Annealing effect on performance and morphology of photovoltaic devices based on poly(3‐hexylthiophene)‐b‐poly(ethylene oxide)

Novel block copolymers, poly(3‐hexylthiophene)‐b‐poly(ethylene oxide) (P3HT‐b‐PEO) were synthesized via Suzuki coupling reaction of P3HT and PEO homopolymers. The copolymers were characterized by NMR, gel permeation chromatography, differential scanning calorimeter, and UV–vis measurements. A series of devices based on the block copolymers with a fullerene derivative were evaluated after thermal or solvent annealing. The device using P3HT‐b‐PEO showed higher efficiency than using P3HT blend after thermal annealing. Phase‐separated structures in the thin films of block copolymer blends were investigated by atomic force microscopy to clarify the relationship between morphologies constructed by annealing and the device performance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Thermal and pH responsive high molecular weight poly(urethane‐amine) with high urethane content

Aliphatic poly(urethane‐amine) (PUA) was synthesized from copolymerization of CO₂ and 2‐methylaziridine (MAZ) using Y(CCl₃COO)₃‐ZnEt₂‐glycerine coordination catalyst, the urethane content of PUA was over 80%, and its yield could reach 90%. PUA with molecular weight as high as 31.0 kg/mol was obtained when the copolymerization reaction was carried out in N,N‐dimethylacetamide (DMAc), mainly due to the good solubility of PUA in DMAc. PUA exhibited reversible thermo‐responsive property in deionized water, and the lower critical solution temperature (LCST) was highly sensitive to its urethane content and molecular weight, which was observed in a broad window from 37 to 90 °C. Furthermore, the phase transition behavior could also be controlled by change of pH value. When the pH value of the PUA aqueous solution changed from 9.2 to 13, the LCST value of the solution decreased from 48.4 °C to 30 °C. Therefore, the PUA showed thermo‐ and pH‐ dual responsive performance in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Peroxidase-like catalytic activity of cubic Pt nanocrystals

Monodispersed cubic platinum (Pt) nanocrystals with an average size of approximately 10 nm were prepared by a reduction method with cetyltrimethylammonium bromide (CTAB) serving as steric stabilizer. The resulting Pt nanocrystals exhibit a peroxidase-like activity and catalyze the H₂O₂-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to produce two colored products with high catalytic activity. The color-generating activity of this system may be influenced by several factors, and we examined several factors to optimize this colorimetric system including buffer types, pH, and concentrations of both H₂O₂ and Pt nanocrystals. The effect of agglomeration of Pt nanocrystals was also investigated, and we find that agglomeration of Pt nanocrystals in aqueous solution distinctly affects Pt nanocrystals catalytic activity. We attribute the catalytic activity of Pt nanocrystals to their acceleration of the electron-transfer process and the consequent facilitation of radical generation.     

Oleanane‐Type Triterpenoids from the Endophytic Fungus Pestalotiopsis clavispora Isolated from the Chinese Mangrove Plant Bruguiera sexangula

Three new triterpenoid derivatives, named (15α)‐15‐hydroxysoyasapogenol B ( 1 ), (7β,15α)‐7,15‐dihydroxysoyasapogenol B ( 2 ), and (7β)‐7,29‐dihydroxysoyasapogenol B ( 3 ), were isolated from cultures of the plant endophytic fungus Pestalotiopsis clavispora. Their structures and relative configurations were elucidated by extensive spectroscopic analysis and X‐ray crystallography.     

Peptide dendrimer-crosslinked inorganic-organic hybrid supramolecular hydrogel for efficient anti-biofouling

A novel kind of inorganic-organic hybrid supramolecular hydrogel with excellent anti-biofouling capability was developed. The hydrogel was formed via ionic interaction between the negative-charged sodium polyacrylate (SPA) entwined clay nanosheets (CNS) and positive-charged polyhedral oligomeric silsesquioxane (POSS) core-based generation one (L-Arginine) dendrimer (POSS-R).     

The relativistic consistent angular-momentum projected shell model study of the <Emphasis Type="Italic">N</Emphasis>=<Emphasis Type="Italic">Z</Emphasis> nucleus <Superscript>52</Superscript>Fe

The relativistic consistent angular-momentum projected shell model(ReCAPS) is used in the study of the structure and electromagnetic transitions of the low-lying states in the N=Z nucleus 52Fe.The model calculations show a reasonably good agreement with the data.The backbending at 12+ is reproduced and the energy level structure suggests that neutron-proton interactions play important roles.     

Reflection-Absorption Infrared Spectroscopy Study of Polyacrylonitrile on Copper at Elevated Temperature

Reflection-absorption infrared spectroscopy (RAIR) has been used to investigate the chemical structural changes in Polyacrylonitrile (PAN) film adsorbed on copper at 200°C for different time. The formation of an almost fully conjugated C-C=C backbone occurs after heating for only 2 h due to the catalytic effect of copper. The freely dangling cyano groups in PAN molecules initially coordinate to copper surface through the triple bond in π-bonded orientation, then convert to [sgrave]-bonding through the donation of the lone pair of electrons of nitrogen. It is suggested that this transition of the types of coordination would relate to the different geometries of PAN on copper during heating. Since the nitrile complexing and cyclization occur at the same time, the reaction process for the pyrolysis of PAN on copper surface is different from that in the bulk.     

A second look at the Gaussian semiclassical soliton ensemble for the focusing nonlinear Schrödinger equation

We study the Gaussian semiclassical soliton ensemble, a collection of multisoliton solutions of the focusing nonlinear Schrödinger equation. The ensemble is generated by adding a particular asymptotically vanishing sequence of perturbations to Gaussian initial data. Recent results (Lee et al., 2012) [21] suggest that, remarkably, these perturbations — interlaced as they are with the integrable structure of the equation — do not excite the acute modulational instabilities known to be present in the semiclassical regime. Our results here highlight the exceptional nature of these perturbations and provide new insight into the sensitivity properties of the related semiclassical limit problem.     

Active control of time-delay in cutting vibration

The system dynamics of turning processes can be described by a delay differential equation. How to improve the stability and suppress the vibration of cutting is of an interesting topic. In this paper, a multiple time-delay controller is developed based on discrete optimal control method for the turning vibrations control. Numerical simulations are carried out to verify the efficiency of the controller. Results indicate the designed controller can suppress the cutting vibration efficiently and improve the stability of the cutting processes. The influence of designed time-delay and sampling time on the control performance is also discussed.