Cyclopolymerization Behavior of Bis(dimethylvinylsilyl)methane

Abstract

ABSTRACT:Anionic cyclopolymerization of bis(dimethylvinylsilyl)methane (BVSM) in hexane, which affords a polymer having six-membered rings as repeating cyclic units, is investigated. Low polymer yields in the polymerization of BVSM with n-butyllithium (n-BuLi) in the absence of N,N,N',N'-tetramethylethylenediamine (TMEDA) are attributed to cross-linking reactions and association of the propagating ends at -lO'C and elimination of lithium hydride from the propagating end at 40°C. Polymerization with n-BuLiiTMEDA is accompanied, though not frequently, by the abstraction of the methylene proton interposed by two silicon atoms, which forms an inactive anion. This abstraction is caused by the propagating end in the six-membered ring. At high monomer concentration, 0.5 moll-1 , cross-linking reaction is not negligible even in the presence of TMEDA. As initiators, n-, s-, t-BuLi are examined, and only s-BuLi/TMEDA is found to cause the proton abstraction from the methylene interposed by two silicon atoms. The effects of the initiator are explained by the nucleophilicity of BuLi and the steric hindrance in the abstraction. The effects of three amines on the polymerization arc evaluated. TMEDA is the most suitable for the cyclopolymerization of BVSM among them.

Mechanism of the Anionic Cyclopolymerization of Bis(dimethylvinylsilyl)methane

“…Unlike the cases of radical cyclopolymerization of 1,6-heptadienes, the resulting polymer contains only six-membered, 1,3-disilacyclohexane rings as repeating cyclic units. Though the polymerization is accompanied by a termination reaction with low frequency, the molecular weight distribution of the polymer is rather narrow . The number-average molecular weight ( M n ) is in accord with the calculated value for the polymer without cross-linking structure.…”

“…We have studied the anionic cyclopolymerization of multivinylsilanes, the compounds having two or more silylvinyl groups per molecule. − The polymerization of methyltrivinylsilane and tetravinylsilane proceeds only in the presence of N,N,N ‘ ,N ‘ -tetramethylethylenediamine (TMEDA), and the resulting polymers contain monocyclic and bicyclic ring structures . Bis(dimethylvinylsilyl)methane (BVSM) undergoes anionic cyclopolymerization with n -butyllithium ( n -BuLi) at −10 °C in hexane in the presence of TMEDA in 100% cyclization efficiency (Scheme ) .…”

Chain‐growth condensation polymerization approach to synthesis of well‐defined polybenzoxazole: Importance of higher reactivity of 3‐amino‐4‐hydroxybenzoic acid ester compared to 4‐amino‐3‐hydroxybenzoic acid ester

“…Even at higher reaction temperature, the reaction mixture was heterogeneous, and polymerization did not proceed. Since the precipitate was thought to consist of aggregates of Li amide of 1a , N,N,N′,N′; ‐tetramethylethylenediamine (TMEDA) was added to the reaction mixture. However, the reaction system was still heterogeneous and polymerization did not proceed.…”

Synthesis of a variety of star‐shaped polybenzamides via chain‐growth condensation polymerization with tetrafunctional porphyrin initiator

“…In chain‐growth condensation polymerization for linear poly( m ‐benzamide)s, the monomer is slowly added to a solution of initiator and LiHMDS,8, 9 so that the monomer concentration in the reaction mixture is lower than that in the chain‐growth condensation polymerization for poly( p ‐benzamide)s, in which the monomer was added at once into a solution of initiator and LiHMDS 2. Therefore, self‐condensation of the monomer in the synthesis of star‐shaped poly( m ‐benzamide)s from tetra‐functional initiator 2 would be suppressed under the same conditions that yield linear poly( m ‐benzamide)s. Thus, a variety of meta‐substituted monomers 3 were polymerized with 2 at 0 °C in the presence of LiCl13, 14 for N ‐alkyl and N ‐OOB monomers8 or N,N,N ′, N ′‐tetramethylethylenediamine (TMEDA)15–18 for N ‐TEG monomer10 according to the reported polymerization method for linear poly( m ‐benzamide)s (Scheme , Table 4). Monomers 3a and 3b with N ‐ethyl and N ‐octyl groups, respectively, afforded the corresponding star polymers with narrow molecular weight distributions at the [ 3 ] 0 /[ 2 ] 0 ratios of 40 and 80 (entries 1–3).…”