ISSN:
0360-6376
Schlagwort(e):
Physics
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Highly purified samples of N-ethyl-3-vinylcarbazole are readily polymerized in CH2Cl2 by conventional initiators of cationic polymerization, including boron trifluoride etherate and tropylium hexachloroantimonate. Reaction rates measured calorimetrically yield an estimate for the free-cation propagation rate coefficient (kp+ = 2 x 10+4 liter/mole-sec) at 0°C, which is some 20 times smaller than that for the closely related monomer N-vinylcarbazole. Distinguishing aspects of the cationic polymerization of N-ethyl-3-vinylcarbazole are the very high molecular weights obtained and the linear dependence of M̄n of the monomer/catalyst mole ratio, indicating that transfer and termination are comparatively unimportant. Polymerizations initiated by tropylium hexachloroantimonate exhibit a characteristic absorption band at 468 nm, tentatively assigned to the propagating cation, which undergoes rapid changes after all monomer has been consumed. The stability of the species responsible for the absorption band at 468 nm appears to be least in conditions where ion pairs are important.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1978.170160404
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