Cationic Core/Shell Polysiloxane Acrylate Emulsion: Synthesis, Film Morphology, and Performance on Cotton Pigment Coloration.

In this paper, acrylate-terminated polysiloxane was synthesised and used as raw materials for the synthesis of cationic core/shell polysiloxane acrylate emulsion, which was applied as binders in the pigment dyeing of cotton fabrics. The experimental results showed that: the cationic core/shell poly siloxane acrylate emulsion in this article is in nano size of 100nm. During the film formation of the emulsion, there are core-core and shell-shell fusion phenomena between the latex particles, and same poly siloxane chain aggregates on the surface of the film. When the emulsion is used in the pigment dyeing of cotton fabrics, the dyed cotton fabrics feel soft, and the soaping fastness and dry/wet rubbing fastness meet the national quality requirements, as soaping fastness can reach grade 4 ~ 5, dry rubbing fastness can reach grade 4 ~ 5, and wet rubbing fastness can reach grade 4.

Micromechanics of Stress-Softening and Hysteresis of Filler Reinforced Elastomers with Applications to Thermo-Oxidative Aging

A micromechanical concept of filler-induced stress-softening and hysteresis is established that describes the complex quasi-static deformation behavior of filler reinforced rubbers upon repeated stretching with increasing amplitude. It is based on a non-affine tube model of rubber elasticity and a distinct deformation and fracture mechanics of filler clusters in the stress field of the rubber matrix. For the description of the clusters we refer to a three-dimensional generalization of the Kantor–Webman model of flexible chain aggregates with distinct bending–twisting and tension deformation of bonds. The bending–twisting deformation dominates the elasticity of filler clusters in elastomers while the tension deformation is assumed to be mainly responsible for fracture. The cluster mechanics is described in detail in the theoretical section, whereby two different fracture criteria of filler–filler bonds are considered, denoted “monodisperse” and “hierarchical” bond fracture mechanism. Both concepts are compared in the experimental section, where stress–strain cycles of a series of ethylene–propylene–diene rubber (EPDM) composites with various thermo-oxidative aging histories are evaluated. It is found that the “hierarchical” bond fracture mechanism delivers better fits and more stable fitting parameters, though the evolution of fitting parameters with aging time is similar for both models. From the adaptations it is concluded that the crosslinking density remains almost constant, indicating that the sulfur bridges in EPDM networks are mono-sulfidic, and hence, quite stable—even at 130 °C aging temperature. The hardening of the composites with increasing aging time is mainly attributed to the relaxation of filler–filler bonds, which results in an increased stiffness and strength of the bonds. Finally, a frame-independent simplified version of the stress-softening model is proposed that allows for an easy implementation into numerical codes for fast FEM simulations

Membrane-mediated aggregation of anisotropically curved nanoparticles

Using systematic numerical simulations, we study the self-assembly of elongated curved nanoparticles on lipid vesicles. Our simulations are based on molecular dynamics of a coarse-grained implicit-solvent model of self-assembled lipid membranes with a Langevin thermostat. Here we consider only the case wherein the nanoparticle–nanoparticle interaction is repulsive, only the concave surface of the nanoparticle interacts attractively with the lipid head groups and only the outer surface of the vesicle is exposed to the nanoparticles. Upon their adhesion on the vesicle, the curved nanoparticles generate local curvature on the membrane. The resulting nanoparticle-generated membrane curvature leads in turn to nanoparticle self-assembly into two main types of aggregates corresponding to chain aggregates at low adhesion strengths and aster aggregates at high adhesion strength. The chain-like aggregates are due to the fact that at low values of adhesion strength, the nanoparticles prefer to lie parallel to each other. As the adhesion strength is increased, a splay angle between the nanoparticles is induced with a magnitude that increases with increasing adhesion strength. The origin of the splay angles between the nanoparticles is shown to be saddle-like membrane deformations induced by a tilt of the lipids around the nanoparticles. This phenomenon of membrane mediated self-assembly of anisotropically curved nanoparticles is explored for systems with varying nanoparticle number densities, adhesion strength, and nanoparticle intrinsic curvature.

