Polyolefin–polar block copolymers from versatile new macromonomers

A new metallocene-based polymerization mechanism is elucidated in which a zirconium hydride center inserts α-methylstyrene at the start of a polymer chain. The hydride is then regenerated by hydrogenation to release a polyolefin containing a single terminal α-methylstyrenyl group. Through the use of the difunctional monomer 1,3-diisopropenylbenzene, this catalytic hydride insertion polymerization is applied to the production of linear polyethylene and ethylene–hexene copolymers containing an isopropenylbenzene end group. Conducting simple radical polymerizations in the presence of this new type of macromonomer leads to diblock copolymers containing a polyolefin attached to an acrylate, methacrylate, vinyl ester, or styrenic segments. The new materials are readily available and exhibit interfacial phenomena, including the mediation of the mixing of immiscible polymer blends

Zirconium-catalyzed polymerization of a styrene : catalyst reactivation mechanisms using alkenes and dihydrogen

Zirconium salicylaldiminates in the presence of AliBu3/[Ph3C][B(C6F5)4] are inactive for the homopolymerization of p-tert-butylstyrene (TBS), but the addition of hexene leads to a highly active system. Analysis of the polymers by NMR and MALDI indicates surprisingly that most of the product chains contain no hexene, while some contain a single hexene unit. Addition of dihydrogen also leads to the production of poly(TBS) without substantial reduction in molecular weight and with main-chain end-group unsaturation. These and other observations lead us to two related mechanisms for the hexene- and dihydrogen-promoted reactions. Synthetic and catalytic studies indicate that the active species is not a typical bis(salicylaldiminato) compound but an amido/alkoxido system. An authentic compound of this class is highly active for the TBS polymerization even in the absence of added aluminum alkyl

Awakening a dormant catalyst : salicylaldimine systems for ethene/tert-butylstyrene copolymerization

A group of readily available zirconium catalysts incapable of ethene-co-styrene polymerization are remarkably active and selective for the production of the new polymer ethene-co-tert-butylstyrene via a single site mechanism