Freeze‐dried cellulose acetate membrane fine structure observation

A freeze-dried cellulose acetate membrane fine structure was observed with an ultrathin sectioning electron microscope. The fine structure for the top surface in this membrane could be seen by lead citrate staining ultrathin sectioning. This network structure was observed among pores, which existed in porous substrate. The pore diameter in the top surface was about 50 A, a value that agrees approximately with the value estimated by gas permeation.