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A series of environmental pH-responsive block copolymers PEG-polyurethane with tertiary amine groups in the main chain and free carboxyl groups in the side chain were synthesized, including poly(ethylene glycol) (PEG), 1,4-bis (hydroxyethyl) piperazine, 1,6-diisocyanato hexamethylene, and 2,2-dimethylolpropionic acid. The chemical structure, molecular weight, and pH-dependent capacity of pH-responsive PEG-polyurethane were examined by 1H-NMR, FTIR, gel permeation chromatography (GPC), and an acid-base titration. Moreover, the fluorescent dye fluorescein isothiocyanate was conjugated with PEG-polyurethane by the similar polymerization method and the obtained polymer was measured by ultraviolet visible spectroscopy (UV-vis) and fluorescent spectroscopy. The results indicated that the pH-responsive PEG-polyurethane showed a pH-buffering phenomenon and fluorescent imaging in a range of pH values. As a result, we demonstrated its potential application for optical imaging; however, it is believed that more applications in the areas of biomedicine will be possible owing to its free carboxyl acid terminal residues in the stimuli-responsive polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Submicrometer core-shell polybutadiene- graft-polystyrene (PB- g-PS) copolymers were synthesized by emulsion grafting polymerization with 1,2-azobisisobutyronitrile as an initiator. Then, PB- g-PS copolymers were blended with high-impact polystyrene (HIPS) and PS to prepare HIPS/PS/PB- g-PS. It is generally accepted that PS could only be toughened by 1-3-μm rubber particles effectively. From the Izod impact test, however, the results showed that PS could be toughened effectively by submicrometer rubber particles (around 300 nm) in our study. Moreover, the impact strength of HIPS/PS/PB- g-PS is much higher than that of HIPS due to the synergism between submicrometer rubber particles and micrometer salami particles. Subsequently, the stress-whitening zones for HIPS, PS/PB- g-PS, and HIPS/PS/PB- g-PS were also observed in detail by transmission electron microscope. Based on mechanical properties and deformation morphologies, the deformation mechanism in the HIPS/PS/PB- g-PS blends was given as follows: crazes could be initiated from large rubber particles, passed through 'craze-bridge' rubber particles, and ended to neighboring small one, which prevented excessively crazing to be form cracks, absorbed energy, and finally enhanced the toughness of PS. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Small reservoirs in the Yangtze River are large in quantity and widely distributed, which have important ecological and economic benefits. It is of great significance to explore the response law of small reservoir water quality to environmental variables for improving reservoir water quality. Based on the measured water quality data of 36 small reservoirs in the upper reaches of the Yangtze River, combined with the measured water quality data, using correlation analysis, redundancy analysis, and other research methods, we divided the environmental variables into three categories:landscape configuration index, landscape composition index, and reservoir characteristic index, and explored their impact on the change in water quality index. The research results showed that:① farms were the main source of NO 3 - -N, TN, and TP, and residential land was the main source of TP. Paddy, forest land, and wasteland had positive effects on the retention and purification of N and P in reservoirs. ② The LPI of farms was significantly positively correlated with the concentrations of TN and NO 3 - -N in the reservoir, and the paddy and forest were significantly negatively correlated with the concentrations of NO 3 - -N and TN in the reservoir. The PD of farms was positively correlated with TP. The LPI was negatively correlated with TP content. ③ The correlation between average reservoir depth and reservoir water quality was the strongest. Reservoir capacity, reservoir average depth, and reservoir LSI had significant positive effects on water quality improvement. ④ Among the environmental variables of the reservoir, landscape configuration index had the highest explanatory rate (24%), followed by that of the reservoir characteristics index (11%) and landscape composition index (9%). Watershed factors were the key factors (55%), and internal factors (19%) also had a significant influence on reservoir water quality. The research results can provide a theoretical basis for controlling water quality degradation of small reservoirs by managing and optimizing the landscape characteristics of reservoirs.