The stereospecific polymerization of isoprene (Ip) was carried out with a modified rare-earth catalyst system which consisting of neodymium tricarboxylate (Nd)

triisobutyl aluminium (Al)

chlorinating agent (CE) and alcohol (OH)

in which CE includes chlorinated hydrocarbon (CE1) and chlorinated carboxylic ester (CE2).The effect of chemical structure of OH and CE2

molar ratio of Al/RE on Ip polymerization

molecular weight

molecular weight distribution and microstructure of the resulting polymers was investigated.The kinetic study on the polymerization was conducted via in situ characterization by Fourier transform infrared spectroscopy in combination with a diamond tipped attenuated tota1 reflectance immersion probe (ATR-FTIR) during polymerization.Detailed characterizations including microstructure

molecular weight and its distribution

sequence and heat capacity of PIp have been carried out by FTIR

GPC

NMR and DSC.The results show that polymerization rate was first-order with respect to monomer concentration

and the apparent propagation activation energy (Ea) was determined to be 69.5 kJmol-1 when polymerization temperature was in the range from 0℃ to 30℃.The catalytic activity and content of cis-1

4 configuration of PIp could be improved and molecular weight distribution could be narrowed by introducing a small amount of CE2 and OH.The monomer conversion increased and molecular weight decreased with increasing Al/RE ratios.Polyisoprene with high cis-1

4-content of more than 98% and narrow molecular weight distribution (Mw/Mn= 1.6 ~2.4) could be achieved by adjusting component ratio and polymerization conditions.