Poly(1-octene) was synthesized by polymerization of I-octene using high performance MgCl2-supported TiCl4 in combination with triethyl aluminum (TEA1) as cocatalyst in n-hexane for 2 h. Two catalysts, C-1 (diester catalyst) having di-isobutyl phthalate as internal donor and C-2 (monoester catalyst) having ethyl benzoate as internal donor were utilized for the atmospheric polymerizations to evaluate the influence of structurally different internal donors on the productivity, rate of polymerization and molecular weight profiles. The kinetic profile assessed in terms of variation of reaction parameters like temperature, cocatalyst to catalyst molar ratio and monomer concentration was found to be dependent on them. From these kinetic analyses, optimize conditions for polymerizations of I-octene using diester as well as monoester catalyst were elucidated. The difference in the performance of diester and monoester catalyst system can be explained in terms of stability of active titanium species and chain transfer process. NMR spectroscopy of synthesized poly(l-octene) indicate predominantly isotactic nature. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115:229-236, 2010