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Mixed Polymer Brushes (mixed + polymer_brush)
Selected AbstractsSynthetic Hydrophilic Materials with Tunable Strength and a Range of Hydrophobic Interactions,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Olha Hoy Abstract The ability to vary, adjust, and control hydrophobic interactions is crucial in manipulating interactions between biological objects and the surface of synthetic materials in aqueous environment. To this end a grafted polymer layer (multi-component mixed polymer brush) is synthesized that is capable of reversibly exposing nanometer-sized hydrophobic fragments at its hydrophilic surface and of tuning, turning on, and turning off the hydrophobic interactions. The reversible switching occurs in response to changes in the environment and alters the strength and range of attractive interactions between the layer and hydrophobic or amphiphilic probes in water. The grafted layer retains its overall hydrophilicity, while local hydrophobic forces enable the grafted layer to sense and attract the hydrophobic domains of protein molecules dissolved in the aqueous environment. The hydrophobic interactions between the material and a hydrophobic probe are investigated using atomic force microscopy measurements and a long-range attractive and contact-adhesive interaction between the material and the probe is observed, which is controlled by environmental conditions. Switching of the layer exterior is also confirmed via protein adsorption measurements. [source] Synthesis of PS and PDMAEMA mixed polymer brushes on the surface of layered silicate and their application in pickering suspension polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Yongfang Yang Abstract An ammonium free radical initiator was ion exchanged onto the surface of clay layers. Polystyrene (PS) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) mixed polymer brushes on the surface of clay layers were prepared by in situ free radical polymerization. PS colloid particles armored by clay layers with mixed polymer brushes were prepared by Pickering suspension polymerization. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the colloid particles. Clay layers on the surface of PS colloid particles can be observed. Because of the cationic nature of the PDMAEMA brushes the colloid particles have positive zeta potentials at low pH values. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface of the colloid particles. N1s binding energy of PDMAEMA chains on the surface of clay layers was detected by XPS. The two peaks of the N1s binding energy indicate two different nitrogen environments on the surface of clay layers. The peak with a lower binding energy is characteristic of neutral nitrogen on PDMAEMA chains, and the peak with a higher binding energy is attributed to protonated nitrogen on PDMAEMA chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5759,5769, 2007 [source] PS/PMMA mixed polymer brushes on the surface of clay layers: Preparation and application in polymer blendsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007Jian Zhang Abstract Polystyrene (PS) and poly(methyl methacrylate) (PMMA) mixed polymer brushes on the surface of clay layers were prepared by using in situ free radical polymerization. Free radical initiator molecules with two quaternary ammonium groups at both ends were intercalated into the interlayer spacing of clay layers. The amount of polymer brushes grafted on the surface of clay layers can be controlled by controlling the polymerization time. Thermogravimetric analysis, X-ray diffraction, and high-resolution transmission electron microscope results indicated successful preparation of the mixed polymer brushes on the surface of clay layers. The kinetics of the grafting of the monomers was also studied. The mixed polymer brushes on the surface of clay layers were used as compatibilizers in blends of PS and PMMA. In the blends, the intercalated clay particles tend to locate at the interface of two phases reducing the interfacial tension. In the meanwhile, PMMA homopolymer chains tend to intercalate into clay layers. The driving force for the intercalation is the compatibility between homo-PMMA chains and PMMA brushes on the surface of clay layers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5329,5338, 2007 [source] In-situ IR synchrotron mapping ellipsometry on stimuli-responsive PAA-b-PS/PEG mixed polymer brushesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010Dennis Aulich Abstract A binary polymer brush consisting of weak polyelectrolytes was investigated with infrared synchrotron mapping ellipsometry in-situ under the influence of different aqueous solutions. Thickness of the brush layer in dry state was ,15 nm. The brush, consisting of poly(ethylene glycol) and poly(acrylic acid)-b-poly(styrene) in a 50/50 composition was switched between two different states by changing the pH of the solution. An IR mapping ellipsometer at the IRIS beamline located at the BESSY II synchrotron facility in Berlin, Germany, was used for high lateral resolution in-situ measurements. The results show strong chemical changes in the brush layer due to COOH , COO, conversion of the PAA's carboxylic groups. Measurements with spot sizes of ,1 mm on different positions on the samples proved good homogeneity of the brush layer and the qualification of this method for investigation of ultrathin organic films in aqueous solutions in-situ with IR ellipsometry. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||