Effect of para‐Substituents in Ethylene Copolymerizations with 1‐Decene, 1‐Dodecene, and with 2‐Methyl‐1‐Pentene Using Phenoxide Modified Half‐Titanocenes‐MAO Catalyst Systems

Abstract

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.

Analysis of Ethylene Copolymers with Long-Chain α-Olefins (1-Dodecene, 1-Tetradecene, 1-Hexadecene): A Transition between Main Chain Crystallization and Side Chain Crystallization

“…As reported recently, , the ethylene/DD copolymerizations afforded poly­(ethylene- co -DD)­s possessing rather high molecular weights with unimodal molecular weight distributions ( M n = 8.9–30.1 × 10 4 , M w / M n = 1.62–2.09) and uniform compositions (confirmed by DSC thermograms shown below). As also reported previously in ethylene/1-hexene copolymerization, the activity (on the basis of polymer yield) was affected by the ethylene pressure and DD concentration charge: the activity increased upon increasing the ethylene pressure.…”

“… e α-Olefin in copolymer (mol %) estimated using 1 H NMR spectra (selected data are shown in SI ). f Polymerization data cited from ref ( 31 ). g α-Olefin in copolymer (mol %) estimated using 13 C NMR spectra (selected data are shown in SI ).…”

“…Ethylene (E) copolymers with 1-dodecene (DD), 1-tetradecene (TD), and 1-hexadecene (HD) were prepared by copolymerization in toluene using Cp*TiCl 2 (O-2,6- i Pr 2 -4-SiEt 3 C 6 H 2 ) (Cp* = C 5 Me 5 ) catalyst in the presence of methylaluminoxane (MAO) cocatalyst. The titanium catalyst has been chosen in this study because the catalyst exhibited notable catalytic activities for E/DD copolymerization with efficient DD incorporation to afford the copolymers. , The catalysts of this type are known to be effective for the synthesis of new ethylene copolymers − with sterically encumbered olefins (disubstituted olefins, branched α-olefins), cyclic olefins, and aromatic vinyl monomers, as well as the synthesis of poly­(LCAO)­s. ,, These copolymerizations were conducted with the termination of low comonomer conversions (less than 10%, short period) to obtain the copolymer with uniform compositions (to avoid changes in the LCAO concentrations during the polymerization runs). The results are summarized in Table .…”

“… a Conditions: total volume, 30 mL; MAO, 2.0 mmol; 6 min (runs 14, 29, 40: total 6.0 mL, 30 min); and 25 °C. b Initial concentration (mmol/mL). c Activity = kg-polymer/mol-Ti·h. d GPC data in o -dichlorobenzene vs polystyrene standards. e α-Olefin in copolymer (mol %) estimated using 1 H NMR spectra (selected data are shown in SI). f Polymerization data cited from ref . g α-Olefin in copolymer (mol %) estimated using 13 C NMR spectra (selected data are shown in SI). h Polymerization at 50 °C. …”

“…50 °C for removing toluene and AlMe 3 and then heated at >100 °C for 1 h for completion). 25 , 30 , 31 , 35 , 36 Cp*TiCl 2 (O-2,6- i Pr 2 -4-SiEt 3 -C 6 H 2 ) was prepared according to a previous report. 30 …”