Photoinduced step-growth polymerizations of thiophene-carbazole based covalent organic polymer


Celiker T., ALTINIŞIK S., Yağcı Y., KOYUNCU S.

Polymer, vol.289, 2023 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 289
  • Publication Date: 2023
  • Doi Number: 10.1016/j.polymer.2023.126473
  • Journal Name: Polymer
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, PASCAL, Aerospace Database, Biotechnology Research Abstracts, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, INSPEC, Metadex, Civil Engineering Abstracts
  • Keywords: Carbazole, Thiophene, Photoinduced electron transfer, Photopolymerization, Step-growth polymerization, Conjugated polymers
  • Çanakkale Onsekiz Mart University Affiliated: Yes

Abstract

A novel metal-free photochemical method for the synthesis of porous conjugated polymers was used to investigate the effects of introducing thiophene co-monomer to the carbazole-based polymer, 4,4′-bis(3,6-di(thiophen-2-yl)-9H-carbazol-9-yl)-1,1′-biphenyl (CBP–Th), in terms of its structural, optical, electrochemical and morphological properties. Irradiation of a CBP-Th monomer solution led to the formation of a dark-colored polymer, PCBP-Th, and the role of thiophene on polymerization was investigated, involving electron transfer between CBP-Th and the iodonium ion in the exciplex produced by proton release and radical coupling reactions. The UV–Vis spectra broadened and redshifted due to the elongation of conjugation and solid-state π-π interactions by extra thiophene additive after the polymerization process. The addition of thiophene co-monomer also resulted in decreasing the onset potentials and thus slightly raised HOMO positions determined by the DPV technique. In theoretical calculations, it has been observed that the charge distribution of PCBP-Th at HOMO is over the entire conjugated structure and it has localization in thiophene-thiophene bridges at LUMO. Since the thiophene co-monomer changes the intermolecular distance, the thermal stability of PCBP-Th polymers decreases and accordingly increases the amorphous characters. According to AFM, TEM and SEM images, introducing the thiophene co-monomer led to the formation of larger clusters, resulting in a more pronounced surface texture on both the powders and thin films.