Investigation of Pluronic (c) F127-Water Solutions Phase Transitions by DSC and Dielectric Spectroscopy

The water solutions of the block copolymers PEOn-PPOm-PEOn, known as pluronics, show a complex thermal behavior, since they are liquid at low temperature (5C), and they can give soft gel when heated at body temperature (37C). These properties are of great interest in biomedical applications. To properly design these applications, a prerequisite is the knowledge of the thermodynamics—how much—and of the kinetics—how fast—with which these transformations take place. In this work, solutions of F127 (the copolymer for which n ¼ 100 and m ¼ 65) were studied by varying the concentration and the temperature and analyzing their behavior when heated under several heating rates. The studies were performed by differential scanning calorimetry (DCS) and dielectric spectroscopy. The investigations carried out under equilibrium conditions allowed us to determine the thermodynamics of the phase transitions, whereas the investigations carried out under varying conditions allowed us to quantify the kinetics of the phase transitions. Empirical models were also proposed to describe both the thermodynamics and the kinetics observed.