Cyclopolymerization

Abstract

Diallylamines readily undergo free‐radical polymerization to form polymers which contain cyclic structures. Five‐membered rings predominate, and this conclusion is supported by ESR spectroscopy of the radicals formed in a flow system, by chemical characterization of the compounds formed under nonpropagating conditions, and by NMR spectroscopy of the polymers. The presence of substituent groups in the diallylamine molecule has an important bearing on the cyclization reaction. For example, methyl groups in the β‐position, (dimethallylamines) form a mixture of 5‐ and 6‐membered rings, and the presence of bulkier groups, as in methyl bis‐2‐tert‐butyl allylamine, can prevent reaction with certain free‐radical initiators. Similarly, increasing temperature results in an increase in the amount of 6‐, relative to 5‐, membered ring structures with N‐methyldimethallylamine. These results are generally similar to those obtained with the carbon analogues. From a theoretical viewpoint, the formation of the 5‐membered ring structure indicates that the generally accepted less stable primary radical is formed in preference to the 6‐membered structure which would contain a secondary radical. This apparent conflict is explained by the kinetics of the reaction and particularly the stereo‐electronic effects which operate in the transition state. Thus, the reaction can be under kinetic control and lead predominantly to 5‐membered ring structures, but when thermodynamic control starts to operate, e.g., at higher temperatures, the more stable 6‐membered ring structures may become significant. Changing the polymer structure from a predominantly 5‐membered one to one containing 6‐membered rings can be expected to alter the properties of the polyelectrolyte. Thus, differences in the titration curves have been noted, and the possibility exists of relating these differences to the polymerization conditions and, hence, to polymer structure.

Genesis of the CSIRO polymer group and the discovery and significance of nitroxide‐mediated living radical polymerization

“…I published on this as early as 1975. 7 Our work on the structure of the cyclopolymers formed from 1,6-diallylamines was to prove the extreme case demonstration that radical stability was not the dominant factor.…”

DD ArtPix

“…Of equal importance was the growing recognition that stereoelectronic and polar effects were the dominant factors in determining the outcome of radical reactions (kinetic control), not the product radical stability (thermodynamic control). I published on this as early as 1975 7. Our work on the structure of the cyclopolymers formed from 1,6‐diallylamines was to prove the extreme case demonstration that radical stability was not the dominant factor.…”