Synthesis of Elastomeric Poly(propylene) (ELPP) Using the Highly Active TiCl4/Dibutyl phthalate (DBP)/MgCl2‐Al(i‐C4H9)3/1‐Allyl‐3,4‐dimethoxybenzene (ADMB) Catalyst

Propene polymerization was first carried out at 70°C using the TiCl₄/DBP/MgCl₂ catalyst in combination with a mixture of ADMB and various alkylaluminium compounds. Both the activity and the molecular weight of the polymer were strongly dependent on the kinds of alkylaluminiums. However, the isotactic index (I.I.) of the polymer was hardly affected by them. In order to control the I.I. value, the propene polymerization was then conducted with the TiCl₄/DBP/MgCl₂‐Al(i‐C₄H₉)₃/ADMB catalyst by changing the polymerization temperature. A suitable selection of polymerization temperatures gave a higher molecular weight PP containing various amounts of APP, i. e., I.I. 4–59%. Mechanical testing indicated that the obtained polymers exhibited a wide range of physical properties from a low modulus thermoplastic elastomer to flexible plastics depending on their stereoregularities. The improved elastic recovery of the obtained PP in the present study could be simply interpreted by the decrease in the [mmmm] or crystallinity of the polymer. Thus, the polymer having the lowest such values was found to have an excellent elastic recovery, which was comparable to that of ELPP as previously reported. The present result is the first example of the synthesis of an elastomeric poly(propylene) using a highly active MgCl₂‐supported Ti catalyst.