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US 5,708,102 AGranted
Living radical polymerization of vinyl monomers
AssigneeE. I. Du Pont de Nemours and Company
InventorsMichael Fryd, Bradford B. Wayland, George Poszmik, Shakti L. Mukerjee
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Abstract
This invention relates generally to a living free radical polymerization of alkene monomers through use of persistent metal centered radicals to attain control of the propagation and termination steps in radical polymerization. This process is useful for controlling the molecular weight of homopolymers or copolymers and for forming block copolymers.
Claims20
A process for the quasi-living free-radical polymerization of an ethylenically unsaturated monomer comprising the steps:
- (i) forming a transition metal initiator or initiator precursor having the formula:
- L--M--(R)n
- wherein
- L is a ligand having a molecular size equal to or greater than phenyl to sterically inhibit hydrogen atom abstraction from the growing polymer radical by L--M;
- M is a transition metal selected from at least one of the elements Cr, Mn, Fe, Co, Ni and Cu;
- L--M inhibits termination by reversibly capping the growing polymer chain;
- R is an organic moiety that initiates polymerization selected from alkyl, aryl and heterocyclic species;
- and
- n is 0 or 1;
- (ii) contacting the ethylenically unsaturated monomer with initiator, L--M--R, or with L--M plus a source of R. from a free-radical initiator external to L--M;
- and
- (iii) polymerizing the monomer by a free-radical mechanism, whereby a narrow polydispersity is maintained and the number average molecular weight of the polymer grows substantially linearly as monomer is converted to polymer.
9 more elements
Dependencies are inferred from the claim text.