Preparation and swelling properties of a pH‐sensitive superabsorbent hydrogel based on psyllium gum

A series of natural polymer‐based superabsorbent hydrogels were prepared by free radical graft copolymerization of partially neutralized acrylic acid (AA) onto psyllium gum (PSY) in aqueous solution, using ammonium persulfate (APS) as the initiator, and N,N′‐methylenebisacrylamide (MBA) as the crosslinker. Fourier transform infrared spectroscopy (FTIR) confirmed that AA monomers have been grafted onto PSY macromolecular chains. The swelling properties of the hydrogels in various saline and pH solutions were investigated, and the swelling kinetics and reswelling ability of the hydrogels were also evaluated systematically. The hydrogels showed excellent responsive properties and reversible On‐Off switching characteristics in various pH buffer solutions, which render the hydrogels available as a candidate for drug delivery system.     

Kinetik der freien,integralen Quellung von chemisch modifiziertem Holz entlang der Wasserdampf‐Sorptionsisotherme unter luftfreien Bedingungen

Die kinetischen, dreidimensionalen Messungen der freien, integralen Quellung wurden an unbehandeltem und an acetyliertem (Acetylgehalt 8,56 %, 20,14 % und 28,63 %) Tannenholz (Abies alba Mill.) entlang der Sorptionsisotherme unter luftfreien Bedingungen durchgeführt. Der zeitliche Verlauf der Quellung in den drei anatomischen Hauptrichtungen und in der transversalen Richtung wurde für das unbehandelte und das acetylierte Holz aufgezeigt sowie der maximale Dimensionsstabilisierungseffekt (ASE) für die jeweilige Modifizierung geschätzt. Die Auswirkung des Partialdruckgradienten des Wasserdampfes auf die mittlere Quellungsgeschwindigkeit wurde behandelt. Kinetic of free integral swelling on chemically modified wood along the water vapour sorption isotherm under air‐free conditions. The kinetic, three‐dimensional measurements of the free integral swelling were accomplished at the untreated and at the acetylated (acetyl content 8.56 %, 20.14 % and 28.63 %) fir wood (Abies alba Mill.) along the sorption isotherm under air‐free conditions. The course of the swelling in the three anatomical main directions and in the transversal direction was presented for the untreated and the acetylated wood. The anti‐swelling efficiency (ASE) for the accomplished modifications was estimated. The effect of the partial pressure gradient of the water vapour on the mean swelling speed was presented.     

Measured and Estimated Suction Indices for Swelling Potential Classification

McKeen’s expansive soil classification methodology relies on a parameter referred to as the “total suction-water content index” for describing the slope of the soil–water characteristic curve on a semilog plot. The swelling potential of expansive soils is qualitatively classified (e.g., “low” or “high”) based on the magnitude of the total suction-water content index. This study examines the validity of using a “benchmark intercept simplification” for indirectly estimating the total suction-water content index when complete soil–water characteristic measurements are not available or economical. Suction indices estimated using the benchmark intercept simplification are compared with indices measured directly using the noncontact filter paper technique for 80 undisturbed expansive shale specimens from the Colorado Front Range Corridor. The results show that the suction-water content index is consistently overestimated using the benchmark simplification by amounts ranging from negligible to 50%, and averaging 23%. For 49 of the 80 specimens (61%), the estimated indices fall in different swelling potential categories than the measured indices. In 44 of the 49 cases (90%), the estimated indices fall in higher swelling potential categories than the measured indices. These discrepancies reflect potential errors that may arise from the use of the benchmark intercept simplification in classifying expansive soils.     

Soft Matter Engineering for the Fabrication of Functionalized Casein Microparticles

The structural features of the most abundant milk protein casein can be exploited for the targeted production of microparticles with desired properties. After the addition of pectin, the so-called casein micelles reversibly form aggregates of several µm in size, which change their shape due to shear and elongation forces. The soft properties are crucial for the subsequent solidification into stable casein microparticles during film drying. Based on pH-dependent experiments, we show how we analyze and tailor the swelling and disintegration properties of the microparticles for future controlled and instant release applications.     

The swelling behaviour of wheat starch granules during isothermal and non-isothermal treatments

The size of wheat starch granules was measured during isothermal and non-isothermal treatments and fitted using mathematical models in order to elucidate the time–temperatures dependence of the swelling phenomenon and to improve our understanding of the mechanism followed by granules during gelatinization. Upon the onset temperature of gelatinization, starch granules size increase rapidly and tend to reach equilibrium values that depend on the temperature and heating rate applied. The most accurate fitting of granule size observed overall isothermal treatments was obtained with the third-order kinetic and the Weibull empirical models. The activation energy of swelling calculated for isothermal treatment varied between 41 and 318 kJ mol⁻¹, depending on the mathematical model considered. Therefore, without a consensus on the mechanism and order of reaction followed during gelatinization, the meaningful of kinetic parameters calculated using mathematical models seems highly questionable. During non-isothermal treatments at lower heating rate, it seems like a limitation of the swelling capacity of granules was induced. This phenomenon was attributed to restructuration occurred inside of granules. So, forecasting the swelling behaviour of starch granules during non-isothermal treatment has to consider both the time–temperature and the heating rate applied.     

