New polyolefin elastomers containing 'reactive' p-methylstyrene units: preparation by metallocene catalysts

摘要

This paper summarizes the experimental results of three new polyolefin elastomers, i.e., poly(l-octene-co-p-methylstyrene (O-p-MS), poly(ethylene-ter-propylene-ter-p-methylstyrene) (EP-p-MS) and poly(ethylene-ter-1-octeneter-p-methylstyrene) (EO-p-MS), containing "reactive" p-MS units. Both Ziegler-Natta and metallocene catalysts were used in studying Co- and ter-polymerization reactions. In the copolymerization of l-octene and p-MS, Ziegler-Natta catalyst TiCl{sub}3/AlEt{sub}3 exhibits higher catalyst reactivity to produce high molecular weight O-p-MS copolymers, containing up to 20 mol % p-MS. However, the copolymers show very broad composition and molecular weight distributions. On the other hand, two EP-p-MS and EO-p-MS terpolymers with narrow molecular weight and composition distributions were prepared by [C{sub}5Me{sub}4(SiMe{sub}2N{sup}(t)Bu)]TiCl{sub}2 metallocene catalyst with constrained ligand geometry. The sharp glass transition temperature (T{sub}g) with flat baseline in each differential scanning calorimetry (DSC) curve indicates homogeneous terpolymer microstructures. The T{sub}g of EP-p-MS is very sensitive to the terpolymer composition (ethylene/propylene ratio and p-MS content). In the compositions with ideal ethylene/propylene ratio ～55/45, the T{sub}g is almost proportional to the content of p-MS. Only with the concentration of p-MS <2 mol %, does the EP-p-MS show a low T{sub}g < -45℃. On the other hand, the EO-p-MS system exhibits a low T{sub}g < -50℃ in a wide range of copolymer compositions, even ones with relatively high p-MS contents (> 7 mol %).