Stereo-structure and monomer sequence distribution of the ethylene-propylene copolymers obtained from half-titanocene catalytic system

(η5-pentamethylcyclopentadienyl) titanium triallyloxide (Cp*Ti(OCH2CH=CH2)3) combined with methylalumiloxane (MAO)

have been investigated by 13C-NMR spectra.The monomer reactivity ratios of the copolymerization with this catalyst were calculated from the monomer sequence distribution in 13C-NMR spectra

r1=7.91±0.06 for ethylene

r2=0.135±0.03 for propylene

and the products r1r2 for all runs in various feeding monomer ratio are almost equal to one (r1r2≈1).The monomer reactivity ratios were also determined according to Fineman-Ross method

the values of r1=7.74

r2=0.134 and r1r2=1.04 are very close to those of calculating dbove by 13C-NMR analysis.These results indicated that the copolymers produced are random ones.The ethylene-propylene copolymers could be fractionated by successive solvent extraction and gave two fractions of ether-soluble and hexane-soluble.These two fractions showed slight differences in their monomer sequence distribution and monomer reactivity ratio.The ether-soluble fraction contained more propylene units

while more ethylene segments existed in the hexane-soluble fraction.