乙丙共聚物的微结构测定及调控

MEASUREMENTS AND CONTROL OF THE MICROSTRUCTURE OF ETHYLENE-PROPYLENE COPOLYMERS

研究了[N,O]螯合钒(Ⅲ)催化剂([PhN C(CH3)CH C(Ph)O]VCl2(THF)2(2a),[PhN CHC6H4O]VCl2(THF)2(2b)和[PhN CHC(Ph)CHO]VCl2(THF)2(2c)催化乙烯和丙烯的共聚合行为.聚合得到了不同丙烯插入率(0 mol%~20 mol%)和较窄分布(M w/M n<3.0)的聚合物.借助高温核磁13CNMR和高温GPC对所得聚合物的共单体插入率、序列结构、分子量及分布进行测试.研究表明,助催化剂、再活化剂、聚合温度以及反应时间等条件对聚合活性、聚合物分子量以及共单体插入率有重大影响.通过计算亚甲基序列分布(x i)以及聚合物链中连续亚甲基数均序列长度n0和n2+,证实了上述条件还能够对聚合物微结构起到微调作用.此外,虽然催化剂的共聚合活性相当,而且所得聚合物中共单体插入率也很接近,但是通过比较不同催化剂所获的聚合物的x i,n0和n2+,所得聚合物的序列结构却有明显差别,2a催化体系最不容易发生单体的反向插入,而且链结构中存在更多长的亚甲基序列.通过Fineman-Ross方法计算出单体的竞聚率乘积r E×r P≈1.0,说明共单体的插入不受链末端单体单元种类的影响,使得k11/k12=k21/k22,催化剂2a^2c均能催化乙烯与丙烯共聚合得到理想的无规共聚物.

The copolymerizations of ethylene with propylene were investigated by the vanadium （ m ） catalysts bearing bidentate [ N, O ] ligands （2a, [ PhN = C （ CH3 ） CHC （Ph） O ] VC12 （THF）2： 2b, [ PhN = CHC6 H40 ] VC12 （THF） 2 ; 2c, [ PhN =- CHC （Ph） CHO ] VCl2 （THF） 2 ）. Ethylene-propylene copolymers with different comonomer incorporations （P = 0 mo1% - 20 mol% ） and narrow molecular weight distributions （ Mw/Mn 〈 3. 0） were obtained. The molecular weights and molecular weight distribution of copolymers were determined by gel permeation chromatograhpy （ GPC）. The incorporation of comonomer and microstructure of copolymers were confirmed by 13C-NMR methods. On activation with cocatalyst （Et2AlCl） and reactive agent （ETA）, catalytic activity,comonomer incorporation, and molecular weights of the resultant polymers can be controlled over a wide range by tuning reaction parameters, such as concentration of EtzA1C1, dosage of ETA, temperature,feed composition and so on. Furthermore, the microstructures of polymer chains can also be adjusted by changing reaction parameters above, which were confirmed by calculating the monomer sequence distribution （xi） and continuous methylene sequence length （n0 and n2＋ ）. The reactivity ratios of copolymerization （r1r2 ≈ 1.0） were evaluated by the Fineman-Ross method, indicating the insertion of comonomers will not be influnced by the kinds of the last inserted monomers, and ideal random copolymer can be obtained by catalysts 2a-2c,which can also be proved by 13C-NMR and calculation of xi ,no and n2＋.