POLYMERIZATION OF 1,2-EPOXYPROPANE AND 1,2-EPOXYCYCLOHEXANE BY DIETHYLZINC-POLYHYDRIC PHENOL AND OR PHENOL OR 1-PHENOXY-2-PROPANOL AS CATALYSTS

1,2-Epoxypropane and 1,2-epoxycyclohexane were polymerized in the presence of catalysts derived from reactions of diethylzinc with a polyhydric phenol (4-tert-butylcatechol, pyrogallol) and/or phenol or 1-phenoxy-2-propanol in 1,4-dioxane solution, varying the polymerization temperature and time. The polymers formed in these polymerizations were analysed by means of H-1 NMR, C-13 NMR and UV spectroscopy in terms of the polymer chain microstructure and chain end-groups. The poly(propylene oxide) (PPO) obtained appeared to be a high-molecular-weight polymer with prevailing isotactic diads (mole fraction in the range of 0,65-0,72). It was found to consist of a predominant amorphous (atactic) fraction and a crystalline (isotactic) fraction. An enhancement of both the crystallinity and the average molecular weight of PPO was observed with an elongation of the duration of the polymerization. Therefore, it was concluded that the catalyst enantioselectivity increases with progressing polymerization. The poly(cyclohexene oxide) (PCHO) obtained appeared to be a polymer with prevailing syndiotactic diads (mole fraction in the range of ca. 0,58-0,80) and threo-enchainement of monomeric units. This was explained in terms of inversion of the configuration at the carbon atom of the epoxide ring upon cleavage. A possible mechanism for the epoxide polymerization by the coordination catalysts studied is presented.