Equilibrium Degree Of Swelling Research Articles

Swelling of rubbers of different chemical natures in supercritical carbon dioxide

Objectives. To investigate the swelling of the main types of rubbers used in the rubber industry in carbon dioxide in a supercritical state (SC-CO2), in order to assess the possibility of obtaining elastomeric materials with porous structures using fluid technology, based on them.Methods. The process of swelling of rubbers in SC-CO2 and subsequent foaming was carried out according to a specially developed technique using the original installation. This is a high-pressure apparatus with transparent windows, allowing for the use of an optical technique to directly measure the geometric dimensions of samples during swelling and foaming using a digital video camera. The study of the porous structure of foamed rubbers was carried out using scanning electron microscopy.Results. The study established experimental curves of the swelling kinetics in SC-CO2 of isoprene, butadiene, styrene butadiene, ethylene propylene, chloroprene, ethylene acrylate, siloxane, and organofluorine rubbers. The influence of temperature and pressure on the rate and equilibrium degree of swelling was studied. The diffusion coefficients of SC-CO2 in rubbers of various chemical natures were also determined.Conclusions. It was shown that the equilibrium swelling degree of rubbers in SC-CO2 depends on the chemical nature of rubbers. It does not correlate with the value of their solubility parameters, changes directly proportional to the diffusion coefficient and increases with increasing temperature and pressure. It was found that irrespective of the degree of swelling in SC-CO2, all the rubbers studied are intensively foamed at a sharp pressure drop. The size of the pores formed is tens of microns: significantly smaller than the size of pores formed when chemical pore formers are used.

Superabsorbent Hydrogel from Cassava Waste Pulp – Acrylamide – Acrylic Acid to Increase Water Holding Capacity in Sandy Soils

In this investigation, a superabsorbent hydrogel was produced from cassava waste pulp (CWP) and acrylic acid (AA) – acrylamide (AAm) in a ratio of 2:1.5:1 (CWP:AA:AAm) by grafting and crosslinking methods. The grafting procedure is initiated with ammonium persulfate (APS) at a concentration of 1%. In this study, cross-linked structures were produced using several concentrations of methylene bisacrylamide (MBA) (0%, 0.5%, 1%, and 1.5%). The impact of MBA concentration on the properties of the superabsorbent hydrogel was observed. The parameters investigated in this study included the equilibrium degree of swelling (EDS), grafting degree, gel fraction, and swelling kinetics (comprising the swelling exponent, swelling constant, and diffusion coefficient). Following this, the hydrogels were sprinkled into sandy soil with the purpose of examining the effects of hydrogel incorporation on the soil’s water holding capacity. The sample with a concentration of 0.5% MBA yielded the highest EDS at 9178% (g/g), as determined by the results. The gel fraction value obtained for the sample was 81.04% (g/g) and the crosslink density of this sample was measured to be 2.78 × 1023 m-3, while the maximal water holding capacity was found to be 54.16%.

Antiproliferative Imidazo-Pyrazole-Based Hydrogel: A Promising Approach for the Development of New Treatments for PLX-Resistant Melanoma.

