ISSN:
0025-116X
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The determination of the structure of the end groups in poly(δ-valerolactone) (poly(δVL)) by using 1H, 31P NMR, and IR spectroscopy showed that in the cationic polymerization of δVL, propagation proceeds via cyclic dialkoxycarbenium ions as active species and the monomer molecules are incorporated into the polyester chains by an alkyl-oxygen bond scission. In the anionic polymerization of δVL, propagation proceeds via alcoholate anions and monomer molecules are added with breaking the acyl-oxygen bond. A similar cationic mechanism operates with alkylating ((CH3)2I⊕SbF6⊖) and acylating (CH3CO⊕SbF6⊖) initiators. However, with the latter, the cyclic dialkoxycarbenium active centers coexist with the acylium cations during the initial period of polymerization. Finally, however, the cyclic dialkoxycarbenium ions become the only active species. The mechanisms of ionic propagation in the polymerization of β-propiolactone, δ-valerolactone, and ε-caprolactone are compared.
Zusätzliches Material:
6 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/macp.1987.021880902
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