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Downloaded by UNIV OF CALIFORNIA SAN DIEGO on July 25, 2016 | http://pubs.acs.org Publication Date: November 30, 1981 | doi: 10.1021/bk-1981-0166.ch019
Use of Cryptates in Anionic Polymerization of Heterocyclic Compounds SYLVIE BOILEAU Laboratoire de Chimie Macromoléculaire associé au CNRS, Collège de France, 11 Place Marcelin-Berthelot, 75231 Paris Cedex 05, France
The anionic polymerization of heterocyclic monomers i n homogeneous media has been relatively less studied than that of vinyl or dienic monomers. The propagation reaction occurs through active centers that are generally much more stable than carbanions, and the polymerization rates are smaller, thus allowing convenient conductance and kinetic measurements (1,2). However only few monomers, namely propylene sulfide and ethylene oxide, which give true l i v i n g polymers, have been studied i n detail. D i f f i c u l t i e s of different types are encountered for several heterocyclic monomers such as the insolubility of the resulting polymers, chain transfer to the monomer or polymer or associations of ion pairs into higher aggregates. Considerable progress has been made i n this f i e l d i n the last few years by the use of macrobicyclic ligands (I) discovered by Lehn (3).
for instance m = n = p = 2 designated
[222]
These ligands form extremely stable cation inclusion complexes, called cryptates, i n which the cation i s completely surrounded by the ligand and hidden inside the molecular cavity, and this leads to a considerable increase of the interionic distance i n the ion pairs. It has been shown that such ligands have a marked activating effect on anionic polymerizations (4,5,6). Moreover, the aggregates are destroyed and simple kinetic results have been obtained i n the case of propylene sulfide (7,8,9), ethylene oxide (9,10,11) and cyclosiloxanes (12) polymerizations. Though the 0097-6156/81/0166-0283$05.75/0 © 1981 American Chemical Society McGrath; Anionic Polymerization ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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ANIONIC POLYMERIZATION
cryptâtes have been used f o r the a n i o n i c polymerization of other h e t e r o c y c l i c monomers l i k e lactones (4,13,14), c y c l i c carbonates (4) and lactams (15), we w i l l present the r e s u l t s obtained with propylene s u l f i d e , ethylene oxide and c y c l o s i l o x a n e s in t h i s paper.
Downloaded by UNIV OF CALIFORNIA SAN DIEGO on July 25, 2016 | http://pubs.acs.org Publication Date: November 30, 1981 | doi: 10.1021/bk-1981-0166.ch019
I.
A n i o n i c P o l y m e r i z a t i o n of Propylene
Sulfide
Propylene s u l f i d e gives polymers with p e r f e c t l y s t a b l e t h i o l a t e l i v i n g ends in e t h e r e a l s o l v e n t s (16). The propagation r e a c t i o n has been s t u d i e d in THF (7-9JL7-2lT"and in THP (8,9,21,22,23) w i t h N a , C s , B U 4 Î F and s e v e r a l cryptâtes as counterions, by d i l a t o m e t r y . I t has been shown that even f o r non cryptated s p e c i e s , the a s s o c i a t i o n s of i o n p a i r s do not g e n e r a l l y occur in the range of concentrations examined ([C...]
