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求翻译谢谢 分不在高 有翻译就行
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求翻译 Experimental Section Styrene from Aldrich Chemical Co. was vacuum distilled prior to use; cetyltrimethylammonium bromide (CTAB) and cetyl-pyridinium chloride (CPC) were from BDH and used as received; 2,2’-azobis(2-methylpropionitrile)(A IBN) from Kodak was recrystallized from methanol; pyrene was obtained from Aldrich and recrystallized from ethanol prior to use. Other chemicals were reagent grade and used as received. Absorption spectra were measured on a Perkin-Elmer 552 spectrophotometer, and fluorescence spectra were measured on a Perkin-Elmer MPF 44B spectrofluorimeter. Excited state lifetimes were measured by using laser flash photolysis equipment, which has been described previously. The Rayonet photoreactor from Rayonet Corporation consists of a cylinder containing fluorescent UV light tubes, of either 254 or 350 nm. The sample is placed in the center of the tubes, a cover is placed on the cylinder for photolysis. A ventilation fan maintains the reaction at approximately room temperature. For the reactions described in the paper, the fan was turned off, resulting in a temperature in the photoreactor around 35 “C. The starting styrene-CTAB-AIBN solutions were thoroughly mixed by using a stir bar and magnetic stirring before initiation of the reaction in the photoreactor. While in the photoreactor, however,no stirring was used. Synthesis of Particles. The polystyrene latex particles were synthesized from a micellar system using cetyltrimethylammonium bromide (CTAB) as a surfactant. The concentrations of styrene and CTAB were both 0.1 M. 2,2’-Azobis(2-methylpropionitrile) (AIBN) was used as a free-radical initiator. CTAB alone forms spherical micelles, which results in a solution with a viscosity like that of water, but the solution of styrene and CTAB was more viscous, suggesting the presence of rodlike micelles. Similar effects have been reported previously, in particular with added electrolyte. l0 The initiator concentration can be varied in order to produce different particle sizes and polystyrene molecular weights. The solution was deoxygenated by using nitrogen gas bubbling before being subjected to 350-nm light in a Rayonet photoreactor. The UV light produced the free-radical form of AIBN, which initiated the polymerization. The reaction was complete within 45 min as determined by monitoring the reaction mixture absorbance on a specrophotometer. In a typical preparation, the absorbance at 250 nm went from 2.6 to 1.9. The product solution had a viscosity of water that suggested the presence of spherical particles. Yields were good on all systems ranging around 50%. Isolation of Polystyrene from the Latex Particles. After polymerization, the polystyrene produced was recovered by diluting the reaction mixture 1:lO in methanol. [ Last edited by yqh9090 on 2012-3-8 at 17:33 ] |
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