Symposium
Editors, J.-P. Vairon, H. Cheradame, P. Hemery, and M. Sepulchre
Editor-in-Chief, Hartwig Hocker
Editors, W. Guth, B. Jung, I. Meisel, and S. Spiegel.
Wiley-VCH (1998), pp. 1-462
ISBN 3-527-29800-2 (ISSN 1022-1360).
Preface
Volume
132 of Macromolecular Symposia contains invited and contributed
lectures presented at the International Symposium on Ionic Polymerization
held 7-11 July 1997 in Paris, France, under the sponsorship of IUPACÕs
Macromolecular Division.
The
Symposium began with a lecture entitled "Quo Vadis Ionic Polymerization?"
by Professor J. P. Kennedy. That was indeed a good question. We think
that the reader will find some answers in this book, or at least will
observe some significant trends.
From
our point of view, one of the more important conclusions was the fact
that it is possible to synthesize block copolymers by switching from
carbocationic to radical polymerization while keeping living behavior.
The generalization of such a synthetic strategy is certainly a challenge
of the near future. The domain of controlled macromolecular architecture
is very active, and examples include, for instance, the design of multifunctional
macroinitiators and supramolecular aggregates of well-defined shape
through carbocationic polymerization, or the polymerization of macromers
leading to segmented polymer networks. Examples showing that it is possible
to combine not only anionic and cationic polymerizations, but also group
transfer (GTP) and anionic polymerizations, are given. It was even shown
that it becomes possible for the polymerization to be independent of
the reactivity of the monomers in anionic polymerization, for instance,
by initiating the polymerization of styrene by a living poly(ethylene
oxide) in the presence of an appropriate disilane additive. Changing
the relative reactivity of the various monomers was a dream that is
beginning to become a reality.
We
were also pleased in see that studies, aimed at understanding many points
that are still unclear in each of the fields of ionic polymerization,
are alive, and that important developments are at hand. It is not possible
here to indulge in detailed descriptions, but we quote those that seem
very promising. There is the case of anionic polymerization of methylmethacrylate
where the classical lithium initiators can be associated with lithium
amino alkoxides, giving a truly living system that is able to proceed
stereospecifically at temperatures as high as 70oC. Similarly, it has
been found that the introduction of Lewis bases, such as esters or some
ethers, can be used in the polymerizations of acrylates and methacrylates
initiated by aluminum alkyls, allowing living behavior up to 0oC. Quaternary
ammonium salts are also worthy of investigation in this context, showing
the potential to control tacticity and molecular characteristics. This
molecular control allowed preparation of stereoregular uniform PMMA
architectures, and also, for instance, the stereocomplex between isotactic
and syndiotactic PMMA.
Cationic
polymerization is still attracting fundamental studies, either on the
structure of the active species and their relationship with the living
behavior or the initial reactions leading to active species. The role
of additives such as electron donors or proton scavengers was also examined
in further detail.
On the side of cyclic monomers, some papers described the polymerization
of cyclic esters, of lactones, of trioxane and oxirane, of cyclocarbonates,
and of cyclosiloxanes. This field is very rich and shows very promising
developments.
Whatever
the mechanism of ionic polymerization applied in the polymerization
of monomers with double bonds or of cyclic monomers, control of the
molar weights and sometimes of microstructure could be achieved in a
much wider temperature range more favorable for industrial developments.
Most of the studies provided ways to control the side reactions (termination
or transfer) and possibly to eliminate them. Finally, this Symposium
saw the triumph of living polymerization, even if there remain unsolved
problems.
Professors
Herve Cheradame and
Jean-Pierre Vairon
Symposium Editors
