Systematic Tuning of 2,1,3-Benzothiadiazole Acceptor Strength by Monofunctionalization with Alkylamine, Thioalkyl, or Alkoxy Groups in Carbazole Donor–Acceptor Polymers

Abstract

A simple route to the preparation of alkylamine, thioalkyl, and alkoxy monofunctionalized 4,7-di(thiophen-2yl)-2,1,3-benzothiadiazole) based monomers is reported from a common fluorinated precursor. Copolymerization with a carbazole comonomer under Suzuki conditions yielded a series of analogous donor−acceptor copolymers in which the only difference was the nature of the heteroatom (N, O, or S) on the benzothiadiazole core. This was shown to have a significant impact on the wavelength and intensity of the intramolecular charge transfer (ICT) absorption peak due to a combination of electronic and steric factors. Substantial differences were also observed in the solar cell performance of blends with PC 71 BM, with the octylamino substituted polymer exhibiting significantly lower performance than the other two polymers. This polymer also exhibited a reversible change in the optical spectra upon exposure to acid, suggesting potential as a sensing material.

Tunable Control of the Hydrophilicity and Wettability of Conjugated Polymers by a Postpolymerization Modification Approach

“…The spectra are similar to the parent F8BT polymer, [47] with all polymers exhibiting two absorption bands in solution and thin films: a high energy band corresponding to the π-π* transition and a low energy band corresponding to intramolecular charge transfer (ICT) to the electron-deficient benzothiadiazole monomer. [51] The parent F8FBT exhibits peaks at 319 and 440 nm in chloroform, similar to the reported spectrum. [48] Substitution of the electron-withdrawing fluoride with the electron-donating ether group results in a slight red-shift of both bands in all examples (Table 2), as well a reduction in the relative intensity of the ICT band with respect to the high energy band, likely as a result of the weakening of the electron-accepting ability of the benzothiadiazole.…”

Post-polymerisation functionalisation of conjugated polymer backbones and its application in multi-functional emissive nanoparticles

“…Polymers containing fluorinated benzotriazole groups ( P4-F ) were also quantitatively substituted, despite the reduced electron accepting nature of benzotriazole compared to FBT. In both of these examples substitution was shown to result in a significant blue shift of the absorption maxima (Supplementary Figure 22a and b ), due to a combination of backbone twisting upon inclusion of the larger thioalkyl group and a reduction in the acceptor strength due to the fluoride substitution 25 , 29 . The backbone twisting could be alleviated by inserting a vinylene spacer group between the BT unit and the comonomer ( P5-F ).…”

“…1b ). This polymer was found to have near identical UV–Vis absorption and 1 H NMR spectra to a comparative polymer P1-SR-Suz , synthesised via the traditional Suzuki copolymerisation of the two appropriate comonomers 25 (Supplementary Figures 1 and 2 ). 19 F NMR spectroscopy on P1-SR indicated a complete absence of fluorine signals demonstrating that the S N Ar reaction can succesfully substitute all of the backbone fluorine groups, without adversely affecting other parts of the polymer backbone (Supplementary Figure 3 ).…”

Small Molecules Derived from Thieno[3,4-c]pyrrole-4,6-dione (TPD) and Their Use in Solution Processed Organic Solar Cells

“…It is important to highlight the use of microwaves because they make the synthesis cheaper than the conventional heating method. Furthermore, the microwave reaction consumes less time of synthesis; in our case, the reaction time was reduced from 48 to 1 h [ 44 , 45 , 46 ]. In addition, it produces higher reactions yields.…”