Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (4): 699-707.doi: 10.3866/PKU.WHXB201402112

• SOFT MATTER • Previous Articles     Next Articles

Temperature Dependant Mixed Micellization Behavior of a Drug-AOT Mixture in an Aqueous Medium

RUB Malik Abdul1,2, ASIRI Abdullah M1,2, KUMAR Dileep3, AZUM Naved1,2, KHAN Farah3   

  1. 1 Chemistry Department, King Abdulaziz University, Jeddah-21589, Saudi Arabia;
    2 Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah-21589, Saudi Arabia;
    3 Department of Chemistry, Aligarh Muslim University, Aligarh-202002, India
  • Received:2013-12-06 Revised:2014-02-10 Published:2014-03-31
  • Contact: RUB Malik Abdul,
  • Supported by:

    The project was supported by the Chemistry Department and Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia.


The mixed micellization behavior of an amphiphilic antidepressant drug amitriptyline hydrochloride (AMT) in the presence of the conventional anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was studied at five different temperatures and compositions by the conductometric technique. The critical micelle concentration (cmc) and critical micelle concentration at the ideal state (cmcid) values show mixed micelle formation between the components (i.e., drug and AOT). The micellar mole fractions of the AOT (X1) values calculated using the Rubingh, Motomura, and Rodenas models show a higher contribution of AOT in the mixed micelles. The interaction parameter (β) is negative at all temperatures and the compositions show attractive interactions between the components. The activity coefficients (f1 and f2) calculated using the different proposed models are always less than unity indicating non-ideality in the systems. The ΔGmθ values were found to be negative for all the binary mixed systems. However, ΔHmθ values for the pure drug as well as the drug-AOT mixed systems are negative at lower temperatures (293.15-303.15 K) and positive at higher temperatures (308.15 K and above). The ΔSmθ values are positive at all temperatures but their magnitude was higher at T=308.15 K and above. The excess free energy of mixing (ΔGex) determined using the different proposed models also explains the stability of the mixed micelles compared to the pure drug (AMT) and surfactant micelles.

Key words: Antidepressant drug, Amitriptyline hydrochloride, cmc, Interaction parameter, Thermodynamic parameters