PES-5Sn nanocomposites by thermal drawing. (a) Schematic of the thermal drawing process. (b) Schematic of the stack and draw iteration. (c) SEM image of the longitudinal cross-section of PES-5Sn nanocomposite fiber with an inset to show high magnification (scale bar: 2 μm, inset: 500 nm). (d) Sn nanoparticle size distribution in PES-5Sn nanocomposites fiber (after the third cycle of the thermal drawing). (e) TEM image of Sn nanoparticles when PES cladding is dissolved after the third cycle of thermal drawing (scale bar: 50 nm). (f) Atomic resolution TEM image of Sn twinned-nanoparticles with polygonal shapes showing many facets as confirmed by their ring patterns (insets) (see Supplemental Table 2 for indexed diffraction patterns) (scale bar: 2 nm).