Abstract: Polyethylenes are disclosed herein which are derived from an ethylene monomer and in which any quaternary carbon atom is not present in a polymeric main chain; and the activation energy (Ea) of melt flow is in the range of 8 to 20 kcal/mol; as well as(1) a Huggins coefficient (k) and an intrinsic viscosity [.eta.] meet the relation of the equationk.gtoreq.0.2+0.0743.times.[.eta.];(2) a molar ratio [CH.sub.3 /CH.sub.2 ] of a methyl group to a methylene group is in a region of 0.005 to 0.1 and meets the equationTm.gtoreq.131-1340[CH.sub.3 /CH.sub.2 ];(3) an Mw and a die swell ratio (DR) meet the equationDR>0.5+0.125.times.log Mw; or(4) in the measurement of a loss elastic modulus, a .beta.-relaxation peak is present in the range of 0 to -100.degree. C.These polyethylenes are different from a usual HDPE, L-LDPE and LDPE, and they are excellent in working properties and permit the control of physical properties such as density, a melting point and crystallinity mainly in the state of a homopolymer.

Abstract: Ethylene copolymers are disclosed herein which are each derived from ethylene and an olefin of C.sub.3 to C.sub.20 and in which any quaternary carbon atom is not present in a polymeric main chain; the activation energy (Ea) of melt flow is in the range of 8 to 20 kcal/mol; and (1) a ratio between a Huggins coefficient (k.sup.1) of the copolymer and a Huggins coefficient (k.sup.2) of a straight-chain ethylene polymer having the same intrinsic viscosity meets the equation 1.12<k.sup.1 /k.sup.2 .ltoreq.5, or (2) a molar ratio ?CH.sub.3 /CH.sub.2 ! of a methyl group to a methylene group in a molecular chain is in the range of 0.005 to 0.1, and the equation Tm.gtoreq.131-1,340 ?CH.sub.3 /CH.sub.2 ! is met, or (3) Mw and a die swell ratio (DR) meet the equation DR>0.5+0.125.times.log Mw.