The synthesis of ultra-high molecular weight polystyrene and polymerization kinetics

Calix[n]Nd/MgBu2n/HMPA is an effective catalytic system for the synthesis of the ultra-high molecular weight polystyrene (UHMWPS) The catalytic activity of different Calix[n]Nd complex decreases in the following order: Calix[6]Nd > Calix[4]Nd > Calix[8]Nd. It shows that the aging of catalyst plays an important role on catalytic activity. The optimum conditions are as follow: Mg/Nd = 20.0 (molar ratio), HMPA/Mg = 1.0 (molar ratio) and aged 2.5 h under 50degreesC. The study of influence of solvent shows that toluene is a good solvent. The polymerization result shows that the conversion is over 80% at 50degreesC, 45 min. The kinetics of styrene polymerization using Calix[6]Nd-20MgBu(2)(n)-20HMPA in toluene were investigated by weight method. It was found that the rate of polymerization is first order with respect to both monomer (St) and Calix[6]Nd concentrations. According to Arrhenius equation, it was found that polymerization activation energy is 41.7 kJ/mol. GPC characterization of obtained polymer shows: M-w = 21.0 x 10(5), MWD = 1.61. H-1-NMR spectra of UHMWPS shows that the content of syndiotactic triad is 81%.