a gel. It was also found that the complex solution shows an evolution of “sol–gel‐separated phase” as the polymer concentration increases, which could be attributed to the enhanced electrostatic attraction between CMC− and PEI+. The viscosity of the gel decreases upon increasing salinity owing to the reduced charge repulsion by the introduced inorganic salt. The CMC−‐PEI+ complex can retain its gel behavior until 60°C, after which the complex collapses. The uptake tests show that 11.34 mg CO2 can be absorbed by each gram of gel composed of 0.9 wt% NaCMC and 0.15 wt% PEI at room temperature and ambient pressure. This work provides an inexpensive route to control gas leakoff and improve CO2 absorption.

Rheological insights on Carboxymethyl cellulose hydrogels

Hydrogels are copiously studied for tissue engineering, drug delivery, and bone regeneration owing to their water content, mechanical strength, and elastic behaviour. The preparation of stable and mechanically strengthened hydrogels without using toxic crosslinkers and expensive approaches is immensely challenging. In this study, we prepared Carboxymethyl cellulose based hydrogels with different polymer concentration via a less expensive physical crosslinking approach without using any toxic crosslinkers and evaluated their mechanical strength. In this hydrogel system, the carbopol concentration was fixed at 1 wt/v% and the Carboxymethyl cellulose concentration was varied between 1 and 5 wt/v%. In this hydrogel system, Carbopol serves as the crosslinker to bridge Carboxymethyl cellulose polymer through hydrogen bonds. Rheological analysis was employed in assessing the mechanical properties of the prepared hydrogel, in particular, the viscoelastic behaviour of the hydrogels. The viscoelastic nature and mechanical strength of the hydrogels increased with an increase in the Carboxymethyl cellulose polymer concentration. Further, our results suggested that gels with Carboxymethyl cellulose concentration between 3 wt/v % and 4 wt/v % with yield stresses of 58.83 Pa and 81.47 Pa, respectively, are potential candidates for use in transdermal drug delivery. The prepared hydrogels possessed high thermal stability and retained their gel network structure even at 50 °C. These findings are beneficial for biomedical applications in transdermal drug delivery and tissue engineering owing to the biocompatibility, stability, and mechanical strength of the prepared hydrogels.