Polymer chemistry cationic polymerization

The concept of flash chemistry can be applied to polymer synthesis. Cationic polymerization can be conducted in a highly controlled manner by virtue of the inherent advantage of extremely fast micromixing and fast heat transfer. An excellent level of molecular weight control and molecular-weight distribution control can be attained without deceleration caused by equilibrium between active species and dormant species. The polymerization is complete within a second or so. The microflow system-controlled cationic polymerization seems to be close to ideal living polymerization within a short residence time. 

Cationic vinyl and ring-opening polymerizations are a well-studied area of polymer chemistry.A wide assortment of electrophilic agents have been documented as initiators for these polymerizations. Many such agents are routinely used both in the laboratory and for commercial purposes to prepare polymers by cationic polymerization. So, the question immediately arises, why use photochemical methods to conduct these polymerizations There are two main reasons that can be cited to justify the use of photo initiation (1) photoinitiation provides access to electrophilic initiators that are otherwise... 

Ledwith, A. and D. C. Sherrington, Reactivity and Mechanism in Cationic Polymerization, Chap. 9 in Reactivity, Mechanism and Structure in Polymer Chemistry, A. D. Jenkins and A. Ledwith, eds., Wiley-Interscience, New York, 1974. 

Cationic polymerizations are among the most important synthetic methods in polymer chemistry. They are used to prepare a variety of commodity and specialty polymers. More recently, controlled cationic polymerizations have been used to synthesize novel functional polymers, block copolymers, and macromolecules with new topologies. The importance of reactions involving cationic active species is continuously increasing, and was recently recognized by the awarding of the 1994 Nobel Prize in Chemistry to George Olah. 

The book is divided into eight chapters. The Introduction is a primer for both synthetic polymer chemistry in general, and cationic polymerizations in particular. More advanced readers may go directly to the following chapters. The second chapter covers the reactions of carbenium ions with various nucleophiles and focuses on the ionization of covalent species and the addition of carbenium ions to alkenes, arenes, and other ir-nucleo-... 

Mitsuo Sawamoto, born in Kyoto, Japan (1951), received his B.S. (1974), M.S. (1976), and Ph.D. (1979) degrees in polymer chemistry from Kyoto University under the direction of Toshinobu Higashimura. After postdoctoral research with Joseph P. Kennedy at the Institute of Polymer Science, The University of Akron, Akron, OH (1980-81), he joined the faculty of the Department of Polymer Chemistry, Kyoto University, in 1981 as a research instructor. He was promoted to Lecturer (1991), to Associate Professor (1993), and to Professor (1994), his current position, of the same department. Sawamoto also serves as one of the three Editors of the Journal of Polymer Science, Part A Polymer Chemistry (1995-present) and as an Editorial Advisory Board member of Macromolecular Chemistry and Physics, the Journal of Macromolecular Science, Chemistry, and e-Polymers, and is the recipient of the 1991 Award of the Society of Polymer Science, Japan, the 1998 Divisional Award of the Chemical Society of Japan, the 2001 Aggarval Lectureship in Polymer Science, Cornell University, and the 2001 Arthur K. Doolittle Award of the ACS PMSE Division. With more than 250 articles and reviews, his research interest covers living radical and cationic polymerizations, precision polymer synthesis, and the chemistry of radical and carbocationic reaction intermediates. 

Cationic polymerization of heterocyclic and vinylic monomers is currently one of the most active areas of polymer chemistry. In the past two years four monographs dedicated to different topics in this field were published Cationic polymerization is also one of the few areas of polymer science that has its own scientific meeting. The fifth meeting was organized in Kyoto (1979) ( the previous meetings were in Akron (1976) ( Rouen (1973) (7) Keele (1952) (8) and Dublin (1949) (9). At the 26th International Union of Pure and Applied Chemistry (lUPAC) International Symposium on... 

Professor Dr. Werner Kern, one of the pioneers of polymer chemistry and particularly of cationic ring-opening polymerization, died on January 18, 1985 at the age of 79. 

Analogous to the initiation of anionic polymerization by addition of nucleophiles to alkenes, cationic polymerization can be initiated by the addition of electrophiles. The alkenes that respond well to cationic polymerization are those that form relatively stable carbocations when protonated. Of these, the one used most often is 2-methylpropene, better known in polymer chemistry by its common name isobutylene. 

Crivello, J.V. liu, S. (2000). Photoinitiated cationic polymerization of epoxy alcohol monomers. Journal of Polymer Science A Polymer Chemistry, Vol.38, No.3, (February 2000), pp. 389-401, ISSN 0887-624X. 

End-functionalized polymers can be prepared by cationic polymerization via the use of functionalized initiators, provided the functional group is not reactive under the polymerization conditions. Protecting group chemistry can be invoked to incorporate reactive functional groups. 

It is worth noting that all these latter examples of materials whose key feature calls upon a specific behaviour of furan moieties, require modest contributions from these heterocycles in terms of its quantitative presence in the macromolecules. This situation is similar to that described in Section 6.5.2, in which furan derivatives were used to modify the end groups of some polymers or to synthesize block copolymers by cationic polymerization. In both instances, therefore, it is not the dominant presence of the heterocycle that determines the specific properties of the final materials (as in the case of polymers and copolymers bearing furan monomer units), but instead the fact that a small or even minute percentage of these structures introduces an original mechanistic feature, associated with the peculiar chemistry of the heterocycle, which transforms the behaviour and properties of the final material. This crucial point will be met again in the context of the application of the DA reaction in Section 6.8. 

J. P. Kennedy, Cationic polymerization, in Macromolecular Science (Vol. 8 of Physical Chemistry Series 1) (C. E. H. Bawn, ed.), MTP International Review of Science, 1972, p. 49. J. P. Kennedy and J. K. Gillham, Cationic polymerization of olefins with alkyl aluminum initiators, Adv. Polym. Sci. 10, 1 (1972). 

G. Zotti, S. Zecchin, G. Schiavon, A. Berlin, Low defect neutral, cationic and anionic conducting polymers from electrochemical polymerization of N-substituted bipyrroles. Synthesis, characterization, and EQCM analysis, Chemistry of Materials 2002, 14, 3607. 

Microfluidic systems (microreactors) provide great benefits, such as precise fluid-manipulation [1] and high controllability of rapid and difficult to control chemical reactions (see Part 2, Bulk and Fine Chemistry). Advantages of microreaction technology have been utilized in polymer chemistry notable examples include the synthesis of fine solid polymeric materials [2,3] and excellent control of exceptionally reactive polymerization through mainly radical and cationic polymerization reactions (see Chapters 13-15). Other polymerizations using microreaction technology are still in their infancy, vhich include step polymerization, that is, polycondensation and polyaddition and other non-radical polymerizations. 

Ariga, T., Takata, T., Endo, T., 1993. Alkyl halide-initiated cationic polymerization of cyclic carbonate. Journal of Polymer Science Part A Polymer Chemistry 31, 581—584. 

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