Abstract
Until the mid 90's, free radical polymerization (FRP) was characterized by producing polymers with high average molecular weights (1x10-1x10) since the beginning of polymerization, index of polidispersity (PDI) greater than 1.5 and wide molecular weight distribution (MWD). When necessary to produce polymers with more defined structure, it was usually used anionic polymerization, which is capable to produce polymers with narrow molecular weight distribution and PDI around 1.0 (1.1-1.2). The ionic polymerization, however, needs to be held in a high degree of purity and in the absence of inhibitors, what make the ionic polymerization expensive and not very practical from the industrial point of view. A promising alternative to ionic polymerization has been the living radical polymerization (LFRP), which is much more robust to the impurities and kind of solvent and it is able to produce polymers with polidispersity close to one. Nevertheless, the LFRP presents lower polymerization rates compared to standard and smaller polymer chains (lower molecular weights averages). In this work the effect of cyclic trifunctional initiator on the Living Free Radical Polymerization is analyzed. The Nitroxide Mediated Radical Polymerization (NMRP) is considered, using TEMPO as controller and styrene as monomer. It can be observed that the polidispersity can vary in a very broad range when this initiator is used, changing from PDI lower than 1.5 until PDI bigger than 4.0, depending on the operating conditions considered.
Published Version
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