Intramolecular-intermolecular chain cyclopolymerization

The radical polymerization of acrylic anhydride(AA) as a typical 1,6-diene has been investigated in detail in terms of cyclopolymerization. Thus, in 1958 Crawshaw and Butler(31) and Jones(32) have independently demonstrated that AA could be polymerized in solution by an alternating intramolecular-intermolecular chain propagation or cyclopolymerization, leading to the formation of saturated, linear polymers consisting exclusively of six-membered ring anhydride structure. Later, Mercier and Smets(33)... 

The hypotheses considered so far share the attempt of explaining the ease of formation of the ring structures in cyclopolymerization taking into account only the relative ability of the double bond pendant from the active chain end, and of the double bonds of an unreacted monomer molecule, to reach the reaction site. No attention is paid to the fact that the intramolecular and intermolecular chain propagation reactions are basically different, in the sense that the former involves an entropy decrease due to the loss of some rotational degrees of freedom at the end of the active chain, whereas the latter involves an entropy decrease... 

The intra- and intermolecular interaction between cationic center and tt-electron system have attracted many chemists and much knowledge on the interaction has been accumulated (1). In 1975, we intended to apply such a kind of interaction to cyclopolymerization. Thus, it is expected that the transition state leading to a strained cyclic unit in the polymerization could be stabilized by the intramolecular attractive interaction between cationic growing-end and ir-system There had been few examples of cyclopolymerizations giving strained units. A paracyclophane unit was employed as a strained cyclic unit in the polymer main chain. In Table I are summarized some cyclophanes with their strain energies. 

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