Aiming at developing a dermal formulation against melanoma, the synthesized imidazo-pyrazoles 2-phenyl-2,3-dihydro-1H-imidazo[1,2-b]pyrazole-7-carboxylic acid (3-methoxy-4-phenoxy-benzylidene)-hydrazide (4G) and 2-phenyl-2,3-dihydro-1H-imidazo[1,2-b]pyrazole-7-carboxylic acid (4-benzyloxy-3-methoxy-benzylidene)-hydrazide (4I) were screened on patient-isolated melanoma cells (MEOV NT) and on Vemurafenib (PLX4032)-resistant (MEOV PLX-R) ones. Since 4I on MEOV PLX-R cells was 1.4-fold more effective than PLX, a hydrogel formulation containing 4I (R4HG-4I) was prepared in parallel with an empty R4-based hydrogel (R4HG) using a synthesized antibacterial resin (R4) as gelling agent. Thanks to its high hydrophilicity, porosity (85%), and excellent swelling capability (552%), R4 allowed to achieve R4HG and R4HG-4I with high equilibrium degree of swelling (EDS) and equilibrium water content (EWC). Chemometric-assisted ATR-FTIR analyses confirmed the chemical structure of swollen and fully dried (R4HG-D and R4HG-4I-D) hydrogels. The morphology of R4HG-D and R4HG-4I-D was examined by optical microscopy and SEM, while UV-vis analyses were carried out to obtain the drug loading (DL%) and the encapsulation efficiency (EE%) of R4HG-4I. Potentiometric titrations were performed to determine the equivalents of NH3+ in both R4HG and R4HG-4I. The swelling and water release profiles of both materials and related kinetics were assessed by equilibrium swelling rate and water loss studies, respectively, while their biodegradability over time was assessed by in vitro degradation experiments determining their mass loss. Rheological experiments established that both R4HG and R4HG-4I are shear-thinning Bingham pseudoplastic fluids with low yield stress, thus assuring easy spreadability in a future topical application. Release studies evidenced a sustained and quantitative release of 4I governed mainly by diffusion. Upon favorable results from further experiments in a more realistic 3D model of melanoma, R4HG-4I could represent a starting point to develop new topical therapeutic options to adjuvate the treatments of melanoma cells also when resistant to currently available drugs.

Simultaneous Interpenetrating Polymer Networks Based on Poly(2‐Oxazoline)s

AbstractInterpenetrating polymer networks (IPNs), comprised of two or more independent crosslinked networks in which the individual networks are interlaced, can be used to enhance material properties and increase functionality for applications such as tissue engineering, drug delivery, and biofabrication. IPNs can be formed by either simultaneous or sequential crosslinking, with sequential crosslinking being complicated by the need to infiltrate the constituents of the second network into the first network. Herein, the study reports the first simultaneous IPN based on the cationic ring‐opening polymerization (CROP) of 2‐methyl‐2‐oxazoline (MeOx) with bis(butyl‐2‐oxazoline) (BBOx) crosslinker and the reversible addition‐fragmentation chain‐transfer (RAFT) polymerization of N,N‐dimethylacrylamide (DMAAm) with N,N`‐methylene bis(acrylamide) (BAM) crosslinker. Specifically, the compatibility of the synthesis techniques is demonstrated for the preparation of simultaneous IPNs, and it is shown that, by varying the amounts of the two crosslinkers and comparing to single‐component networks, the equilibrium degree of swelling (EDS) in water and compressive modulus can be tuned. The results reported demonstrate the utility of CROP and RAFT for preparing IPNs and suggest that with appropriate optimization the technique can be expanded to other monomer pairs which are polymerizable via CROP and RAFT.

Cationic Polystyrene-Based Hydrogels as Efficient Adsorbents to Remove Methyl Orange and Fluorescein Dye Pollutants from Industrial Wastewater.

