The influence of solid‐state microstructure on the origin and yield of long‐lived photogenerated charge in neat semiconducting polymers

The influence of solid‐state microstructure on the optoelectronic properties of conjugated polymers is widely recognized, but still poorly understood. Here, we show how the microstructure of conjugated polymers controls the yield and decay dynamics of long‐lived photogenerated charge in neat films. Poly(3‐hexylthiophene) was used as a model system. By varying the molecular weight, we drive a transition in the polymer microstructure from nonentangled, chain‐extended, paraffinic‐like to entangled, semicrystalline (M_W = 5.5–347 kg/mol). The molecular weight range at which this transition occurs (M_W = 40–50 kg/mol) can be deduced from the drastic change in elongation at break found in tensile tests. Linear absorption measurements of free‐exciton bandwidth and time‐resolved microwave conductivity (TRMC) measurements of transient photoconductance track the concomitant evolution in optoelectronic properties of the polymer as a function of M_W. TRMC measurements show that the yield of free photogenerated charge increases with increasing molecular weight in the paraffinic regime and saturates at the transition into the entangled, semicrystalline regime. This transition in carrier yield correlates with a sharp transition in free‐exciton bandwidth and decay dynamics at a similar molecular weight. We propose that the transition in microstructure controls the yield and decay dynamics of long‐lived photogenerated charge. The evolution of a semicrystalline structure with well‐defined interfaces between amorphous and crystalline domains of the polymer is required for spatial separation of the electron and hole. This structural characteristic not only largely controls the yield of free charges, but also serves as a recombination center, where mobile holes encounter a bath of dark electrons resident in the amorphous phase and recombine with quasi first‐order kinetics. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Synthesis of Vegetable Oil‐Based Polyurethane: A Study on Curing Kinetics Behavior

In the present study, biobased polyurethane (BPU) samples were synthesized from three different polyols along with polymeric hexamethylene diisocyanate. The three different polyols were synthesized by reacting castor oil with ethylene glycol, triethylene glycol, and triethanolamine. The synthesized polyols were confirmed using proton nuclear magnetic resonance (¹H NMR) spectra analysis. BPU samples were confirmed by the disappearance of isocyanate peak in the FTIR spectra. The cross‐linking densities of all BPU samples were determined using swelling studies. Curing kinetics behavior of all BPU samples were analyzed using differential scanning calorimetry at three different heating rates (5, 7.5, and 10°C/min). The curing kinetic parameters were studied using three nonisothermal methods such as Kissinger, Flynn–Wall–Ozawa, and Ozawa, respectively. The activation energies were found to increase with increasing degree of cure (α). Surface properties of all the synthesized BPU samples were evaluated by dynamic mechanical analysis and scanning electron microscopy.     

Studies on heterocyclic polyurea–epoxy resin condensation products

Polyureas having different heterocyclic groups were reacted, respectively, with commercial epoxy resins, i.e., diglicidyle ether of bisphenol A and brominated DGEBA. The resultant polyurea–epoxy systems were designated as I_(a–f) and II_(a–f), respectively. All the polyurea–epoxy systems were characterized by FTIR spectral studies, thermogravimetric analysis and number average molecular weight, estimated by non-aqueous conductometric titration. The polyurea–epoxy systems were then mixed with appropriate amounts of DGEBA epoxy resin, monitored for differential scanning calorimetry, and, based on this, glass fiber-reinforced composites were prepared. All the resultant laminates were characterized by physical and mechanical properties.     

Removal of Mercury by Emulsion Liquid Membranes: Studies on Emulsion Stability and Scale Up

Emulsion liquid membranes (ELM) have received significant attention in the separation of various metal ions from industrial wastewater. Still efforts are needed to get the desired level of stability to overcome the hindrance in the application of ELM at industrial scale. In this paper, the effects of various parameters such as emulsification speed, concentration of cosurfactant, surfactant, carrier and impeller speed during extraction on the stability of an emulsion liquid membrane are studied. Dispersion destabilization of w/o emulsion is checked by Turbiscan. Drop size distribution and photomicrographs of the emulsions are also analyzed to evaluate stability of the emulsion. Instability of emulsion liquid membrane during extraction process is measured in terms of membrane breakage. A stable emulsion is used for the extraction of mercury from aqueous solution in small scale as well as in large scale.     

