| The aim of this volume is to summarize in one reference the vast amount of information published in the chemical literature on cyclopolymerization since its inception and discovery about four decades ago. The topic is broadly defined as any type of addition polymerization that leads to the introduction of cyclic structures into the main polymer chain. Its scope is broad, including (at least conceptually) not only symmetrical diene counterparts of all known monomers capable of undergoing addition polymerization, but the unsymmetrical ones as well. Many of the latter have not been investigated. Thus, the scope of cyclopolymerization is considerably broader than that of addition polymerization itself, which includes vinyl, alkyl, carbonyl, isocyanate, nitrile, and epoxy polymerizations, topics that are covered in numerous volumes. Cyclopolymerization represents an exception to the general principle of polymerization established by Staudinger (Nobel Laureate, 1953) in 1934 that nonconjugated dienes, when polymerized, lead to cross-linked, and therefore nonsoluble and nonlinear, polymers or copolymers. It also represents an exception to the generally accepted hypothesis advanced by Flory (Nobel Laureate, 1974) in 1937, which states that the more stable intermediate controls the course of propagation in vinyl polymerization. Numerous studies have shown that, in many cases, cyclopolymerization does not conform to this hypothesis, but forms cyclic structures derived via propagation through the less stable intermediate. |
| Examples of monomers that cyclopolymerize in addition to both symmetrical and unsymmetrical nonconjugated dienes are diynes, dialdehydes, diisocyanates, diepoxides, dinitriles, and some organometallic monomers. Also, certain monomers that contain two different polymerizable functional groups cyclopolymerize. A variety of cyclopolymerizable monomers undergo copolymerization with their monofunctional counterparts or with other copolymerizable monomers. Reactivity ratios and other copolymer parameters have been obtained for some comonomer pairs. Certain 1,4-bis-multiple bonded structures undergo cyclopolymerization with suitable monofunctional structures to form six-membered cycles via an apparent 4 + 2 process. Post cyclopolymerization of suitable preformed polymers leads to polymers that contain extensive blocks of ladder structures. |
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