Design and synthesis of new cyanopyridine based conjugated polymers for optoelectronic applications

Abstract

Conducting polymers (CPs) have been widely investigated due to their several advantages over the traditional materials, such as wide and tunable electrical conductivity, facile production approach, high thermal stability, light-weight, low-cost and ease in material processing. Consequently, they are potential candidates for several applications in the field optoelectronics. In recent years, a great deal of interest has been focused on the synthesis of novel D-A configured conjugated polymers with desired properties through proper structural modifications, particularly for PLED application. 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 as good emissive materials. Based on the literature review, six new series of D-A type conjugated polymers (Series 1-6) carrying various electron donor and acceptor moieties have been designed with possible applications in PLEDs. Required bi-functional monomers have been prepared using appropriate synthetic procedures. Structures of new intermediates/monomers have been evidenced using spectral and elemental analyses. From these monomers, six new series of target polymers, viz. (i) phenylene-cyanopyridine based polymers having vinylene linkage as π-conjugated spacers, VPPy1-3 (Series-1), (ii) thiophene-cyanopyridine based polymers carrying vinylene linkage as π- conjugated spacers, VTPy1-3 (Series-2), (iii) phenylene-cyanopyridine based polymers containing phenylene as auxiliary donors, PPy1-3 (Series-3), (iv) thiophene-cyanopyridine based polymers containing phenylene as auxiliary donors, TPy1-3 (Series-4), (v) cyanopyridine based polymers carrying thiadiazole units, TDPy1-4 (Series-5), and (vi) heteroaromatic-cyanopyridine based polymers carrying imine linkage as π-conjugated spacers, Py1-4 (Series-6) have been successfully synthesized and their synthetic protocols have been established. Their structures have been confirmed by different spectroscopy 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 and photophysical properties have been evaluated by UV-visible absorption and PL spectroscopy. Their fluorescent quantum yields have been determined. Finally, their electroluminescence behaviour has been investigated. Most of the polymers have exhibited promising results in the device. Also, their structureproperty correlation studies have been carried out.