Observation of the internal network structure of a polymer-stabilized liquid crystal via transmission electron microscopy

The internal structure of the network component of a polymer-stabilized liquid crystal has been observed for the first time. These are systems in which a small amount of a monomer is dissolved within a LC host and then polymerized in situ to produce a network. Studies performed on a system prepared using the diacrylate monomer RM60 and the nematic mixture BL087 are presented. The concentration of the monomer was I wt %. After formation of the network through photopolymerization of the monomer between Melinex layers within a glass cell, the LC host was removed by dissolving it in heptane. Subsequent observation of the internal network structure by transmission electron microscopy was made possible by bromine staining of the network, followed by embedding and ultramicrotomy. A collection of solid, near-circular objects was observed, of mean diameter 0.13 mu m. These objects were found to be highly permeable to bromine vapour, suggesting an open, but homogeneous structure.