Some structural transformations in TTAB aggregated ternary systems as seen by positron lifetime spectroscopy

Abstract

Positron lifetime spectroscopy (PLS) has been used to investigate structural transformations in TTAB aggregated ternary systems. Positron lifetime measurements were performed as a function of the concentration of pentanol in tetradecyl trimethyl ammonium bromide (TTAB)/water/pentanol systems having initial concentrations of TTAB in water as 20, 30 and 40 wt.%. For the systems studied, characteristic changes were observed in the positron lifetime parameters whenever a phase transformation occurs. The various phase boundaries demarcated by this technique agrees well with those obtained by other conventional techniques. Besides this, the present work suggests the existence of two kinds of lamellar structures referred to as D I and D II phases in the system, which were otherwise considered to be a single D phase by other conventional techniques. The existence of such lamellar structures has been demonstrated by a change in the trend of ortho-positronium ( o-Ps) lifetime when the system passes from one type of lamellar structure to the other type.