Thermodynamics of Pluronic 103 Micellization in Mannitol Solution: Analyses Based on Isothermal Titration Calorimetry

This study describes the effect of sugar incorporation upon micellization behaviour of pluronic 103 (P103), a linear triblock copolymer. Mannitol (MTL) was used as a sugar and its effect was investigated over a concentration range of 0.1-1 M. Our interpretations on changes in the thermodynamics of P103 micellization are based on isothermal titration calorimetry (ITC) experiments. Thermodynamic parameters were calculated after plotting the enthalpy against temperature and MTL concentration. The data were acquired at six temperatures between 302.5 and 312.5 K. A significant reduction in CMC was witnessed following increase in solution temperature and MTL incorporation. We show that enthalpy barrier of micellization reduced in the presence of MTL. The data of Gibb's free energy of micellization (& UDelta;Gomic) exhibited a steady decline during increase in MTL concentration. These changes were attributed to modulation of water structures in the microenvironment of micelle interface. Linearity of enthalpy-entropy compensation underscored the role of temperature in regulating copolymer-solvent interactions.