Growth process for fractal polymer aggregates formed by perfluorooctyltriethoxysilane. Time-resolved small-angle X-ray scattering spectra and the application of the unified equation

The time-resolved small-angle X-ray scattering (SAXS) profiles, obtained during the polymerization of perfluorooctyltrimethoxysilane catalyzed by different HCl concentrations, have been analyzed using the unified Guinier/power-law equation introduced by Beaucage. SAXS profiles, time-sliced for the reaction mixture catalyzed by dilute HCl, can be perfectly fitted by a simple Beaucage function with only one step of structural hierarchy. The time-resolved SAXS profiles, obtained from the reaction mixtures catalyzed by more concentrated HCl, have led to the conclusion that the growth process of the polymeric aggregate occurs in two steps. This result was successfully explained by application of the unified equation at two structural levels. This conclusion is now corroborated by application of the unified Beaucage equation to evaluation of the growth process of the polymeric precursors.