Separation of Pt(IV) from Industrial Wastewater Using Rice Husk Adsorbent and Its Derivatives

Some novel adsorbents were prepared by rice husk (RH). The esterified rice husk (RHS) was prepared by treating RH with anhydride of succinic acid to introduce carboxylic function to rice husk. This RHS was used to anchor various polyamines, viz., ethylenediamine (ED) and diethylenetriamine (DT) to prepare new adsorbents. These adsorbents were used to separate Pt(IV) from synthetic as well as industrial wastewaters. Adsorbents were characterized by Fourier transform infrared spectra, elemental analysis, scanning electron microscopy, and energy dispersive x-ray spectrometry. The selectivity order for Pt(IV) removal found was: RHS-DT > RHS-ED > RH > RHS. The Freundlich isotherm provided the high correlation (0.9750–0.9938) for the adsorption with low SSE (0.00215–0.00785) value of Pt(IV) for all the adsorbents. Among the kinetic models, pseudo-second order kinetic model was found to best fit with high correlation for all the adsorbents. The results of thermodynamic parameters suggest that the Pt(IV) adsorption was spontaneous and endothermic in nature. The maximum percentage of desorption of Pt(IV) metal ion was obtained when the reagent HCl–thiourea mixture was used as desorbing agent.     

Canine Parvovirus Type 2a (CPV-2a)-Induced Apoptosis in MDCK Involves Both Extrinsic and Intrinsic Pathways

The canine parvovirus type 2 (CPV-2) causes an acute disease in dogs. It has been found to induce cell cycle arrest and DNA damage leading to cellular lysis. In this paper, we evaluated the apoptotic potential of the “new CPV-2a” in MDCK cells and elucidated the mechanism of the induction of apoptosis. The exposure of MDCK cells to the virus was found to trigger apoptotic response. Apoptosis was confirmed by phosphatidylserine translocation, DNA fragmentation assays, and cell cycle analysis. Activation of caspases-3, -8, -9, and -12 and decrease in mitochondrial potential in CPV-2a-infected MDCK cells suggested that the CPV-2a-induced apoptosis is caspase dependent involving extrinsic, intrinsic, and endoplasmic reticulum pathways. Increase in p53 and Bax/Bcl2 ratio was also observed in CPV-2a-infected cells.     

Rhodanine-based biologically active molecules: synthesis,characterization, and biological evaluation

To investigate the antimicrobial properties of the rhodanine (2-thioxo-4-thiazolidinone) structure, several 2-[(5Z)-5-benzylidene-4-oxo-2-thioxo-1,3-thiazolidin-3-yl]-N-phenylacetamide derivatives were synthesized by use of an efficient procedure. Variation of the functional group on the 5-benzylidine ring of rhodanine led to compounds containing a 2-thioxo-4-thiazolidinone group attached to N-phenyl acetamide. The chemical structures of the compounds were confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy, ESI mass spectrometry, and elemental analysis. The antibacterial and antifungal activity of the compounds were tested, at seven concentrations, against Gram-positive bacterial strains (Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922), Gram-negative bacterial strains (Staphylococcus aureus ATCC 25923 and Bacillus subtilis ATCC 11774), and fungal strains (Candida albicans ATCC 66027 and Aspergillus niger ATCC 6275), by use of the Kirby Bauer disk-diffusion technique and the serial broth dilution technique. The results obtained were compared with those for reference drugs. Relationships between structure and their antimicrobial activity are discussed.     

Strategy for purifying maltose binding protein fusion proteins by affinity precipitation

The maltose binding protein (MBP) affinity tag has been extensively used for protein purification. A commercial grade cationic starch could precipitate MBP or an MBP-tagged protein quantitatively by simultaneous addition of 10% (w/v) polyethylene glycol (PEG) and 50 mM calcium chloride. The precipitated MBP or MBP-tagged protein could be selectively dissociated by suspending the precipitate in 1 M NaCl. In the case of a soluble MBP fusion with a fragment of human immunodeficiency virus protein gp120, 38% of the contaminating proteins could be removed by precipitation with PEG/CaCl(2) and 100% of the fusion protein was recovered. In all cases, the purified proteins showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the expected changes in fluorescence emission spectra upon binding to maltose.     

Analysis and evaluation of biobased polyester of PTT/PBAT blend: thermal,dynamic mechanical,interfacial bonding,and morphological properties

Novel blends were prepared from biobased poly(trimethylene terephthalate) (PTT) and poly(butylene adipate‐co‐terephthalate) (PBAT) using a twin screw extrusion process as a function of different weight ratios. Thermal stability, mechanical, and interfacial properties of PTT/PBAT blends were investigated using a thermogravimetric analyzer and mechanical analyzer. Phase behavior and surface morphology of the blends were characterized using scanning electron microscopy. Interfacial bonding value of the PTT/PBAT blend was evaluated from the Pukanszky empirical relationship. Viscoelastic properties of PTT/PBAT blends were investigated using the dynamic mechanical analyzer. PTT/PBAT blend exhibited higher thermal stability than the neat PTT matrix. The entire blend showed better interfacial adhesion between the matrixes. Storage and loss modulus of the PTT/PBAT blend reduces with increasing PBAT content. PTT/PBAT blend exhibited higher impact energy than the neat PTT matrix, because of its flexible and amorphous nature of PBAT polymer and increasing toughness. Copyright © 2016 John Wiley & Sons, Ltd.