Intramolecular vs. Intermolecular Condensation Rates in the Acidic Polymerization of Octaethoxytrisiloxane

Abstract

Octaethoxytrisiloxane, (EtO)3Si-O-Si(OEt)2-O-Si(OEt)3, was synthesized and then polymerized in water/alcohol-solution in the presence of an acid catalyst. The reaction was monitored with 29Si-NMR. The rate constants of linear and cyclic condensation were estimated by curve-fitting and were compared. No evidence of depolymerization was found, indicating that condensation is irreversible in our conditions. In addition, it was found that the formation of trimeric cyclic species by ring closure is fast and competes effectively with chain extension condensation. These observations are consistent with previous suggestions, but in addition they provide a quantitative measure of selectivity that is much needed. Quantitative kinetic models for silicon alkoxide sol-gel processes need to account for cyclization at very early stages of the polymerization.

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Document Details

Document Type
Technical Report
Publication Date
Jul 12, 1993
Accession Number
ADA266982

Entities

People

  • A. V. Mccormick
  • J. Sanchez

Organizations

  • University of Minnesota

Tags

Communities of Interest

  • Advanced Electronics

DTIC Thesaurus Topics

  • Chemical Engineering
  • Chemical Kinetics
  • Chemical Reaction Properties
  • Chemical Reactions
  • Chromatography
  • Condensation
  • Curve Fitting
  • Depolymerization
  • Engineering
  • Gas Chromatography
  • Kinetics
  • Materials
  • Materials Engineering
  • Materials Science
  • Military Research
  • Polymerization
  • Sol Gel Processes

Fields of Study

  • Chemistry

Readers

  • Combustion science or combustion engineering.
  • Computational Modeling and Simulation
  • Organic Chemistry