Polymerization coordinative chain transfer

COORDINATIVE CHAIN TRANSFER POLYMERIZATION AND COPOLYMERIZATION BY MEANS OF RARE EARTH ORGANOMETALLIC CATALYSTS FOR THE SYNTHESIS OF TAILOR-MADE POLYMERS... 

Coordinative chain transfer polymerization (CCTP, also called catalytic chain transfer polymerization) is typically a process that comprises a chain transfer step that must be i) reversible and ii) much faster than propagation. The growing polymer chain is exchanged between a CTA and the catalyst when attached to the CTA, it is just a dormant chain, whereas propagation takes place on the catalyst (Scheme 27.1). As a consequence, if the CTA is in excess, several macromolecular chains can be produced per catalyst molecule, and ideally (if the transfer rate is not determining), all chains will have the same length. 

CATALYTIC SYSTEMS AND THEIR APPLICATIONS IN COORDINATIVE CHAIN TRANSFER POLYMERIZATION... 

Scheme 27.4 Coordinative chain transfer polymerization (CCTP) of myrcene with neodymium borohydride/dialkyl magnesium catalysts.

The versatility of chain transfer polymerization together with its easiness of use relative to the synthetic effort that would require a one catalyst, one material approach or to the difficulties encountered by other routes explored for fine-tuning polymerization selectivities makes this approach undoubtedly an attractive and promising field for the future of coordination polymerization. CCTP renders the emergence of the one catalyst, several materials paradigm a reality. 

Zhang W, Sita LR. Highly efficient, living coordinative chain-transfer polymerization of propene with ZnEt practical production of ultrahigh to very low molecular weight amorphous atactic polypropenes of extremely narrow polydispersity. JAm Chem Soc 2008 130 442-443. 

Zhang W, Wei J, Sita LR. Living coordinative chain-transfer polymerization and copolymerization of ethene, a-olefins, and a,co-nonconjugated dienes using dialkylzinc as surrogate chain-growth sites. Macromolecules 2008 41 7829-7833. 

Hustad, P.D., Kuhlman, ILL., Arriola, D.J. et al. (2007) Continuous production of ethylene-based diblock copolymers using coordinative chain transfer polymerization. Macromolecules, 40,7061-7064. 

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