Microstructural evolution,swelling and hardening of CVD-SiC induced by He ions irradiation at 650 °C

In the present study, chemical vapor deposited (CVD) SiC samples were irradiated by 500 keV He ions to different doses at 650 °C. The microstructural evolution, surface swelling and nanohardness change caused by irradiation versus He ion dose were investigated using TEM, AFM and nanoindentation. Results showed that a high number density of He bubbles and dislocation loops were formed in the sample irradiated to the high dose, resulting in a swelling of 1.53%. Meanwhile, the hardness of the samples increased after He ions irradiation, which was attributed to the pinning effect of the irradiation induced defects and bubbles. The irradiation hardening degree increased and tended to be saturated with the increasing He ion dose.     

Formulation and in vitro evaluation of κ‐carrageenan‐pregelatinized starch‐based mucoadhesive gels containing miconazole

The aim of this work was to investigate the effects of using κ‐carrageenan (κ‐Carr) with pregelatinized starch (PGS) in the improvement of swelling and erosion behaviors of mucoadhesive gels containing 2% of miconazole. Polymer blends containing carrageenan and PGS were used for the formulation, and the effect of varying polymer concentrations on the drug release was studied. The matrices were prepared using different biopolymer (starch hydrogel) concentrations. Swelling and erosion characteristics of the matrices were carried out in various media and their impact on drug release were studied. The swelling action of the gel matrix was controlled by the rate of its hydration in the medium. Release studies have showed that the swelling and erosion of matrices influence the drug release. In addition, the presence of κ‐Carr in the gel formula improves the bioadhesive properties. The release data showed a good fit into the power law or Korsmeyer–Peppas equation indicating the combined effects of diffusion and erosion mechanisms of drug release. Most of the formulations released miconazole by an anomalous (non‐Fickian) transport mechanism, except those matrices that contained PGS alone which showed zero‐order release.     

New Starch Phosphate Carbamides of High Swelling Ability: Synthesis and Characterization

The paper describes the synthesis of starch phosphate carbamides by reacting starch with phosphoric acid and urea. A solid state technique in vacuum at elevated temperatures is used. The degree of substitution of phosphate (DS_P) and carbamide groups (DS_C) can be adjusted by the molar ratio of starch: phosphoric acid: urea, the reaction temperature, and time. The starch derivatives prepared show remarkable swelling if the DS_P ranges between 0.2 and 0.3. With increasing content of urea in the reaction mixture the water‐holding ability is still significantly improved, which is explained by chemically and especially physically introduced urea into the starch polymer. Furthermore, the ratio of amylose: amylopectin of the starch samples influences both the DS values and the physicochemical properties, e.g., swelling power and multivalent metal ion adsorption of the products. The structure of the new polymers was determined by means of FTIR, ¹³C‐ and ³¹P NMR spectroscopy as well as by gel permeation chromatography (GPC).     

Smart porous microparticles based on gelatin/sodium alginate polyelectrolyte complex

Porous microparticles of different sizes were prepared by polyelectrolyte complexation of biopolymers gelatine A and sodium alginate for microencapsulation of food bioactives. The optimum pH and ratio between the polymers sodium alginate and gelatine for maximum complexation was found as 3.7 and 1:3.5 respectively. Effect of various factors like amount of surfactant, concentration of polymer and crosslinker on the formation, size and porous/nonporous nature of the microparticles were investigated. The particles’ diameter on swelling at pH = 7.4 was twice that at pH = 1.2 indicating the pH responsiveness. These microparticles were used as carrier for ascorbic acid. The surface morphology and sizes of the microparticles were investigated by scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) study indicated the formation of polyelectrolyte complex between gelatine and sodium alginate and successful encapsulation of ascorbic acid into the microparticles. The microparticles were further characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) study.     

空气雾化钻井井壁稳定剂的室内评价研究

采用“化学剂的水化膨胀抑制率”作评价指标，对一些典型的水基泥浆页岩水化抑制剂及两种自制成膜剂进行了室内评价研究。结果表明：在空气雾化钻井中应用水基泥浆钻井的页岩水化抑制剂对稳定井壁有一定的作用，但不理想，而成膜剂却具有稳定井壁的良好效果。