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

A superhydrophobic surface is a surface with a water contact angle close to or higher than 150°. In this feature article, we review the historical and present research on superhydrophobic surfaces, including the characterization of superhydrophobicity, different ways to fabricate rough surfaces, and low-surface-energy modifications on inorganic and organic rough surfaces. It is the combination of surface roughness and low-surface-energy modification that leads to superhydrophobicity. Notably, research on superhydrophobic surfaces has not only fundamental interest but various possible functional applications in micro- and nano-materials and devices.

Superhydrophobic surfaces: from structural control to functional application

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

Research into extreme water-repellent surfaces began many decades ago, although it was only relatively recently that the term superhydrophobicity appeared in literature Here we review the work on the preparation of superhydrophobic surfaces, with focus on the different techniques used and how they have developed over the years, with particular focus on the last two years We discuss the origins of water-repellent surfaces, examining how size and shape of surface features are used to control surface characteristics, in particular how techniques have progressed to form multi-scaled roughness to mimic the lotus leaf effect There are notable differences in the terminology used to describe the varying properties of water-repellent surfaces, so we suggest some key definitions

Progess in superhydrophobic surface development.

Inorganic colloidal nanoparticles are very small, nanoscale objects with inorganic cores that are dispersed in a solvent. Depending on the material they consist of, nanoparticles can possess a number of different properties such as high electron density and strong optical absorption (e.g. metal particles, in particular Au), photoluminescence in the form of fluorescence (semiconductor quantum dots, e.g. CdSe or CdTe) or phosphorescence (doped oxide materials, e.g. Y(2)O(3)), or magnetic moment (e.g. iron oxide or cobalt nanoparticles). Prerequisite for every possible application is the proper surface functionalization of such nanoparticles, which determines their interaction with the environment. These interactions ultimately affect the colloidal stability of the particles, and may yield to a controlled assembly or to the delivery of nanoparticles to a target, e.g. by appropriate functional molecules on the particle surface. This work aims to review different strategies of surface modification and functionalization of inorganic colloidal nanoparticles with a special focus on the material systems gold and semiconductor nanoparticles, such as CdSe/ZnS. However, the discussed strategies are often of general nature and apply in the same way to nanoparticles of other materials.

https://faculty.washington.edu/mzhang/mse599/Surface-modification.full.pdf

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

Electrolyte Species Dependent Hydration Forces between Silica Surfaces

Superhydrophobic surfaces, already present in the nature as observed with leaves of plants (lotus) or feathers of some birds, correspond to hydrophobic surface whose water contact angle is higher than 150°. Before running the synthesis of such surface, one must understand the corresponding phenomenon and define the pertinent characteristics. Most of the techniques already developed lead to surfaces with weak physical properties such as optical and mechanical ones. Here, the synthesis in dry medium (plasma) is proposed leading to stable and transparent polymeric superhydrophobic surfaces. Two routes are possible; the first one corresponds to the one-step synthesis (CF 4 plasma modification of low density polyethylene (LDPE)), the second one to the two steps (O 2 plasma treatment followed by CF 4 plasma onto LDPE). The plasma parameters are defined to optimize the degradation and/or the functionalization and the obtained surface structures are characterized. The O 2 plasma allows to create a variable roughness while CF 4 plasma emphasizes this roughness and creates the apolar layer. By the two-step treatments, several plasma parameters were found to elaborate stable transparent superhydrophobic surfaces with a controlled roughness and whose chemical structure is close to a Teflon-like structure. It has been shown that superhydrophobic surface can be obtained even with a low roughness, around 20 nm.

Synthesis of transparent superhydrophobic polyethylene surfaces

Rare earth cerium oxide (ceria) nanoparticles are stabilized using end-functional phosphonated-PEG oligomers. The complexation process and structure of the resulting hybrid core−shell singlet nanocolloids are described, characterized, and modeled using light and neutron scattering data. The adsorption mechanism is nonstoichiometric, yielding the number of adsorbed chains per particle Nads = 270 at saturation. Adsorption isotherms show a high affinity of the phosphonate head for the ceria surface (adsorption energy ΔGads ≈ −16kT) suggesting an electrostatic driving force for the complexation. The ease, efficiency, and integrity of the complexation is highlighted by the formation of nanometric sized cerium oxide particles covered with a well anchored PEG layer, maintaining the characteristics of the original sol. This solvating brushlike layer is sufficient to solubilize the particles and greatly expand the stability range of the original sol (<pH 3) up to pH = 9. We underscore two key attributes of the tai...

/pdf/redispersible-hybrid-nanopowders-cerium-oxide-nanoparticle-1wu3bx2m0e.pdf

Redispersible Hybrid Nanopowders: Cerium Oxide Nanoparticle Complexes with Phosphonated-PEG Oligomers

Engineered nanoparticles made from noble metals, rare-earth oxides or semiconductors are emerging as the central constituents of future nanotech developments. In this review, a survey of the complexing strategies between nanoparticles and oppositely charged polyelectrolytes developed during the last three years and based on electrostatic interactions is presented. These strategies include the one-step synthesis of stable and functionalized nanoparticles, the one- and multilayer coating of individual nano-objects, the controlled clustering of particles and the generation of capsules and thin films with superior functionalities. Among the formulation processes reported, three main classes are identified: the direct mixing route, the desalting transition pathway and the well-known layer by layer method. Finally, some latter developments, trends and applications of electrostatic assemblies in materials science and nanomedicine are highlighted.

Versatile electrostatic assembly of nanoparticles and polyelectrolytes: Coating, clustering and layer-by-layer processes

Monofunctional alkylsilanes, CH3(CH2)n-1Si(CH3)2R with n varying from 4 to 30 and the hydrolyzable group R = Cl or N(CH3)2, were deposited on quartz slides and on nanometric silica. Due to the presence of only one hydrolyzable group for these alkylsilanes, silane monolayers result from the grafting process. Two methods for silanization were considered:  deposition from a solvent (derived from Sagiv's process) and vapor phase deposition (derived from Kovats's process). In vapor phase deposition, the physisorbed water is mainly removed from the surface during the conditioning of the specimens, whereas this is not the case for the solvent method. In addition, the two deposition processes do not take place at the same temperature:  the silane needs to be heated under vacuum for the vapor deposition method, whereas the reaction takes place at room temperature for the solvent method. Characterizations of the grafting efficiency and of the structure of the grafted layers were performed with different techniques ...

Jean-Paul Chapel

Papers

Electrolyte Species Dependent Hydration Forces between Silica Surfaces

Synthesis of transparent superhydrophobic polyethylene surfaces

Redispersible Hybrid Nanopowders: Cerium Oxide Nanoparticle Complexes with Phosphonated-PEG Oligomers

Versatile electrostatic assembly of nanoparticles and polyelectrolytes: Coating, clustering and layer-by-layer processes

Influence of the Deposition Process on the Structure of Grafted Alkylsilane Layers