CORRELATION APPROACH TO STUDY CRYSTALLIZATION IN LOW-MOLECULAR-WEIGHT POLYMERS

The small-angle X-ray scattering (SAXS) has been applied successfully to investigate the structure of semi-crystalline polymers, the inhomogeneities being of colloidal dimensions. Fourier transformation of scattering curves yields position correlation functions, a forceful tool to follow the crystallization path in a polymeric substance. The SAXS curves on ultra-long n-alkanes obtained by Ungar and Keller at different times after reaching the crystallization temperature have been Fourier analysed and the correlation curves so obtained at different temperatures and different annealing times reflect sensitively all those morphological features which are broadly characteristic of the scattering curves. In addition the correlation curves beautifully show a transition from a non-integer-fraction (NIF) length to extended (E) chain structure. some other parameters characterizing the kinetics of morphological features, which are not easily observable in SAXS, such as crystalline and amorphous lengths, degree of order and halfwidths of correlation peaks are also reported.