Cationic ring opening polymerization of octamethylcyclotetrasiloxane initiated by acid treated bentonite

Abstract

Abstract: Cationic ring opening polymerization of octamethylcyclotetrasiloxane (D4) initiated by acid treated bentonite was investigated. The experimental conditions were chosen on the basis of preliminary experiments. Higher temperature was found beneficial for the reaction process while stirring intensity beyond a certain level showed no obvious effect on the reaction rate. Polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance (1H-NMR) and gel permeation chromotography. The width of molecular mass distribution was found ranging between 1.2 and 1.4, which is extraordinarily narrow compared with that of cationic polymerizations reported elsewhere (＞1.9). The results were believed due to the absence of free proton and counter ion which simplifies the polymerization process and the huge steric hindrance provided by bentonite particles which keeps the propagation of polysiloxane onto the surface of bentonite particles in a much more regular way. A feasible mecha-nism is proposed and seems to be supported well by experiments. Additionally, from the results of α, ω-dihydrogen terminated polysiloxanes prepared, the possibility of applying this potential environmentally friendly heterogeneous catalyst in industrial polymerization of cyclosiloxanes is anticipated.

Key words: octamethylcyclotetrasiloxane, cationic polymerization, polysiloxane

摘要： Cationic ring opening polymerization of octamethylcyclotetrasiloxane (D4) initiated by acid treated bentonite was investigated. The experimental conditions were chosen on the basis of preliminary experiments. Higher temperature was found beneficial for the reaction process while stirring intensity beyond a certain level showed no obvious effect on the reaction rate. Polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance (1H-NMR) and gel permeation chromotography. The width of molecular mass distribution was found ranging between 1.2 and 1.4, which is extraordinarily narrow compared with that of cationic polymerizations reported elsewhere (＞1.9). The results were believed due to the absence of free proton and counter ion which simplifies the polymerization process and the huge steric hindrance provided by bentonite particles which keeps the propagation of polysiloxane onto the surface of bentonite particles in a much more regular way. A feasible mecha-nism is proposed and seems to be supported well by experiments. Additionally, from the results of α, ω-dihydrogen terminated polysiloxanes prepared, the possibility of applying this potential environmentally friendly heterogeneous catalyst in industrial polymerization of cyclosiloxanes is anticipated.

关键词: octamethylcyclotetrasiloxane;cationic polymerization;polysiloxane

CHEN Bi, ZHAN Xiaoli, YI Lingmin, CHEN Fengqiu. Cationic ring opening polymerization of octamethylcyclotetrasiloxane initiated by acid treated bentonite[J]. , DOI: .

陈碧, 詹晓力, 易玲敏, 陈丰秋. 酸白土催化体系开环八甲基环四硅氧烷的研究及机理探讨[J]. , DOI: .

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