Keywords: Fragmentation Chain-Transfer ; Self-Assembled Monolayers ; Walled Carbon Nanotubes ; Well-Defined Polymer ; Nitroxide-Mediated Polymerization ; Block-Copolymer Brushes ; Poly(Methyl Methacrylate) Brushes ; Transfer Raft Polymerization ; Quartz-Crystal Microbalance ; Poly(Acrylic Acid) Brushes Reference EPFL-REVIEW-148464doi:10.1021/cr900045aView record in Web of Science Record created on 2010-04-23, modified on 2017-05-10

Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications

The layer-by-layer (LbL) adsorption technique offers an easy and inexpensive process for multilayer formation and allows a variety of materials to be incorporated within the film structures. Therefore, the LbL assembly method can be regarded as a versatile bottom-up nanofabrication technique. Research fields concerned with LbL assembly have developed rapidly but some important physicochemical aspects remain uninvestigated. In this review, we will introduce several examples from physicochemical investigations regarding the basics of this method to advanced research aimed at practical applications. These are selected mostly from recent reports and should stimulate many physical chemists and chemical physicists in the further development of LbL assembly. In order to further understand the mechanism of the LbL assembly process, theoretical work, including thermodynamics calculations, has been conducted. Additionally, the use of molecular dynamics simulation has been proposed. Recently, many kinds of physicochemical molecular interactions, including hydrogen bonding, charge transfer interactions, and stereo-complex formation, have been used. The combination of the LbL method with other fabrication techniques such as spin-coating, spraying, and photolithography has also been extensively researched. These improvements have enabled preparation of LbL films composed of various materials contained in well-designed nanostructures. The resulting structures can be used to investigate basic physicochemical phenomena where relative distances between interacting groups is of great importance. Similarly, LbL structures prepared by such advanced techniques are used widely for development of functional systems for physical applications from photovoltaic devices and field effect transistors to biochemical applications including nano-sized reactors and drug delivery systems.

Layer-by-Layer Assembly as a Versatile Bottom-Up Nanofabrication Technique for Exploratory Research and Realistic Application

Templated Techniques for the Synthesis and Assembly of Plasmonic Nanostructures

Porous anodic aluminum oxide: anodization and templated synthesis of functional nanostructures.

We have evaluated the catalytic properties of Au-based nanostructures (including nanocages, nanoboxes, and solid nanoparticles) using a model reaction based on the reduction of p-nitrophenol by NaBH4. From the average reaction rate constants at three different temperatures, we determined the activation energy, the entropy of activation, and the pre-exponential factor for each type of Au nanostructure. The kinetic data indicate that the Au-based nanocages are catalytically more active than both the nanoboxes and nanoparticles probably due to their extremely thin but electrically continuous walls, the high content of Au, and the accessibility of both inner and outer surfaces through the pores in the walls. In addition, a compensation effect was observed in this Au-based catalytic system, which can be primarily interpreted by a model based on kinetic regime switching.

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A comparison study of the catalytic properties of Au-based nanocages, nanoboxes, and nanoparticles.

Layer-by-layer adsorption of polyelectrolytes and gold nanoparticles within porous supports provides a convenient method for forming catalytic membranes. The polyelectrolyte film effectively immobilizes the gold nanoparticles without inhibiting access to catalytic sites, as shown by the similar rate constants for nanoparticle-catalyzed 4-nitrophenol reduction in solution and in membranes. Modified alumina membranes reduce >99% of 0.4 mM 4-nitrophenol at linear flow rates of 0.98 cm/s, and the modification process is also applicable to track-etched polycarbonate supports.

Catalytic membranes prepared using layer-by-layer adsorption of polyelectrolyte/metal nanoparticle films in porous supports.

Polymeric coatings with high protein-binding capacities are important for increasing the output of affinity-based protein purification and decreasing the detection limits of antibody microarrays. This report describes the use of thick poly(acrylic acid) (PAA) brushes to immobilize as much as 80 monolayers of protein. The brushes were prepared using a recently developed procedure that allows polymerization of 100-nm-thick poly(tert-butyl acrylate) films from a surface in just 5 min along with hydrolysis of these films to PAA in 15 min. Covalent binding of bovine serum albumin (BSA) to PAA brushes that were activated using standard coupling agents, however, resulted in immobilization of less than two monolayers of BSA because of competitive hydrolysis of the esters in the activated film. In contrast, derivatization of PAA with nitrilotriacetate (NTA)−Cu2+ complexes yielded films capable of binding many monolayers of protein via metal-ion affinity interactions. For example, derivatization of 55-nm-thick PAA ...

High-capacity binding of proteins by poly(acrylic acid) brushes and their derivatives.

The use of atom transfer radical polymerization to grow poly(2-hydroxyethyl methacrylate) (PHEMA) brushes in porous alumina followed by functionalization of the PHEMA with nitrilotriacetate−Cu2+ complexes yields membranes that adsorb proteins via coordination of Cu2+ to histidine residues. Adsorption isotherms show that these membranes have binding capacities as high as 0.9 mg of bovine serum albumin (BSA)/cm2 of external membrane surface area (150 mg/cm3 of membrane), and breakthrough curves indicate that saturation of the membranes with BSA or myoglobin occurs in less than 15 min. The efficiency of protein elution with ethylenediaminetetraacetic acid (EDTA) solutions is essentially 100%, and the membranes show no detectable decrease in capacity over nine cycles of binding, elution, and regeneration with Cu2+. The unusually high capacity of these membranes for rapid protein binding makes them attractive for applications such as purification of His-tag proteins.

High-Capacity, Protein-Binding Membranes Based on Polymer Brushes Grown in Porous Substrates

High-capacity purification of His-tagged proteins by affinity membranes containing functionalized polymer brushes.

Atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate from initiators immobilized on porous supports yields high-flux pervaporation membranes that can be readily modified to co...

Lei Sun

Papers

Catalytic membranes prepared using layer-by-layer adsorption of polyelectrolyte/metal nanoparticle films in porous supports.

High-capacity binding of proteins by poly(acrylic acid) brushes and their derivatives.

High-Capacity, Protein-Binding Membranes Based on Polymer Brushes Grown in Porous Substrates

High-capacity purification of His-tagged proteins by affinity membranes containing functionalized polymer brushes.

Polymer Brush Membranes for Pervaporation of Organic Solvents from Water