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Document Type:Latin Dissertation
Language of Document:English
Record Number:55504
Doc. No:TL25458
Call number:‭3200271‬
Main Entry:Xinwei Wang
Title & Author:Electrosynthesis of polysilanes and polycarbosilanes and their oligomersXinwei Wang
College:State University of New York College of Environmental Science and Forestry
Date:2005
Degree:Ph.D.
student score:2005
Page No:271
Abstract:Electropolymerization of polysilanes and polycarbosilanes using monomeric dichlorosilanes (RR'SiCl2) and chloroalkylchlorosilanes (Cl-R-Si(CH 3)3-mClm) has been explored. A novel gas diffusion hydrogen anode has been developed as an effective alterative to the sacrificial anodes for electrosynthesis of alkyl and aryl-substituted oligosilane (up to 8 silicon units) at ∼70% yield, and polysilanes having Mn up to 6,400 at up to 12.6% yield. The one-pot electropolymerization of linear and branched polycarbosilanes, with Mn up to ∼56,000 and M w up to ∼178,000 at up to 34.0% polymer yield has been discovered. Structural details of these polymeric products have been studied using GPC, FT-IR, 1H-, 13C- and 29Si-NMR, UV and emission spectroscopy, and computational modeling. The initiation of polysilane electropolymerization has been investigated using room- and low-temperature cyclic voltammetry (CV) and simulative CV techniques. The results show that the reduction of RR'SiCl2 proceeds by an EC mechanism. Correlation of the Taft's substituent constants to the reduction potential indicated that for dialkyl-substituted chlorosilanes, the steric effect of substituents is largely responsible for the stability of the SN2 transition state during the electron transfer. High molecular weight polysilane can be obtained at 2.5 mA/cm2 of current density in a THF/HMPA (1/1, v/v) solvent using a GDHA with the completion of 2.0 F/mol of electricity. A series of R-bridged linear and branched oligo- and polycarbosilanes have been electropolymerized from monomers of type Cl-R-Si(CH3) 3-mClm (R = CH2, C2H4, C 3H6, and -CH2-C6H4-C 2H4-). The formation of reactive centers (carbanion) is promoted by an α-silyl or phenyl group attached to the CH2-Cl group, or in the presence of a redox catalyst (i.e., the electrogenerated silylanion radical). Products formed from polymerization of Cl-CH2-Si(CH 3)3-mClm are strongly dependent on the anodic materials (Mg, Al, Zn), solvents (THF, TDA-1, HMPA), supporting electrolytes, such as, Bu4N+BF4-, Bu 4N+ClO4-, Bu4N +BPh4-, and monomer concentrations.
Subject:Pure sciences; Chlorosilanes; Polycarbosilanes; Polysilanes; Polymers; Chemistry; Organic chemistry; 0495:Polymers; 0490:Organic chemistry; 0494:Chemistry
Added Entry:I. Cabasso
Added Entry:State University of New York College of Environmental Science and Forestry