Hydrogen-Bond-Mediated Phase Behavior of Complexes of Small Molecule Additives with Poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) Triblock Copolymer Surfactants

Abstract

The addition of multifunctional additives comprised of single- or double-ring aromatic cores decorated at their periphery with multiple hydrogen-bond-donating groups such as carboxylic acid and phenol is shown to induce microphase segregation of otherwise disordered Pluronic BCP (poly(ethylene oxide-propylene oxide-ethylene oxide)) surfactant melts, resulting in the formation of well-ordered supramolecular assemblies with domain spacings ranging between 12.5 and 14.5 nm at additive loadings up to 40%. As the concentration of additives is increased, the general tendency is that the disordered system evolves into an ordered morphology and then undergoes an order-order transition before transitioning into a disordered phase, in one case. The scaling of interplanar spacing reveals that the additives are selectively incorporated in the poly(ethylene oxide) phase. Differential scanning calorimetry indicated that progressive increases in the loading of additives causes a decrease in the melting temperature and melting enthalpy of poly(ethylene oxide) crystallites. This behavior is consistent with good dispersion and strong interaction of the additives with the poly(ethylene oxide) phase. The principles invoked in this additive driven assembly process can be generally applied to the design of ordered functional BCP-nanoparticle hybrid materials while the specific materials described here could be of interest as etch masks.