CORRELATION APPROACH TO STUDY CRYSTALLIZATION IN LOW-MOLECULAR-WEIGHTPOLYMERS

The small-angle X-ray scattering (SAXS) has been applied successfully to investigate the structure of semi-crystalline polymers, the inhomog eneities being of colloidal dimensions. Fourier transformation of scat tering curves yields position correlation functions, a forceful tool t o follow the crystallization path in a polymeric substance. The SAXS c urves on ultra-long n-alkanes obtained by Ungar and Keller at differen t times after reaching the crystallization temperature have been Fouri er analysed and the correlation curves so obtained at different temper atures and different annealing times reflect sensitively all those mor phological features which are broadly characteristic of the scattering curves. In addition the correlation curves beautifully show a transit ion from a non-integer-fraction (NIF) length to extended (E) chain str ucture. some other parameters characterizing the kinetics of morpholog ical features, which are not easily observable in SAXS, such as crysta lline and amorphous lengths, degree of order and halfwidths of correla tion peaks are also reported.