Search results for "Colloid"
showing 10 items of 1288 documents
Inside Front Cover: Redox-Tunable Defects in Colloidal Photonic Crystals (Adv. Mater. 20/2005)
2005
The inside front cover illustrates reversible tuning of an intragap transmitting state induced by redox cycling, accomplished using a redox-active polyferrocenylsilane polyelectrolyte multilayer planar defect embedded in a colloidal photonic crystal (CPC) synthesized by a bottom–up method combining colloidal self-assembly and microcontact printing. In work reported on p. 2455 by Manners, Ozin, and co-workers, the wavelength position of the defect state can be changed by changing the oxidation state of the ferrocene moieties in the polymer backbone. This could find applications in electrochemically tunable microcavities, and—if light emitters are incorporated—electrochemically tunable CPC-ba…
Towards completely miscible PMMA nanocomposites reinforced by shear-stiff, nano-mica
2014
Abstract Optimizing the reinforcement of polymers with nanoplatelets requires optimization of the aspect ratio and the moduli of the filler while providing a complete stress transfer. Employing a novel shear-stiff, nano-mica with large aspect ratio, we focus on maximizing the interfacial interaction between filler and matrix. External surfaces of the nano-mica were selectively modified by a polycationic macro-initiator and two PMMA-polymer brushes of length below and above critical entanglement length, respectively, and the mechanical properties of the three PMMA nanocomposites were measured. The multiple electrostatic anchoring groups of the macro-initiator not only provide reliable adhesi…
Ultrastrong composites from dopamine modified-polymer-infiltrated colloidal crystals
2015
Although strong and stiff synthetic composites have long been developed, the microstructure of today's most advanced composites has yet to achieve the sophisticated hierarchy of hybrid materials built up by living organisms. We have assembled hard and tough multilayered nanocomposites, which contain alternating layers of Fe3O4 nanoparticles and a 3-hydroxy-tyramine (dopamine) substituted polymer (dopamine modified polymer), strongly cemented together by chelation through infiltration of the polymer into the Fe3O4 mesocrystal. With a Young's modulus of 17 ± 3 GPa and a hardness of 1.3 ± 0.4 GPa the nanocomposite exhibits high resistance against elastic as well as plastic deformation. Key fea…
Polymer brushes under flow and in other out-of-equilibrium conditions
2011
Polymer brushes are formed from flexible linear macromolecules tethered at one chain end to a solid substrate, forming a dense polymeric layer of polymer chains which are more or less stretched in the direction perpendicular to the substrate surface. These systems find interest also due to numerous applications (colloid stabilization, improvement of lubrication properties when the surfaces are exposed to shear, protection of the surface against adsorption of nanoparticles or proteins, etc.), for which often the dynamic non-equilibrium response of these brushes to external perturbation is important. The present review summarizes recent computer simulation studies pertinent to these questions…
Functional Opals from Reactive Polymers: Complex Structures, Sensors, and Modified Photoluminescence
2007
This paper describes the synthesis and properties of functional opal structures, so-called colloidal photonic crystals (CPCs), from a variety of reactive polymers. Photoprocessable opals are presented as well as opals with incorporated smart defect layers that can be actively addressed by external stimuli. In addition, opals with functional bio-macromolecular defects have been developed. They present a new class of materials for optical biomonitoring through shifts of the induced photonic defect mode. Strong modification of photoluminescence according to the photonic bandstructure is observed from opals with embedded exclusively luminescent defect layer.
Simulations of Polymers in Confined Geometries
1991
The properties of flexible polymers moving inside porous structures are believed to be relevant to practical problems such as filtration, gel permeation chromatography, heterogeneous catalysis, oil recuperation, etc.1. Similarly the adsorption of macromolecules on interfaces plays an important role for problems such as adhesion, flocculation and stabilisation of colloid particles, biological membrane function, artificial organs in medicine, etc. 2. Aside from this eventual practical application, the configurational statistics of polymers in such confined geometries is a challenging problem of theoretical physics. The present brief review will be concerned with the study of a single long fle…
Polymerization of mono- and multilayer forming diacetylenes
1977
Heptadeca-2,4-diine-1-ol and Heptadeca-2,4-diine-1-acid were synthesized and their polymerization behaviour in the solid state was investigated. Both compounds polymerize thermally below the melting point and photochemically under the action of uv-light to form polymers via 1,4-addition to the conjugated triple bonds with a backbone of conjugated double-and triple-bonds. The photoresponse spectra resemble the absorption spectra exhibiting maxima of photoreactivity in the absorption band of the conjugated triple bonds of the monomers.
Polymeric amphiphiles with hydrophilic main chain spacers: Studies in monolayers and Langmuir-Blodgett multilayers
1988
A methacrylic lipid was polymerized to form an amphiphilic homopolymer and random copolymers with various levels of acrylic acid comonomers. The behavior of these polymeric lipids was investigated in monolayers at the air-water interface and in Langmuir-Blodgett multilayers on polymer foil supports. The acrylic acid acts as a hydrophilic spacer along the polymer backbone, and improves the ability of the polymer to self-organize into highly ordered monolayers and ultimately LB multilayers. It is shown that the quality and stability of the multilayers increase substantially with the increase in comonomer content.
Diffusion of spherical micronetworks in polymer diluent systems and melts studied by dynamic light scattering techniques
1994
Spherical polystyrene (PS) micronetworks can be prepared in microemulsion with bulk radii of 5–60 nm and different cross-linking densities. The diffusion of these PS spheres has been studied in polymer diluent systems ranging from dilute solutions to plasticized melts by using forced Rayleigh scattering and photon correlation spectroscopy. On increasing the PS concentration, a colloid glass transition is observed at a volume fraction ΦC ≈ 0.64 of the swollen spheres. At higher concentration inside the “colloid glass” state the sphere diffusion is slowed down and becomes very complex but can be observed up to the limit of a melt of collapsed spheres.
Artificial Opals as Effect Pigments in Clear-Coatings
2004
In this paper, we describe the use of artificial opals from polymer beads as effect pigments in transparent industial and automotive coatings. For this purpose, we synthesized monodisperse colloids from fluorinated methacrylates by surfactant-free emulsion polymerization. The fluorinated monomers, in combination with crosslinking, lead to a refractive index contrast, thermal stability, and solvent resistivity necessary for use as effect pigments. After crystallization of the monodisperse polymer beads, crystal flakes with iridescent colors can be obtained. The crystal flakes can act as effect pigments in various transpartent industrial and automotive coatings. due to photonic crystal behavi…