Crystal Structure of Single-Crystalline High-Density Polyethylene in Solution

Although the lattice of single-crystalline high-density polyethylene (HDPE) in the solution state differs from that in the dry state because of crushing and deformation during drying, almost all physical properties of HDPE reported to date correspond to the dry state. To bridge this gap, we herein examined the crystal lattices of HDPE single crystals in solution and dry states using wide-angle X-ray diffraction and infrared spectroscopy, revealing that drying (solvent removal) in-duced lattice contraction and increased the degree of structural disorder, i.e., destroyed the precise crystal lattice ob-served in the solution state. Thermal lattice expansion of HDPE single crystals in the solution state was more pronounced than that in the dry state because of the restrictive effects of cohesive forces in the latter case. The obtained insights shed light on the underexplored structural properties of isolated HDPE single crystals in solution and may therefore facilitate the basic science of polymer crystals.