Monomer-bound ion pairs in the stereoregular polymerization of propylene oxide by the Pruitt-Baggett catalyst

AKSOY Ş., Altinok H., TÜMTÜRK H., Alyürük K.

Polymer, vol.31, no.6, pp.1142-1148, 1990 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 31 Issue: 6
  • Publication Date: 1990
  • Doi Number: 10.1016/0032-3861(90)90264-y
  • Journal Name: Polymer
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1142-1148
  • Keywords: electrical conductivity, monomer-bound ion pairs, propylene oxide, Pruitt-Baggett catalyst, solution properties, stereoregular polymerization
  • Ankara University Affiliated: No

Abstract

The Pruitt-Baggett adduct (PBA) (MW = 438 g mol-1) that formed from the reaction of FeCl3 with propylene oxide (PO) was hydrolysed in diethyl ether (ether) solutions at different r = H2O Fe molar ratios. The hydrolysates ( PBH r), which were insoluble in ether, could be converted into catalytically active form ( PBC r) by a thermal treatment. PBC r (r < 1) was soluble in etheric solvents and in pyridine. These solutions, in contrast to PBA and PBH r, were electrical conductors. Profound differences in the electrical conductivity of PBC r was observed by varying the hydrolysis ratio r. The observed conductivity decayed and finally vanished with a kinetically second-order process. This is explained by the free ions, formed from PBC 0.67 (MW = 4400 g mol-1), being bound together with an ether (or PO) molecule to yield ether- (or PO-) bound ion pairs (PBCB). PBC 0.67 and the electrical conductivity of its freshly prepared solutions could be retrieved by 'driving off' (by drying under vacuum at 40°C) the 'binding molecule' (ether or PO) from PBCB. In contrast to this system, the electrical conductivity of solutions of PBC 0.20 (which shows inferior catalytic activity) did not change with ageing. © 1990.