Comments on the optical properties of fully conjugated polymers: Analogy between polyenes and polydiacetylenes

The similarity of the π‐electron backbones of the polyenes and the polydiacetylenes suggests an analogy between these two fully conjugated, linear polymers. The extent of the analogy is discussed through the examination of a series of model compounds: the polyenes and the polyenynes. The optical band gaps and the polarizabilities of polyenynes are compared to those of the polyenes and to the predictions of a modified free‐electron model. It is concluded that the chain‐dependent electronic properties of the polyenes may be extrapolated with some confidence to the polydiacetylenes.