Water pollution from dyes is harmful to the environment, plants, animals, and humans and is one of the most widespread problems afflicting people throughout the world. Adsorption is a widely used method to remove contaminants derived from the textile industry, food colorants, printing, and cosmetic manufacturing from water. Here, aiming to develop new low-cost and up-scalable adsorbent materials for anionic dye remediation and water decontamination by electrostatic interactions, two cationic resins (R1 and R2) were prepared. In particular, they were obtained by copolymerizing 4-ammonium methyl and ethyl styrene monomers (M1 and M2) with dimethylacrylamide (DMAA), using N-(2-acryloylamino-ethyl)-acrylamide (AAEA) as cross-linker. Once characterized by several analytical techniques, upon their dispersion in an excess of water, R1 and R2 provided the R1- and R2-based hydrogels (namely R1HG and R2HG) with equilibrium degrees of swelling (EDS) of 900% and 1000% and equilibrium water contents (EWC) of 90 and 91%, respectively. By applying Cross' rheology equation to the data of R1HG and R2HG's viscosity vs. shear rate, it was established that both hydrogels are shear thinning fluids with pseudoplastic/Bingham plastic behavior depending on share rate. The equivalents of -NH3+ groups, essential for the electrostatic-based absorbent activity, were estimated by the method of Gaur and Gupta on R1 and R2 and by potentiometric titrations on R1HG and R2HG. In absorption experiments in bulk, R1HG and R2HG showed high removal efficiency (97-100%) towards methyl orange (MO) azo dye, fluorescein (F), and their mixture (MOF). Using F or MO solutions (pH = 7.5, room temperature), the maximum absorption was 47.8 mg/g in 90' (F) and 47.7 mg/g in 120' (MO) for R1, while that of R2 was 49.0 mg/g in 20' (F) and 48.5 mg/g in 30' (MO). Additionally, R1HG and R2HG-based columns, mimicking decontamination systems by filtration, were capable of removing MO, F, and MOF from water with a 100% removal efficiency, in different conditions of use. R1HG and R2HG represent low-cost and up-scalable column packing materials that are promising for application in industrial wastewater treatment.

Hydrogel Formulations of Antibacterial Pyrazoles Using a Synthesized Polystyrene-Based Cationic Resin as a Gelling Agent.

Here, to develop new topical antibacterial formulations to treat staphylococcal infections, two pyrazoles (3c and 4b) previously reported as antibacterial agents, especially against staphylococci, were formulated as hydrogels (R1-HG-3c and R1HG-4b) using a cationic polystyrene-based resin (R1) and here synthetized and characterized as gelling agents. Thanks to the high hydrophilicity, high-level porosity, and excellent swelling capabilities of R1, R1HG-3c and R1HG-4b were achieved with an equilibrium degree of swelling (EDS) of 765% (R1HG-3c) and 675% (R1HG-4b) and equilibrium water content (EWC) of 88% and 87%, respectively. The chemical structure of soaked and dried gels was investigated by PCA-assisted attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy, while their morphology was investigated by optical microscopy. Weight loss studies were carried out with R1HG-3c and R1HG-4b to investigate their water release profiles and the related kinetics, while their stability was evaluated over time both by monitoring their inversion properties to detect possible impairments of the 3D network and by PCA-assisted ATR-FTIR spectroscopy to detect possible structural changes. The flow and dynamic rheological characterization of the gels was assessed by determining their viscosity vs. shear rate, applying the Cross rheological equation to achieve the curves of shear stress vs. shear rate, and carrying out amplitude and frequency sweep experiments. Finally, their content in NH3+ groups was determined by potentiometric titrations. Due to their favorable physicochemical characteristic and the antibacterial effects of 3c and 4b possibly improved by the cationic R1, the pyrazole-enriched gels reported here could represent new weapons to treat severe skin and wound infections sustained by MDR bacteria of staphylococcal species.

Fabrication and evaluation of antibacterial properties of Cu2O/sepiolite-PVA nanocomposite hydrogels against multidrug-resistant bacteria

Chronic wound infection is a serious healthcare issue across the globe. Herein, the nanocomposite hydrogels comprising cuprous oxide nanoparticles grafted sepiolite (Cu2O/Sep) and poly(vinyl alcohol) (PVA) were prepared via the freeze-thaw method. The physical, structural, mechanical, and antibacterial properties of the nanocomposite hydrogels were determined. The moisture retention capacities, swelling ratio, equilibrium degree of swelling, and porosity of nanocomposite hydrogels were enhanced with the use of Cu2O/Sep. In-vitro release studies demonstrated that the cumulative release of Cu from nanocomposite hydrogels followed the quasi-Fickain-diffusion mechanism. The nanocomposite hydrogels exhibited good percent elongation and ultimate tensile strength under a wet environment due to the presence of Cu2O/Sep. The antibacterial properties of the nanocomposite hydrogels were evaluated against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Escherichia coli, multidrug-resistant Pseudomonas aeruginosa, and multidrug-resistant Klebsiella pneumoniae bacterial strains. The bactericidal effects of nanocomposite hydrogels were significantly higher against Gram-positive bacteria than Gram-negative ones. Hence, the nanocomposite hydrogels demonstrate their potential use as a wound dressing material for the treatment of multidrug resistant infected wounds.

