EFFECT OF THE EXTERNAL DONORS ON THE POLYMERIZATION OF 4-METHYL-1-PENTENE WITH HIGH-ACTIVITY MGCL2 TICL4 CATALYTIC-SYSTEM/

In order to find out correlations between the structure of an external donor and the obtained polymer, the effects of different external don ors on the activity and stereospecificity of the MgCl2/TiCl4 catalytic system in the bulk polymerization of 4-methyl-1-pentene (4MP) were ca refully studied. Different silane compounds of the structure RnSi(OR') 4-n (where: n = 1 - 3, R = alkyl/phenyl, R' = alkyl) and AI(i-Bu)3 (TI BA) were used as external donors and cocatalyst, respectively. The eff ect of the donor/TIBA mole ratio on the activity and stereospecificity of the catalytic system was studied. Some major effects were observed for the three different external donors, namely, Me3Si(OMe), Me2Si(OM e)2 and MeSi(OBu)3, in the 4MP polymerization process. It was observed that the effect of the external silane donor on the polymerization st rongly depends upon the size of the alkoxy and hydrocarbon (alkyl/phen yl) groups which are attached to the silicon atom. A selective deactiv ation of the non-stereospecific centers, as well as a transformation o f the non-stereospecific into isospecific centers, is assumed to occur . On the basis of the obtained results and literature data available f or the propene polymerization, the concept of structural conformity be tween the ligand-surrounded active center and the monomer molecule was carried forward.