Enthalpy-driven Micellization of Oligocarbonate-Fluorene End-Functionalized Poly(ethylene glycol)

Published

November 24, 2017

Author(s)

Vivek M. Prabhu, Guangmin Wei, Shrinivas Venkataraman, Yi Yan Yang, James Hedrick

Abstract

Fluorescent pyrene probe method was employed to measure critical micelle concentration (CMC) of oligocarbonate-fluorene end-functionalized poly(ethylene glycol) (FmE445Fm) triblock copolymers in water. It was found that CMC has dependence on both temperature and hydrophobic block length m. The lower the temperature and the higher the m values, the smaller the CMC would be. Smaller CMC indicates a higher probability of micelle formation and a better thermodynamic stability of micelles against dilution in in vivo circulation. Thermodynamic functions of G°mic, H°mic and S°mic are calculated from temperature dependence of CMCs. The negative H°mic plus a very small S°mic of FmE445Fm indicates an enthalpy driven micellization, which is different from the previous studies of EnPmEn and CmE8 (entropy driven). The enthalpy driven micellization of FmE445Fm is probably resulted from the little hydration of individual hydrophobic F block, leading to few hydrogen-bonded waters ware released during F blocks association. However, we found that EnPmEn and CmE8, and FmE445Fm all obey enthalpy-entropy compensation with a common H*mic and Tc, indicating a same physical feature of hydrophobic self-assembly, no matter the micellization is entropy or enthalpy driven.

Citation

Macromolecules

Volume

134

Pub Type

Journals

Keywords

micellization, polymer, pyrene fluorescence

Citation

Prabhu, V. , Wei, G. , Venkataraman, S. , , Y. and Hedrick, J. (2017), Enthalpy-driven Micellization of Oligocarbonate-Fluorene End-Functionalized Poly(ethylene glycol), Macromolecules (Accessed December 30, 2024)