Abstract
Novel multihalide compounds which were readily obtained by derivatization of 4-tert-butylcalix[4,6,8]arenes were used to initiate the atom transfer radical polymerization (ATRP) of styrene, tert-butyl acrylate (t-BuA), and methyl methacrylate (MMA), in the presence of CuX (X = Br or Cl) and 2,2‘-bipyridyl. Well-defined polystyrene (PS) stars constituted of precisely four, six, and eight arms could be synthesized with a narrow polydispersity in this way. For instance, octafunctional polystyrene stars exhibiting molar masses as high as 600 000 g mol-1 could be prepared. However, the polymerization had to be restricted to low conversion, typically below 15−20% to prevent stars from mutually coupling and avoid their contamination with species of higher functionality. Besides the concentration of polymeric radicals [P•], the factor that was found to play a significant role in the occurrence of star−star coupling is their overlapping concentration (C*): intermolecular coupling indeed appeared to be enhanced whe...
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