Eur. Polym. J. Vol. 23, No. 1, pp. 63~o7, 1987 0014-3057/87 $3.00+0.00 Printed in Great Britain Pergamon Journals Ltd EPOXIDE POLYMERIZATION--IX. STYRENE OXIDE POLYMERIZATION USING THE DIPHENYLZINC-WATER SYSTEM IN BENZENE AT VARIOUS TEMPERATURES FRANCO M. RABAGLIATI* and JESUS M. CONTRERAS Grupo de Polimeros, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, M6rida 5101, Venezuela (Received 1 May 1986) Abstract--The diphenylzinc-water system was used as a catalyst for styrene oxide polymerization in benzene solution at 25, 60 and 90 °. The system, as for polymerization of ethylene oxide or propylene oxide, is greatly influenced by the molar ratio of water to diphenylzinc; unlike the other monomers however diphenylzinc by itself produced the best yield to polymer and conversion to poly(styrene oxide) (PSO) diminished when water was added. GPC results confirm the presence of more than one active species for the system; ~3C-NMR analysis indicates that the resulting PSO always has a head-to-tail arrangement, independent of the molar ratio of H20/Ph2Zn. From viscometry results, a viscometric equation for PSO in chloroform at 40 °, was derived, viz. [tl] = 4.49 x 10 -5 x ~/0873. INTRODUCTION Styrene oxide (SO) has been polymerized by metal halides and their complexes [1, 2], by metal alkoxides [3-5], by organometallics with addition of water or alcohols or some chelates [6-11], and by some less studied processes including radiation [12] and radical initiation [13]. When organometallic/cocatalyst sys- tems were used, water was the most studied cocatalyst and high molecular weight poly(styrene oxide) (PSO) was obtained. Jedlinski et al., when using sodium methoxide [4], established that the ring-opening of SO occurred almost exclusively at the fl-position but, when using aluminium isopropoxide [5], they obtained a rela- tively high molecular weight, head-to-tail PSO to- gether with some oligomers. They concluded that, although there may be ~- and fl-opening of propylene oxide, the SO polymerization by Al(OiPr)3 proceeds with ring opening exclusively at the a-position. The ~- and fl-ring opening for cationic oxirane polymerization and the fl-opening for its anionic polymerization showed that it is not a general occur- rence. Jedlinski [14] concluded that the course of oxirane polymerization depends on the kind of ini- tiator as well as on the type of substituent at the oxirane ring. In previous papers, we have reported the poly- merization of ethylene oxide (EO) and of propylene oxide (PO) using the diphenylzinc-water system [15-17]. According to those results, it was postulated that the polymerization involved more than one *Present address for correspondence: Dr Franco M. Raba- gliati, Departmento de Quimica, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 5659, Correo 2, Santiago, Chile. 63 EPJ 23/I--E active species capable of producing poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) re- spectively. At the same time, it was established that the polymerization system is greatly influenced by the molar ratio, H20/Ph2Zn. Furthermore, from 13C-NMR spectroscopy, it was established that the crude PPO obtained has only head-to-tail sequences when H20/Ph2Zn = 1.0, and also a small content of head-to-head tail-to-tail linkages when the molar ratio, H20/Ph2Zn was 0.25 or 0.50 [17, 18]. The crude PPO obtained through our Ph2Zn-H20 system con- tained a variable portion of crystalline polymer at a percentage depending on the molar ratio of H20/Ph2Zn used. The crystalline polymer portion always turned out to be isotactic PPO according to 13C-NMR spectra. The present paper describes the polymerization of SO in benzene solution initiated by the diphenylzinc-water system at various molar ratios, H20/Ph2Zn, at 25, 60 and 90 °. EXPERIMENTAL Styrene oxide (Aldrich Chemical Co.) was first dried by standing for 24hr over calcium hydride at room tem- perature, then distilled twice at reduced pressure (40mm Hg) collecting the 130-2 ~ fraction. The distillate was kept over Call 2 under its vapour pressure. SO was transferred by syringe, under argon, to the polymerization reactors. Polymerizations were carried out in benzene at 25, 60 and 90 °, in vials filled using a vacuum line technique [15, 16]. The polymers were isolated by precipitation with methanol, dissolved in benzene and then freeze-dried. In other cases, the reaction products were isolated by vacuum distillation of volatiles. Intrinsic viscosities, [q], were measured at 25 ~ in toluene and at 40 ° in chloroform. Values of.~,/v were calculated from [r/] values obtained at 25 ° in toluene according to the equation [19]: [r/] = 6.79 × l0 -5 x j~r0v'766.