Fabrication of Alternating Copolymers Based on Cyclopentadithiophene-Benzothiadiazole Dicarboxylic Imide with Reduced Optical Band Gap: Synthesis, Optical, Electrochemical, Thermal, and Structural Properties

Abstract

A series of alternating copolymers containing cyclopentadithiophene (CPDT) flanked by thienyl moieties as electron-donor units and benzothiadiazole dicarboxylic imide (BTDI) as electron-acceptor units were designed and synthesized for solar cell applications. Different solubilizing side chains, including 2-ethylhexyl chains and n-octyl chains were attached to CPDT units, whereas 3,7-dimethyloctyl chains and n-octyl chains were anchored to the BTDI moieties. The impact of these substituents on the solubilities, molecular weights, optical and electrochemical properties, and thermal and structural properties of the resulting polymers was investigated. PCPDTDTBTDI-EH, DMO was synthesized via Suzuki polymerization, whereas PCPDTDTBTDI-8, DMO, and PCPDTDTBTDI-EH, 8 were prepared through direct arylation polymerization. PCPDTDTBTDI-8, DMO has the highest number average molecular weight (Mn = 17,400 g mol−1) among all polymers prepared. The PCPDTDTBTDI-8, DMO and PCPDTDTBTDI-8, 8 which have n-octyl substituents on their CPDT units have comparable optical band gaps (Eg ~ 1.3 eV), which are around 0.1 eV lower than PCPDTDTBTDI-EH, DMO analogues that have 2-ethylhexyl substituents on their CPDT units. The polymers have their HOMO levels between −5.10 and −5.22 eV with PCPDTDTBTDI-EH, DMO having the deepest highest occupied molecular orbital (HOMO) energy level. The lowest unoccupied molecular orbital (LUMO) levels of the polymers are between −3.4 and −3.5 eV. All polymers exhibit good thermal stability with decomposition temperatures surpassing 350 °C. Powder X-ray diffraction (XRD) studies have shown that all polymers have the amorphous nature in solid state.

FeCoP2 Nanoparticles Embedded in N and P Co-doped Hierarchically Porous Carbon for Efficient Electrocatalytic Water Splitting

“…Then, the formed slurry was freeze-dried. The XRD result of this polymer in Figure S2a (Supporting Information) shows a diffraction peak at 2θ = 23.0°, indicating that the metal-ion-containing polymer possesses an amorphous structure . The morphology of the polymer was detected by SEM measurement.…”

“…The XRD result of this polymer in Figure S2a (Supporting Information) shows a diffraction peak at 2θ = 23.0°, indicating that the metal-ion-containing polymer possesses an amorphous structure. 43 The morphology of the polymer was detected by SEM measurement. As seen from Figure S2b (Supporting Information), a gel-like bulk material with a smooth surface was observed.…”

D–A–D organic small molecules with AIE effect for fluorescence imaging guided photothermal therapy

“…For detailed synthesis steps of TDA molecules, see ESI S1-7. † Through a series of reactions, [32][33][34][35][36][37][38] we successfully prepared a fluorescent D-A-D organic small molecule (TDA) with AIE characteristics. To weaken the aggregation caused quenching (ACQ) effect of the TDA molecule and improve its water solubility, we used the nano-precipitation method to encapsulate it with DSPE-mPEG 2000 (S7 †) to prepare TDA NPs (Fig.…”

Synthesis of a Low-Cost Thiophene-Indoloquinoxaline Polymer Donor and Its Application to Polymer Solar Cells

“…PIQ solution exhibited absorption edge at 663 nm, which red-shifted over 188 nm relative to the monomer 3 solution. Introduction of the electron-donating thiophene to conjugated backbone can significantly enhance electronic delocalization along the chain axis via intramolecular charge transfer [40][41][42]. The monomer 3 solution has a strong absorption at 400-470 nm with a maximum absorption coefficient (ε) of 1.25×10 5 M −1 cm −1 , whereas the polymer PIQ solution has a much larger range of absorption, showing strong absorption in the 400-660 nm range with a slightly higher maximum absorption coefficient of 1.37 × 10 5 M −1 cm −1 (Figure 2b).…”