In situ Raman Spectroscopic Observation of Polymer Chains in Semi-Crystalline Polyethylene Solids

Abstract

Abstract In situ Raman spectroscopy is applied for polyethylene solid under various environments to elucidate the morphological and conformational changes. The trans conformation retains up to higher temperature for high-density polyethylene, reflecting higher stability of the orthorhombic crystals composed of stacked trans chains. It is suggested that the conversion of the non-crystalline trans chains to the crystalline phase is the microscopic origin of thermal history in the crystallinity, whereas the transformation between the trans and gauche conformers is practically in thermal equilibrium. Microscopic and dynamic mechanism of deformation during uniaxial stretching is investigated for the molecular orientation and the microscopic load sharing on the crystalline and amorphous chains. Lower crystallinity results in smoother and higher orientation toward the stretching direction, as well as higher load on the amorphous chains, during tensile elongation.