PHOTOINDUCED ABSORPTION IN POLYACETYLENE POLYNORBORNENE AND POLYACETYLENE-POLYSTYRENE BLOCK-COPOLYMERS

We report Photoinduced Absorption (PIA) measurements on several block copolymers containing polyacetylene (PA) sequences. There is a twofold motivation for the investigation of this class of materials: (1) if long and soluble partners are chosen the material can be ''solution processed'' in contrast to pure PA. The other reason (2) is the dilute distribution of PA sequences whose optical properties are probed in an inert matrix, which does not interact with the photons that excite the PA. The effective conjugation-length of the PA sequences is determined by the synthesis of the used prepolymers itself and in the case of the Polyacetylene-Polystyrene (PA-PS) by the conditions of the thermal isomerization. So we could also study the influence of this parameter on the intensity and the energetic position of the photoinduced absorption. Together with Raman- and optical absorption measurements on this class of materials ([1],[2] presented at this meeting) a very comprehensive picture of the influence of conjugation length on the electronic structure can be drawn.