Superparamagnetic Fe(3)O(4) nanoparticles prepared by a classical coprecipitation method were used as the stabilizer to prepare magnetic Pickering emulsions, and the effects of particle concentration, oil/water volume ratio, and oil polarity on the type, stability, composition, and morphology of these functional emulsions were investigated. The three-phase contact angle (θ(ow)) of the Fe(3)O(4) nanoparticles at the oil-water interface was evaluated using the Washburn method, and the results showed that for nonpolar and weakly polar oils of dodecane and silicone, θ(ow) is close to 90°, whereas for strongly polar oils of butyl butyrate and 1-decanol, θ(ow) is far below 90°. Inherently hydrophilic Fe(3)O(4) nanoparticles can be used to prepare stable dodecane-water and silicone-water emulsions, but they cannot stabilize butyl butyrate-water and decanol-water mixtures with macroscopic phase separation occurring, which is in good agreement with the contact angle data. Emulsions are of the oil-in-water type for both dodecane and silicone oil, and the average droplet size increases with an increase in the oil volume fraction. For stable emulsions, not all of the particles are adsorbed to drop interfaces; the fraction adsorbed decreases with an increase in the initial oil volume fraction. Changes in the particle concentration have no obvious influence on the stability of these emulsions, even though the droplet size decreases with concentration.

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Linear viscoelastic behavior was examined for a series of binary blends of linear polyisoprenes (PI). These blends contained high molecular weight (M) component chains (probe chains) that were dilute and entangled only with the lower-M matrix chains. The PI probe exhibited the Rouse-like constraint release (CR) relaxation in the matrix chains much shorter than the probe, but this CR-dominance vanished on a moderate increase of the matrix molecular weight because of the competition with other mechanisms (such as reptation). These features are qualitatively similar to, but quantitatively different from, those noted for binary blends of linear polystyrenes (PS): The CR-dominance was more easily achieved in the PI/PI blends than in the PS/PS blends, which suggests that the entanglement dynamics is not uniquely determined by the number of entanglement segments per chain and the relaxation time within this segment but is affected by additional molecular factors such as the local CR gate number considered by Graessley (Adv Polym Sci, 47, 67 (1982)).

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The effects of nonlinear deformation on the melt rheology of low molecular weight lightly sulfonated polystyrene ionomers (SPS) were investigated with dynamic, steady shear, and transient shear experiments. Changes in the viscosity and elasticity of the ionomers that occurred in large deformation flows were explained in terms of changes in the nanodomain microstructure of the ionomers. Large strains (or strain rates) significantly reduced the elasticity that resulted from a physical network produced by the ionic nanodomain structure. Recovery of the viscoelastic properties was rapid once the strain (strain rate) was removed. A three-region viscosity vs shear rate flow curve was observed, and the different regions were explained in terms of changes in the microstructure of the ionomer. Increasing the sulfonation level or the Coulomb energy of the ion-pair generally shifted the flow curve to higher shear rates. Shear flows produced no stress overshoot behavior upon start-up of the flow and the stress growth was relatively rapid even for low shear rates. In general, while the nanodomain microstructure produced high elasticity of the ionomers, the nonlinear rheological behavior of SPS differed significantly from that produced by chain entanglements. ■ INTRODUCTIONIonomers are relatively hydrophobic polymers that contain a small amount of ionic groups chemically bonded to the polymer backbone. They have attracted much attention due to the dramatic effects of the ionic species on their physical, mechanical and rheological properties. 1 Applications of ionomers include membranes (e.g., electrolytic cells, 2 fuel cells 3 and reverse osmosis, 4 packaging, 5 blend compatibilization, 6 thermoplastic elastomers, 7 drilling fluids, 8 and shapememory polymers. 9 Intermolecular dipolar interactions of the ionic species produce microphase separation of nanometersized ionic aggregates, which provide a physical-cross-linked network that affects the properties of ionomers. The cross-links are not permanent and can be reversibly disrupted by applying heat, solvent or stress, which permits melt or solvent processability.It is generally thought that melt fluidity of ionomers at elevated temperatures occurs due to "ion hopping" of ion-pairs from one aggregate to another, 10 even though a microphase separated structure persists to extremely high temperatures. 11 The association and aggregation of the ionic species increase the melt elasticity and melt viscosity of ionomers. Because of their high viscosities and the long relaxation times of the dipole−dipole or ionic interactions, 12,13 most rheological studies of ionomers, especially for sulfonated polymers, have focused on the linear behavior. 14−17 Linear behavior, though, is generally observed only for a limited range of low strain or strain rates.Polymer processing operations are usually performed with nonlinear stresses and strains that can affect the ionomer microstructure. Thus, nonlinear rheological characterization is important for understanding how these complex materials beha...

Pancreatic cancer (PaC) consists of a bulk of stroma cells which contribute to tumor progression by releasing angiogenic factors. Recent studies have found that periostin (POSTN) is closely associate with the metastatic potential and prognosis of PaC. The purpose of this study is to determine the role of POSTN in tumor angiogenesis and explore the precise mechanisms. In this study, we used lentiviral shRNA and human recombinant POSTN protein (rPOSTN) to negatively and positively regulate POSTN expression in vitro. We found that increased POSTN expression promoted the tubule formation dependent on human umbilical vein endothelial cells (HUVECs). Moreover, knockdown of POSTN in PaC cells reduced tumor growth and VEGF expression in vivo. In accordance with these observations, we found that Erk phosphorylation and its downstream VEGF expression were upregulated achieved in rPOSTN-treated groups, opposing results were obversed in POSTN-slienced group. Meanwhile, Erk inhibitor SCH772984 significantly decreased VEGF expression as well as tubule formation of HUVECs in rPOSTN-treated PaC cells. Taken together, these findings suggest that POSTN promotes tumor angiogenesis via Erk/VEGF signaling in PaC and POSTN may be a new target for cancer anti-vascular treatment.