Search results for "Stability"

A Combined Top-Down/Bottom-Up Approach for the Nanoscale Patterning of Spin-Crossover Coordination Polymers

2007

Molecular spin-crossover complexes of 3d–3d transitionmetal ions have been the focus of many researchers’ work because of their fascinating properties associated with the bistability of their electronic states (high spin (HS) or low spin (LS)). Although the origin of the spin-crossover phenomenon is purely molecular, the macroscopic behavior of these systems in the solid state is strongly determined by the interactions, of mainly elastic origin, between the transition-metal ions. Recently, remarkable progress has been made in the area of spin-crossover complexes with infinite one-, two-, or three-dimensional (1D, 2D, 3D) networks, the so-called coordination polymers. The purpose of this app…

Inside Front Cover: A Combined Top-Down/Bottom-Up Approach for the Nanoscale Patterning of Spin-Crossover Coordination Polymers (Adv. Mater. 16/2007)

2007

The background scanning electron microscopy image shows nanometric patterns of the 3D spin crossover coordination polymer Fe(pyrazine)[Pt(CN)4] (see schematic structure in the circle), which have been fabricated using a combination of lift-off and multilayer sequential assembly methods. These patterns, reported by Gabor Molnar, Azzedine Bousseksou, and co-workers on p. 2163, exhibit a bistability of their electronic states (1A1 ⇌ 5T2), and thus represent a novel platform for a wide array of potential applications.

Fabrication of Robust High-Quality ORMOCER® Inverse Opals

2006

The nanostructuring of ORMOCER® to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER®. After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER® inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER® and high temperature stability up to 350 °C.

Tuning the Properties of Photonic Films from Polymer Beads by Chemistry

2002

This paper describes the preparation of monodisperse colloids from various methacrylates. These colloids sediment well on glass slides and formin the dried statelarge three-dimensional face-centered cubic photonic crystal films with Bragg reflection in the visible region. Depending on crystallization conditions, the domain sizes vary between 50 and 300 μm. By cross-linking the polymer within the colloids, it is possible to increase the thermal stability of the polymeric photonic structure tremendously (up to 1 h at 200 °C). These photonic structures soften above Tg (rubbery photonic structure), but they cannot fuse. Cross-linked colloids from poly(tert-butyl methacrylate) can either thermal…

Synthesis and thermal behavior of Janus dendrimers, part 2

2010

Abstract The thermal properties of twelve Janus-type dendrimers up to the second generation were evaluated by termogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Compounds consist of the dendritic bisMPA based polyester moieties, and either 3,4-bis-dodecyloxybenzoic acid, 3,5-bis-dodecyloxybenzoic acid or 3,4,5-tris-dodecyloxybenzoic acid moieties, attached to opposite sides of the pentaerythritol core. The thermal stability of the compounds was evaluated by TGA, displaying onset decomposition temperatures ( T d ) at around 250 °C. DSC measurements upon heating and cooling confirmed that OH terminated Janus dendrimers featuring large polarity difference in opposite …

Influence of the modification, induced by zirconia nanoparticles, on the structure and properties of polycarbonate

2013

Melt compounding was used to prepare polycarbonate (PC)–zirconia nanocomposites with different amounts of zirconia. The effect of the zirconia loading, in the range of 1–5 wt.%, on the structure, mechanical properties and thermal degradation kinetics was investigated. The zirconia nanoparticle aggregates were well dispersed in the PC matrix and induced the appearance of a local lamellar order in the polycarbonate as inferred by SAXS findings. This order could be a consequence of the intermolecular interactions between zirconia and the polymer, in particular with the quaternary carbon bonded to the methyl groups and the methyl carbon as inferred from the NMR results. The presence of zirconia…

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…

Rheological behavior and thermal stability of poly(phenylene sulfide)/vectra-B950 blends

1994

Blends of polyphenylene sulfide (PPS) with a commercial, wholly aromatic, liquid crystalline polymer (LCP), Vectra-B950, have been prepared by melt-blending. Their rheological behavior has been studied in order to determine if the LCP displays a processing aid ability, and under what conditions it gives rise to potentially reinforcing fibrils dispersed in the PPS matrix. The problem of the thermal stability of PPS/LCP blends, which has been considered by some authors as the main obstacle to the production of usable materials due to the evolution of gaseous substances during processing, has been discussed. © 1994 John Wiley & Sons, Inc.

2019

Abstract The preparation method of a polymer composite and the filler loading are amongst the factors that influence the properties of the final composites. This article studies the effect of these factors on the thermal stability and thermal degradation kinetics of poly(methyl methacrylate) (PMMA)/mesoporous silica (MCM-41) composites filled with small amounts of MCM-41. The PMMA/MCM-41 composites were prepared through in situ polymerisation and melt mixing methods, with MCM-41 loadings of 0.1, 0.3, and 0.5 wt.%. The presence of MCM-41 increased the thermal stability of PMMA/MCM-41 composites prepared by melt mixing, but in the case of the in situ polymerised samples, the MCM-41 accelerate…

Cementing agents involved in the macro- and microaggregation of a Mediterranean shrubland soil under laboratory heating

2014

The heating effect on aggregation and cementing agents of a Mediterranean soil was studied in two fractions (macro- and microaggregates) in different environments: under Quercus coccifera soil (UQ), under Rosmarinus officinalis soil (UR) and between plants or bare soil (BS). Samples were heated under laboratory conditions at different temperatures (220, 380, 500, 750 and 1000. °C) to establish their effects on the studied soil properties by comparison with unheated control samples (25. °C). Increasing temperature treatments caused significant changes in most soil variables. In both soil fractions, the presence of vegetation contributed to increase of the soil organic matter (SOM) content, w…