Ethylene copolymerization with 2-vinylnaphthalene (VN) by ((BuC5H4)-Bu-t)TiCl2(O-2,6-(Pr2C6H3)-Pr-i) (1)-MAO catalyst system afforded high-molecular-weight amorphous copolymers with unimodal molecular weight distributions as well as uniform compositions (M-n = 18 100-39 900, M-w/M-n = 1.23-1.47, T-g = 24-75 degrees C, VN 21.6-44.8 mol %). Copolymerization with 4-vinylbiphenyl (VB) using 1- and (1,2,4-Me3C5H2)TiCl2(O-2,6-(Pr2C6H3)-Pr-i) (2)-MAO catalyst systems also yielded high-molecular-weight copolymers (M-n = 96 200-222 000, M-w/M-n = 1.33-2.06), and synthesis of the copolymers with high VB contents (>50 mol %) has been demonstrated. These copolymerizations in the presence of a [Me2Si(C5Me4)((NBu)-Bu-t)]TiCl2 (4)-MAO catalyst system afforded semicrystalline polymers (possessing melting temperatures of 91-103 degrees C). Linear relationships between the glass transition temperature (T-g) and the comonomer (VN, VB) content have been demonstrated. The T-g values in the same comonomer content increased in the order VN > VB > styrene, suggesting that introduction of an aromatic substituent to the side pendent group affects the thermal properties (T-g values). These copolymers possess resonances ascribed to repeated VN (VB) incorporations on the basis of microstructural analysis of poly(ethylene-co-VN)s and poly(ethylene-co-VB)s through C-13 nuclear magnetic resonance (NMR) spectra, and the regioselectivity as well as the degree of the head-to-tail repeated insertions is affected by the cyclopentadienyl fragment and the comonomer (VN, VB, styrene) employed. Synthesis of high-molecular-weight amorphous poly(ethylene-co-VB) with high VB content, which possesses high T-g with a uniform composition (M-n = 130 000, M-w/M-n = 1.51, T-g = 156 degrees C, VB 87.5 mol %), has thus been attained by copolymerization using the 2-MAO catalyst system.