Nanostructured Polymer Blends: From Core/Shell Nanoobjects to Continuous Three‐Phase Morphologies

A PS‐b‐PIP‐b‐PMMA copolymer has been melt‐blended with homo‐PMMA with a similar molecular weight as the PMMA block. For a 50:50 wt.‐% mixture, the components form 3D bicontinuous lamellae. Upon annealing at 190 °C, a more regular network is observed, which consists of PMMA and 55 nm‐thick bilayered lamellae of triblock copolymer, both being continuous. This co‐continuity persists even when $\overline {M} _{{\rm n}} $ of the homo‐PMMA is twice that of the PMMA block in the copolymer. For 30:70 and 20:80 wt.‐% copolymer/homopolymer pair, the copolymer forms cylindrical and spherical phases, respectively. Blends have also been prepared by solvent casting. Large domains of copolymer interconnected by few lamellae are observed in the 50:50 blend that reorganize into a bicontinuous network upon annealing.

     

Synthesis and Surface-Active Properties of Uronic Amide Derivatives,Surfactants from Renewable Organic Raw Materials

Short chemical syntheses were developed to produce a new set of surfactants from uronic acids derived from widely available raw materials. Three different strategies were used to synthesize uronic amide derivatives, the structures of which were totally characterized by spectrometric methods (IR, MS, ¹H-RMN and ¹³C-RMN). The best one, using an acid chloride as the synthetic intermediate, furnished the expected amides as a mixture of anomers in 46–58% global yield. Surface-active properties (CMC, γ_cmc, Γ_max, A _min) of homologous series of uronic acid N-alkylamides from C8 to C18 were also assessed. In general, these sugar-based surfactants exhibited good surface-activities, and appeared as valuable nonionic surfactants compared to octylphenol 9–10 ethylene oxide condensate, the most well-known nonionic surfactant. Increasing the alkyl chain length influenced the CMC values for both glucuronic and galacturonic N-alkylamide derivatives. The galacturonic N-alkylamides decreased γ_cmc at slower values than their counterpart’s glucuronic N-alkylamides.     

Multidimensional characterization,Landau levels and Density of States in epitaxial graphene grown on SiC substrates

Using high-temperature annealing conditions with a graphite cap covering the C-face of, both, on axis and 8° off-axis 4H-SiC samples, large and homogeneous single epitaxial graphene layers have been grown. Raman spectroscopy shows evidence of the almost free-standing character of these monolayer graphene sheets, which was confirmed by magneto-transport measurements. On the best samples, we find a moderate p-type doping, a high-carrier mobility and resolve the half-integer quantum Hall effect typical of high-quality graphene samples. A rough estimation of the density of states is given from temperature measurements.     

Effects of mechanical interactions on the hydrostatic stress in randomly distributed rubber particles in an amorphous polymer matrix

The equivalent inclusion method (EIM) assuming linear elasticity is used to calculate the mechanical interactions between spherical rubber particles in an amorphous matrix, as in a rubber toughened polymer. The influences of the various calculation parameters are examined and it is shown that the method can provide reliable results with regard to the level of hydrostatic stress in the particles. Damage of the material is simulated by replacing the most stressed particles by voids. Numerical simulations for several hundreds of interacting particles give information on the kinetics and spatial organisation of the damage. It appears that, as the volume fraction of particles increases from 10 to 20%, the spatial configuration of the damage evolves from a localised to a diffuse mode. These results are discussed in relation to the efficiency of rubber toughening.     

Emulsifying and foaming properties of native and chemically modified peptides from the 2S and 12S proteins of rapeseed (Brassica napus L.)

The 2S and 12S proteins of rapeseed were isolated and subsequently hydrolyzed by pepsin or a combination of pepsin plus trypsin. The resulting hydrolysates had a 15% degree of hydrolysis and were purified by gel filtration chromatography in order to obtain homogeneous peptide fractions. Three major fractions, having an average peptide chain length of 7.5–11 amino acids, were recovered. Purified peptide fractions were acylated with butyric anhydride and sulfamidated with p-toluenesulfonyl chloride. The degree of modification was always higher than 90%. Emulsifying and foaming properties of native and chemically modified peptides were studied and compared to those of sodium dodecyl sulfate (SDS) as standard. A peptide fraction from the 15% hydrolysis of the 12S protein exhibited the best foaming properties. After sulfamidation, this peptide fraction showed a foam formation similar to that of SDS. Whereas the attachment of toluene groups generally improved the surface properties, the incorporation of an aliphatic chain of four atoms of carbon was detrimental in most of the cases. On the other hand, none of the native or hydrophobized peptide fractions was able to form a stable emulsion.     

