There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

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Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

Li-ion battery materials: present and future

Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.

Emerging applications of stimuli-responsive polymer materials

The present study was focused on permanent grafting of poly(ethylene glycol) (PEG) layers (brushes) from the melt to adsorbed reactive macromolecules. A poly(glycidyl methacrylate) (PGMA) was used to form the reactive primary adsorbed layer. It was found that a thin (1.5 nm) PGMA layer had a high grafting efficiency, and elevated temperatures considerably accelerated the grafting process. The grafting extent was eventually limited by concentration and accessibility of functional reactive groups in the primary adsorbed layer. Several distinct types of brush morphologies were observed depending on the grafted layer height. Isolated crystals were detected for brushes possessing lower grafting density. At higher levels of PEG attachment, the crystalline formations uniformly covered the entire surface of the substrate. The development of highly extended crystalline formations on the surface and marked expansion of the PEG brushes in water indicated that an extremely high grafting density was attained. The deve...

Synthesis and Surface Morphology of High-Density Poly(ethylene glycol) Grafted Layers

We report on the application of mixed polymer brushes to the reversible in situ switching colloidal systems (suspensions of responsive 200 nm in diameter particles in individual solvents and immiscible liquids). We used mixed copolymer brushes to fabricate responsive nanoparticles and employed the particles to prepare responsive colloidal systems, which demonstrated drastic transformation/switching of material properties upon external stimuli. The interaction between the particles themselves and the particles and their environment can be precisely tuned by a change of solvent and pH. We show that this behavior can be used for a reversible formation of particle aggregates, stabilization and switching between w/o and o/w emulsions, and regulation of the particle transport between immiscible liquids across the interface. We demonstrate an example of the application of the responsive colloids for the fabrication of ultrahydrophobic coatings with textured surfaces from aqueous dispersion, and no surfactant application, using the switching properties of the responsive particles.

Stimuli‐Responsive Colloidal Systems from Mixed Brush‐Coated Nanoparticles

Dense and homogeneous grafted polymer layers were anchored from the melt onto a silicon wafer modified with a macromolecular anchoring layer rich in epoxy functional groups. A monolayer of poly(gly...

Polystyrene Layers Grafted to Macromolecular Anchoring Layer

Macromolecular anchoring layer approach was used for preparation of an effective macroinitiator for the synthesis of grafted polymer layers by atom transfer radical polymerization (ATRP) initiated from the surface. For the initial surface modification, a thin layer of poly(glycidyl methacrylate) (PGMA) was deposited on the surface of a silicon wafer. The ATRP macroinitiator was synthesized on the substrate surface by the reaction between epoxy groups of PGMA and carboxy functionality of bromoacetic acid (BAA). Variation of the time and temperature of the BAA deposition as well as PGMA layer thickness allowed control over the amount of BAA attached to the surface. The PGMA anchoring layer allowed the achievement of initiator surface density significantly higher than that reported for a self-assembled monolayer of ATRP initiators. Polymer brushes were synthesized on the PGMA/BAA-modified substrates by ATRP. Different surface concentrations of BAA were used in our grafting experiments to acquire knowledge ab...

Polymer Grafting via ATRP Initiated from Macroinitiator Synthesized on Surface

Smart surfaces can be described as surfaces that have the ability to respond in a controllable fashion to specific environmental stimuli. A heterogeneous (mixed) polymer brush (HPB) can provide a synthetic route to designing smart polymer surfaces. In this research we study HPB comprised of end-grafted polystyrene (PS) and poly(2-vinyl pyridine) (P2VP). The synthesis of the HPB involves the use of an "intermolecular glue" acting as a binding/anchoring interlayer between the polymer brush and the substrate, a silicon wafer. We compare anchoring layers of epoxysilane (GPS), which forms a self-assembled monolayer with epoxy functionality, to poly(glycidyl methacrylate) (PGMA), which forms a macromolecular monolayer with epoxy functionality. The PS and P2VP were deposited onto the wafers in a sequential fashion to chemically graft PS in a first step and subsequently graft P2VP. Rinsing the HPB in selective solvents and observing the change in water contact angle as a function of the HPB composition studied the switching nature of the HPB. Scanning probe microscopy was used to probe the topography and phase imagery of the HPB. The nature of the anchoring layer significantly affected the wettability and morphology of the mixed brushes.

Igor Luzinov

Papers

Synthesis and Surface Morphology of High-Density Poly(ethylene glycol) Grafted Layers

Stimuli‐Responsive Colloidal Systems from Mixed Brush‐Coated Nanoparticles

Polystyrene Layers Grafted to Macromolecular Anchoring Layer

Polymer Grafting via ATRP Initiated from Macroinitiator Synthesized on Surface

Mixed polymer brushes by sequential polymer addition: anchoring layer effect.