We study the morphological change of crystalline polymer films by annealing using atomic force microscope, X-ray diffraction, and Fourier transform infrared spectroscopy techniques. As typical samples, we employ high-density and low-density polyethylene films prepared by the cast method. After annealing at 135°C for 4 h, the surface roughness of polyethylene films by the atomic force microscope significantly increases, and the crystallite size by the X-ray diffraction also shows some increase, while the Fourier transform infrared spectroscopy spectrum hardly exhibits any change. This can be well explained as a result of the growth of crystal structure by recrystallization during annealing. More interestingly, we find that the choice of the substrate and also the heating/cooling rates for annealing significantly influences the surface roughness of the films.
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