Radiation-induced polymerization of dimethylcyclosiloxanes in the liquid state: I. Influence of drying and nature of the propagation mechanism
| Autor: | V. T. Stannett, D.M. Naylor, Alain Deffieux, Pierre Sigwalt |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Polymers and Plastics
Organic Chemistry Cationic polymerization Photochemistry Octamethylcyclotetrasiloxane Ring-opening polymerization chemistry.chemical_compound Monomer Chain-growth polymerization chemistry Polymerization Materials Chemistry Precipitation polymerization Organic chemistry Ionic polymerization |
| Zdroj: | Polymer. 31:954-957 |
| ISSN: | 0032-3861 |
| DOI: | 10.1016/0032-3861(90)90063-5 |
| Popis: | The radiation (cobalt 60 γ)-induced polymerization of octamethylcyclotetrasiloxane D 4 and decamethyl-cyclopentasiloxane D 5 has been studied in the liquid state. Progressive drying of the monomers over a succession of sodium mirrors led to increased rates and a levelling off at higher conversions. After 12 mirrors no further increases in rates were observed and the rates were reproducible. With the D 4 monomer a square-root dependence of the rate on the dose rate was found in agreement with the Hayashi-Williams equation for radiation-induced ionic polymerization under completely pure conditions. The conversions to polymer and cyclic byproducts were followed directly in nuclear magnetic resonance (n.m.r.) tubes with 13 C n.m.r. No post-radiation effects were observable. The complete inhibition of both the polymerization and the formation of cyclic byproducts by trimethylamine and ammonia clearly indicated a cationic mechanism. Triethylamine only partly inhibited the reactions, this is ascribed to steric interference with the growing chains or initiating species. |
| Databáze: | OpenAIRE |
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