Xunchang Wang

Microporous organic polymers based on tetraethynyl building blocks with N-functionalized pore surfaces: synthesis, porosity and carbon dioxide sorption

A series of microporous organic polymers (MOPs) based on tetraethynyl monomers such as tetrakis(4-ethynylphenyl)methane and tetrakis(4-ethynylphenyl)silane was synthesized via conventional Sonogashira–Hagihara coupling reaction. The resulting MOPs were characterized by thermogravimetric analyses, IR-spectra, scanning electron microscopies, and the Brunauer–Emmett–Teller (BET) method. The incorporation of triphenylamine or azobenzene moieties into the polymer skeleton increases the number of electron donating basic nitrogen sites in the porous frameworks. Thus, these MOPs could exhibit efficient adsorption of Lewis acidic CO2 molecules and display good CO2-over-N2 selectivity. The triphenylamine-based polymer, TEPM-TPA, shows a high BET specific surface area up to 1072 m2 g−1 with a moderate CO2 uptake capacity of 2.41 mmol g−1 at 273 K and 1.13 bar. As for separation of CO2, both TEPM-Azo and TEPS-Azo exhibit relatively high CO2-over-N2 selectivities of 70.8 and 64.7 at 273 K, respectively, due to the N2-phobic feature of azo-based polymers.

Large branched alkylthienyl bridged naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole-containing low bandgap copolymers: Synthesis and photovoltaic application

ABSTRACT Two donor-acceptor (D-A) type low bandgap (LBG) alternating conjugated copolymers containing larger conjugation planarity and stronger electro-withdrawing ability naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT) unit, namely, poly[4,8-bis(5-(n-octylthio)thien-2-yl)-benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-4,9-bis(4-(2-decyltetradecyl)thien-2-yl)naphtho- [1,2-c:5,6-c′]bis[1,2,5]thiadiazole-5,5′-diyl] (PBDT-TS-DTNT-DT) and poly[4,8-bis(triiso-propylsilylethynyl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-4,9-bis(4-(2-decyltetradecyl)-thien-2-yl)naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole-5,5′-diyl] (PBDT-TIPS-DTNT-DT), were prepared by the palladium-catalyzed Stille polycondensation and characterized by gel permeation chromatography (GPC), UV-Vis absorption, thermal gravimetric analysis (TGA), cyclic voltammetry (CV) etc. PBDT-TS-DTNT-DT and PBDT-TIPS-DTNT-DT show the broader absorption and deeper highest occupied molecular orbital (HOMO) energy level approximately −5.45 and −5.62 eV, respectively. Bulk-heterojuction solar cells based on the resulted polymers and [6,6] phenyl-C61 butyric acid methyl ester (PC61BM) blends, with the device configuration of ITO/PFN/polymer:PC61BM/MoO3/Ag were prepared and investigated. The results showed the power conversion efficiency (PCE) of 2.67% for PBDT-TS-DTNT-DT/PC61BM (w:w, 1:2) and 0.64% for PBDT-TIPS-DTNT-DT/PC61BM (w:w, 1:1), with relatively high open-circuit voltage (VOC) of 0.86 and 1.05 V, small short-circuit current (JSC) of 5.41 and 0.97 mA cm−2 and moderate fill factor (FF) of 57.8% and 62.4%, under an AM1.5 simulator (100 mWcm−2), respectively.

NMR and UV-Vis study on phenyl-capped oligoaniline salts

Phenyl-capped oligoanilines in the oxidized state and their salts (by camphor sulfonic acid, CSA) were comparatively studied by UV-Vis and NMR spectroscopy. The UV-Vis spectra revealed a similar electron transfer behaviour and similar structure in the tetraaniline to those in polyaniline. Upon formation of the salt, H-1 NMR CH peaks of the oligomers showed large shifts to lower fields. The longer the molecule of a oligomer is, the more the shift, indicating that the charge brought into the N atoms by the proton was redistributed over the whole molecule. The CH and quaternary carbon peak-shifts support the electron cloud motion route H -->C -->C -->N -->H. This is in agreement with the four ring BQ derivatives model.

Synthesis and Photovoltaic Properties of 2D-Conjugated Polymers Based on Alkylthiothienyl-Substituted Benzodithiophene and Different Accepting Units

Two new low bandgap conjugated polymers, PBDTS-ID and PBDTS-DTNT, containing isoindigo (ID) and naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (NT), respectively, as an electron-deficient unit and alkylthiothienyl-substituted benzodithiophene (BDTS) as an electron-rich unit, were designed and synthesized by palladium-catalyzed Stille polycondensation. Both polymers showed good thermal stability up to 330 °C and broad absorption ranging from 300 to 842 nm. Electrochemical measurement revealed that PBDTS-ID and PBDTS-DTNT exhibited relatively low-lying highest occupied molecular orbital energy levels at −5.40 and −5.24 eV, respectively. These features might be beneficial for obtaining reasonable high open-circuit voltage and high short-circuit current. Polymer solar cells (PSCs) were fabricated with an inverted structure of indium-tin oxide/poly(ethylenimine ethoxylate)/polymer:PC71BM/MoO3/Ag. As a preliminary result, the PSCs based on PBDTS-ID and PBDTS-DTNT exhibited moderate power conversion efficiencies of 2.70% and 2.71%, respectively.

Synthesis and characterization of phenyl-capped oligoanilines

A series of phenyl-capped oligoanilines were prepared by chemical oxidation coupling. By comparing the FTIR spectra of fully reduced oligoanilines with those of oxidized oligoanilines, the intensity ratio of 1600cm(-1) to 1500cm(-1) was correlated to the content of the quinoid rings in the oligomer. In UV-Vis spectra of the oligoanilines in their oxidized state, the maximum absorption near 600nm redshifted from 540nm to 610nm with increasing polarity of the solvent, indicating the existence of tautomers in oxidized oilgoanilines.

The effect of molecular structure and fluorination on the properties of pyrene-benzothiadiazole-based conjugated polymers for visible-light-driven hydrogen evolution

The development of highly efficient organic photocatalysts for water splitting into hydrogen is one of the key challenges in materials chemistry. Herein, we have designed and synthesized a series of conjugated polymers with either a one- or three-dimensional framework consisting of pyrene and benzothiadiazole with different numbers of fluorine substitutions (0 or 2). The effect of molecular structure and fluorine substitution on their catalytic activity was investigated. It was found that the linear non-fluorinated polymer L-PyBT exhibited the highest hydrogen evolution rate up to 83.7 μmol h−1 under visible light irradiation among the prepared polymers because of its broad light absorption, suitable energy bandgap, and enhanced charge generation and separation process.