Structure and property of comb-like polyolefins derived from highly Stereospecific homo-polymerization of higher α-olefins

Abstract

A series of comb-like polyolefins possessing ultrahigh absolute molecular weight (Mw = 0.32–3.83 × 106), relatively narrow molecular weight distributions (PDIs ≤ 1.78) and high isotacticity were synthesized via the homopolymerization of higher α-olefins, from 1-octene to 1-eicosylene, by (pyridyl-amido)hafnium catalyst combined with very low loading of [Ph3C][B(C6F5)4] and Al (iBu)3, with surprisingly high catalytic activities (0.81–2.78 × 107 gpolymer/molHf·h). More noteworthily, comprehensive structure-property relationships of the resultant comb-like polyolefins were systematically investigated for the first time. The thermogravimetric analysis (TGA) characterizations demonstrated that increasing the side chain length led to the higher thermal stability of the polymers. The results of differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) measurements together confirmed that the poly (α-olefin)s became more crystalline with lengthening the side chain. Moreover, as the side-chain length increased, the poly (α-olefin) materials became stronger and more brittle.