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How to Polymerize Ethylene in a Highly Controlled Fashion?
Author(s) -
Kempe Rhett
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601842
Subject(s) - lanthanide , chain transfer , ethylene , polymerization , polymer chemistry , polymer , chemistry , transition metal , polyethylene , metal , diffusion , main group element , catalysis , zinc , atom transfer radical polymerization , living polymerization , chain (unit) , radical polymerization , organic chemistry , thermodynamics , astronomy , ion , physics
Very fast, reversible, polyethylene (PE) chain transfer or complex‐catalysed “Aufbaureaktion” describes a “living” chain‐growing process on a main‐group metal or zinc atom; this process is catalysed by an organo‐transition‐metal or lanthanide complex. PE chains are transferred very fast between the two metal sites and chain growth takes place through ethylene insertion into the transition‐metal‐ or lanthanide‐carbon bond—coordinative chain‐transfer polymerisation (CCTP). The transferred chains “rest” at the main‐group or zinc centre, at which chain‐termination processes like β‐H transfer/elimination are of low significance. Such protocols can be used to synthesise very narrowly distributed PE materials ( M w / M n <1.1 up to a molecular weight of about 4000 g mol −1 ) with differently functionalised end groups. Higher molecular‐weight polymers can be obtained with a slightly increased M w / M n , since diffusion control and precipitation of the polymers influences the chain‐transfer process. Recently, a few transition‐metal‐ or lanthanide‐based catalyst systems that catalyse such a highly reversible chain‐growing process have been described. They are summarised and compared within this contribution.