Synthesis of Polyethylene Containing a Terminal p-Methylstyrene Group:  Metallocene-Mediated Ethylene Polymerization with a Consecutive Chain Transfer Reaction to p-Methylstyrene and Hydrogen

Abstract

This paper discusses a novel polymerization process for preparing polyethylene having a terminal p-methylstyrene (p-MS) group. The chemistry involves metallocene-mediated ethylene polymerization in the presence of p-MS and hydrogen. Apparently, the reaction mechanism, including the copolymerization and chain transfer reactions, can be controlled with a favorable combination of metallocene catalyst and hydrogen concentration. Under some specific reaction conditions, the Cp2ZrCl2/MAO catalyst selectively forms PE with a terminal p-MS terminal group (PE-t-p-MS) via a consecutive chain transfer reaction to p-MS and then hydrogen. The catalyst activity increases with the hydrogen concentration, and the polymer molecular weight is inversely proportional to the p-MS concentration. In contrast, [C5Me4(SiMe2N t Bu)]TiCl2/MAO initiates a copolymerization reaction between ethylene and p-MS, and hydrogen has little effect on the catalyst activity. The terminal p-MS unit at the PE chain end is a valuable reactive group that can be metalated to form a stable polymeric anion, which can be used to prepare functionalized PE polymers containing a polar terminal group or diblock copolymers.

Zirconium-Catalyzed Polymerization of a Styrene: Catalyst Reactivation Mechanisms Using Alkenes and Dihydrogen

“…As we have described above, benzylic dormant species are prevalent in E/S copolymerizations, and Chung has exploited this in the production of p-methylstyreneterminated PE simply by addition of dihydrogen. 44 This produces an alkyl-terminated polymer and regenerates the catalyst by the mechanism shown in Figure 6. We were thus pleased to find that under 1 atm of H 2 , with no additional olefin "promoter", P(TBS) was formed (run 10, Table 2).…”

Regiochemistry‐Aligned Copolymerization of Propylene with p‐Methylstyrene and 1,4‐Diviny­lbenzene Using an ansa‐Metallocene Catalyst

“…It has also been reasonably interpreted as the result of an insertion regiochemistry conflict between propylene (mainly primary, 1,2‐) and the styrenic monomers (mainly secondary, 2,1‐) that causes steric jamming around the active centers inhibiting consecutive monomer insertion. As a matter of fact, we have well utilized this phenomenon to generate i PP with a variety of end reactive groups using hydrogen to restore the polymerization . Oliva et al however added small amounts of ethylene to help with the copolymerization of propylene and p ‐MS with rac ‐Et(Ind) 2 ZrCl 2 /methylaluminoxane (MAO) and obtained i PP/ p ‐MS copolymers intermitted by ethylene sequences …”

Effect of Clay Types on the Mechanical, Dynamic Mechanical and Morphological Properties of Polypropylene Nanocomposites

“…Manias et al [18] achieved clay polypropylene nanocomposite formation in different ways either by using functionalized polypropylenes and common organo-montmorillonites, or by using neat=unmodified polypropylene and a semi-fluorinated organic modification for silicates. Recently, a facile route has been reported in which reactive chain transfer agents was used to prepare end-functionalized polyolefins [19][20][21][22][23] containing a terminal functional group (-OH, -NH 2 , -COOH, anhydride, etc. ).…”