Cyclopolymerization ring size

Table 4.4 Ring Sizes Formed in Cyclopolymerization of Symmetrical 1,6-Diene...

Ottenbrite, R.M. and Shillady, D.D., "Ring Size on Cyclopolymerization" Polymeric Amines and Ammonium Salts, E. Goethals, Ed. Pergamon Press Oxford, 1980. 

Another approach to the study of the cyclic units formed in these cyclopolymerizations is through the study of the radical cyclization reaction of selected model compounds. Thus, extensive studies have shown that the five-membered ring is predominant, while new evidence indicates that radical stability exerts a marked influence on the ring size. These conflicting aspects of cyclopolymerization have been discussed in detail by Butler(L7) he has pointed out that considerably more investigations will be necessary before definite conclusions can be drawn with respect to the ratio of five- to six-membered rings in the many cyclopolymers already synthesized, and a satisfactory explanation for these extensive variations from one system to another is available. 

On the other hand, we reexamined in detail the ring size of the cyclic structural units of poly-AA s by means of IR, 1H-NMR, and C-NMR spectroscopy these analytical procedures were applied to the structural analysis of poly-AA, the poly(acrylic acid) derived from hydrolysis of the poly-AA, and the poly(methyl acrylate) obtained by subsequent esterification of the poly(acryl-ic acid) in comparison with the corresponding model polymers of five- or six-membered ring structure. Then, we investigated in detail the effects of polymerization conditions on the ring size of poly-AA s, i.e., on the intramolecular addition modes in the cyclopolymerization of AA since five- or six-membered ring anhydride structure can be formed via intramolecular hh or ht addition of the uncyclized radical to the internal double bond(22,23). 

The principle of cyclopolymerization has been applied to the synthesis of macrocyclic ether-containing polymers which may simulate the properties of crown ethers. l,2-Bis(ethenyloxy)benzene (a 1,7-diene) and l,2-bis(2-ethenyloxyethoxy)benzene (a 1,13-diene) are typical of the monomers synthesized. Homopolymerization of the 1,7-diene via radical and cationic initiation led to cyclopolymers of different ring sizes homopolymerization of the 1,13-diene led to cyclic polymer only via cationic initiation. Both monomer types were copolymerized with maleic anhydride to yield predominantly alternating copolymers having macro-cyclic ether-containing rings in the polymer backbone. 

Polymerization of a series of dienes of formula [106] has been studied (/i, 16, 93). The polymers that were obtained consisted of both soluble and cross-linked, insoluble fractions. Quantitative infrared and bromination experiments indicated that the soluble polymers possessed cyclic as well as open-chain structures. The percent of cyclization depended on the size of the incipient cycle and corresponded roughly to what is obtained in other cyclization reactions. The results are summarized in the accompanying table. A similar effect of ring size versus tendency toward cyclopolymerization was observed for monomers of structures [107] (92). 

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