Oil-in-Water Emulsion Templated and Crystallization-Driven Self Assembly Formation of Poly(L-lactide)-Polyoxyethylene-Poly(L-lactide) Fibers

摘要

A molecular solution of an amphiphilic block copolymer may act as an oil phase by dispersing into an aqueous micellar system of small-molecular surfactant, forming oil-in-water (O/W) emulsion droplets. In this paper, an as-synthesized triblock copolymer poly(L-lactide) polyoxyethylene poly(L-lactide) (PLLA-PEO-PLLA) was dissolved in tetrahydrofuran (THF) and then added to an aqueous micellar solution of nonaethylene glycol monododecyl ether (AEO-9), forming initially coalescent O/W emulsion droplets in the size range of 35 nm-1.3 mu m. Along with gradual volatilization of THF and simultaneous concentration of PLLA-PEO-PLLA molecules, the amphiphilic copolymer backbones themselves experience solution-based self-assembly, forming inverted core corona aggregates within an oil-phase domain. Anisotropic coalescence of adjacent O/W emulsion droplets occurs, accompanied by further volatilization of THF. The hydrophilic block crystallization of core-forming PEOs and the hydrophobic chain stretch of corona-forming PLLAs together induce the intermediate formation of rod-like architectures with an average diameter of 300-800 nm, and this leads to a large-scale deposition of the triblock copolymer fibers with an average diameter of similar to 2.0 mu m. Consequently, this strategy could be of general interest in the self assembly formation of amphiphilic block copolymer fibers and could also provide access to aqueous solution crystallization of hydrophilic segments of these copolymers.