Photoinduced Cross-Linking Approach to the Fabrication of Conjugated Polymer Micropatterns

Abstract

The results described in this thesis research has led to the development of new approaches for the fabrication of conjugated polymer patterns. For this purpose, two representative conjugate polymers PPV and PEDOT:PSS were employed. By taking advantage of the photocross-linking ability of self-assembled diacetylene (DA) which results in the insoluble part upon UV irradiation, we were able to generate patterned PPV and PEDOT:PSS on solid substrates. First part of the thesis research focused on the generation of PPV patterns. DA moiety was introduced as a pendant sidechain of PPV and the significance of the DA group was demonstrated by the fact that no patterned images were observed with a structurally analogous conjugated polymer (i.e., MEH-PPV). A 10 micron-sized fluorescent pattern of PPV was readily achieved on the solid substrate by using a photolithography method. In the second part of thesis research, a photopolymerizable and water soluble diacetylene diol (DADOL) was added to an aqueous PEDOT:PSS solution. A sequential photomasked 254 nm UV irradiation to the thin polymer film of DADOL and PEDOT:PSS followed by development in water resulted in the fabrication of conducting polymer patterns on various solid substrates including glass, silicon wafer and flexible PET. Among DADOLs tested, DADOL-1 having one methylene unit between the photopolymerizable diacetylene and alcohol groups was found to be most effective. The improved conductivity of PEDOT:PSS was analyzed through XRD and Raman spectroscopy analysis. We believe the simple but efficient strategies described in this thesis research will be useful for the fabrication of conjugated polymer patterns.