A Neodymium-Based Catalyst For Styrene Coordination Polymerization

The coordination polymerization of styrene with a modified catalyst system composed of neodymium tricarboxylate (Nd), Al(i-Bu)₃ (Al) and chlorinating agent(CL) such as MECF, ECA, EDCA, ETCA was carried out in cyclohexane. The effects of preparation procedure of the catalyst system, such as CL/Nd molar ratio, Al/Nd molar ratio, ageing temperature and ageing time, and the reaction conditions on polymerization were investigated. The monomer conversion was determined gravimetrically and thus catalytic activity was calculated. The reaction between the components in the catalyst system was characterized by UV spectra. The molecular weight and molecular weight distribution of the resultant polystyrene were determined by GPC. The microstructure and morphology of the polymer were characterized by ¹³C-NMR and polarizing microscope. The experimental results indicate that as follows.The catalyst system of Nd/Al/MECF exhibited high catalytic activity of 7.29×10⁴ g PSt/ (mol Nd ? h) at 60 ℃, but the molecular weight of polymer products was relatively low, number-average molecular weight (M_n) was in the range of 2000 to7000 g/mol.The catalyst system of Nd/Al/MECF is relatively favorable to increase the molecular weight, softening temperature range and the stereoregularity of polymer at low Al concentration or at low ageing temperature or at lower polymerization temperature. When a small...