A series of novel cyclic olefin copolymers (COCs), including ethylene/tricyclo[4.3.0.12,5]deca‐3‐ene (TDE), ethylene/tricyclo[4.4.0.12,5]undec‐3‐ene (TUE), and ethylene/tricyclo[6.4.0.19,12]tridec‐10‐ene (TTE) copolymers, have been synthesized via effective copolymerizations of ethylene with bulk cyclic olefin comonomers using bis(β‐enaminoketonato) titanium catalysts (1a [PhNC(CH3)CHC(CF3)O]2TiCl2; 1b: [PhNC(CF3)CHC(Ph)O]2TiCl2). With modified methylaluminoxane as a cocatalyst, both catalysts exhibit high catalytic activities, producing high molecular weight copolymers with high comonomer incorporations and unimodal molecular weight distributions. The microstructures of obtained ethylene/COCs are established by combination of 1H, 13C NMR, 13C DEPT, HSQC 1H13C, and 1H1H COSY NMR spectra. DSC analyses indicate that the glass transition temperature (Tg) increases with the enhancement of comonomer volume (TDE < TUE < TTE). High Tg value up to 180 °C is easily attained in ethylene/TTE copolymer with the low content of 35.8 mol %. TGA analyses reveal that these copolymers all possess high thermal stability with degradation temperatures (Td) higher than 370 °C in N2 and air. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3144–3152

A new titanium complex [PhN=C(Ph)CHC(CF3)O]2TiCl2 (2a), with an asymmetric β‐enaminoketonato [N,O] ligand, has been synthesized and fully characterized. With modified methylaluminoxane as a cocatalyst, the behaviors of ethylene polymerization, and ethylene/α‐olefin and ethylene/norbornene copolymerization have been explored in detail. Relative to its regioisomer 2b ([PhN=C(CF3)CHC(Ph)O]2TiCl2), the present catalyst exhibits significant predominance. The catalytic activity in 2a‐catalyzed homo‐ and copolymerization are much higher than those in 2b‐catalyzed (co)polymerization. Furthermore, compared with 2b, catalyst 2a possesses an obviously stronger ability towards copolymerization, due to a wide coordination space caused by exchanging the position of the phenyl group and trifluoromethyl group on the framework.