Anvil microphysical signatures associated with lightning-produced NO_<i>x</i>

Thunderstorm anvils were studied during the Deep Convective Clouds and Chemistry experiment (DC3), using in situ measurements and observations of ice particles and NOx together with radar and lightning mapping array measurements. A characteristic ice particle and NOx signature was found in the anvils from three storms, each containing high lightning flash rates in the storm core prior to anvil sampling. This signature exhibits high concentrations of frozen droplets (as measured by a Cloud Droplet Probe) coincident with lower NOx on the edges of the anvil. The central portion of these anvils exhibited a high degree of aggregation of these frozen droplets and higher levels of NOx. In contrast, a deep convective cell with low lightning flash rates had high concentrations of frozen droplets in its anvil's central region. A conceptual model for these results is presented. The abundance of frozen drop (chain) aggregates vs. individual frozen droplets in the central anvil region of the strong thunderstorms that were studied appears to be related to the degree of electrification (marked by increased lightning flash rates). Accordingly, the highest NOx concentrations coexist with regions where the most aggregation of frozen droplets has occurred. These observations between anvil microphysics and lightning/NOx signatures suggest that lightning data may be an important tool to characterize or infer the microphysical, radiative and chemical properties of thunderstorm anvils.

The Study of the Mobility Coefficient for Chain Aggregates in Quasi-Two-Dimensional Samples of Magnetic Fluids

The paper deals with the study of the mobility coefficients for the chain aggregates of different structures in quasi-two-dimensional magnetic fluids. Note that the quasi-two-dimensional samples contain rings also, not only chains, but this work is devoted to the investigation of the chain mobility only. We have used the Density Functional Theory to obtain the equilibrium concentrations for chain aggregates of different structures. When we know the concentrations we can obtain the mobility coefficients of chains.

Solvent-dependent rheological behavior of concentrated solutions of a cationic acrylic terpolymer containing self-assembled chains

It has been proved that alcohol molecules exist as cyclic and chain aggregates of different sizes in pure or mixed solvent systems. Here, it will be shown that these aggregates can radically change the rheological properties of a concentrated polymer solution containing self-assembled chains. In a previous study by the same authors, the existence of self-assembled structures in dilute solution of poly(dimethylaminoethyl methacrylate-co-methyl methacrylate-co-butyl methacrylate) in an alcoholic solvent mixture was shown according to small angle X-ray scattering results, showing that these structure were much more compact than those in acetone. This finding is based on the role of alcohol aggregates as physical cross-linkers. Here, the existence of self-assembled structures in concentrated solutions of the same terpolymer was confirmed by atomic force microscopy and rheology results both in acetone (a good solvent) and in a solvent mixture composed of acetone, ethanol and 1-propanol. For the terpolymer solutions in the solvent mixture, very little decrease in complex viscosity and shear thickening were observed at high strains and frequencies, respectively. It can be concluded that the alcohol aggregates can cause the formation of strong self-assembled structures that can even resist high shear forces or strains.

Formation of assemblies on cell membranes by secreted proteins: molecular studies of free λ light chain aggregates found on the surface of myeloma cells

We have described the presence of cell-membrane-associated κFLCs (free immunoglobulin light chains) on the surface of myeloma cells. Notably, the anti-κFLC mAb (monoclonal antibody) MDX-1097 is being assessed in clinical trials as a therapy for κ light chain isotype multiple myeloma. Despite the clinical potential of anti-FLC mAbs, there have been limited studies on characterizing membrane-associated FLCs at a molecular level. Furthermore, it is not known whether λFLCs can associate with cell membranes of myeloma cells. In the present paper, we describe the presence of λFLCs on the surface of myeloma cells. We found that cell-surface-associated λFLCs are bound directly to the membrane and in an aggregated form. Subsequently, membrane interaction studies revealed that λFLCs interact with saturated zwitterionic lipids such as phosphatidylcholine and phosphatidylethanolamine, and using automated docking, we characterize a potential recognition site for these lipids. Atomic force microscopy confirmed that membrane-associated λFLCs are aggregated. Given the present findings, we propose a model whereby individual FLCs show modest affinity for zwitterionic lipids, with aggregation stabilizing the interaction due to multivalency. Notably, this is the first study to image FLCs bound to phospholipids and provides important insights into the possible mechanisms of membrane association by this unique myeloma surface antigen.