Miscibility of natural polyhydroxyalkanoate blend with controllable material properties

Polyhydroxyalkanoate (PHA) copolyesters were synthesized by Cupriavidus necator cells in continuous feeding of cosubstrates. During the PHA accumulation phase, the composition of 3‐hydroxybutyrate (3HB), 3‐hydroxyvalerate (3HV), and 4‐hydroxyvalerate (4HV) of the copolyesters changed with time, resulting in a change in their miscibility. The as‐produced PHA finally became a miscible blend of copolymers with a broad chemical composition distribution. The good miscibility and low crystallinity of the natural P(3HB‐co‐3HV‐co‐4HV) blend lead to a remarkable increase in ductility and elongation at break. It indicates that the material properties of copolyesters can be tailored via feeding control of cosubstrates. It was also found that the fractions of natural PHA blend exhibited distinctive thermal behavior and the overall behavior of the as‐produced PHA blend was primarily dependent on a fraction of high 3HB content. The material properties of a PHA blend are therefore not determined by its overall chemical composition but more likely by the combined effect of individual copolyesters or fractions. Moreover, the degree of X‐ray crystallinity of random P(3HB‐co‐3HV‐co‐4HV) blend declined significantly with the increase of 3HV and 4HV content, in contrast to the high crystallinity of well‐known P(3HB‐co‐3HV) copolyesters. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Superiorization methodology and perturbation resilience of inertial proximal gradient algorithm with application to signal recovery

The Journal of Supercomputing - In this paper, we construct a novel algorithm for solving non-smooth composite optimization problems. By using inertial technique, we propose a modified proximal...     

Quantitative analysis of oxygen-containing species adsorbed on the Pt surface of a polymer electrolyte fuel cell membrane electrode assembly electrode using stripping voltammetry

The quantity of oxygen-containing species adsorbed on Pt surface of a single-cell polymer electrolyte fuel cell membrane electrode assembly (PEFC MEA) in the gas-phase system was measured by stripping voltammetry (SV), of which the adsorbed amount is considered in terms of the quantity of electric charge required for stripping. The effect of different experimental parameters on the adsorption quantity was analyzed and an optimum condition for applying SV to a PEFC MEA electrode was then suggested. The electric charge required for stripping was observed to be linearly proportional to the potential and arose from 0.7 V vs. RHE. The adsorption amount of oxygen-containing species for the PEFC MEA at a cell temperature of 60 °C was 384 μC cm⁻²-Pt at a potential of 1.0 V vs. RHE. More importantly, considering the effect of O₂ partial pressure on the adsorption in the gas-phase PEFC MEAs, water is suggested to be the main source of the oxygen in adsorbed oxygen-containing species. The present method is well applicable to quantitative studies of the oxygen-containing species adsorbed on electrodes of PEFC MEAs.     

Cover Image,Volume 138, Issue 42

Methacrylate-containing polyesters exploited for digital light processing (DLP) are generally prepared through ring-opening polymerization followed by photoactivation via methacrylation, which commonly requires the additional chemical and reaction workup. Herein, such a drawback is overcome by introducing a facile method of sequential addition of ester monomer and glycidyl methacrylate into the reaction. Two different hydroxyl beginning monomers, that is, ethylene glycol and glycerol, were utilized. The chemical structures and molecular weights of the resultant copolymers were analyzed using ¹H-NMR and ATR-FTIR spectroscopy and size exclusion chromatography, respectively. The effects of the copolymer structures on the properties of both resins formulated with and without hydroxyapatite, for example, rheological behavior and printability, and DLP-printed specimens, for example, mechanical property and cytotoxicity, were assessed. By controlling the beginning monomer to monomer feeding ratio from 1:6 to 1:14, the M_n values of the resultant copolymers fell in the range of 1.7 to 2.5 kDa. The DLP-printed specimens possessed compressive moduli in the range of 10.20 ± 0.16 MPa and 18.65 ± 0.75 MPa. The cytotoxicity result suggested that the DLP-printed specimens were noncytotoxic to porcine chondrocytes. Altogether, these methacrylate-containing polyesters simply synthesized via a concise one-pot reaction revealed great potential for DLP printing resins in biomedical applications.     

A Thiophene‐Based Anchoring Ligand and Its Heteroleptic Ru(II)‐Complex for Efficient Thin‐Film Dye‐Sensitized Solar Cells

A novel heteroleptic Ru^II complex (BTC‐2) employing 5,5′‐(2,2′‐bipyridine‐4,4′‐diyl)‐bis(thiophene‐2‐carboxylic acid) (BTC) as the anchoring group and 4,4′‐ dinonyl‐2,2′‐bipiridyl and two thiocyanates as ligands is prepared. The photovoltaic performance and device stability achieved with this sensitizer are compared to those of the Z‐907 dye, which lacks the thiophene moieties. For thin mesoporous TiO₂ films, the devices with BTC‐2 achieve higher power conversion efficiencies than those of Z‐907 but with a double‐layer thicker film the device performance is similar. Using a volatile electrolyte and a double layer 7 + 5 μm mesoporous TiO₂ film, BTC‐2 achieves a solar‐to‐electricity conversion efficiency of 9.1% under standard global AM 1.5 sunlight. Using this sensitizer in combination with a low volatile electrolyte, a photovoltaic efficiency of 8.3% is obtained under standard global AM 1.5 sunlight. These devices show excellent stability when subjected to light soaking at 60 °C for 1000 h. Electrochemical impedance spectroscopy and transient photovoltage decay measurements are performed to help understand the changes in the photovoltaic parameters during the aging process. In solid state dye‐sensitized solar cells (DSSCs) using an organic hole‐transporting material (spiro‐MeOTAD, 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene), the BTC‐2 sensitizer exhibits an overall power conversion efficiency of 3.6% under AM 1.5 solar (100 mW cm^?2) irradiation.     

Thermal stability and degradation of biological terpolyesters over a broad temperature range

Because of high susceptibility to thermal degradation during conventional melt processing of poly(3‐hydroxybutyrate) (P3HB) homopolymer, incorporation of a second or third monomer unit in the polyester backbones is expected to reduce the melting temperature and crystallinity, resulting in a controlled thermal degradation with improved stability. In this work, random poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate‐co‐4‐hydroxyvalerate) (P3HB3HV4HV) terpolyesters biologically synthesized by Cupriavidus necator were investigated for the thermal stability and degradation over a broad temperature range (100–300°C) in comparison with P3HB homopolyester. The work revealed that below the complete melting point (around 150°C), the terpolyester exhibited a high thermal stability and became an amorphous semisolid suitable for conventional thermal processing. Size exclusion chromatography plus nuclear magnetic resonance analysis was used to examine the thermal degradation products and the vulnerability of different monomer units at high temperatures (240–290°C). We found that 3HV unit in P3HB3HV4HV copolymers was more vulnerable to thermal degradation than 3HB unit under air. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41715.