engleski

Solid State Transitions of Dissymmetric Gemini Surfactants

A series of dissymmetric gemini surfactants were prepared from n-dodecyldimethylammonium and n-tetradecyldimethylammonium bromide and linked by polymethylene chains (spacer), the number of carbon atoms in a spacer being 2, 6 and 10. Their solid phase properties were examined by X-ray diffraction, spectral, thermal and optical microscopic studies. The increase of the number of carbon atoms in the spacer changed the structure and thickness of bilayers. On heating, successive phase transitions (several solid crystalline-solid crystalline, solid crystalline-liquid crystalline and liquid crystalline-isotropic liquid) were observed. The number of polymorphs depended on the lengths of the spacer. Polarizing microscopy revealed a characteristic texture of the smectic phase. Crystallization from melted samples was kinetically controlled.

phase transitions ; surfactants ; liquid crystals

nije evidentirano