The crystallization and melting of poly(ethylene oxide) (PEG) have been examined in detail using polarized light microscopy (PLM), polarized infrared microspectroscopy (FIRM) and differential scanning calorimetry (DSC). Examination of the orientation of the crystalline stems within the spherulites by FIRM supports the hypothesis that the dominant crystal growth face of PEO changes from the (010) crystallographic plane at crystallization temperatures (T-c) < 51 degrees C to the (120) plane at T-c > 51 degrees C. The cusp in the logarithmic growth rate-temperature plot appears to be the result of this phenomenon. Analysis of spherulitic growth rate data for the monodisperse sample (M-w = 1.8 x 10(5)) fails to provide evidence in support of the regime II/III transition proposed in a previous literature study and indicates that in the range 45-56 degrees C crystallization occurs solely within regime III. The larger value for the product of the lateral and fold surface free energies in the case of(010) growth appears to arise from the higher fold surface free energy of this growth face. The difference in the fold surface free energies of the different growth faces, 41 erg/cm(2) for the (010) face as compared with 29 erg/cm(2) for the (120) face, can be accounted for by the corresponding differences in the minimum chain length required for chain folding in the case of adjacent re-entry.