Abstract. Semi-IPNs with varying contents of poly(vinyl alcohol) (PVA), poly acrylamide (PAM) and crosslinker N,N'-methylene bis acrylamide (MBA) were prepared by redox polymerization method. The structural and morphological properties were studied by Fourier transform infrared (FTIR) spectroscopy, environmental scanning electron microscopy (ESEM) and X-ray diffraction (XRD) methods, respectively. It was found that the surface of the hydrogel is heterogeneous with separated domains. XRD result shows the semi-crystalline nature of the semi-IPNs. The prepared semi-IPNs of different compositions were subjected to gamma irradiation (2 to 250 kGy) and the radiation induced effects on their strength of the semi-IPNs were studied by measuring the surface microhardness using a Vickers microhardness tester. Significant changes were observed in the Vickers microhardness, which were correlated with molecular architecture of the prepared semi-IPNs.
Semi-interpenetrating polymer networks (semi-IPNs) based on polyvinyl alcohol (PVA) and crosslinked polyacrylamide (PAM) were prepared by redox polymerization and further characterized by FTIR, ESEM, and XRD techniques. The semi-IPNs of varying compositions were investigated for their water sorption behavior, and the network parameters like average molecular weight between crosslinks (M C ) and crosslink density were evaluated from water imbibition measurements. The semi-IPNs were also judged for their in vitro blood compatibility by blood clot formation and percent hemolysis test. It was noticed that the chemical architecture exert a profound effect on the over all performance of the biomaterials.
Semi-IPNs based on polyvinyl alcohol (PVA) and crosslinked polyacrylamide (PAM) were prepared and characterized. Various compositions of semi-interpenetrating polymer networks (semi-IPNs) were prepared by varying concentrations of PVA, acrylamide (AM) and crosslinker N,N'-methylene bis acrylamide (MBA) in the feed mixtures and polymerized using a suitable redox system comprising of potassium persulphate and metabisulphite. The prepared semi-IPNs were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The prepared semi-IPNs were also investigated for microhardness measurements.
Semi-interpenetrating polymer networks (semiIPNs) based on polyvinyl alcohol (PVA) and crosslinked polyacrylamide (PAM) were prepared by redox polymerization. Various specimens were prepared by varying concentration of PVA, acrylamide (AM) and crosslinker MBA to study the effect of different compositions on the structural and mechanical property of semi-IPNs. The structural and morphological characterizations of prepared semi-IPNs were obtained from the studies of FTIR spectroscopy, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM). The mechanical properties of pure PVA and semi-IPNs like tensile strength, percentage elongation and deformation under stress were obtained by load-displacement curves. A similar profile for deformation is obtained for all the semi-IPNs. It was found that the elastic modulus, necking behaviour and ultimate failure are largely affected by the chemical composition of the semi-IPNs.
Flooding stress (FS) induced changes in pigment and protein contents and in photochemical efficiency of thylakoid membranes of chloroplasts were investigated during senescence of primary leaves of rice seedlings. Leaf senescence was accompanied by loss in 2,6-dichlorophenolindophenol (DCPIP) photoreduction, rate of oxygen evolution, quantum yield of photosystem 2 with an increase in MDA accumulation, and non-photochemical quenching (NPQ) of chlorophyll fluorescence. These changes were further aggravated when the leaves during this period experienced FS. The increase in NPQ value under stress may indicate photosynthetic adaptation to FS.Additional key words: adaptation to stress; carotenoids; chlorophyll; non-photochemical quenching; photosystem 2; quantum yield; senescence.--Prolonged water-logging of rice plants is a major problem in rice growing countries. The work conducted so far to understand the mechanism of damage and adaptation of photosynthetic apparatus of green plants experiencing flooding stress (FS) is meager (Mauchamp and Methy 2004, Panda et al. 2006). The photosynthetic apparatus, especially its photosystem (PS) 2 is very sensitive to different abiotic stresses (Strasser and Tsimilli-Michael 2001, 2006, Deo et al. 2006. The degree of stress induced damage and stress adaptations can therefore be examined by monitoring the behaviour of the photosystem exposed to FS.Most of the studies related to stress have been conducted in developing or mature leaves with scant regard to investigate the stress response in senescence phase. This is why we examined the photosynthetic response of leaves of a local cultivar of rice plant subjected to FS. The primary leaves of intact rice seedlings experiencing flooding stress were used for measurement of PS2 photochemistry during senescence to examine the stress induced damage of the photosystem and the possible adaptation mechanism the leaves develop to counter the stress effect.FS was imposed by growing the rice seedlings on soil in submerged conditions as described by Panda et al. (2006). Rice (Oryza sativa L. cv. Swarna) seedlings were grown in 0.15×0.15 m pots with soil from the rice field around the campus of Sambalpur University for 7 d in continuous "white fluorescent light" (60 μmol m -2 s -1 ) at 25±2 ºC in the laboratory. One set of 7-d-old seedlings was completely submerged in a thermocol tank of depth 0.6 m till 15 th d whereas another set kept without submergence was taken as control. The photosynthetic response of plants to FS was studied during senescence (11-15 d) phase. In all cases the primary leaves of the rice seedlings were used for experiments. Pigments were extracted from leaves with chilled 80 % acetone. Estimation of chlorophyll (Chl) was performed spectrophotometrically as per Arnon (1949) and that of carotenoids as per Liaaen-Jensen and Jensen (1971). Total protein extracted from leaves was estimated following the method of Lowry et al. (1951). Chloroplasts from primary leaves of rice seedlings were isolated and 2,6-dichlorophenol indophen...
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