Defining Dry Eye from a Clinical Perspective

Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint.     

Mechanistic investigation and selectivity of the grafting onto C60 of macroradicals prepared by cobalt-mediated radical polymerization

The grafting mechanism of poly(vinyl acetate) macroradicals prepared by cobalt-mediated radical polymerization onto C₆₀ is investigated. The experimental conditions directly impact the nature and stability of the PVAc/C₆₀ adducts. In the presence of residual initiating radicals that can compete with PVAc° macroradicals for addition onto C₆₀, mixtures of PVAc/C₆₀ adducts having between one and eight polymer chains per C₆₀ are formed. PVAc/C₆₀ adducts prepared with low [PVAc]:[C₆₀] ratios may contain weak C₆₀–C₆₀ bonds that further dissociate and account for the instability of the products. The formation of such dimers can be lessened by increasing the temperature from 30 °C to 100 °C. The temperature increase also allows a complete dissociation of the PVAc-Co dormant species into PVAc° macroradicals and an almost quantitative grafting of eight PVAc chains onto C₆₀, leading to well-defined C₆₀(PVAc)₈ octa-adducts. These results might shed new light on the grafting onto C₆₀ of macroradicals prepared by other CRP techniques.     

Association between plasticized starch and polyesters: Processing and performances of injected biodegradable systems

Different formulations of wheat thermoplastic starch (TPS) have been processed with various plasticizer/starch ratios and moisture contents. The biodegradable polyesters tested are polycaprolactone (PCL), polyester amide (PEA), polybutylene succinate adipate (PBSA) and polybutylene adipate co terephtalate (PBAT). TPS and polyesters are melt blended in different proportions by extrusion and then injected to obtain dumbbell specimens. Various properties are evaluated such as the mechanical properties (tensile and impact tests), and the hydrophilic character with contact angle measurements. Additionally, uniaxial shrinkage is evaluated. Results show that the addition of polyester to TPS increases the dimensional post‐injection stability. Blend modulus values are close to the results of the classical rule of mixture. Elongation at break, resilience values and SEM observations seem to give some indications about the compatibility between both polymeric systems. PBAT and PEA present better results than PCL and PBSA. Contact angle measurement show that we have a drastic increase of the hydrophobic character from 10% of polyester in the blend. The different combinations of TPS and polyesters give a wide range of mechanical behavior for compostable materials, to be developed in specific applications.     

Synthesis,Chiral Separation,Absolute Configuration Assignment,and Biological Activity of Enantiomers of Retro‐1 as Potent Inhibitors of Shiga Toxin

The Shiga toxin (Stx) family is composed of related protein toxins produced by the bacteria Shigella dysenteriae and certain pathogenic strains of E. coli. No effective therapies for Stx intoxication have been developed yet. However, inhibitors that act on the intracellular trafficking of these toxins may provide new options for the development of therapeutic strategies. This study reports the synthesis, chromatographic separation, and pharmacological evaluation of the two enantiomers of Retro‐1, a compound active against Stx and other such protein toxins. Retro‐1 works by inhibiting retrograde transport of these toxins inside cells. In vitro experiments proved that the configuration of the stereocenter at position 5 is not crucial for the activity of this compound. X‐ray diffraction data revealed (S)‐Retro‐1 to be slightly more active than (R)‐Retro‐1.     

Extraction of polymer stress–strain behavior in the presence of self‐heating by the use of a simple model for the elastic–plastic deformation

Polymer materials are well known to be sensitive to strain rate and temperature. Self‐heating and friction effects also play an important role in the mechanical response of these materials. Numerous constitutive laws and phenomenological models have been developed to take into account these dependencies. This article proposes a simplified phenomenological model based on a mapping technique for the strain rate and temperature dependence. The effects of friction and adiabatic heating are also analyzed in this work. Relatively good results are obtained compared to experimental results for polypropylene and polychlorotrifluoroethylene. A parametric investigation of the effects of the interfacial equivalent stress (between the specimen and the compressive bars) and the fraction of plastic work converted into heat was performed. This parametric study allowed for a good approximation of these two parameters for the two studied polymers. POLYM. ENG. SCI., 55:2474–2481, 2015. © 2015 Society of Plastics Engineers