43 research outputs found
Nanoparticle-regulated phase behavior of ordered block copolymers
This document is the accepted manuscript version of a published article. Published by The Royal Society of Chemistry in the journal "Soft Matter" issue 8, DOI: 10.1039/b805540hAlthough block copolymer motifs have received considerable
attention as supramolecular templates for inorganic nanoparticles,
experimental observations of a nanostructured diblock copolymer
containing inorganic nanoparticles—supported by theoretical trends
predicted from a hybrid self-consistent field/density functional
theory—confirm that nanoparticle size and selectivity can likewise
stabilize the copolymer nanostructure by increasing its order–
disorder transition temperature.Research Council of Norway under the NANOMAT Program
Los Alamos National Laboratory || Contract No. DE-AC52-06NA25396
NSERC of Canada
GEM Fellowship and a NOBCChE Procter and Gamble Fellowship
Band Formation during Gaseous Diffusion in Aerogels
We study experimentally how gaseous HCl and NH_3 diffuse from opposite sides
of and react in silica aerogel rods with porosity of 92 % and average pore size
of about 50 nm. The reaction leads to solid NH_4Cl, which is deposited in thin
sheet-like structures. We present a numerical study of the phenomenon. Due to
the difference in boundary conditions between this system and those usually
studied, we find the sheet-like structures in the aerogel to differ
significantly from older studies. The influence of random nucleation centers
and inhomogeneities in the aerogel is studied numerically.Comment: 7 pages RevTex and 8 figures. Figs. 4-8 in Postscript, Figs. 1-3 on
request from author
Nanoparticle Network Formation in Nanostructured and Disordered Block Copolymer Matrices
Incorporation of nanoparticles composed of surface-functionalized fumed silica (FS) or native colloidal silica (CS) into a nanostructured block copolymer yields hybrid nanocomposites whose mechanical properties can be tuned by nanoparticle concentration and surface chemistry. In this work, dynamic rheology is used to probe the frequency and thermal responses of nanocomposites composed of a symmetric poly(styrene-b-methyl methacrylate) (SM) diblock copolymer and varying in nanoparticle concentration and surface functionality. At sufficiently high loading levels, FS nanoparticle aggregates establish a load-bearing colloidal network within the copolymer matrix. Transmission electron microscopy images reveal the morphological characteristics of the nanocomposites under these conditions
The response of microstructure to processing in a series of poly(siloxaneimide) copolymers
Studies of Fractal Aspects of Cement
Small angle neutron scattering can be used to reveal the fractal nature of matter. The problems of fractal aspects of the structure of cement are related to those of fractal aspects of silica aerogels. Natural cement, when mixed with water, transforms after a series of chemical reactions (in a large part) into an amorphous phase called C-S-H. It is believed that the cationic sublattice composed of CaO octahedrons constitutes the C-S-H structural basis, to which the SiO tetrahedral chains are attached. It is a layer structure in which the cation sublattice determines the way of SiO condensation. It is natural to expect that in this way one may obtain a really amorphous substance, since some tetrahedrons may be lacking, which leads to defects. We present here the results of a small angle neutron scattering and X-ray diffraction study of several samples with the pure C-S-H phase for which during the process of chemical synthesis various ratios of molar contents of CaO and SiO were used (various C/S ratios). We obtained a gradual change of fractal characteristics with the change of C/S ratio
The effect of medium chain length alcohols on the micellar properties of sodium dodecyl sulfate in brine solutions
Micro- and macrostructural studies of sodium deoxycholate micellar complexes in aqueous solutions
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