It is generally accepted that a new material is often developed by ?nding a new synthesis
method of reaction or a new reaction catalyst. Historically a typical example may be referred
to as a Ziegler¿Natta catalyst which has allowed large-scale production of petroleum-based
polyole?ns since the middle of the 20th century. New polymer synthesis therefore will
hopefully lead to creation of new polymer materials in the 21st century. This special issue
contributed by three groups focuses on recent advances in polymer synthesis methods which
handle the cutting-edge aspects of the advanced technology. The ?rst article by Yokozawa and
coworkers contains an overview of the - action control in various condensation polymerizations
(polycondensations). Advanced technologies enabled the control of stereochemistry (regio- g-
metrical- and enantio-selections) chemoselectivity chain topology and st- chiometry of
monomers giving a high molecular weight polymer. It has been recognized for a long time
however that polycondensation is a dif?cult p- cess in controlling the reaction pathway
because the reaction is of step-growth and the reactivity of monomers oligomers and polymers
are almost the same during the reaction and hence the molecular weight of polymers and its d-
tribution (M M ) are impossible to regulate. The authors¿ group developed w n a new reaction
system (chain-growth condensation polymerization) changing the nature of polycondensation from
step-growth to chain-growth namely the propagating chain-end is active allowing for control
of the product molecular weight as well as the distribution.
