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Macromol. Symp., Vol. 132, 1998, pp. 1 - 462


Ionic Polymerization

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 IUPAC’s 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

 


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