Maleic anhydride was used to preparare polyvinyl alcohol/poly (sodium maleate-co-sodium acrylate) hydrogels (PVA/poly(SMA-SAA)) by a repeated frostdefrost process because of its higher charge density and potential electric stimuli sensitivity. The bending angle was measured in a noncontact electric field using carbon as plate electrodes. It was found that the bending angle was dependent on various factors, including composition of hydrogel, concentration of NaCl solution, types of electrolyte solution, and electric voltage. It exhibited that the bending angle increased when the concentration of NaCl solutions and the electric voltages increased. An abnormal bending direction was observed, and it was affected not only by the kinds of hydrogels, but also by the exterior variations. The hydrogel showed good reversibility in on-off electric field and could be a candidate for practical application.
Semi-interpenetrating polymer network (IPN) hydrogels, with acrylic acid (AA) and poly(diallydimethylammonium chloride) (PDMDAAC), were constructed by a sequential IPN method. The characterizations of the IPN hydrogels were investigated by FTIR, DTA, and swelling tests under various conditions. The prepared semi-IPN hydrogels exhibited relatively high swelling capacity, in the range of 477-630 g/g at 258C. The results show that the swelling capacity of AA/PDMDAAC semi-IPN hydrogels was pH and temperature dependent. Swelling behaviors were also studied in the different salt solutions. Swelling kinetic parameters are given.
Juvenile sole (Cymoglossus robustus) were exposed to BDE-47 and BDE-99 through feeding in the laboratory for 60 days, followed by 60 days of clean food, to examine bioaccumulation and potential thyroid hormone disruption effect. The results show that both BDE-47 and BDE-99 accumulate in fish tissues. The free tri-iodothyronine (T3) concentrations in the plasma of sole varied significantly throughout the experiment but were not related to PBDEs exposure. In contrast, plasma levels of thyroxine levels (T4) were lower in both groups of PBDE-exposed fish compared with control fish after 60 days of exposure, suggesting that PBDEs may influence thyroid homeostasis.
The ecotoxicity of penta-BDE in nanosized TiO2 (nTiO2) water suspensions was examined using a method developed based on the standard OECD Guidelines for the Testing of Chemicals ( i . e . OECD 202). The water flea (Daphnia magna) were used as the testing organisms. The results showed that penta-BDE alone has no acute toxicities to the testing organisms, but exhibited acute toxicities in nTiO2 water suspensions. The 72 h NOEC of penta-BDE with 1 mg L-1 nTiO2 to D. magna was calculated as less than 0.1 μg L-1 , and the 72 h EC50 and LC50 are 50.2 μg L-1 (95% CI: 0.872.45) and 100.2 μg L-1(95% CI: 1.222.86), respectively. The toxicity results indicate that nanoparticles might pose potential environmental impact through increasing toxicities of organic pollutants. Further research on the joint ecotoxicity of nanoparticles and organic pollutants is warranted in order to minimize the adverse ecological effects and human health risk of nanotechnology development.
High acrylamide content hydrogel was synthesized under mild condition through a copolymerization reaction between acrylic acid (AA) and acrylamide (AM) using N, N-methylenebis-acrylamide as crosslinker and potassium persulfate combination with sodium sulfite as initiator in aqueous solution. The factors with influence on water absorbency performance including molar ratio of AM to AA, neutralization degree, content of crosslinker and initiator were investigated. Further orthogonal experiment with four factors and three levels were employed to determine the optimized conditions, in which not only water absorbency but also gel strength was taken into account.
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