It is well known that liquids confined to small nanoscopic pores and droplets exhibit thermal behavior very different from bulk samples. Less is known about liquids spontaneously confined through self-assembly into micellar structures. Here we demonstrate, using a very well-defined n-alkyl-poly(ethylene oxide) polymer system with a tunable structure, that $n$-alkane(s) forming 2–3 nm small micellar cores are affected considerably by confinement in the form of melting point depressions. Moreover, comparing the reduction in melting points, $\mathrm{\Delta }{T}_m$, determined through volumetric and calorimetric methods with the micellar core radius, $R_c$, obtained from small-angle x-ray scattering, we find excellent agreement with the well-known Gibbs-Thomson equation, $\mathrm{\Delta }{T}_m\sim R_c^{-1}$. This demonstrates that the reduced size, i.e., the Laplace pressure, is the dominant parameter governing the melting point depression in micellar systems.

• Received 17 July 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.238305