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  • 1
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The results of previous studies carried out on the polymerization of isobutene initiated by diethylaluminium halides plus halogens are compared with results obtained with other syncatalytic systems such as diethylaluminium chloride (or triethylaluminium) plus hydrochloric acid (or tert-butyl chloride), as well as with results obtained with aluminium compounds such as ethylaluminium dichloride or aluminium trichloride which do not require co-initiators to initiate the polymerization of isobutene. The kinetic data indicate clearly that the polymerization of isobutene initiated by syncatalytic systems is characterized by a relatively slow initiation and by the absence of important termination reactions and of transfer with monomer. In contrast to this, the polymerizations initiated by strong Lewis acids such as ethylaluminium dichloride or aluminium trichloride show a much faster initiation and stop at incomplete conversion which indicates that at least one efficient termination reaction is operative. It is also demonstrated that this termination reaction produces at least one substance which acts as a co-initiator for the isobutene polymerization initiated by diethylaluminium halides or triethylaluminium.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerizations of isobutene and its copolymerizations with isoprene by syncatalytic systems consisting of an aluminium compound R2AlX (with R = alkyl and X = alkyl or halogen) and of a halogen or an interhalogen compound are initiated by the addition of a positive halogen ion to the monomer. Chlorine is the best co-initiator. Whereas in this syncatalyzed polymerization of isobutene the initiation is relatively slow and monomer transfer and termination are unimportant, in the polymerization of isobutene by AlCl3 or EtAlCl2 the initiation is very fast and there is at least one efficient termination. Our interpretation of these results includes a discussion of the different initiations and chain-breaking reactions.In the syncatalyzed polymerizations the initiation rate is governed by the relatively slow interaction of initiator and co-initiator. Since the termination reactions are relatively unimportant, second and subsequent portions of monomer polymerize completely and faster than the first. The polymerizations initiated by AlCl3 or EtAlCl2 stop at incomplete conversion because of a termination which is chlorination of the carbenium ions by the anions; the AlCl3 thus formed is complexed by the unreacted monomer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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