Controlled radical polymerization: Control of molecular weight, composition and stereoregularity in homogeneous and heterogeneous systems

The kinetics of CRP based upon alkoxyamines/nitroxides mediated systems, are described. The possibility to control the stereoregularity via this technique is shown. Trans-2,2,5,5-substituted pyrrolidine based nitroxides, which preferred a half-chair (C2) conformation at room temp., were synthesized. The prepn. of alkoxyamines with a racemic mixt. of trans-2,5-bis(methoxycarbonyl)-2,5-dimethyl-1-oxypyrrolidine and styrene, acrylonitrile, Me acrylate and Me methacrylate all showed exclusively one pair of diastereoisomeric enantiomers. The parameters for the Arrhenius equation for the homolytic dissocn. of 1-t-butoxy-2-phenyl-2-(1-oxy-2,2,6,6-tetramethylpiperidinyl)-ethane were detd. Ea = 138.8 kJ/mol +- 18 kJ/mol and ln(A) = 34.5 +- 0.6. A method to det. both the chain-length and viscosity dependence of the rate parameters of radical trapping by the nitroxide and bimol. termination based upon the kinetics in a CRP system is given