Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1996-09-12
1998-01-13
Zitomer, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526171, 526217, 5262181, 5263031, 5263171, 526319, 526341, 526342, 526347, C08F 444, C08F 406, C08F 410, C08F 450
Patent
active
057081026
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to living free radical polymerization of vinyl monomers using metal complexes as reversible radical capping agents.
2. Description of the Prior Art
The term living polymerization pertains to a polymerization process where the growing polymer chains contain one or more active sites that are capable of promoting further polymerization. One general strategy for obtaining living polymerization is to have a chemical species reversibly cap the active center that promotes polymerization. In ionic polymerizations initiated by anions (anionic polymerization) or cations (cationic polymerization) the counter cation or anion respectively function as a capping agent. When the ions are bound together polymerization stops, but reversible dissociation into ionic fragments provides a controlled source of sites that promote further ionic polymerization. Living ionic polymerizations are widely utilized in forming block copolymers by sequential addition of different alkene monomers.
In contrast to living ionic polymerizations, previous efforts to attain living free radical polymerizations have utilized polymerization initiators (R--X) that can fragment into an alkyl radical (R.) that promotes polymerization of alkene monomers and a second radical (X..dbd.Ar.sub.3 C., R.sub.2 NO., (CH.sub.3).sub.2 NCS.sub.2.) where the unpaired electron resides on a main group atomic center (C, O, S) which functions to cap the growing polymer radical (RM.sub.n X).
Regarding previous attempts at living polymerization, see Webster, O. W. Science 251, 887 (1991); Otzu, T., Matsunaga, T., Kuriyama, A., Yoshaka, M. Eur. Polym. J. 25, 643 (1989); Bledzki, A., Braun, D., Titzschkaw, K. Makromol. Chem. 184, 745 (1983); and Solomon, D. H., Rizzardo, E., Cacioli, P. U.S. Pat. No. 4,581,429 (1986).
These prior art approaches have had only limited success in producing block and end-functionalized polymers. The inability to maintain narrow dispersities at relatively high molecular weights, and to produce pure block copolymers illustrates the deficiencies of this prior technology. In no instance has a main group capping agent been demonstrated to attain or even approach the ideal characteristics for an authentic living radical polymerization.
SUMMARY OF THE INVENTION
This invention broadly concerns a process for the quasi-living free-radical polymerization of an ethylenically unsaturated monomer comprising the steps: formula: hydrogen atom abstraction from the growing polymer radical by L--M; 28, 40 through 46, and 72 through 78 of the periodic table; and is incpable of initiating polymerization; L--M--R, or with L--M plus a source of R. from a free-radical initiator external to L--M; and narrow polydispersity is maintained and the number average molecular weight of the polymer grows substantially linearly as monomer is converted to polymer.
Preferred processes of this invention include the following embodiments of the broad process described above: initiator L--M--R, external source of R., iminohydroxyimino compounds and their bridged derivatives, diazadihydroxyiminodialkyldecadienes and -undecadienes and their bridged derivatives, tetraazatetraalkyl-cyclotetradecatetraenes and -dodecatetraenes, N,N,-bis(salicylidene)ethylenediamines and dialkyldiazadioxodialkyldodecadienes and -tridecadienes, a carbon-to-carbon bond, species or a substituted derivative of one of these species which is capable of homolyric dissociation from the metal ion on heating or on irradiation with visible or ultraviolet light, CH.sub.3)CH.sub.2 CH.sub.3, derived from an azo initiator, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (more preferred), group consisting of acrylic acid, its esters and amides, substituted or unsubstituted styrene, acrylonitrile or mixtures thereof (more preferred), components of at least one of the following units acrylic acid, its esters and amides, substituted or unsubstituted styrene, acrylonitrile or mixtures thereof (more preferred), copolymer, 2, does not exceed 1.5 (
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Fryd Michael
Mukerjee Shakti L.
Poszmik George
Wayland Bradford B.
Costello James A.
E. I. Du Pont de Nemours and Company
Zitomer Fred
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