ELECTRON-MICROSCOPY STUDY OF N-BUTYLAMMONIUM VERMICULITE SWELLING

Electron microscopy was used to study swollen samples of n-butylammoni um vermiculite prepared in dilute aqueous solutions of n-butylammonium chloride. Three electrolyte concentrations were studied, 0.1 M, 0.01 M and 0.001 M. The 0.1 M samples studied were in a tactoid phase, exhi biting crystalline regions of about ten layers separated by large irre gular aqueous regions. The dilute samples were studied in their gel ph ase, exhibiting regular spacings of 85 nm and 55 nm in the 0.001 M and 0.01,M solutions, respectively. These spacings are much larger than t hose measured previously by neutron scattering, probably due to an add itional expansion of the interlayers during the freezing process emplo yed in preparing the replicas. In all examples, the structures were fo und to be lamellar over regions of several microns.