کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5187102 1381121 2006 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Mechanistic investigation of 9-bromoanthracene photodimers as initiators in atom transfer radical polymerization
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Mechanistic investigation of 9-bromoanthracene photodimers as initiators in atom transfer radical polymerization
چکیده انگلیسی

Mechanistic pathways accounting for the lack of control in polymerizations employing photodimers of 9-bromoanthracene as alkyl halide initiators in atom transfer radical polymerization (ATRP) reactions are presented. Converting the aryl bromide on the anthracene moiety into an alkyl bromide via a [4+4] cycloaddition reaction effectively generated the photodimer with two alkyl halide sites, which were investigated as potential initiating sites for the ATRP of styrene and n-butyl acrylate. Polymers synthesized using these photodimers as initiators possessed relatively broad polydispersity index (PDI) values and displayed a non-linear relationship between their number average molecular weights (Mn) and monomer consumption, consistent with slow initiation from the bridgehead alkyl halide. Reactions performed at 80 °C in bulk or THF generated polystyrene with Mn values 3-5 times higher than calculated based on monomer-to-initiator ratios. UV-vis spectrometry of the products demonstrated absorbance bands indicative of polymer-bound anthracene, caused by thermal degradation of the photodimer during the polymerization. When the initiator was introduced last into the reaction mixture in an attempt to suppress photodimer cleavage prior to initiation, PDI values and Mn values were generally lowered with the resulting polymers showing similarly high anthracene content. Composition of polystyrene and poly(n-butyl acrylate) products was also studied as a function of reaction temperature, with decreased anthracene labeling observed at lower temperatures (40 and 60 °C), further validating a model of heat-induced cleavage of the photodimer.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 47, Issue 10, 3 May 2006, Pages 3325-3335
نویسندگان
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