Impact of Freezing Conditions on the Morphology and Mechanics of PVA‐Based Sponge‐Like Materials

AbstractHighly porous polymer materials have been studied a lot for applications in biotechnology and biomedicine, because of their high surface area and percolated pore structure. Varying processing conditions, in this study, can tune the morphology, mechanical, and physicochemical characteristics of the materials. In the present work, cross‐linked poly(vinyl alcohol)‐based freeze‐dried sponges linked by glutaraldehyde are studied. The current study analyzes the influence of cooling speed on the sponge's morphology and mechanical properties. Complex analysis of the tests carried out shows agreement in morphology, surface area, equilibrium degree of swelling, and mechanical properties of the sponges with dependence on the amount of cross‐linking agent and freezing conditions.

Synthesis and Rheological Characterization of a Novel Salecan Hydrogel.

Salecan (Sal) is a novel microbial polysaccharide. In the present research, thermal treatment was performed to fabricate Sal hydrogel. The effect of Sal concentration on water holding capacity, swelling properties, texture properties, and microstructure of the hydrogels was discussed. It was found that the equilibrium degree of swelling (EDS) of Sal hydrogels was above 1500%, inferred Sal was a highly hydrophilic polysaccharide. As Sal concentration increased from 3.5 to 8.0 wt%, the hardness increased from 0.88 to 2.07 N and the water hold capability (WHC) increased from 91.3% to 98.2%. Furthermore, the internal network structure of Sal hydrogel also became denser and more uniform. Rheological studies suggested that elastic hydrogel formed under the gelation process. All these results demonstrated that Sal hydrogel prepared by thermal treatment had good gelling properties, which opened up a new safe way for the preparation of Sal hydrogel and broadened the application range of Sal.

Temperature- and pH-sensitive hydrogels of sequential Ti-containing interpenetrating polymer networks

Hydrogels of sequential Ti-containing interpenetrating polymer networks based on hydrophilic cross-linked polyurethanes with different molecular weight of polyethylene glycols and Ti-containing copolymer were synthesized based on 2-hydroxyethyl methacrylate and titanium isopropoxide. The composition of sequential interpenetrating polymer networks was determined by the degree of equilibrium swelling of the polyurethane networks in 2-hydroxyethyl methacrylate and Ti-containing comonomer. It was established that the content of the second component of the interpenetrating polymer networks increases with increasing the average molecular weight value of the polyurethane network. It was shown that the obtained highly sensitive hydrogels of Ti-containing interpenetrating polymer networks react to the changes in the temperature and pH. These factors significantly change the equilibrium water content in the hydrogels. Differential scanning calorimetry allowed determining the phase transitions that are characteristic of bound and free water, which is a part of the hydrogel of polyurethanes, interpenetrating polymer networks and Ti-containing interpenetrating polymer networks. The results showed that the content of bound water and the degree of its binding to the components of the interpenetrating polymer networks depend on the chemical structure of the network, the nature of a second polymer component (which is a part of the interpenetrating polymer networks), the polarity and hydrophilicity of macromolecules, and the size of hydrogel cells. Regardless of the nature of the second polymer component, there is a general trend for all interpenetrating polymer networks: the total water content increases with increasing the average molecular weight of the polyurethane matrix networks.

