Design and Synthesis of New Donor-Acceptor Type Conjugated Polymers for Photonic Applications

Abstract

In recent years, a great deal of interest has been focused on the synthesis of novel D-A type conjugated polymers because of their excellent photonic properties. Recently, lots of attentions have been dedicated towards the development of new D-A type polymers with desired properties through proper structural modifications. In this context, the proposed research work has been aimed at design and synthesis of new D-A type conjugated polymers with improved photonic properties. Based on the literature review, five new series of D-A type conjugated polymers (P1-P20) carrying various electron donors and acceptor moieties have been designed. Seven series of bi-functional monomers required for the synthesis of new polymers have been prepared using appropriate synthetic procedures. Structures of new intermediates and monomers have been evidenced using spectral and elemental analyses. Starting from these monomers, five new series of target polymers, viz. (i) poly(3,4-ditetradecyloxythiophene)s carrying thiophene, naphthalene, isopthalyl, vinyl and pyrazole moieties as π-conjugated spacers (Series 1, P1-P5), (ii) poly(cyanopyridines) containing phenyl, carbazole, alkoxythiophene phenothiazine and dipenyl amine based electron donating bridges (Series 2, P6-P10), (iii) poly(3,4- ditetradecyloxythiophene)s involving vinylene π-conjugated spacers (Series 3, P11- P14), (iv) poly(3,4-ditetradecyloxythiophene)s carrying aromatic conjugated cyclic imides (Series 4, P15 and P16), and (v) poly(3,4-ditetradecyloxythiophene)s with imine functionalized electron donors as π-conjugated bridges (Series 5, P17-P20), have been successfully synthesized and their synthetic protocols have been established. Their structures have been confirmed by different spectroscopic and elemental analyses. Their molecular weights have been determined by GPC technique and thermal properties have been evaluated by TGA studies. Electrochemical properties have been studied using CV experiments. The linear optical characteristics have been estimated by UV-visible absorption and fluorescence emission spectroscopy. Their fluorescent quantum yields and solvatochromic behavior have been determined. Finally, their third-order NLO properties have been investigated using open aperture Z-scan technique to investigate their optical limiting behavior. Most of the polymers have exhibited promising results.