Combining renewable gum rosin and lignin: Towards hydrophobic polymer composites by controlled polymerization

Rosin polymer–grafted lignin composites were prepared via “grafting from” atom transfer radical polymerization (ATRP) with the aid of 2‐bromoisobutyryl ester‐modified lignin as macroinitiators. Three different monomers derived from dehydroabietic acid (DA) were used for execution of grafting from ATRP, while DA was separately attached onto lignin by a simple esterification reaction. Kinetic studies indicated controlled and “living” characteristics of all monomer polymerizations. Thermal studies indicated that rosin polymer–grafted lignin composites exhibited glass transition temperatures in a broad temperature range from ～20 to 100°C. The grafting of both DA and rosin polymers significantly enhanced hydrophobicity of lignin. Static contact angle measurement of water droplets showed ～90° for all these rosin modified lignin composites. X‐ray photoelectron spectroscopy demonstrated that the surface of rosin–lignin composites was dominated with chemical compositions originating from the hydrocarbon rich rosin moiety. The impartation of hydrophobicity of rosin into lignin provided excellent water resistance of this class of renewable polymers, as all rosin‐modified lignin composites showed water uptake below 1.0 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Palladium(II)-catalyzed oxidative Heck coupling of thiazole-4-carboxylates

Oxidative Heck coupling of thiazole-4-carboxylates via palladium(II)-catalyzed C-H bond activation has been achieved in moderate to good yields. No ligand, and no acidic additive were used in the reaction. The results showed that this protocol tolerated a series of substitutions on the thiazole ring. A preliminary attempt of direct arylation with p-xylene via Pd(II)-catalyzed C-H bond activation has also been done.     

K3PO4 promoted dipolar [3+3] cyclization: Direct synthesis of pyrazino[2,1-a]isoquinoline derivatives

A K₃PO₄ promoted dipolar [3+3] cyclization of dihydroisoquinoline imines and arylacyl bromides has been developed. This process realized the direct synthesis of pyrazino[2,1-a]isoquinoline derivatives in 44–69% yields. A head to tail dimerization was proposed as key step for this procedure.     

Equilibrium Studies on Reactive Extraction of α-Cyclohexylmandelic Enantiomers Using Hydrophilic β-Cyclodextrin Derivatives Extractants

β‐Cyclodextrin (β‐CD) is negligibly soluble in organic liquids and can be modified to achieve a higher solubility in water. In this paper, racemic α‐cyclohexyl‐mandelic acid (α‐CHMA) was separated by chiral reactive extraction with aqueous β‐cyclodextrin derivatives. Hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), hydroxyethyl‐β‐cyclodextrin (HE‐β‐CD), and methyl‐β‐cyclodextrin (Me‐β‐CD) were selected as chiral selectors for reactive extraction of α‐CHMA enantiomers from organic phase to aqueous phase. Factors affecting the extraction efficiency were investigated, including the types of organic solvents and β‐CD derivatives, the concentrations of the chiral selector and α‐CHMA enantiomers, pH and temperature. The experimental results demonstrate that HP‐β‐CD, HE‐β‐CD, and Me‐β‐CD have stronger recognition abilities for S‐α‐CHMA than for R‐α‐CHMA. Among the three derivatives, HP‐β‐CD shows the strongest separation factor for α‐CHMA enantiomers. A high enantioseparation efficiency with a maximum separation factor (α) of 2.02 is observed at pH 2.5 and 5°C.     

Large-size oxyfluoride glasses used for vis–IR-transmitting windows

Windows for infrared sensors on missiles, aircraft and high energy laser systems must be of excellent spectral properties, high optical quality, large and durable enough to protect delicate sensors from harsh operating conditions. This paper describes work being done for IR window applications on heavy metal oxyfluoride (HMOF) glasses, which provide a combination of infrared transparency, strength, hardness, and environmental stability in a largely-sized formable material, and represents potential candidate materials for infrared windows.     

Electrophoretic deposition of titanate nanotube films with extremely large wetting contrast

A facile electrophoretic deposition (EPD) process has been developed to prepare thin films consisting of titanate nanotubes (TNTs) that were synthesized by a hydrothermal approach. Such an EPD process offers easy control in the film thickness and the adhesion to the substrate was found to be strong. The chemical composition and structure of the products have been characterized by XRD, HRTEM, and FESEM. It was found that the functionalization of TNTs plays a key role on the electrolyte stability and the formation of a uniform TNT film with good adhesion. The as-prepared TNT films show exceptional superhydrophilic behavior with ultra-fast spreading, while it converts to superhydrophobicity yet with strong adhesion after 1H,1H,2H,2H-perfluorooctyl-triethoxysilane modification. This study provides an interesting method to prepare films with extremely high wettability contrast that are useful for producing different types of functional materials.     

Experimental and numerical investigation on air-side performance of fin-and-tube heat exchangers with various fin patterns

Air-side heat transfer and friction characteristics of five kinds of fin-and-tube heat exchangers, with the number of tube rows (N = 12) and the diameter of tubes (D_o = 18 mm), have been experimentally investigated. The test samples consist of five types of fin configurations: crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators (VGs) and mixed fin with front 6-row vortex-generator fin and rear 6-row slit fin. The heat transfer and friction factor correlations for different types of heat exchangers were obtained with the Reynolds numbers ranging from 4000 to 10000. It was found that crimped spiral fin provides higher heat transfer and pressure drop than the other four fins. The air-side performance of heat exchangers with the above five fins has been evaluated under three sets of criteria and it was shown that the heat exchanger with mixed fin (front vortex-generator fin and rear slit fin) has better performance than that with fin with delta-wing vortex generators, and the slit fin offers best heat transfer performance at high Reynolds numbers. Based on the correlations of numerical data, Genetic Algorithm optimization was carried out, and the optimization results indicated that the increase of VG attack angle or length, or decrease of VG height may enhance the performance of vortex-generator fin. The heat transfer performances for optimized vortex-generator fin and slit fin at hand have been compared with numerical method.     

DNA nanostructure-based nucleic acid probes: construction and biological applications

In recent years, DNA has been widely noted as a kind of material that can be used to construct building blocks for biosensing, in vivo imaging, drug development, and disease therapy because of its advantages of good biocompatibility and programmable properties. However, traditional DNA-based sensing processes are mostly achieved by random diffusion of free DNA probes, which were restricted by limited dynamics and relatively low efficiency. Moreover, in the application of biosystems, single-stranded DNA probes face challenges such as being difficult to internalize into cells and being easily decomposed in the cellular microenvironment. To overcome the above limitations, DNA nanostructure-based probes have attracted intense attention. This kind of probe showed a series of advantages compared to the conventional ones, including increased biostability, enhanced cell internalization efficiency, accelerated reaction rate, and amplified signal output, and thus improved in vitro and in vivo applications. Therefore, reviewing and summarizing the important roles of DNA nanostructures in improving biosensor design is very necessary for the development of DNA nanotechnology and its applications in biology and pharmacology. In this perspective, DNA nanostructure-based probes are reviewed and summarized from several aspects: probe classification according to the dimensions of DNA nanostructures (one, two, and three-dimensional nanostructures), the common connection modes between nucleic acid probes and DNA nanostructures, and the most important advantages of DNA self-assembled nanostructures in the applications of biosensing, imaging analysis, cell assembly, cell capture, and theranostics. Finally, the challenges and prospects for the future development of DNA nanostructure-based nucleic acid probes are also discussed.

In recent years, DNA has been widely noted as a kind of material that can be used to construct building blocks for biosensing, in vivo imaging, drug development, and disease therapy because of its advantages of good biocompatibility and programmable properties.