Alternating polymer architecture

An alternative polymerization mechanism and polymer architecture has been proposed by Kirchhoff [1, 2, 3], Tan and Arnold [77], By this mechanism, polybenzocyclobutenes which do not contain reactive sites of unsaturation are proposed to polymerize by the 1,4 addition of the o-quinodimethane intermediates to give a substantially linear poly(o-xylylene) structure. Since the monomers all contain at least two benzocyclobutene units the net result of this reaction will to a first approximation be a ladder type polymer as shown in Fig. 17. The formation of a true ladder polymer however would require that all... 

The main feature of polymers is their MMD, which is well known and understood today. However, several other properties in which the breadth of distribution are important and influence polymer behavior (see Figure 1) include physical, the classical chain-length distribution chemical, two or more comonomers are incorporated in different fractions topological, polymer architecture may differ (e.g., linear, branched, grafted, cyclic, star or comb-like, and dendritic) structural, comonomer placement may be random, block, alternating, and so on and functional, distribution of chain functions (e.g., all chain ends or only some carry specific groups). Other properties the polymers may disperse (tacticity and crystallite dimensions) are not of the same general interest or cannot be characterized by solution methods. 

The synthesis of well-defined polymers and of complex polymer architectures has been greatly facilitated by recent developments in controlled radical polymerization, which has opened up new possibilities in the design and also in the preparation of functional nanostructures based on supramolecular assembly. Controlled radical polymerization is an attractive alternative to anionic polymerization for preparing polymeric building blocks of well-defined size and a low polydispersity index... 

Although anionic polymerisation remains an important technique today for the preparation of block copolymers and other controlled polymer architecture, recent developments in controlled free-radical polymerisation has presented an alternative approach which may complement this methodology. 

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