1995 Fiscal Year Final Research Report Summary
Novel Living Cationic Polymerizations via・pi-Ligand Systems
| Project/Area Number |
06453149
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
高分子合成
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
SAWAMOTO Mitsuo Kyoto University, Graduate School of Engineering, Professor, 工学研究科, 教授 (90150325)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Cationic Polymerization / Living polymerization / pi-ligand system / Growing Carbocation / Polymerization Catalysts / Vinyl Ether / Stirene / Lewis Acid |
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| Research Abstract |
This 2-year research project consisted of two major objectives :
(a) To develop novel initiating systems for living cationic polymerizations based on the new concept, "carbocation stabilization via pi-ligand systems" ;
(b) To analyze the growing species in these living polymerizations by NMR.
1.Search of pi-Ligand Systems and New Initiating Systems
An extensive search of pi-ligand systems revealed the following three classes of compounds to be suitable for living cationic polymerization of stirene and vinyl ethers :
(1) pi-Ligand systems in counteranions : tetraphenylborate and related anions ;
(2) pi-Ligand systems in additives : imidazole and related nitrogen-nucleophiles ;
(3) pi-Ligand systems in activators : titanium halides with phenoxy ligands.
2.Direct In-Situ NMR Analysis on Living Cationic Polymerization
Model reactions of these living processes were analyzed, directly and in-situ, by multinuclear NMR spectroscopy. The initial phase established that this method is highly effective to detect and analyze he growing carbocations, for the first time in this field. The following analysis revealed that in the living processes, the cation concentration is remarkably reduced by thepi-ligand systems, which is due to their strong interaction with the activators, either inter- (class 1 and 2) or intramolecularly (class 3) so as to modulate their Lewis acidity. This effect in turn stabilizes the growing carbocations and thereby suppresses chain transfer and other side-reactions.
Thus, this research has established the concept "carbocation stabilization via pi-ligand systems" is a general principle to achieve living cationic polymerizations.
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