Ring-chain equilibration, polyester cyclic

A much better agreement between theory and experiment is found in the closely-related field of macrocyclisation equilibria. Investigations of the cyclic populations in ring-chain equilibrates set up in typical polymeric systems such as polyesters, polyethers, polysiloxanes, and polyamides take a major advantage from the relative ease with which the cyclic fraction can be separated from the linear fraction and analysed for the relative abundance of the individual oligomeric rings. This is conveniently done by means of modern analytical techniques such as gas-liquid and gel-permeation chromatography (Semiyen, 1976). 

POLYESTER CYCLIC OLIGOMERS VIA RING-CHAIN EQUILIBRATION (DEPOLYMERIZATION)... 

Investigations of the cyclic populations of simple ring-chain equilibrates such as those set up in polysiloxane and polyester systems have at least two major advantages over the study of ring formation in more complex systems, such as kinetically-controlled non-linear polymerisations. 

Despite the numerous polyesters described in the literature, it is only recently that the cyclic populations of ring-chain equilibrates of linear aliphatic polyesters have been characterised. This characterisation was based on the well-known investigations of Carothers 121, 122) and his co-workers and the studies of Billmeyer 123-125) and his group. In particular, Billmeyer s wodc established tetraisopropyltitanate as a catalyst for producing equilibrium between ring and chain molecules in polyester systems. This is in contrast to the catalyst, p-toluene sulphonic acid, used by Jacobson, Beckmann and Stockmayer 127) in what was effectively the first attempt to study experimentally and theoretically the change in the total cyclic population of... 

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