4-quinolin-8-yloxy Linked Triphenylamine Based Polyimides: Blue Light Emissive and Potential Hole-Transport Materials

Abstract

A series of fluorescent donor- acceptor (D-A) alternating copolyimides (P1, P2, P3 and P4) with 4-quinolin-8-yloxy linked triphenylamine main polymer chain have been synthesized by conventional polycondensation. All the synthesized co-polyimides were characterized by elemental, gel permeation chromatography and FTIR spectral analysis. These newly prepared PIs possess HOMO energy levels in range of - 4.74 to - 4.78 eV and have medium optical band gaps. The photoluminescence spectral analysis revealed blue to violet emission with appreciable efficiency with lower onset oxidation potentials suitable for the facile hole injection materials. All the photophysical and electrochemical properties were also explored in context of effect of the pendant 4- quinolin-8-yloxy, indicating suitable combination of donor (TPA) on one hand and imide and pendant as acceptor on both ends.Graphical Abstract.

Investigation of thermal and fluorescent properties of benzoxazole-linked triphenylamine-based co-polyimides

“…The synthesized PIs possess high-lying HOMO levels due to the presence of pendant benzoxazole ring and thereby, the potential use of PIs as hole transport materials. The optical bandgaps for ODA-based polyimides and 4-quinolin-8-yloxy-linked TPA and ODA-based co-polyimides were ranged from 3.42 eV to 3.83 eV 32 and −4.74 eV to −4.78 eV respectively, 43,44 while for these newly synthesized co-polyimides (1-PIs) from 2.84 to 3.05. The decrease in bandgap is mainly attributable to incorporation of TPA and benzoxazole-based diamine.…”

“…The PL emission spectra of thin films (spin-coated PI 10 μM solution on glass slide) displayed an additional small shoulder emission bands with bathochromic shift which may be due to excimer emission as also discussed in our previous article with carbazole-TPA-based and 4-quinoline 8-yloxy-based blue light emitting polyimides (Figure 5(c)). 44…”

“…In our previous work on the electroactive polyimides, we have reported polyimides with TPA-based carbazole, naphthoxy, and 4-quinoline-8-yloxy pendant groups having potential optical and photophysical properties, suitable for electrochromic applications. 43,44 Herein, we report synthesis and characterization of a series of co-polyimide by reacting two diamines, one bearing electron-rich TPA unit with benzoxazole as pendant group and the other 4,4′-oxydianiline (ODA) widely known to impart good film-forming ability with commercially available dianhydrides. It has been reported that rigid structure of benzoxazole and intramolecular hydrogen bonding greatly enhances the regularity of polymer backbone leading to improved properties like high thermal decomposition temperature, glass transition temperature, and better optical properties with good solubility.…”

Deep-blue emissive and colourless polyimides: optical property tuning by triphenylamino and carbazole chromophores

“…This phenomenon was observed earlier. 24 When comparing the polyimide cores, TFMB-6FDA vs. BAPP-CHDA, films made of the latter possess significantly blue-shifted emission ( e.g. λ E max = 518/383 nm for PI-1.2a/PI-2.2a ), which can be ascribed to the fluorinated TFMB-6FDA aromatic structure vs. semi-aliphatic BAPP-CHDA.…”

“…16 Besides thermal robustness, optical transparency is often a required parameter of emissive PI films. 17,18 Some emissive PIs containing TPA subunits 19–21 and featuring electrochromic 22,23 or luminescent 24 properties have been described.…”