Biomedical subjects

Alexander Sidorenko

Publications and source records attributed to Alexander Sidorenko.

3 recordsLinked to original sources

PubMed2005

Stimuli-responsive mixed grafted polymer films with gradually changing properties: direct determination of chemical composition.

Infrared spectroscopic ellipsometry (IRSE) and visible monochromatic ellipsometry (VISE) approaches were applied to investigate the chemical structure and thickness of ultrathin polymer films. Mixed polystyrene-poly(2-vinylpyridine) and polystyrene-poly(tert-butyl acrylate) polymer grafted films (mixed brushes) with gradually changing composition (1D gradient mixed brush) along the sample were prepared on a temperature gradient stage via two subsequent "grafting to" reactions. The films were characterized by high-precision mapping VISE at a single wavelength (632.8 nm) and IRSE. The set of 1D IRSE spectra of the polymer brush films obtained by mapping the 1D gradient brush were used to estimate the thickness and the local composition of the film and to construct the 1D map of the film in terms of the chemical composition of the brush. The results were compared with the data obtained using monochromatic ellipsometry where the brush composition was estimated from the results of two subsequent measurements followed each grafting step. The measurements of the brush thickness and composition with both methods were found to be in gratifying agreement. The results demonstrate the high potential of IRSE methods for the one-step characterization (by thickness and chemical composition) of ultrathin polymer films of complex composition.

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PubMed2004

Inverse and reversible switching gradient surfaces from mixed polyelectrolyte brushes.

We report on a thin polyelectrolyte film (mixed polyelectrolyte brush) with a gradual change of the composition (ratio between two different oppositely charged surface-grafted weak polyelectrolytes) across the sample. The gradient of surface composition creates a gradient in surface charge density and, consequently, a gradient of the wetting behavior. The gradient film is sensitive to a pH signal and can be reversibly switched via pH change.

Journal Article↗

PubMed2003

Ordered reactive nanomembranes/nanotemplates from thin films of block copolymer supramolecular assembly.

We report on a unique, very simple method of preparation of reactive membranes and nanotemplates with nanoscopic cylindrical channels on the surface of various inorganic and polymeric substrates. Well-ordered nanostructured thin polymer films have been fabricated from the supramolecular assembly of poly(styrene-block-4-vinylpyridine) (PS-PVP) and 2-(4'-hydroxybenzeneazo)benzoic acid (HABA), consisting of cylindrical nanodomains formed by PVP-HABA associates surrounded by PS. Alignment of the domains has been shown to be switched upon exposure to vapors of different solvents from the parallel to perpendicular orientation to the confining surface and vice versa. The alignment of the cylindrical nanodomains is insensitive to the composition of the confining surface due to the self-adaptive behavior of the supramolecular PVP-HABA assembly. Extraction of HABA with selective solvent results in nanomembranes with a hexagonal lattice (24 nm in the period) of hollow channels of 8 nm in the diameter crossing the membrane from the top to the bottom. The walls of the channels are constituted from reactive PVP chains. The channels were filled with Ni clusters via the electrodeposition method to fabricate the ordered array of metallic nanodots of 1.2 tera per cm(2).

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