Specific features of molecular motion in lamellar polyethylene between 100 and 400 K

Abstract Changes of configurational heat capacity ΔC p have been determined between 100 and 400 K by differential scanning calorimetry applied to polyethylene samples of different molar mass and degree of branching, crystallized under different conditions. A novel interpretation, based on a confrontation of differential scanning calorimetry and NMR data, on the heights of activation energy barriers to the motion, Q ( T ), heats of “thawing” of kinetic, e ( T ), and also on structural information, is proposed for the molecular motion in the four relaxation regions of polyethylene. It has been shown that the contribution of intracrystalline motion to ΔC p is negligibly small. The relaxation transitions at 150–170 and 240–270 K are shown to be related to quasi-independent, cooperative motion of sections in neighbouring chains, comparable in size to Kuhn's segment, i.e., they correspond to the β- and α-transitions in amorphous polymers, respectively.