A NEW FORM OF CONTROLLED GROWTH FREE-RADICAL POLYMERIZATION

A new form of controlled growth free radical polymerization leading to narrow polydispersity polymers and/or block copolymers is described. The process is based on the polymerization of monomers in the presence of macromonomers of general structure CH2=C(Z)CH2(A)(n) [(A)(n) = rad ical leaving group, Z = activating group] and displays many of the cha racteristics of living polymerizations. The process is most suited to methacrylic monomers but with the appropriate choice of reaction condi tions (high temperatures and/or low conversions) it can also be applie d to acrylic and styrenic monomers. The macromonomers are conveniently prepared by catalytic chain transfer to alkyl cobalt(III) complexes o r by addition-fragmentation chain transfer. The factors which determin e the efficiency of cobalt complexes for molecular weight reduction in free radical emulsion and solution polymerization of methyl methacryl ate are also discussed.