Synthesis and characterization of plant based thiophene and 3-hexylthiophene copolymers

Abstract

Polythiophene and its derivatives have become more desirable due to their applications in various fields. These applications arise due to their inherent properties, such as optical and electronic conductive properties; as well as thermal and environmental stability. Precursors of polythiophenes are generally obtained from petroleum by-products, which are non-renewable. It has been reported that precursors of polythiophenes and its derivatives are naturally available in different types of Tagetes species such as Tagetes erecta, Tagetes tenuifolia, etc. A number of thiophene derivatives such as 2, 2’:5’, 2’’-terthienyl (Alpha-T), 5- (3-buten-1-ynyl)-2, 20-bithienyl (BBT), 5-(4-hydroxy-1-butynyl)-2, 20-bithienyl (BBTOH), and 5-(4-acetoxy-1-butynyl)-2, 20-bithienyl (BBTOAc), were found and identified, specifically in the roots of Tagetes species. The current study reports the polymerization of the extracted thiophene derivatives from Tagetes erecta and 3-hexylthiophene (3HT) to obtain a random copolymer of poly (thiophenes-3-hexylthiophene). The extracted thiophene derivatives were partially purified and characterized. The mixture of plant based thiophenes and commercial 3HT with various weight compositions were selectively polymerized on the direct one-step chemical oxidative free radical polymerization to obtain co-polymers. Structural characterization of the synthetic products was done using Fourier Transformation Infrared, Proton Nuclear Magnetic Resonance, Ultra Violet Visible and X-ray Diffraction techniques. Homopolymers of polythiophene obtained from plant based thiophenes have limited processability of solar cells due to poor solubility in common organic solvents. 'However, a significant progress of the solubility was observed with copolymers having partial contribution of 3HT.