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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'.

cis-1,3-Pentadiene (2) and trans-l,3-pentadiene (3) were copolymerized with isobutene (1) in the presence of (C2H5)2AIC1+(CH3)3CCI or (C2H5)2A1CI+CIz in the range of temperatures between -35 and -70°C. The reactivity ratios, determined at -55°C are: rl.2= 5.0 and r 1 . 3~ 2,3, while the chain transfer coefficients are K1.2= 50 and K,.1= 113. The activation energies are: Ea..2= -13,8 kJ/mol (-3,3 kcal/mol) and EU\..I= -16,7 kJ/mol(-4,0 kcal/mol). Spectroscopic analyses (IR, 'H-NMR) showed that in both copolymers the 1,4-trans structure is prevalent over the 1.2-trans-enchainment. The fact that 3 is more reactive than 2 can be correlated with a greater electron-density ( ' 'C-NMR data) on C-I in compound 3. ZUSAMMENFASSUNG:cis-1.3-Pentadien (2) und trcrns-1,3-Pentadien (3) wurden mit Isobuten ( I ) in Gegenwart von (C2H~)2AICI+(CH3)3CCI oder (C2HSj2AIC1+CI2 im Temperaturbereich von -35 bis -70°C copolymerisiert. Die Copolymerisationsparameter, bestimmt bei -55 "C. sind: r1,2=5,0 und rl,3=2,3; die Ubertragungskonstanten sind: K1.2=50 und K1.3= 113. Die Aktivierungsenergien betragen: E,g,,2 = -13.8 kJ/mol (-3,3 kcal/mol) und E,,.,= -16,7 kJ/mol ( -4,0 kcal/mol).Spektroskopische Analysen (IR, 'H-NMR) zeigten, daB in beiden Copolymeren die 1,4-trans-Struktur die 1,2-trans-Verkettung uberwiegt. Die hohere Reaktivitat von 3 im Vergleich mit 2 kann durch die hohere Elektronendichte (aus I3C-NMR-Daten) am C-l in der Verbindung 3 bedingt sein.

The synthesis of novel butadiene (B)-isobutene (I) copolymers, prepared with coordination catalysts, is reported and discussed. The best results were obtained by using at -40°C ternary systems, based on TiC14, (i-C4H9)3A1 or (i-C4H&A1H, and benzophenone or acetophenone, previously aged at -78 "C. The fomation of the novel B-I copolymers was accompanied by polybutadiene (cis-and rrans-l,4-units were prevalent) and, sometimes by cationic I-B copolymer. The new copolymers, after isolation, underwent thorough spectroscopic investigations. IR analysis yielded the microstructure of *B units: trans-l,4 = 55%, cis-1,4=31%, and 1,2= 14%. 'H NMR spectroscopy showed that I unit is present only in alternating triad BIB and ruled out the presence of any I homosequence. The study, by "C NMR, of both the original and hydrogenated copolymer evidenced that only trans-l,4-B is linked to I units and hence the copolymer structure is described by IBI and 1B.I (where n a 2 ) sequences. A copolymer containing 30% of I showed the following mole fractions of triads centered on B: FIBI =0,158; FBBI+IBB = 0,382; and FBBB = 0,462. The mechanistic implications of the copolymer structure are discussed.