稀土配合物催化的乙烯、环烯烃和1-辛烯三元共聚

Terpolymerization of Ethylene,Cyclic Olefin and 1-Octene Catalyzed by Rare Earth Complexes

环烯烃共聚物通常由乙烯和环烯烃共聚制得,因其具有较好的透明性和水汽阻隔性等特性,已经被用于制造光学器件和医疗容器等。通常,为了保证共聚物具有较高的玻璃化转变温度(Tg),需要提高环烯单体的插入率,但往往会导致材料韧性降低,限制了环烯烃共聚物在某些领域的应用。因而,将长链α-烯烃单体引入研究较为广泛的乙烯/环烯烃二元共聚物中,期望提高材料韧性、从而拓展环烯烃共聚物的应用领域。鉴于稀土催化剂在烯烃聚合领域中优异的催化性能,研究了由官能化的环戊二烯基稀土钪催化剂1-3、有机硼盐[Ph_(3)C][B(C_(6)F_(5))_(4)]和三异丁基铝AliBu_(3)组成的催化体系对乙烯/降冰片烯/1-辛烯、乙烯/双环戊二烯/1-辛烯的三元共聚合能力及相应共聚物的拉伸性能。稀土催化剂对上述三元共聚活性较高,为4.4×10^(5)~21.4×10^(5)g(/mo(l Sc)·h·bar);所得共聚物数均相对分子质量(Mn)为3.8×10^(4)~20.3×10^(4);相对分子质量的多分散指数(PDI=1.2~2.4)分布较窄。1-辛烯的引入显著提高了乙烯/降冰片烯/1-辛烯共聚物的韧性,P3样品(Mn 13.7×10^(4),降冰片烯37.1%,1-辛烯11.0%)比P1样品(Mn 14.0×10^(4),降冰片烯42.6%,1-辛烯6.4%)的断裂伸长率提高约2.0倍(29.9%vs.9.9%)。

Cyclic olefin copolymer(COC)is produced through the copolymerization of ethylene and cyclic olefins,and has been used for the manufacturing of optical devices and diagnostic containers due to its high transparency and excellent water vapor barrier.However,COC with high glass-transition temperature usually needs high cycloolefin insertion in copolymer and has increased brittleness,which has significantly hampered its many end uses.The introduction of α-olefin into ethylene/cycloolefin binary copolymers that have been extensively studied is expected to expand the application of cyclic olefin copolymers.In this paper,we report the terpolymerization of ethylene/norbornene/1-octene and ethylene/dicyclopentadiene/1-octene catalyzed by modified cyclopentadienyl scandium complexes 1-3 activated with[Ph_(3)C][B(C_(6)F_(5))_(4)]and AliBu_(3) because rare earth catalysts have shown excellent catalytic performance towards olefin polymerization.These rare earth catalysts exhibit high catalytic activities(4.4×10^(5)~21.4×10^(5) g(/mo(l Sc)·h·bar)).The resultant terpolymers show moderate number average molecular weight(Mn=3.8×10^(4)~20.3×10^(4))and relatively narrow polydispersity index(PDI=1.2~2.4).The introduction of 1-octene significantly improves the toughness of ethylene/norbornene/1-octene terpolymers,and the P3 sample(Mn 13.7×10^(4),norbornene 37.1%,1-octene 11.0%)exhibits 2.0 times higher elongation at break(29.9%vs.9.9%)than the P1 sample(Mn 14.0×10^(4),NB 42.6%,OCT 6.4%)