Conjugated polymers are highly desirable for the photovoltaic applications. We report the synthesis, characterization, optoelectronic properties, and solar cell application of two polymers, namely, poly[(9,9-didodecylfluorene-2,7-diyl)-alt-(2,2′:5′,2″-terthiophene-5,5″-diyl)] (P1) and poly[(1,4-bis(dodecyloxy)benzene-2,5-diyl)-alt-(2,2′:5′,2″-terthiophene-5,5″-diyl)] (P2). The polymers were synthesized via Stille cross-coupling reaction, and were characterized by the gel permeation chromatography, nuclear magnetic resonance, Fourier transform infrared, UV–vis, thermogravimetric analysis, and cyclic voltammetry analyses. The two copolymers are processable due to their good solubility in organic solvents (tetrahydrofuran, CHCl₃, toluene, chlorobenzene, and o-dichlorobenzene). The optical band gaps (UV–vis, film, and E_g^opt) of the P1 and P2 are 2.04 and 2.00 eV, respectively. The density functional theory output structures showed that S^…O space interaction is likely responsible for the higher planarity of P2. The polymers showed low HOMO energy levels (P1: −5.33 eV, P2: −5.05 eV). The E_HOMO for P1 is close to the E_HOMO (−5.4 eV) of an ideal polymer, which is an important, rare, and main origin of the observed higher V_oc (801–808 mV). The onset decomposition temperatures (T_d) for the P1 and P2 are 418°C and 365°C, respectively. The polymer solar cell based on the P1: C₆₀ (1: 1) and P2: C₆₀ (1: 1) blend showed a power conversion efficiency (PCE) of 0.94 and 0.71%, respectively. The composite polymer : PC₆₀BM = 1 : 2 increased PCE of the P1 (1.65%) and P2 (1.09%) under AM 1.5 illumination (100 mW/cm²). The study provided important examples to design donor–donor (D–D) polymers for the photovoltaic applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42147.

Polyimides (PIs) are highly desirable materials due to their excellent physical, chemical properties, and widespread applications. In this article, a new PI containing bipyrimidine units was prepared from a newly synthesized 5,5′-bis[(4-amino) phenoxy]-2,2′-bipyrimidine and 3‚3′‚4‚4′-biphenyltetracarboxylic dianhydride via a two-step method. The as-synthesized PI not only showed high thermal stability and excellent mechanical properties, but also possessed high dielectric constant (7.1, 100 Hz) and low dielectric loss (below 0.04) in a wide frequency range from 100 Hz to 10⁵ Hz. The obtained PI promises potential applications in electronic products. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40828.

High-strength and high-toughness nanofibers were made from polyimide 6F-PI through electrospinning. The 6F-PI had a backbone made up with 3,3′,4, 4′-biphenyl-tetracarboxylic dianhydride and 2,2-bis[4-(4-aminophenoxy)phenyl]-hexafluoro-propane residues. Electrospun 6F-PI precursor nanofibers were collected in the form of aligned fiber sheet on the rim of a rotating disc. Heating process converted the precursor fiber sheets to 6F-PI nanofiber sheets. Gel permeation chromatography and Ostwald Viscometer were used to determine the molecular weight and the molecular weight distribution of the 6F-PI precursor, i.e., the 6F-polyamic acid. Scanning electron microscopy, infrared spectroscopy, X-ray scattering, tensile testing, dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry were employed to characterize the surface morphology, thermal stability, and mechanical properties of the 6F-PI nanofiber sheets. Experimental results show that the nanofibers were well aligned in the sheets with fiber diameters ranging from 50 to 300 nm. The nanofiber sheets were stable to over 450°C, with a glass transition at 265.2°C. The uniaxial tension test showed that the 6F-PI nanofiber sheets had superior mechanical properties. The ultimate tensile strength, modulus, toughness, and elongation to break of the 6F-PI nanofiber sheets are respectively, 308 ± 14 MPa, 2.08 ± 0.25 GPa, 365 ± 20 MPa, and 202 ± 7%. It is expected that electrospun PI nanofibers with such high toughness and high ultimate tensile strength can find applications in high-performance textiles and composites, for example. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Palladium nanoparticle-loaded carbon nanofibers (Pd/CNFs) were synthesized by the combination of electrospinning and thermal treatment processes. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that spherical Pd nanoparticles (NPs) are well-dispersed on the surfaces of CNFs or embedded in CNFs. X-ray diffraction (XRD) pattern indicates that cubic phase of Pd was formed during the reduction and carbonization processes, and the presence of Pd NPs promoted the graphitization of CNFs. This nanocomposite material exhibited high electric conductivity and accelerated the electron transfer, as verified by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The Pd/CNF-modified carbon paste electrode (Pd/CNF-CPE) demonstrated direct and mediatorless responses to H₂O₂ and NADH at low potentials. The analytical performances of the Pd/CNF-CPEs towards reduction of H₂O₂ and oxidation of NADH were evaluated. The high sensitivity, wider linear range, good reproducibility, and the minimal surface fouling make this Pd/CNF-CPE a promising candidate for amperometric H₂O₂ or NADH sensor.