Direct C-H coupling polymerization of asymmetric monomer: Synthesis and properties of regioregular poly(alkyl thiophene-3-carboxylates). (December 2018)

• Record Type: Journal Article
• Authors: Deng, Ludi; Zhang, Qiang; Zhao, Linlin; Lu, Yan
• Is Part Of: European polymer journal. Volume 109(2018)
• Page Start: 72
• Page End: 81
• Publication Date: 2018-12
• Subjects: C-C coupling -- Regioregular polythiophene -- Asymmetric monomer -- Pd-catalyzed oxidative; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2018.09.001
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: The role of alkyl ester groups on the side-chain of polythiophene on the direct CH coupling polymerization reaction as well as the crystallinity and photoelectrical properties of the resultant polymers was systematically studied. Highlights: A series of P3ET with high HT regioregularity were prepared via DCHCP method. The effect of monomer's structure on polymerization reaction was studied. The role of ester side chains on the polymers' properties was explored. Abstract: A series of poly(alkyl thiophene-3-carboxylates), herein referred to as poly(3-alkylesterthiophenes) (P3ET) (P1 -P6 ) with high head-to-tail (HT) coupled regioregularity up to ∼92% were synthesized by a direct CH coupling polymerization (DCHCP). The substitutions with various alkyl ester side-chains on the 3-position of the thiophene ring were performed by changing the length and size of alkyl groups, with a view to investigate the role of the alkyl ester side chain on DCHCP reaction as well as on the crystallinity, optical and electrochemical properties of these resultant polymers. It was found that the longer and bigger size alkyl ester side chains on 3-position of thiophene monomers, the higher HT regioregularity of the corresponding polymer products. X-ray diffraction (XRD) measurements manifested that all polymers (P1 -P6 ) existed in not highly ordered state in solid films especially in the π-stacking direction. Red shift of the UV–Vis absorption maxima of the resultant polymers in the film state confirmed more effective electron delocalization along the polymer chain than that in solution state. Cyclic voltammetry (CV) study indicated that the introduction of 3-alkyl ester side chain on the thiophene ring lowered the products' highest occupied molecular orbital (HOMO) energy level and enhanced their electrochemical band gaps significantly in comparison with the corresponding HT regioregular poly(3-alkylthiophenes).