Optimized ciprofloxacin release from citric acid crosslinked starch-PVA hydrogel film: modelling with mixture design

Projecting optimal composition for hydrogel blends, while designing sustained release formulation of hydrophilic drug, is of paramount importance. In present study, composite hydrogel incorporating ciprofloxacin (0.2% w/w) was prepared by sequential addition of polyvinyl alcohol (PVA) (20–95% w/w), starch (0–75% w/w), citric acid (5–80% w/w) as cross-linker in a heat-induced gelatinization process. A constrained simplex mixture design was adopted to rationalize the proportion of ingredients in hydrogel composition while modelling the time required for 50% drug release from the hydrogel under in-vitro conditions. Prepared hydrogels were also characterized for swelling ratio, tensile strength, and antimicrobial disc-diffusion assay. Decreasing proportion of starch relative to PVA results in a transparent hydrogel, with a high degree of equilibrium swelling (up to 104%). Drug release from all hydrogel blend arguably followed Korsmeyer-Peppas release kinetics with quasi-Fickian to non-Fickian release behaviour. The time required for 50% drug release and the hydrogel dissolution was proportional, indicating disintegration-controlled release rate. Reduced cubic-model based on the forward selection offered good agreement with experimental data (R2, 0.98 and adjusted R2 of 0.91). Optimal blend projection by the model with a mass ratio of 0.38:0.21:0.41 for PVA: Starch: citric acid was verified to be reasonably correct.

Utilizing Alginate to Improve Elasticity and Moisture Balance of Polyvinyl Alcohol/Chitosan Hydrogel Wound Dressing

Uncontrolled hemorrhage is the leading cause of death. The efficient hemostatic dressings are needed to promote coagulation and hold ongoing hemorrhage. Hydrogels are hydrophilic polymers with three-dimensional network structures with high swelling capacity to prevent accumulation of exudates. Hydrogels prepared from polyvinyl alcohol (PVA) grafted with chitosan have attracted considerable attentions due to their biocompatibility, high moisture balance property, and transparency. In this study, alginate was utilized to improve elasticity and thermal stability, also enhance hydrophilicity and increase swelling ability. The hydrogels composed of PVA (7.5 % w/v), chitosan (0.05 % w/v), and alginate (0.2, 0.4, and 0.6 % w/v) were synthesized by gamma irradiation technique at total dose of 15 kGy. The results showed that the increasing of alginate concentration in the total reactant mixture can improve elasticity, swelling capacity and the equilibrium degree of swelling (EDS), and decrease water vapour transmitted rate/moisture vapour transmitted rate (MVTR). The hydrogel wound dressing with 0.6 % of alginate concentration was the best product in this study with 79.49 % gel content, 608.65 % swelling ratio, 628.32 % EDS in 22 hours, elasticity 62.58 KPa, evaporation rate (MVTR) 105g/m2 h, degraded at temperature of 298.89oC, and the weight loss was reached 88.84 % (w/w).

Poly(2-oxazoline)-based magnetic hydrogels: Synthesis, performance and cytotoxicity

Research on the subject of smart biomaterials has become a cornerstone of tissue engineering and regenerative medicine. Herein, the authors report on developing magnetic hydrogels that combine high biocompatibility and remarkable activity in magnetic fields. We fabricated magnetic hydrogels based on poly(2-ethyl-2-oxazoline) (POx) via living ring-opening cationic polymerization with in-situ embedding of the carbonyl iron (CI) particles. Investigation was made as to the effect exerted by the concentration of CI on magnetic, viscoelastic/magnetorheological properties, the degree of equilibrium swelling, and cytotoxicity. The hydrogels exhibited an open pore structure, as evidenced by computed tomography (CT) imaging. Susceptibility measurements revealed the concentration-dependent field-induced particle restructuration indicating elongation/contraction of the material, thereby determining the potential for magneto-mechanical stimulation of the cells. The POx-based magnetic hydrogels were amphiphilic in character, showing decrease in their capability to hold liquid alongside increase in CI concentration. Viscoelastic measurements suggested that interaction occurred between the particles and matrix based on inconsistency between the experimental storage modulus and the Krieger–Dougherty model. The synthesized materials exhibited excellent biocompatibility toward the 3T3 fibroblast cell line in tests of extract toxicity and direct contact cytotoxicity (ISO standards). The unique combination of properties exhibited by the material - magneto-mechanical activity and biocompatibility - could prove favorable in fields such as biomedicine and biomechanics.

