Development of elastic recovering 4-methyl-1-pentene/propylene copolymer

We investigated the solid structures and mechanism of the rubber elastic behavior of 4-methyl-1-pentene/propylene random copolymers (PMPCs), which were prepared using metallocene catalyst, by time-resolved wide-angle X-ray diffraction and small-angle X-ray scattering measurements. PMPC becomes an amorphous polymer and exhibits rubber elasticity in the propylene content (PC) ranging from 28 mol% to 75 mol%. However, the amorphous structure and the elastic recovery largely differ depending on PC. PMPC with PC = 75 mol% had an amorphous structure similar to that of polypropylene and developed rubber elasticity. This was because of the entropic elastic behavior caused by entanglements of polymer chains in a manner that was same as that in amorphous polymers. On the other hand, PMPCs with PC = 28 and 40 mol% had unique amorphous structures. The structures had the interactions between molecular chains and the inhomogeneous structure. These phenomena are presumed to exhibit excellent rubber elasticity, because the two structures change reversibly by deformation. [Display omitted] •4 MP-propylene random copolymers (PMPCs) becomes an amorphous polymer and exhibits rubber elasticity in the propylene content (PC) ranging from 28 mol% to 75 mol%.•PMPCs with PC = 28 and 40 mol% had a unique amrphous structure.•PMPCs with PC = 28 and 40 mol% exhibited excellent elastic recovery (ER).•The structures involved in the interaction between the molecular chains and the heterogeneous structure changed reversibly by deformation.