The adsorption process of end-hydroxylated poly (dimethyisiloxane) chains upon silica particles is compared with that of end-methylated chains. Four variables were used to analyse the adsorption process : the chain molecular weight M., the initial concentration of silica c~t, the amount of adsorbed polymer QI, and the relative number of fixed monomeric units Za, observed from n.m.r. Both polymer species were found to obey two simple equivalent laws of adsorption: Q~ 0c x/~. and zB oc 1/x/~ .. Several features characterize the adsorption process: equal specific amounts of hydroxylated chains are adsorbed for two silica concentrations, c~t = 0.17 or 0.29 (w/w); for a given chain length, the specific amount of adsorbed hydroxylated chains is higher than that of methylated ones ; a partial desorption of methylated chains is induced by washing mixtures with c~ = 0.17 (w/w); the process of adsorption of hydroxylated chains is about 10 times faster than that of methylated ones, at 343 K.
Посилання на статтю:
Silica-siloxane mixtures. Investigations into adsorption properties of end-methylated and end-hydroxylated chains / J. P. Cohen-Addad and R. Ebengou // Polymer. – 1992. – Vol 33. – P. 379-383.