单茂钛/MAO体系催化乙烯/丙烯共聚合研究Ⅱ.乙烯/丙烯共聚物的核磁共振分析

用13C NMR测定了由单茂基钛化合物 /mMAO催化体系制备的乙烯 /丙烯共聚物大分子链的立体结构和单体序列分布 ,计算了单体的竞聚率r1=7 91± 0 0 6 ,r2 =0 135± 0 0 3 ,其乘积r1r2 ≈ 1.Fineman Ross计算得到的单体竞聚率与13C NMR测定值相近 ,即r1=7.94,r2 =0 .134,其乘积r1r2 =1 0 4.这表明共聚物是立构无规的 .共聚物经溶剂萃取后 ,乙醚可溶和己烷可溶两个级分中单体的序列分布和竞聚率略有不同 .乙醚可溶级分中丙烯链段稍长 ,而己烷可溶级分中乙烯链段稍长

ETHYLENE/PROPYLENE COPOLYMERIZATION WITH HALF-TITANOCENE/MAO CATALYST Ⅱ . 13C-NMR ANALYSIS OF ETHYLENE-PROPYLENE COPOLYMER

Stereo\|structure and monomer sequence distribution of the ethylene\|propylene copolymers obtained from half\|titanocene catalytic system,( η \+5\|pentamethylcyclopentadienyl) titanium triallyloxide (Cp\+*Ti(OCH\-2 CH CH\-2)\-3) combined with methylalumiloxane (MAO),have been investigated by 13 C\|NMR spectra.The monomer reactivity ratios of the copolymerization with this catalyst were calculated from the monomer sequence distribution in 13 C\|NMR spectra, r 1=7 91±0 06 for ethylene, r 2=0 135±0 03 for propylene,and the products r 1 r 2 for all runs in various feeding monomer ratio are almost equal to one( r 1 r 2≈1).The monomer reactivity ratios were also determined according to Fineman\|Ross method,the values of r 1=7 74, r 2=0 134 and r 1 r 2=1 04 are very close to those of calculating above by 13 C\|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.