PHOTO-CROSS-LINKABLE POLY(P-PHENYLENE)S - SYNTHESIS, LANGMUIR-BLODGETT MULTILAYER FILM PROPERTIES AND PATTERN-FORMATION

We describe the synthesis of a soluble poly(p-phenylene) (PPP) derivat ive with hydroxy-functionalities in the side chain by copolycondensati on. This allows the introduction of further functionalities by polymer analogous reactions. Esterification with cinnamoyl chloride leads to a photo-reactive material that can be processed by the Langmuir-Blodge tt (LB)-technique to form ultrathin, highly anisotropic films. Photo-i rradiation of these films leads to the formation of cross-links which lock in the long range ordered structure of the layered films which th en becomes stable to temperatures of more than 160 degrees C. Cross-li nking is achieved by direct irradiation into the absorption band of th e photo-reactive units or by use of sensitizers, which gives rise to m ore efficient reaction conditions with fewer side-reactions. Since the cross-linked film is insoluble in all solvents, the photo-reactive ma terial serves as photo-resist. Irradiation through a mask followed by dissolution of the non-cross-linked film can be used for microlithogra phy at micron scale resolution.