Evaluation of surfactant monomer concentrations in equilibrium with micelles and their temperature dependence for oxyethylene/oxypropylene/oxyethylene triblock copolymers using DSC

Effect of hydroxypropyl β-cyclodextrin on the self-assembling and thermogelation properties of Poloxamer 407

“…The energy required to raise the temperature of the entire solution was measured, that is the heat capacity (C p ) at constant pressure (3 atm). Under these experimental conditions, the copolymer shows two endothermic peaks: the first one (centered at cmT) has a large amplitude and corresponds to the formation of the micelles; the second one (centered at sgT), which occurs at a higher temperature and is superimposed to the end of the first peak corresponds to micelle rearrangement (cause of thermogelation), in agreement with data present in the literature (Alexandridis and Hatton, 1995;Alexandridis et al, 1994;Wanka et al, 1990;Michels et al, 2001;Yu et al, 1992;Hecht and Hoffman, 1994;Wanka et al, 1994;Patterson et al, 1996). The results indicate that DSC is more sensible to the onset of the rapid micelle formation and less to the occurrence of the sol/gel transition.…”

Volumes of aqueous block copolymers based on poly(propylene oxides) and poly(ethylene oxides) in a large temperature range: A quantitative description

“…The profiles of the apparent excess heat capacity of some copolymers vs. temperature curves [31][32][33][34][35] are equal to those for E U in agreement with the fact that both properties are second derivatives of Gibbs free energy. The large maximum of the heat capacity was quantitatively fitted by Patterson et al [33] through a high endothermic value of the enthalpy of aggregation.…”

DSC Analysis of Surfactant-Based Microstructures

“…Although cooperative, the micellization process was rather long and spanned a temperature range of 10-20°C due to the temperature dependence of the amount of unimers in equilibrium with the micelles (as temperature increases, more copolymer molecules associate into micelles) [159,160] as well as to the size polydispersity inherent in copolymers. The strongly endothermic enthalpy indicates that the micellization is an entropydriven process, since micellization is a spontaneous phenomenon.…”

“…DSC has also been used to evaluate the surfactant monomer concentration in equilibrium with micelles and its temperature dependence for triblock copolymers [160]. The output of scanning calorimetry is a data set of power (heat flow in joules per second) versus temperature.…”