Multilamellar Thermoresponsive Emulsions Stabilized with Biocompatible Semicrystalline Block Copolymers

Abstract

We demonstrate specific interface-templated crystallization behavior of biocompatible amphiphilic poly(ethylene oxide)-<i>b</i>-poly(ε-caprolactone) (PEO-<i>b</i>-PCL) block copolymers enabling triggered shaping of the curvature of the oil/water interface and controlled phase inversion, including the formation of stable multiple emulsions. Water-born anisotropic micelles of PEO-<i>b</i>-PCL block copolymers self-assemble at the oil-water interface in a multilayer form and undergo conformational rearrangements into unique semicrystalline multilamellar shells, for which curvature (type of emulsion) can be tuned by the molecular architecture (volume fractions of the blocks) and/or by the temperature. The latter trigger affects both the solubility of the PEO block in water and the semicrystalline state of the PCL block. Remarkably, multilamellar semicrystalline shells provide both long-term stability and enhanced barrier properties of toluene-water emulsions, as well as the fast change of the bending, leading to thermo-induced phase inversion. These findings signify the development of novel practical mechanisms for controlled triggered encapsulation and release systems.