RAFT‐mediated synthesis and temperature‐induced responsive properties of poly(2‐(2‐methoxyethoxy)ethyl methacrylate) brushes

Well‐defined, high‐density poly(2‐(2‐methoxyethoxy)ethyl methacrylate) [poly(MEO₂MA)] brushes were fabricated through a reliable strategy by the combination of self‐assembly of a monolayer of 3‐aminopropyltrimethoxy silane on silicon surface to immobilize 4‐cyano‐4‐(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid chain transfer agent and reversible addition‐fragmentation chain transfer‐mediated polymerization of MEO₂MA. The whole fabrication process of the poly(MEO₂MA) brushes was followed by water contact angle, grazing angle‐Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and atomic force microscopy. Characterization of the poly(MEO₂MA) brushes, such as molecular weight and thickness determination, were measured by gel permeation chromatography and ellipsometry, and the grafting density was estimated. The temperature‐responsive property of the poly(MEO₂MA) brushes was further investigated and the result verified the brush‐to‐mushroom phase transition of the poly(MEO₂MA) chains from low to high temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Stable P-N bridged cyclophosphazenes with a spiro or ansa arrangement

Deprotonation reactions of cyclophosphazenes containing secondary amino groups in the side chain lead to a doubly bridged tricyclophosphazene structure or to a cyclophosphazene-cyclophosphazane-cyclophosphazene compound, which are very stable and could be used as building blocks for larger structures.     

Design,synthesis and biological evaluation of novel N1,N8-bis(((4-((5-aryl-1,3,4-oxadiazol-2-yl)methoxy)phenyl)amino)oxy)-1-naphthamide derivatives

A new series of 1,8-bis(4-((5-phenyl-1,3,4-oxadiazol-2-yl) methoxy)-substituted aryl) naphthalene-1,8-dicarboxamide derivatives (6a–j) were synthesized in the presence of POCl₃ and obtained good yields. All the synthesized novel compounds were characterized by IR, ¹H NMR, ¹³C NMR, HRMS spectroscopic data and elemental analysis. All the synthesized compounds evaluated for their antibacterial and antifungal activities. The antibacterial activity screened against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli and used standard reference drug ciprofloxacin. The antifungal activity screened against two pathogenic fungal strains Aspergillus niger and Candida albicans used a reference standard drug Voriconazole. All these compounds (6a–j) demonstrate good antibacterial and antifungal activity. Among them, compounds 6h and 6c show highest antibacterial and antifungal activity.     

Spectral Characterization and Antimicrobial Activity of Some Schiff Bases Derived from 4‐Methyl‐2‐aminophenol

A series of N‐(5‐methyl‐2‐hydroxyphenyl)‐(2/3/4/5‐substituted)‐benzaldimines ( I – XIII ) were synthesized using appropriate synthetic route. Their structures were characterized by FT‐IR, UV‐Visible, ESI‐MS, ¹H‐ and ¹³C‐NMR spectroscopic techniques and analytical methods. The crystal structure of N‐(5‐methyl‐2‐hydroxyphenyl)‐3,4‐dimethoxybenzaldimine ( XIII ) was determined by X‐ray diffraction at room temperature. Relationship between the melting points and the structures of the compounds were examined. Antibacterial activities of the compounds were evaluated against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Proteus mirabilis. Antifungal activities were reported for Candida albicans. Some of the Schiff bases showed considerable antimicrobial activity against S. aureus and C. albicans.     

RAFT‐mediated synthesis of poly[(oligoethylene glycol) methyl ether acrylate] brushes for biological functions

The synthesis of poly[(oligoethylene glycol) methyl ether acrylate] [poly(OEGA)] brushes was achieved via reversible addition‐fragmentation chain transfer (RAFT) polymerization and used to selectively immobilize streptavidin proteins. Initially, gold surfaces were modified with a trithiocarbonate‐based RAFT chain transfer agent (CTA) by using an ester reaction involving a gold substrate modified with 11‐mercapto‐1‐undecanol and bis(2‐butyric acid)trithiocarbonate. poly(OEGA) brushes were then prepared via RAFT‐mediated polymerization from the surface‐immobilized CTA. The immobilization of CTA on the gold surface and the subsequent polymer formation were followed by ellipsometry, X‐ray photoelectron spectroscopy, grazing angle‐Fourier transform infrared spectroscopy, atomic force microscopy, and water contact‐angle measurements. RAFT‐mediated polymerization method gave CTA groups to grafted poly(OEGA) termini, which can be converted to various biofunctional groups. The terminal carboxylic acid groups of poly(OEGA) chains were functionalized with amine‐functionalized biotin units to provide selective attachment points for streptavidin proteins. Fluorescence microscopy measurements confirmed the successful immobilization of streptavidin molecules on the polymer brushes. It is demonstrated that this fabrication method may be successfully applied for specific protein recognition and immobilization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Tracing pore-space heterogeneities in X-type zeolites by diffusion studies

Pore-space homogeneity of zeolite NaX was probed by pulsed field gradient (PFG) NMR diffusion studies with n-butane as a guest molecule. At a loading of 0.75 molecules per supercage, a wide spectrum of diffusivities was observed. Guest molecules in the (well-shaped) zeolite crystallites were thus found to experience pore spaces of quite different properties. After loading enhancement to 3 molecules per supercage, however, molecular propagation ideally followed the laws of normal diffusion in homogeneous media. At sufficiently high guest concentrations, sample heterogeneity was thus found to be of no perceptible influence on the guest mobilities anymore.     

Characterisation of temperature-dependent phase transitions in 2,2-trimethylenedioxy- 4,4,6,6-tetrachlorocyclotriphosphazene, N3P3Cl4[O(CH2)3O]

Background  

The crystal structure of 2,2-trimethylenedioxy-4,4,6,6-tetrachlorocyclo triphosphazene has been determined at 120, 274 and 293 K. The result at 293 K confirms the room temperature Cmc2 ₁ structure, but at the lower temperatures the space group is Pna2 ₁. Nevertheless the basic structure remains the same, with only small displacements of the atoms, amounting to an average of 25 pm between 120 and 293 K.     

On homotopically equivalent relations for fiber bundles

In this paper, we prove the homotopically equivalent relation to the polyhedron property that play an important role in fiber bundle theory over the suspensions of polyhedron space.     

Symmetry reductions,exact solutions and conservation laws of a new coupled KdV system

Lie symmetry analysis is performed on a new coupled KdV system, which arises in the analysis of various problems in theoretical physics and many scientific applications. The similarity reductions and new exact solutions are obtained. The solutions obtained include the solitary waves, cnoidal and snoidal waves. In addition, we derive the conservation laws of the coupled KdV system.