Jsm 7000f analytical sem

A concentrated sample
(Φ_P = 0.207) was prepared
as described above, except that a bare silicon substrate was used
in place of one of the glass coverslips. The sample was then plunged
into a cryogenic liquid mixture of 37% ethane and 63% propane^{54 (link)} and transferred into a dish of liquid nitrogen.
While under the liquid nitrogen, the glass coverslip was removed to
expose the frozen polymer/solvent film. The frozen sample was then
rapidly transferred into a sealed thermal stage (Linkam LTS420), which
was initially held at −190 ^°C under a nitrogen
atmosphere. The frozen sample was placed under vacuum and continuously
monitored via optical microscopy over a period of ∼5 h as the
temperature was slowly increased until the solvent was observed to
be fully removed (without bulk melting of the film). The prepared
samples were then mounted in a cross-sectional holder and imaged using
a JEOL JSM-7000F analytical SEM at a low accelerating voltage (2.5
kV).

Details on freeze-drying of solution samples are present in section S4. Solid samples were freeze-fractured in liquid nitrogen to preserve their internal structure. Best results were obtained by delaminating printed films from silicon substrates with a clean razor blade and placing between copper tape with a portion of the sample unsupported. After placing the sample in liquid nitrogen for an extended period (~20 min), the exposed portion of the film was scraped within the nitrogen bath to create a clean interface. Samples were then mounted in a mini vise holder and coated with ~10-nm Au-Pd using an Emitech K575 sputter coater at the Illinois MRL. Final micrographs were obtained using a JEOL JSM-7000F Analytical SEM at 3-kV accelerating voltage at the Illinois MRL and processed using the software package ImageJ2 (50 (link)).