BILAYER STUDIES IN MIXED N-DECANOL N-TETRADECANOL COMPLEXES OF N-DECYLAMMONIUM BEIDELLITE

Complexes have been prepared by treatment of n-decylammonium beidellit e with mixtures of n-decanol and n-tetradecanol with different concent rations. Measurements of the basal spacings of the obtained complexes have been performed in a wide range of temperatures. Three different b ilayer phases have been established between (20 and 70 degrees C: the beta(i)(C-10) phases ( = bilayers of n-decyl chains); the beta(i)(C-10 /C-14) phases ( = mixed bilayers of n-decyl and n-tetradecyl chains in molar ratio approximately 1:1) and the beta(i)(C-14) phases ( = bilay er of n-tetradecyl chains with the n-decylammonium ions included). In all bilayer phases the chains stand perpendicular to the silicate inte rfaces. In definite concentration ranges two of the phases coexist, i. e., miscibility gaps occur, which disappear at temperatures higher tha n the temperature of the beta(1)/alpha transition. The miscibility gap s are reversible with temperature. The composition of the intercalated bilayers has been studied by HPLC of the excess alkanol mixture separ ated from the beidellite complexes after the equilibrium has been reac hed. There is preferential adsorption of one of two alkanols from the mixture, which is in agreement with the observed miscibility gaps. The space filling problem as well as the structure of the three bilayer p hases observed have been discussed.