2.5. Freeze fracture
In order to examine their internal structure, the films were freeze-fractured using the following procedure. A 1 mm thick cylinder of film was obtained by casting multiple layers of film-forming latex/starch mixtures between two copper cups. The cylinders were then frozen at −150 °C and under reduced pressure before being fractured with a blade. The freeze-fractured surfaces were shadowed with platinum and then with carbon. The replicas were then isolated from the samples by washing in DMSO and acetone before being placed on a copper grid. Finally they were observed on a Philips CM120 TEM.