Formation and microstructure transition of F127/TX-100 complex.

Formation and structure transition of the complex composed of triblock copolymer F127 and nonionic surfactant TX-100 have been investigated by 1H NMR spectroscopy, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC). Three TX-100 concentration regions are identified, within which TX-100/20 mg/mL F127 complex undergoes different temperature-induced structure transitions. In low concentration region (< 9.42 mM), F127 single molecular species (unimers) wrap around TX-100 micelles forming F127/TX-100 complex with TX-100 micelle as the skeleton at a lower temperature (5 degrees C), and the skeleton transfers to F127 micelle at higher temperature (40 degrees C); in intermediate TX-100 concentration region (9.42-94.85 mM), the skeleton of F127/TX-100 complex transfers from TX-100 micelle successively into F127 micelle and TX-100 micelle again upon heating. The interaction of F127 with TX-100 is saturated in high TX-100 concentration region (> 157.57 mM), and free TX-100 micelles coexist with larger clusters of F127/TX-100 complexes. In addition, TX-100-induced F127/TX-100 complex formation and structure transition are also investigated at constant temperatures. The results show that within 5-10 degrees C, F127 unimers mainly adsorb on the surface of TX-100 micelles just like normal water soluble polymers; in the temperature region of 15-25 degrees C, TX-100 micelles prompts F127 micelle formation. Within 30-40 degrees C, TX-100 inserts into F127 micelles leading to the breakdown of F127 aggregates at higher TX-100 concentrations, and the obtained unimers thread through TX-100 micelles forming complex with TX-100 micelle as skeleton.