Production and Kinetics of Swelling in Water of Biocompatible Branched Polyvinyl Alcohol Films

The interrelation of the synthesis conditions of polyvinyl alcohol chain branching products under the action of epichlorohydrin in an alkaline medium was established with the kinetic laws of swelling of films based on them in water. It was shown that conditions conducing to an increase in the branching density of the polyvinyl alcohol chain lead to an increase in the equilibrium degree of swelling in water. The possibility of growing cells of the M-22 line on the surface of branched polyvinyl alcohol films was demonstrated, which indicates their biocompatibility.

Modification of PTFE Flat Sheet Film via Radiation Induced Grafting Polymerization with Acrylic Acid

Polytetrafluoroethylene (PTFE) flat sheet film was modified with acrylic acid (AAC) by radiation induced grafting polymerization (RIGP) method using electron beam. The adsorbed doses were varied from 10 to 50 kGy, time of grafting from 1 to 3 h and monomer concentration and temperature were kept constant at 30 wt. % and 40°C. The degree of grafting (Dg) and equilibrium degree of swelling (EDS) of the grafted films were then determined. The films were further characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), and optical water contact angle. Dg within the range of 17% to 210% were obtained for doses from 10 to 50 kGy within time of grafting from 1 to 3 h. The grafted film (PTFE-g-AAC) showed increased hydrophilicity leading to an increase in EDS. The successful grafting process was confirmed by FTIR results that showed characteristics peaks for carbonyl and hydroxyl group and a decrease in crystallinity for the PTFE-g-AACfilm. SEM images showed that PTFE-g-AAC films had less fibrillar compared to PTFE film and was consistent with the decrease in roughness for the PTFE-g-AAC film. This study indicated that modifying PTFE film by grafting AAC could significantly improve the hydrophilicity of PTFE film. The PTFE-g-AAC films has potential as a heavy metal adsorbent as it can remove at least 75% of Fe ion and 50 % of Pb ion from competitive media.

Biodegradable starch particles for controlled release applications: Swelling and leaching mechanisms

AbstractStarch‐extruded particles have only found infrequent use as delivery systems for active ingredients. We have previously shown that these particles are attractive for releasing hydrophobic compounds in water media. Here, we cover a range of amylose–amylopectin ratios and evaluate the presence of the thyme essential oil (TEO) as active compound to understand the dominant release mechanism in relation to the physicochemical properties of the starch matrices. Starch blends with high amylopectin content (1.8 and 15% amylose) could not be shaped into regular particles. For amylose contents higher than 28%, the equilibrium degree of swelling in water decreased with increasing amylose contents, from nearly 300% for an amylose content of 28–90% at an amylose content of 70%. For both lowest amylose contents, 1.8 and 15%, leaching of solids and disintegration of the particles resulted in a low apparent degree of swelling. The presence of TEO reduces the degree of swelling of the gelatinized starch matrix. This is explained by the formation of thymol–amylose complexes, which is confirmed by Fourier transform infrared spectroscopy analysis and X‐ray diffraction.

Synthesis and evaluation of CMC-g-AMPS/Fe/Al/AC composite hydrogel and their use in fluoride removal from aqueous solution

