A highly ordered metal nanohole array (platinum and gold) was fabricated by a two-step replication of the honeycomb structure of anodic porous alumina. Preparation of the negative porous structure of porous alumina followed by the formation of the positive structure with metal resulted in a honeycomb metallic structure. The metal hole array of the film has a uniform, closely packed honeycomb structure approximately 70 nanometers in diameter and from 1 to 3 micrometers thick. Because of its textured surface, the metal hole array of gold showed a notable color change compared with bulk gold.

https://science.sciencemag.org/content/sci/268/5216/1466.full.pdf

Ordered Metal Nanohole Arrays Made by a Two-Step Replication of Honeycomb Structures of Anodic Alumina

About Supramolecular Assemblies of π-Conjugated Systems

A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Nanotechnology is being used to enhance conventional ceramic and polymeric water treatment membrane materials through various avenues. Among the numerous concepts proposed, the most promising to date include zeolitic and catalytic nanoparticle coated ceramic membranes, hybrid inorganic–organic nanocomposite membranes, and bio-inspired membranes such as hybrid protein–polymer biomimetic membranes, aligned nanotube membranes, and isoporous block copolymer membranes. A semi-quantitative ranking system was proposed considering projected performance enhancement (over state-of-the-art analogs) and state of commercial readiness. Performance enhancement was based on water permeability, solute selectivity, and operational robustness, while commercial readiness was based on known or anticipated material costs, scalability (for large scale water treatment applications), and compatibility with existing manufacturing infrastructure. Overall, bio-inspired membranes are farthest from commercial reality, but offer the most promise for performance enhancements; however, nanocomposite membranes offering significant performance enhancements are already commercially available. Zeolitic and catalytic membranes appear reasonably far from commercial reality and offer small to moderate performance enhancements. The ranking of each membrane nanotechnology is discussed along with the key commercialization hurdles for each membrane nanotechnology.

/pdf/a-review-of-water-treatment-membrane-nanotechnologies-1np07if946.pdf

A review of water treatment membrane nanotechnologies

Dingcai Wu,*,† Fei Xu,† Bin Sun,† Ruowen Fu,† Hongkun He,‡ and Krzysztof Matyjaszewski*,‡ †Materials Science Institute, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China ‡Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States

Design and Preparation of Porous Polymers

AN important challenge in the preparation of porous polymer membranes for technological applications is to control both the size distribution and the relative positions of the pores. We have found a way to generate polymer films with an essentially monodisperse pore size, in which the pores are organized spontaneously into periodic hexagonal arrays. The films, which are 10–30 um thick, are produced by evaporating solutions of star-shaped polystyrene or polystyrene-polyparaphenylene block copolymers in carbon di-sulphide under a flow of moist gas. Empty spherical cells, about 0.2–10 µm in diameter, appear spontaneously in a hexagonal array, and the cells are open at the film surface. The use of star polymers, or of polymeric micelles, seems to be essential for obtaining this morphology. These membranes might find application in controlled release of drugs or other bioactive species, or as materials with useful optical properties, moulds or scaffolding for forming ordered microstructures, and model substrates for surface science.

Self-organized honeycomb morphology of star-polymer polystyrene films

Light-emitting diodes (LED5) based on organic semiconductors have received much attention recently due to their promise as cheap, novel light sources for electro-optical applications. Unlike conventional diodes, light emission from these organic LEDs is achieved by double injection of electrons from a low-work-function electrode and holes from a high-work-function electrode into the organic polymer light-emitting layer. By appropriately engineering the polymer backbone, emission of various visible colors has been demonstrated. Our work in this field has concentrated on organic block copolymers as the active light-emitting materials. We demonstrate that the use of copolymer systems leads to large enhancement of device performance.

Light-emitting diodes based on copolymer organic semiconductors

Blue Light-Emission from a Nanostructured Organic Polymer Semiconductor

Les copolymeres sequences polystyrene-polyparaphenylene (PS-PPP) sont solubles dans les solvants du PS. Leur caracterisation par Chromatographie de Permeation sur Gel (CPG) demontre qu’ils sont agreges en solution. Nous presentons ici une etude de ces agregats par diffusion de la lumiere et par diffusion des neutrons. La diffusion de la lumiere montre que ces copolymeres ont un caractere amphiphile lorsque la composition en PPP est suffisamment faible. L’etude par diffusion des neutrons montre que le nombre d’agregation et la compacite de la structure du coeur dependent de la composition des copolymeres et de la longueur de conjugaison. Le coeur des agregats est en moyenne faiblement anisotrope.

Étude de l’agrégation des copolymères séquences polystyrène-polyparaphénylène par diffusion de la lumière et des neutrons

Summary form only given. The n-doping effect on the aggregation of polystyrene-potyparaphenylene (PS-PPP) block copolymers has been investigated through small-angle neutron scattering. A copolymer with a deuteriated PS sequence was synthesized and a 4% by weight solution in deuteriated tetrahydrofuran (d/sub 8/THF) was doped with potassium (K). K-doping was then performed in an aggregated structure and we were mainly interested in its influence on the PPP partial structure factor (the d/sub 8/THF scattering length density is close to that of PSd/sub 8/). Neutron scattering experiments show that both the size and relative arrangement of the PPP cores of PS-PPP aggregates are modified by K-doping. The size of PPP cores increases with the doping rate and an 80% change in volume is reached for the maximum rate. The packing of PPP chains inside cores of aggregates is therefore less compact with a coinsertion of solvent molecules. This is presumably related to a decrease in cristallinity. On the other hand, an increase of attractive interactions between aggregates is achieved by K-doping. Indeed, further associations were observed when PS-PPP aggregates were doped. Such a weak floculation effect corresponds to an increase in the polarizability due to an extended /spl pi/ electron delocalization, as observed by visible absorption spectroscopy. Doped PS-PPP aggregates have therefore a higher Hamaker constant, without localized charge. Finally, K-doped PS-PPP copolymers allow the production of fine conducting PPP dispersions in an insulating PS matrix.

G. Widawski

Papers

Self-organized honeycomb morphology of star-polymer polystyrene films

Light-emitting diodes based on copolymer organic semiconductors

Blue Light-Emission from a Nanostructured Organic Polymer Semiconductor

Étude de l’agrégation des copolymères séquences polystyrène-polyparaphénylène par diffusion de la lumière et des neutrons

Aggregation of n-doped polystyrene-polyparaphenylene block-copolymers : a neutron scattering study