The polymerizations of isobutene and its copolymerizations with isoprene by syncatalytic systems consisting of an aluminium compound RzAIX (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 AICI3 or EtA1Cl2 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 byAICI3 or EtAICI2 stop at incomplete conversion because of a termination which is chlorination of the carbenium ions by the anions; the AICI3 thus formed is complexed by the unreacted monomer.

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. *) Part 5: cf.6'.

The general procedures which were developed for the study of the polymerization and copolymerization of isobutene, initiated by novel syncatalytic systems based on dialkyl aluminium halides and halogens or interhalogen compounds, are described. The results of preliminary experiments on polymerization and copolymerization carried out with the goal of identifying the most promising catalytic systems from the point of view of efficiency and of polymer molecular weight are described briefly. The best results were obtained with the systems (C2H5)2A1CI + CI,, (C2H5)2A1Cl + ICI, and (C2H5)2AII+ 12. ZUSAMMENFASSUNG:Die allgemeinen Methoden, welche fur das Studium der Polymerisation und der Copolymerisation des Isobutens durch neue synkatalytische Systeme entwickelt wurden, werden beschrieben. Diese Systeme bestehen aus Alkylaluminiumhalogeniden zusammen mit Halogenen oder Interhalogen-Verbindungen. Die Ergebnisse vorlaufiger Experimente werden beschrieben, welche dahin zielten, das wirksamste katalytische System im Hinblick auf Ausbeute und Molekulargewicht der Polymeren aufzufinden. Die besten Ergebnisse wurden mit den folgenden Kombinationen erzielt : (C2H5),AICI + CI2, (C2H5)2AICI + JC1 und (C2H5),AIJ + J2.Grammes of polymer produced per mole of co-initiator. h,Calc. with respect to the aluminium compound.

In the course of studies on polymerizations of isobutene (1) by syncatalysts consisting of ethylaluminium halides and halogens, it became necessary to study the separate reactions between the components of the reaction mixtures. The results showed: a) that in general alkyl chlorides d o not react with halogens in the dark at -35°C and below, but do react in the light; b) that at low temperatures 1 and its dimers react with chlorine more easily by substitution than by addition; c) that ethylaluminium halides react with halogens by forming aluminium halides, ethyl halides and ethylene.The findings of the present study enabled us to design polymerization conditions and procedures which minimize undesirable side-reactions in the polymerization of 1 with syncatalysts.The experiments with the dimer of 1 (i.e. 2,4,4-trimethyl-l-pentene), which is a nonpolymerizable model compound for I, supported our view that initiation occurs by a halonium ion. ZUSAMMENFASSUNG:Im Verlauf von Untersuchungen der Polymerisation von Isobuten (1) durch Synkatalysatoren aus Athylaluminiumhalogeniden und Halogenen, wurde eine Untersuchung der einzelnen Reaktionen zwischen den Komponenten der Reaktionsgemische notwendig. Die Ergebnisse zeigten: a) daB Alkylchloride mit Halogenen im Dunkeln bei -35°C und darunter nicht reagieren. Die Reaktion findet jedoch im Licht statt; b) daR bei niedrigen Temperaturen 1 und seine Dimeren mit Chlor leichter Substitutions-als Additions-Reaktionen unterliegen; c) dal3 Athylaluminiumhalogenide mit Halogenen unter Bildung von Aluminiumhalogeniden, Athylhalogeniden und Athylen reagieren. *I Part 1 : cf.? 2289 A. Priola, S. Cesca, G. Ferraris, and M. di Maina Die Ergebnisse der vorliegenden Untersuchung ermoglichten Polymerisationsbedingungen und -verfahren zu bestimmen, die unerwunschte Nebenreaktionen bei der Polymerisation von 1 mit Synkatalysatoren auf ein Mindestmal3 verringern. Die Versuche mit Dimerem von 1 (2.B. 2,4,4-Trimethyl-l -penten), das eine unpolymerisierbare Modellverbindung fur 1 darstellt, bestatigen unsere Annahme, dal3 die Initiierung durch ein Haloniumion stattfindet.

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