Crystal Structure of Poly(α-methylene-δ-valerolactone)

The crystal structure of poly(α-methylene-δ-valerolactone), P(MVL)ROP, synthesized by chemoselective ring-opening polymerization of α-methylene-δ-valerolactone, was determined through a combination of X-ray diffraction analysis and density functional theory (DFT) calculation. The results reveal a triclinic crystal system (space group P1̅) with unit cell parameters: a = 7.26 Å, b = 6.86 Å, c = 7.39 Å, α = 122.09°, β = 89.14°, and γ = 104.88°. The P(MVL)ROP chain adopts an all-trans conformation, as validated by DFT optimization and infrared spectroscopy analysis. Unlike conventional polyesters, P(MVL)ROP, featured with unsaturated bonds on the side chain, exhibits a distinctive triclinic unit cell, with two antiparallel chains included. Independent Gradient Model based on Hirshfeld partition (IGMH) analysis revealed that a series of distinct C–H···O═C interactions between adjacent parallel or antiparallel chains are the key stabilizing forces for the interchain packing.