Abstract Cellulose based hydrogels are emerging adsorbents for treating aqueous pollutants due to their modifiable surface characteristics and superabsorbent properties. This study investigates the sorption of fluoride (F − ) on CMC-g-AMPS/Fe/Al composite hydrogel impregnated with activated charcoal. Statistically valid Plackett–Burman design of experiments was employed for determination of most significant factors affecting F − removal. The maximum defluoridation efficiency of metal oxide incorporated HG (CMC-g-AMPS/Fe/Al/AC) was found to be 84.67% at pH 6 at an initial F − concentration of 5 mg/L which is significantly higher compared to control HG (CMC-g-AMPS/AC). Analysis of variance (ANOVA) revealed the effect of pH followed by contact time as the most significant parameter (P value − removal. The experimental data fitted well with the Langmuir isotherm model, with the maximum F − adsorption of 67.114 mg/g. The modification mechanism and adsorption process on HGs were examined with equilibrium degree of swelling (EDS), FT-IR spectra, SEM, EDX and XRD analysis. Characterization analysis of CMC-g-AMPS/Fe/Al/AC HG confirms a parallel hydrolysis reaction on fibrous polycrystalline lattice along with the desired metal incorporation and higher gel strength making it an excellent anionic polymer with high F − binding capacity.

The effect of saccharides on equilibrium swelling of thermo-responsive gels.

Mechanical and optical properties of thermo-responsive (TR) gels change drastically at their volume phase transition temperature. As the critical temperature is strongly affected by the presence of small amounts of additives in aqueous solutions, TR gels can be employed as sensors for detection and recognition of multiple analytes (from specific ions to hazardous biochemicals to pathogenic proteins) and actuators for biomedical applications. A simplified mean-field model is developed for equilibrium swelling of TR gels in aqueous solutions of additives. Its advantage is that the model involves a relatively small (compared with the conventional approaches) number of material constants and accounts for changes in the thermo-mechanical response at transition from the swollen to collapsed state. The ability of the model to describe experimental swelling diagrams and to predict the influence of additives on the equilibrium degree of swelling and the volume phase transition temperature of TR gels is confirmed by comparison of observations on poly(N-isopropylacrylamide) gel in aqueous solutions of saccharides (glucose, sucrose and galactose) with results of numerical analysis.

Copolymerization of starch-acrylamide by gamma irradiation for hydrogel

The present study aimed to synthesize and evaluate copolymerization of starch-acrylamide by gamma irradiation for hydrogel Copolymerization of gelatinized starch and acrylamide (AAm) in aqueous medium using γ-irradiation was carried out. The preparation conditions, such as irradiation dose and AAm concentration, were investigated. The copolymers were characterized by FTIR spectroscopy, thermo-gravimetric analysis (TGA), and scanning electron microscopy (SEM). The results show that by increasing of irradiation dose, the gel fraction increases till the dose of 15 kGy. Above the stating dose, the gel fraction decreases. The Equilibrium Degree of Swelling (EDS) value slightly increases with increasing irradiation dose, and after a dose of 15 kGy is decreasing. The swelling of starch- AAm hydrogels reduced as the gel content increases. The results indicated that the optimum condition for obtaining hydrogels with desirable properties is irradiated at a dose of 15 kGy. The results indicated that SEM revealed that the higher the dose, the lower the copolymer pore size. The starch-AAm copolymers have thermal stability higher than that for starch individually.

Rheological, dynamic mechanical and transport properties of compatibilized starch/synthetic copolymer blends

The method of mechanical activation due to shear stress in the rotor-stator device (RSD) was used to combine the gelatinized starch and the latex of the styrene-acrylic copolymer (SAC). The influence of composition and method of mechanical activation on the rheological behavior of the aqueous starch/SAC blends, as well as on the dynamic mechanical properties, water sorption and salt transfer of the films was studied. A decrease in the starch content in water mixtures and joint activation were shown to promote a decrease in their viscosity and consistency index in the Ostwald-deWaele equation. The temperature dependences of the storage modulus (E′) and the mechanical loss tangent (tanδ) were obtained at tension of the starch/SAC films. An increase in E′ and a decrease in tanδ with increasing starch content have been established. Anomalous rise in rigidity was noted as the result of introduction of 20% SAC in starch. The increase in starch content is accompanied by a marked decrease in the rate and a rise in the equilibrium degree of swelling. An increase in the starch content from 20 to 80% results in a ninefold increase in the NaCl permeability coefficient.