کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5185432 | 1381077 | 2010 | 12 صفحه PDF | دانلود رایگان |
Living cationic polymerization of styrene was achieved with a series of initiating systems consisting of a HX-styrenic monomer adduct (X = Br, Cl) and ferric chloride (FeCl3) in conjunction with added salts such as tetrabutylammonium halides (nBu4N+Yâ; Yâ = Brâ, Clâ, Iâ) or tetraalkylphosphonium bromides [nRâ²4PBr; Râ²Â = CH3CH2-, CH3(CH2)2CH2-, CH3(CH2)6CH2-] or tetraphenylphosphonium bromide [(C6H5)4PBr] in dichloromethane (CH2Cl2) and in toluene. Comparison of the molecular weight distributions (MWDs) of the polystyrenes prepared at different temperatures (e.g., â25 °C, 0 °C and 25 °C) showed that the polymerization is better controlled at ambient temperature (25 °C). The polymerization was almost instantaneous (completed within 1 min) and quantitative (yield â¼100%) in CH2Cl2. In CH2Cl2, polystyrenes with moderately narrow (Mw/Mn â¼Â 1.33-1.40) and broad (Mw/Mn â¼Â 1.5-2.4) MWDs were obtained respectively with and without nBu4N+Yâ. However, in toluene, the MWDs of the polystyrenes obtained respectively with and without nBu4N+Yâ/nRâ²4P+Brâ were moderately narrow (Mw/Mn = 1.33-1.5) and extremely narrow (Mw/Mn = 1.05-1.17). Livingness of this polymerization in CH2Cl2 was confirmed via monomer-addition experiment as well as from the study of molecular weights of obtained polystyrenes prepared simply by varying monomer to initiator ratio. A possible mechanistic pathway for this polymerization was suggested based on the results of the 1H NMR spectroscopic analysis of the model reactions as well as the end group analysis of the obtained polymer.
Journal: Polymer - Volume 51, Issue 6, 11 March 2010, Pages 1258-1269