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Hydrophobic Block (hydrophobic + block)

Distribution by Scientific Domains

Polymers and Materials Science	83%

Selected Abstracts

Biofunctionalized block copolymer nanoparticles based on ring-opening metathesis polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006
Alvaro Carrillo
Abstract We present an approach to the synthesis of biofunctionalized block copolymer nanoparticles based on ring-opening metathesis polymerization; these nanoparticles may serve as novel scaffolds for the multivalent display of ligands. The nanoparticles are formed by the self-assembly of diblock copolymers composed of a hydrophobic block and a hydrophilic activated block that can be functionalized with thiolated ligands in aqueous media. The activated block enables control over the orientation of the displayed ligands, which may be sugars, peptides, or proteins engineered to contain cysteine residues at suitable locations. The nanoparticle diameter can be varied over a wide range through changes in the composition of the block copolymer, and biofunctionalization of the nanoparticles has been demonstrated by the attachment of a peptide previously shown to inhibit the assembly of anthrax toxin. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 928,939, 2006 [source]

Surfactant characteristics of polystyrene/poly(ethylene oxide) macromonomers in aqueous solution and on polystyrene latex particles: Two-step emulsion polymerizations

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2001
Sebastien Gibanel
Abstract Macromonomers were synthesized by anionic "living" polymerization. They comprised a poly(ethylene oxide) hydrophilic block and a hydrophobic block or sequence terminated with an unsaturation. The surface activity properties of these materials (critical micelle concentration and parking area) were determined, and the values were compared and discussed in terms of the molecular structure of these new surfactants. Some of the macromonomers were employed as emulsifiers in two-step emulsion polymerizations. The data obtained were discussed while taking into account the different chemical structures of the macromonomers and the efficiency of these species as emulsifiers in the polymerization recipes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2767,2776, 2001 [source]

Amphiphilic Block Copolymers Bearing Ortho Ester Side-Chains: pH-Dependent Hydrolysis and Self-Assembly in Water

MACROMOLECULAR BIOSCIENCE, Issue 2 2010
Rupei Tang
Abstract A new type of pH-responsive block copolymer nanoparticle has been synthesized and characterized. The amphiphilic diblock copolymer, PEG- b -PMYM, contains acid-labile ortho ester side-chains in the hydrophobic block and can self-assemble into micelle-like nanoparticles in water at neutral pH. Hydrolysis of the ortho ester side-chains follows a distinct exocyclic mechanism and shows pH-dependent kinetics, which triggers changes in nanoparticle size and morphology. The nanoparticles have been found to be non-toxic to cells in vitro. The ability to tune the size and morphology of biocompatible block copolymer nanoparticles by controlling the pH-sensitive side-chain hydrolysis represents a unique approach that may be exploited to improve the efficacy of nanometer-scale drug delivery. [source]

Novel Amphiphilic Styrene-Based Block Copolymers for Induced Surface Reconstruction

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2008
Lutz Funk
Abstract This paper describes the synthesis of amphiphilic block copolymers by living radical polymerization (NMP) of new styrene-like monomers. The polar monomers (ethylene oxide side chains and free hydroxyl- or amino-groups after deprotection) were polymerized in a "protected form" to adjust the solubility of the monomers. In this way high molar mass polymers with a narrow polydispersity (around or below 1.2) were accessible. In the bulk state hydrophobic and hydrophilic domains demix. By exposing thin films of these polymers to vacuum (air) or alternatively to water or a hydrophilic surface it becomes possible to switch the surface polarity reversibly between contact angles of about 105° and 83° as a result of surface reconstruction. Through side chains of different length and with different functionalities, it was possible to adjust the glass transition temperatures to values between ,2,°C to 140,°C for the hydrophilic blocks and ,30,°C to 100,°C for the hydrophobic block. The wide range of the glass temperatures allowed it to find a block copolymer system with a slow kinetic concerning the surface reconstruction process, so that a mechanistic examination of the process by AFM was possible. It got, thereby, possible to detect the break-up of the hydrophobic surface lamella and the upfold of the hydrophilic lamella in contact with water. [source]

Synthesis and Self-Assembly of Novel Amphiphilic Six-Armed Star Copolymers TP[PDMAEMA -b- PSt]6

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2009
Kang Tao
Abstract A triphenylene (TP)-based hexafunctional initiator was prepared and used in successive ATRP of DMAEMA and St. Well-defined six-armed star block copolymers TP[PDMAEMA -b- PSt]6 bearing hydrophilic backbones inside and hydrophobic blocks outside were successfully synthesized. The self-assembly behaviors of the novel amphiphilic copolymer were further investigated. Co-existing spherical and bowl-shaped aggregates were observed from their neutral aqueous solution, while large spherical structures with different dimensions were obtained from their diluted HCl and CF3COOH aqueous solution, respectively. Dynamic light scattering in different aqueous solutions were conducted to give further confirmation. The possible mechanism of the morphology formation was proposed. [source]

A New Method for the Study of Processes at the Liquid,Liquid Interface Using an Array of Microdroplets on a Au Electrode

CHEMPHYSCHEM, Issue 12 2006
Andrew O. Simm Dr.
Abstract We report the fabrication of partially blocked gold electrodes, with regularly and hexagonally spaced inert hydrophobic blocks on their surface. The hydrophobic blocks, with diameters of 5 ,m, are used to support liquid 5-nonyl-salicylaldoxime (Acorga-P50) droplets on the surface. By voltametrically monitoring the transport-controlled reduction rate of CuII (in pH 5 solution) at the unblocked part of the gold surface it is possible to deduce, via simulation, the parameters controlling the rate of uptake of CuII at the droplet,aqueous solution interface as the droplet "fills up" with CuII. Experimentally, it is recorded that the reduction current increases until the droplet is filled completely; after this, there is no further noticeable effect of the droplet coating. A rigorous theoretical analysis of the transients permits the deduction of partition coefficients between the aqueous solution and the organic-droplet phase and of diffusion coefficients within the droplet. The partition coefficient for CuII between water and 5-nonyl-salicylaldoxime was found to be 200 at 25,°C and the diffusion coefficient of CuII inside the organic phase was determined to be 5×10,11 cm2,s,1. [source]