La polymérisation anionique en masse de l'α-méthyl styrène. I. Etude de la stabilité des centres actifs

Abstract

R e~u le 1 avril 198 1 DOMINIQUE ADES, MICHEL FONTANILLE et JACQUES LEONARD. Can. J . Chem. 60,564 (1982). Lapolymerisation anionique en masse de I'a-methyl styrene (EMS) a ete realisee en utilisant comme amorceur le tert-butyllithium (t-BuLi) avec ou sans N,N,N1,N'-tetramethyl ethylene diamine (TMEDA). En absence de TMEDA, les centres actifs formes se degradent rapidement a 62°C tandis qu'ils sont relativement plus stables a 25°C. En presence de TMEDA, la stabilite des centres actifs est beaucoup plus grande mais elle est fonction de I'ordre dans lequel le t-BuLi et la TMEDA sont ajoutes a I'ctMS. La stabilite des centres actifs est aussi fonction du rapport r = The anionic bulk polymerization of cc-methylstyrene (EMS) has been carried out using tert-butyllithium (t-BuLi) as initiator with or without N,N,N1,N'-tetramethylethylenediamine (TMEDA). In absence of TMEDA, the "livingends" are rapidly deactivated at 62°C whereas they are relatively more stable at 25°C. The "living ends" are much more stable in presence of TMEDA; however, their stability is a function of the order in which t-BuLi and TMEDA are added to EMS. The stability of "living ends" is also a function of the ratio r = [TMEDA]l[t-BuLi] and best results are obtained with a one to one ratio. At high temperature, the formation of species with absorption bands at 390 and 424 nm and the broadening of the molecular weight distribution are observed. These results are explained in terms of a transfer reaction to the monomer or to the deactivated polymer.

Synthesis and Characterization of Well-Defined Poly(α-methylstyrene)-b-poly(dimethylsiloxane) Block Copolymers

“…A purchased PAMS-PS-PDMS sample from Dow (presumably synthesized by Saam's method 1 ) had a relatively wide MWD (D ) 1.51). This is consistent with the following: (a) slow initiation of D 3 by PAMS-PSLi, (b) competing hydride elimination and protonation by THF of the benzylic anions, [22][23][24][25] (c) lithium silanolate redistribution reactions and/or lithium silanolate aggregation during the D 3 polymerizations (Scheme 2). 11,27 Synthesis of PAMS(A)-PS-EDS-b-PDMS(B) Block Copolymers.…”