ISSN:
0449-2951
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Gas-liquid chromatography was used to determine the amounts of cyclic molecules present in an equilibrium polymerization mixture of high polymer and cyclic dimethylsiloxane molecules. The study was carried out as a function of polymerization temperature. For [(CH3)2SiO]4-10 the equilibrium concentration is shown to be independent of temperature. The change in cyclic concentration as a function of n for [(CH3)2SiO]4-10 does not follow the theoretical Stockmayer-Jacobson distribution. The concentrations of [(CH3)2SiO]3,4 are qualitatively predictable by the Stockmayer-Jacobson theory and by the model proposed by Carmichael and Kinsinger. For [(CH3)2SiO]4, Kexp = 0.74 mole —SiO—/l. The model calculations yield 0.12 (Stockmayer-Jacobson) and 0.36 Carmichael-Kinsinger. For [(CH3)2SiO]3, Kexp = 0.024 mole —SiO—/l. Model calculations yield 0.017-0.16 (Stockmayer-Jacobson) and 0.056-0.52 (Carmichael-Kinsinger). The range of values rises because of uncertainty in the cyclic strain energy.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1965.100030311
