A Novel Cryo‐SEM Technique for Imaging Vegetable Oil Based Organogels

Abstract

AbstractGels were prepared by cooling dilute solutions (2% wt/wt) of 12‐hydroxystearic acid (12‐HSA) in canola oil and storing them at 30 °C for 24 h. The gel's in‐situ supramolecular network structure was imaged using four techniques: polarized light microscopy (PLM), 3‐dimensional deconvolution polarized light microscopy (3DPLM), and cryo‐scanning electron microscopy (cryo‐SEM) of the xerogel and of an osmium tetroxide vapor fixed gel washed with isobutanol. Most of the canola oil was immobilized in the gel by fixation with osmium tetroxide therefore very little of the canola oil was removed during washing unlike the xerogel where all of the canola oil has been displaced. The in‐situ supramolecular network structure as observed by PLM, was comparable to that seen through the new cryo‐SEM method for fixed organogel. Cryo‐SEM images of the xerogel did not show similar length scales or strand thickness as compared to the PLM images. The lengths of the network strands were much shorter for the xerogel as compared to the osmium tetroxide treated sample and the structures visualized by PLM. Furthermore, the thickness of the strands observed using PLM or cryo‐SEM were in the size range of 3–10 μm while the xerogels had strands in the range of 0.01–0.1 μm thick. Therefore, the removal of canola oil from the gel using 80/20% v/v hexane/acetone with no fixation disrupted the supramolecular network.