The utility of the Shear method in obtaining thin single crystal films of polydiacetylenes has been demonstrated previously. In this paper the principles of the Shear method are elucidated with analogy to the well-known L-B method. Both the methods, L-B and Shear, utilize the polar molecular interactions with the substrates as a control parameter for the molecular organization. The major difference between the two is that one (L-B) utilizes a liquid as the subphase while the other (Shear) uses solid substrates. Because of the nature of the interface the L-B approach leads to only one-dimensional organization and poor optical quality for the films while the Shear method provides 3-D organization and excellent optical quality.
Thin single crystal films of a specific polydiacetylene, PTS, are prepared on oxide coated silicon substrates by the Shear method. Waveguiding through the PTS films is demonstrated for the first time. Much progress is also made in the waveguide-structural fabrication of PTS films. The results are quite encouraging in terms of device applications of polydiacetylenes as optical switches and logic gates.