Abstract
ABSTRACT This is a study of results obtained from polymerization runs of propylene, carried out at temperatures ranging from 40 to 175°C in the presence of catalysts based on TiCl4 or α-TiCl3 and Al(C2H5)3, prepared and prestabilized at 175°C before their use. Both catalytic systems yield polymers whose steric regularity decreases when the polymerization temperature increases. The steric irregularities observed in the polymeric chains are to be attributed to the inversion phenomena of steric configuration of the monomeric units during their polymerization. A hypothesis is proposed for such inversion phenomena to be connected with the dissociation, followed by a re-association, of the complex which consists of the transition metal and of organometallic compounds, and to which the polymeric growing chain is bound. A method proposed for establishing the number of inversions in the polymeric chains, is based on the application of Flory's equation for determining the melting temperature of the copolymers.
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