Ethylene/Styrene Copolymerization by Various (Cyclopentadienyl)(aryloxy)titanium(IV) Complexes−MAO Catalyst Systems

Abstract

Copolymerizations of ethylene with styrene by various (cyclopentadienyl)(aryloxy)titanium(IV) complexes of the type Cp′TiCl2(O-2,6-i Pr2C6H3) [Cp′ ) t BuC5H4 (2), 1,3-Me2C5H3 (3), 1,2,3-Me3C5H3 (4), 1,2,4-Me3C5H3 (5)] have been explored in the presence of methylaluminoxane (MAO) as the cocatalyst. Effect of cyclopentadienyl fragment was explored and the catalytic activity increased in the order 3, 4 > 2 > 5, suggesting that effects of both electronic and steric bulk play an essential role for the copolymerization. Resultant polymers by these catalyst systems were poly(ethylene-co-styrene)s exclusively in all cases, and the use of 4 was quite effective for preparing relatively high molecular weight polymer with unimodal molecular weight distribution as well as with efficient styrene incorporation. The styrene incorporation efficiency did not strongly depend upon the cyclopentadienyl fragment used, and this is somewhat different from those obtained by the linked cyclopentadienyl-amide titanium catalyst [Me 2Si-(C5Me4)(NR)]TiCl2 [R ) tert-Bu (6), cyclohexyl (7)]. The resultant copolymers possessed unimodal comonomer distributions (single composition) confirmed by both cross-fractionation chromatography (CFC) and GPC/FT-IR. The microstructure for the resultant copolymer by 2-5 was different from those prepared by a linked type catalyst (6) and was fairly dependent upon the cyclopentadienyl fragment used.

Nuclearity and cooperativity effects in binuclear catalysts and cocatalysts for olefin polymerization

“…26, which is published as supporting information on the PNAS web site). When styrene incorporation is Ͼ50%, at least three consecutive head-to-tail coupled styrene units are observed in addition to tail-to-tail coupled dyads (41,42). This result contrasts markedly with conventional mononuclear CGCs that incorporate a maximum of 50% styrene, regardless of the feed ratio, and where, of the three possible dyads, only tail-to-tail coupling is observed (34).…”

Half-Titanocenes Containing Anionic Ancillary Donor Ligands: Effective Catalyst Precursors for Ethylene/Styrene Copolymerization

“…; X = halogen, alkyl), are effective not only for syndiospecific styrene polymerization, but also for ethylene/styrene copolymerization to exclusively give poly(ethylene-co-styrene)s [15,17,[52][53][54][55][56][57][58][59][60][61][62][63]. Linked halftitanocenes (so-called "constrained geometry type") are also effective for copolymerization [5,[64][65][66][67][68][69][70][71][72][73][74][75][76][77], although these complexes exhibited extremely low catalytic activities for styrene polymerization [64,73].…”

“…C NMR spectra (methylene and methine regions) of the copolymers, including assignment of the monomer sequences, are shown in Figure 1 [53]. As described below, the microstructures for the resultant poly(ethylene-co-styrene)s depend on the catalysts used.…”

“…[80], but also exhibited efficient comonomer incorporations for copolymerization of ethylene with α-olefin [81][82][83], as well as with styrene [52][53][54][55][56] in the presence of MAO (Scheme 1). [52,53], whereas the Cp* analogue (4), which exhibited remarkable activities and comonomer incorporations in ethylene/α-olefin copolymerization [80][81][82][83], exhibited lower activities than 1-3 (Table 1) [52][53][54][55][56]. The resultant polymers are poly(ethylene-co-styrene)s exclusively without by-producing polyethylene and/or syndiotactic polystyrene [52,53].…”

Synthesis of ethylene–styrene copolymer containing syndiotactic polystyrene sequence by trivalent titanium catalyst

“…7,8 Recently, several researchers have reported the development of more efficient catalysts for the copolymerization of ethylene and styrene: a half-titanocene featuring an aryloxy-type ligand, a titanium complex having a pendant-type cyclopentadienyl ligand and a rare-earth metal-based catalyst. [9][10][11][12][13][14][15][16][17] However, there have been only limited reports on the synthesis of copolymers containing long syndiotactic styrene-styrene sequences. Hou and co-workers 18 have reported that rare-earth metal-based catalyst systems promote not only the syndiotactic homopolymerization of styrene, but also copolymerization with ethylene, in which the Cp¢Sc(CH 2 SiTMS) 2 /Ph 3 CÁB(C 6 F 5 ) 4 [Cp¢¼C 5 Me 4 (CH 2 TMS)] catalyst system produces a multi-block copolymer consisting of a crystalline SPS part and an ethylene-rich part.…”