SYNTHESIS OF ISOTACTIC POLYSTYRENE WITH A RARE-EARTH CATALYST

Polymerization of styrene with the neodymium phosphonate Nd(P-507)/H2O /Al(i-Bu)(3) catalytic system has been examined. The polymer obtained was separated into a soluble and an insoluble fraction by 2-butanone e xtraction. C-13-NMR spectra indicate that the insoluble fraction is is otactic polystyrene and the soluble one is syndiotactic-rich atactic p olystyrene. The polymerization features are described and discussed. T he optimum conditions for the polymerization are as follows: [Nd] = (3 .5-5.0) x 10(-2) mol/L; [styrene] = 5 mol/L; [Al]/[Nd] = 6-8 mol/mol; [H2O]/[Al] = 0.05-0.08 mol/mol; polymerization temperature around 70 d egrees C. The percent yield of isotactic polystyrene (TY) is markedly affected by catalyst aging temperature. With increase of the aging tem perature from 40 to 70 degrees C, TY increases from 9% to 48%. Using A lEt3 and Al(i-Bu)(2)H instead of Al(i-Bu)(3) decreases the yield of is otactic polystyrene. Different neodymium compounds give the following activity order: Nd(P-507)(3) > Nd(P-204)(3) > Nd(OPri)(3) > NdCl3 + C2 HF5OH > Nd(naph)(3). With Nd(naph)(3) as catalyst, only atactic polyst yrene is obtained. (C) 1998 John Wiley & Sons, Inc.