Controlled high-speed anionic polymerization of propylene oxide initiated by alkali metal alkoxide/trialkylaluminum systems

被引:118
作者
Billouard, C
Carlotti, S
Desbois, P
Deffieux, A
机构
[1] Univ Bordeaux 1, UMR 5629 CNRS, ENSCPB, Lab Chim Polymeres Organ, F-33607 Pessac, France
[2] BASF AG, Polymer Lab, D-67056 Ludwigshafen, Germany
关键词
D O I
10.1021/ma035768t
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
The anionic polymerization of propylene oxide initiated by alkali metal alkoxide suffers from several drawbacks such as a slow polymerization rate in nonpolar solvents and an important chain transfer reaction to monomer. We found that the addition of trialkylaluminum to the alkali metal alkoxide/propylene oxide system in hydrocarbon media strongly enhances the polymerization rate and strongly reduces the transfer reactions, thus allowing the controlled synthesis of poly(propylene oxide) with relatively high molar masses (up to 20 000 g/mol). At constant monomer and alkali metal alkoxide concentrations the polymerization rate increases with increasing trialkylaluminum concentration. Kinetic data and H-1 NMR studies indicate that the trialkylaluminum derivative is involved in the formation of two distinct complexes, one with the alkali metal alkoxide and another with the PO monomer. The strong electron-withdrawing on PO alpha-carbons associated with AIR(3) complexation makes the monomer much more susceptible to ring opening. Moreover, since the withdrawing effect is much less pronounced on the PO methyl group, the complexation also results in a higher selectivity of the nucleophilic species toward the ring-opening reaction to the detriment of the proton abstraction process yielding transfer to monomer.
引用
收藏
页码:4038 / 4043
页数:6
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