Remarkable effects of SiMe 3 and SiEt 3 parasubstituents in the phenoxide-modified half-titanocenes, Cp*TiCl 2 (O-2,6-i Pr 2-4-R-C 6 H 2) [R= SiMe 3 (6), SiEt 3 (7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9decen-1-ol (DC-OH) have been demonstrated. The activities by 6, 7 at 50 8C showed higher than those conducted at 25 8C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by 7, which showed better DC-OH (HX-OH) incorporation at 50 8C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81 10 5 kg-polymer mol À1-Ti h, M n = 6.55-10.0 10 4 , DC-OH 2.3-3.6 mol %). Scheme 1. Synthesis of Cp*TiCl 2 (O-2,6-i Pr 2-4-R-C 6 H 2). R = Ph (3), CHPh 2 (4), CPh 3 (5), SiMe 3 (6), SiEt 3 (7)].

The synthesis of ethylene/myrcene copolymers was performed using half-titanocene catalysts in the presence of a methylaluminoxane (MAO) cocatalyst. Cyclopentadienyl-phenoxide catalysts, Cp*TiCl 2 (O-2,6-i Pr 2 -4-RC 6 H 2 ) [R = H (1), SiEt 3 (2)], showed rather efficient myrcene (My) incorporation to afford high-molecular-weight (semicrystalline or amorphous, depending on the My content) copolymers, which possess unimodal molecular weight distributions as well as uniform compositions. Microstructural analysis of poly(ethylene-co-My)s by NMR spectroscopy revealed that the resultant copolymers possessed cyclopentane units with a My pendant arm (−CH 2 CHCMe 2 ), formed by 2,1-or 1,4-My insertion and subsequent cyclization after ethylene insertion. The resultant copolymer showed promising elastic properties; the elongation at break increased upon increasing the My content, accompanied by a decrease in the tensile strength and toughness.

A series of ethylene copolymers with long-chain α-olefins [LCAOs, 1-dodecene (DD), 1-tetradecene (TD), 1-hexadecene (HD)] and various LCAO contents were prepared, and their thermal properties, including effects of LCAO content and side chain length, were explored. The Cp*TiCl 2 (O-2,6- i Pr 2 -4-SiEt 3 -C 6 H 2 )–MAO catalyst system afforded rather high-molecular-weight copolymers with unimodal molecular weight distributions and uniform compositions (confirmed by DSC thermograms). In addition to the melting temperatures ( T m values) corresponding to the so-called main chain crystallization (samples with low LCAO contents, the T m value decreased upon increasing the LCAO content) and the side chain crystallization [polymer samples with high LCAO contents, by intermolecular interaction of side chains as observed in poly(DD), poly(TD), and poly(HD)], the other T m value was observed, especially in poly(ethylene- co -HD)s (assumed to be due to co-crystallization of the branch and the main chain through an interaction of the main chain and the long side chains). The presence of another crystalline phase in poly(ethylene- co -HD)s was also suggested by a wide-angle X-ray diffraction (WAXD) analysis. These T m values in poly(ethylene- co -TD)s and poly(ethylene- co -DD)s with rather high TD or DD contents were affected by the heating conditions in the measurement of DSC thermograms (5 or 10 °C/min), suggesting that the driving force for formation of the crystal packing (observed as T m ) is weak and affected by the alkyl side chain lengths.

Effect of para‐substituents in the ethylene (E) copolymerization with 1‐decene (DC), 1‐dodecene (DD), and with 2‐methyl‐1‐pentene (2M1P) using a series of Cp*TiCl2(O‐2,6‐iPr2‐4‐R‐C6H2) [R=H (1), tBu (2), Ph (3), CHPh2 (4), CPh3 (5), SiMe3 (6), SiEt3 (7), and newly prepared 4‐tBuC6H4 (8) and 3,5‐Me2C6H3 (9)]‐MAO catalyst systems has been studied. The activities in these copolymerization reactions were affected by the para‐substituent, and the SiMe3 (6), SiEt3 (7) and 3,5‐Me2C6H3 (9) analogues showed the higher activities at 50 °C in the E copolymerization reactions with DC (1.06–1.44×106 kg‐polymer/mol‐Ti⋅h), DD (1.04–1.88×106 kg‐polymer/mol‐Ti⋅h) than the others, whereas no significant differences were observed in the comonomer incorporations. Complexes 6 and 7 also showed the higher activities at 50 °C in the E/2M1P copolymerization, and the 2M1P incorporation was affected by the para‐substituent and the polymerization temperature; complex 9 showed better 2M1P incorporation at 25 °C.

Ethylene copolymerizations with 2-methyl-1-pentene, 1-dodecene (DD), vinylcyclohexane (VCH), [Me 2 Si(C 5 Me 4 )-(N t Bu)]TiCl 2 (1), Cp*TiMe 2 (O-2,6-i Pr 2 -4-RC 6 H 2 ) [R = H (2), SiEt 3 (3)]−borate, and [A(H)] + [BAr 4 ] − [Ar = C 6 F 5 ; A(H) + = N + (H)Me(n-C 18 H 37 ) 2 , N + (H)(CH 2 CF 3 )(n-C 18 H 37 ) 2 , HO + (n-C 14 H 29 ) 2 •O(n-C 14 H 29 ) 2 , HO + (n-C 16 H 33 ) 2 •O(n-C 16 H 33 ) 2 ; Ar = C 10 F 7 , A(H) + = HO + (n-C 14 H 29 ) 2 •O(n-C 14 H 29 ) 2 (B5), N + (H)-(CH 2 CF 3 )(n-C 18 H 37 ) 2 ] catalyst systems conducted in methylcyclohexane (MCH) exhibited better comonomer incorporation than those conducted in toluene (in the presence of methylaluminoxane (MAO) or borate cocatalysts). The activity was affected by the borate cocatalyst and 1,3−B5 catalyst systems in MCH and showed the highest activity in the ethylene copolymerizations with VCH and DD.