Chain Transfer to Polymer in Polymerization of THF

Chain transfer to poly-THF in the polymerization of THF has never been systematically studied. Nevertheless, there are a few reports in whidi the rate constant of transfer to polymer was estimated or at least provided data making this estimatkin possible. 

Chain transfer to polymer in the polymerization of THF is discussed separately, because THF is the model mononKr for which the polymerization is best understood. This transfer leads to the transformation of cyclic, strained tertiary oxonium ions into non-strained oxonium ions, linear or macrocyclic, e.g. (for the intermolecular transfer resulting in a linear structure)  

This reaction is manifested by the following changes in the system  

1) The a and j3 methylene CHj groups (endo- and exocyclic ones) change their diem-ical environment. In the new environnffint their chemical shifts in the H- and C-NMR spectra differ from the previous ones. The corre ronding ectra cannot, however, discriminate between the intermolecular and intramolecular (backbiting) chain transfer, because in the non-strained rit formed by back-biting. 

2) The viscosity of the living system containing oxonium ions at the junction points of two macromolecules, uld be h er than for the same system, after decomposition, which annihilates the junctk n points. 

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