The initiation and catalysis of isobutylene polymerization from several new metallocene and nonmetallocene initiator‐catalysts that contain the noncoordinating anions (NCA), B(C6F5)4− and RB(C6F6)3−, is reported. Application of these initiator‐catalysts is extended to styrenics and vinyl ethers. The NCA does not contribute to termination and can be used in low concentrations compared with conventional Lewis acids. These qualities provide for isobutylene polymerizations that yield low Mn oligomers or high Mn polymer, dependent upon the initiator and polymerization conditions. Mechanistic aspects of initiation, transfer and termination as well as the participation of adventitious water are considered for each class of initiator‐catalyst. The influence of the NCA on the stereoregularity of cationic styrene polymerization is also considered. NCAs do not cause the stereospecific carbocationic polymerization of styrene. We suggest that under conditions not conducive to carbocationic polymerization, NCA/metallocenes mediate the coordination polymerization of styrene. © 1997 John Wiley & Sons, Inc.

The first examples of dimethylaluminum chloride catalyzed living isobutylene polymerizations are presented. The polymerizations are carried out with conventional tertiary alkyl chloride initiators and 60/40 v/v nonpolar/polar solvent mixtures, the most common solvent systems used for isobutylene triblock synthesis. Additives like proton traps and electron donors are not required. The "living" nature of these polymerizations is demonstrated at -75 to -80 °C in both 60/40 v/v hexane/methylene chloride and hexane/methyl chloride solvent systems using first-order rate plots, trends in M n and Mw/Mn versus conversion, and delayed incremental-monomer-addition experiments. Polyisobutylenes are prepared with Mn ) 150 kDa and Mw/Mn ) 1.2. Since initiation from adventitious moisture is of minor concern in this system, experiments were also run in the presence of dimethyl phthalate. "Livingness" was preserved though polymerization rates are slower with dimethyl phthalate than in its absence.

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Polyisobutylene is unique among elastomeric polymers in that while the glass transition temperature is low (−70 °C), segmental dynamics at temperatures above T g are relatively slow due to steric constraints resulting from the molecular packing of methyl groups. We describe results from NMR experiments on solid polyisobutylene (PIB) and copolymers with p-methylstyrene (PIB−PMS) in which the dynamics of chain motion in PIB homopolymers and PIB−PMS copolymers are compared as a function of temperature. Our one- and two-dimensional solid-state 1H, 13C, and 2H results clarify previously published reports on local vs correlated segmental dynamics for the PIB homopolymer, which differ by 4−5 orders of magnitude in their correlation times. Distinct differences in aromatic ring dynamics as a function of PMS concentration are also observed for PIB−PMS copolymers. While PMS dynamics are found to be sensitive to PMS concentration in the copolymer, PIB motions appear to be independent of the comonomer incorporation. These results may be understood based on the clustered or blocky incorporation of PMS comonomer segments in the polymer chain. This copolymer system represents a regime intermediate between random copolymers and phase-separated block polymers and may be considered a correlated random copolymer. Relaxation and 2D HETCOR experiments are used to define morphology for the PMS clusters in the copolymer, and the results are consistent with a 3 nm domain size for the clusters. Finally, the effects of curing on dynamics at the cross-link site for functionalized PIB−PMS copolymers are selectively examined using 2H wide-line experiments.

Addition of 50 equiv of benzaldehyde to a benzene solution of (Ph3P)2Rh(?y3-CH2C(Ph)0) (1) resulted in rapid disproportionation of the aldehyde, yielding benzyl benzoate in near quantitative yield. Similar disproportionation reactions occurred with isobutyraldehyde, n-heptanal, and furfural; however, the yields in these reactions were lower. The catalytic efficiency of the (?73-oxaallyl)rhodium(I) complex depended on the -substitution pattern of the aldehyde, the concentration of the aldehyde, and the polarity of the aldehyde. The labeled complex (Ph3P)2Rh(773-CH213C(Ph)0) (1SC-1) transformed during catalysis into two carbonlabeled products, demonstrating that the ?/3-oxaallyl complex served as a precursor to the actual catalyst. The (i/3-allyl)rhodium(I) complex (Ph3P)2Rh(?73-CH2CHCH2) (5) failed to react with benzaldehyde, but upon addition of 4 equiv of hydrogen gas, catalysis ensued with near quantitative disproportionation of the aldehyde. Rapid disproportionation of benzaldehyde also occurred when (DIPH0S)Rh(C6H6)+C10,T and 18-crown-6-solubilized PhCH20_K+ were mixed, establishing the intermediacy of a rhodium alkoxide. A complete mechanistic scheme for oxaallyl modification and disproportionation catalysis is presented.