The kinetics of 4-methylpentene-1 (4MP1) polymerization by use of Ziegler-Natta-type catalyst systems, M(acac)(3)-AlEt3 (M = Cr, Mn, Fe, and Co), are investigated in benzene medium at 40degreesC. The effect of various parameters such as Al/M ratio, reaction time, aging time, temperature, catalyst, and monomer concentrations on the rate of polymerization and yield are examined. The rate of polymerization increased linearly with increasing monomer concentration with first-order dependence, whereas the rate of polymerization with respect to catalyst concentration is found to be 0.5. For all cases, the polymer yield is maximum at an Al/M ratio of 2. The activation energies obtained from linear Arrhenius plots are in the range of 25.27-33.51 kJ mol(-1). It is found that the aging time to give maximum percentage yield of the polymer varies with the catalyst systems. Based on the experimental results, a plausible mechanism is proposed that envisages a free-radical mechanism. Characterization of the resulting polymer product, for all the cases, through FTIR, H-1-NMR, and C-13-NMR studies, showed isomerized polymeric structures with 1,4structure as dominant. (C) 2003 Wiley Periodicals, Inc.