Steric and electronic effects of the R in IndTiCl(2)(OR) catalysts on the syndiospecific polymerization of styrene

Four alkoxyl ligand substituted indenyl titanium dichloride complexes, IndT iCl(2)(OR) (R = Me (2), Et (3), Pr-i (4), cyclohexyl (5)) were prepared, an d evaluated as catalysts for the syndiospecific polymerization of styrene w hen activated with methylaluminoxane (MAO). Alkoxyl ligand substituted comp lexes showed higher catalytic activities than IndTiCl(3) (1) except for com plex 5. When R = Et, the catalyst 3 showed the highest activity. A study of the steric and electronic effects of alkoxyl ligand revealed that the more electron-donating and less steric bulky R group was more suitable for the improvement of the catalytic activity. When the polymerization was carried in solution at high molar ratio of Al/Ti = 4000, the s-PS% of obtained poly mer were in the range of 99.0-99.6%. The highest melting point of 276.9 deg reesC was obtained by using 2 as catalyst. The influence of polymerization temperature was also investigated. The maximum polymerization activities we re found at 50 degreesC for all of the above complexes, but the percentages of s-PS were insensitive to the polymerization temperature. (C) 2001 Elsev ier Science B.V. All rights reserved.