The changes of the polyoxymethylene (POM) structure by introducing comonomer units possessing side substituents (R) to the -O-CH2-CH(R) units were studied. Various glycidyl ethers such as butyl (BGE), isooctyl (iOGE), and phenyl (PhGE) were used as comonomers with side groups of different size, volume, and steric hindrance. The influence of the quantity of the incorporated glycidyl ether (GE) comonomer units along the POM chain as well as both the type and size of the side substituent were investigated. The changes of crystallinity, melting temperature, heating and defect enthalpy, and the volume (Angstrom(3)) of the crystal lattice were calculated. Both the structure changes and thermal behavior were confirmed using differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). Transmission electron microscopy (TEM), diffraction (TEMD) as well as scanning electron microscopy were used to investigate both structure and morphology.