Design of eco-friendly fabric softeners: structure, rheology and interaction with cellulose nanocrystals

Concentrated fabric softeners are water-based formulations containing around 10 - 15 wt. % of double tailed esterquat surfactants primarily synthesized from palm oil. In recent patents, it was shown that a significant part of the surfactant contained in today formulations can be reduced by circa 50 % and replaced by natural guar polymers without detrimental effects on the deposition and softening performances. We presently study the structure and rheology of these softener formulations and identify the mechanisms at the origin of these effects. The polymer additives used are guar gum polysaccharides, one cationic and one modified through addition of hydroxypropyl groups. Formulations with and without guar polymers are investigated using optical and cryo-transmission electron microscopy, small-angle light and Xray scattering and finally rheology. Similar techniques are applied to study the phase behavior of softener and cellulose nanocrystals considered here as a model for cotton. The esterquat surfactants are shown to assemble into micron-sized vesicles in the dilute and concentrated regimes. In the former, guar addition in small amounts does not impair the vesicular structure and stability. In the concentrated regime, cationic guars induce a local crowding associated to depletion interactions and leads to the formation of a local lamellar order. In rheology, adjusting the polymer concentration at one tenth that of the surfactant is sufficient to offset the decrease of the elastic property associated with the surfactant reduction. In conclusion, we have shown that through an appropriate choice of natural additives it is possible to lower the concentration of surfactants in fabric conditioners by about half, a result that could represent a significant breakthrough in current home care formulations.Comment: 10 pages 8 figure

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Structures cristallines formées par les triglycérides du lait identification par diffraction des rayons X en utilisant le rayonnement synchrotron (INRA en lumière 5 ans de partenariat soleil)

il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : REPORTThe formation of concentrated layers of proteinsat the membrane surface during filtrationwas followed using small angle X-ray scatteringon the SWING beamline. It allowed to followboth the concentration profiles ( and theirreversibility ) in the course of time with a resolutionof 50 μm and the structural modificationsof the proteins in the concentrated layers.L'établissement de couches concentrées deprotéines à la surface des membranes encours de filtration a été suivi par diffusion derayons X aux petits angles ( SA XS ) sur la lignede lumière SWING. Cela a permis d'une partd'accéder aux profils de concentration et àleur réversibilité au cours du temps avec unerésolution de 50 μm, et d'autre part de suivreles modifications structurales des protéinesdans ces couches

Self-assembly of poly(ethylene oxide)-b-poly(e-caprolactone) copolymers in aqueous solution

The associative behavior of monodisperse diblock copolymers consisting of a hydrophilic poly(ethylene oxide) block and a hydrophobic poly(epsilon-caprolactone) or poly(gamma-methyl-epsilon-caprolactone) block has been studied in aqueous solution. Copolymers have been directly dissolved in water. The solution properties have been studied by surface tension, in relation to mesoscopic analyses by NMR (self-diffusion coefficients), transmission electron microscopy, and small-angle neutron and X-ray scattering. The experimental results suggest that micellization occurs at low concentration (approximately 0.002 wt %) and results in a mixture of unimers and spherical micelles that exchange slowly. The radius of the micelles has been measured (ca. 11 nm), and the micellar substructure has been extracted from the fitting of the SANS data with two analytical models. The core radius and the aggregation number change with the hydrophobic block length according to scaling laws as reported in the scientific literature. The poly(ethylene oxide) blocks are in a moderately extended conformation in the corona, which corresponds to about 25% of the completely extended chain. No significant modification is observed when poly(gamma-methyl-epsilon-caprolactone) replaces poly(epsilon-caprolactone) in the diblocks

Phase transitions of saturated triglycerides

The α → β phase transition of Tristearin (SSS) has been investigated both by Differential Scanning Calorimetry and Small Angle X-Ray Diffraction as a function of temperature at the same heating rate (2 deg/min) in order to elucidate either this transition occurs in the solid state or is melt mediated

First stages of crystallization of the poly(ethylene oxide)-resorcinol molecular complex

Time-resolved SAXS has been used to follow isothermal crystallization in the PEO 6000/Resorcinol molecular complex. It has been shown that the complex exhibit crystals with PEO chains in the fully extended form. The initial stages of crystallization are strongly dependent on the temperature : at high supercooling transient once-folded chains crystals are evidenced. They thicken in a single step to give extended chain crystals

Thermal and structural behavior of anhydrous milk fat. 3. Influence of cooling rate

The crystallization behavior of anhydrous milk fat has been examined with a new instrument coupling time-resolved synchrotron x-ray diffraction as a function of temperature (XRDT) at both small and wide angles and high-sensitivity differential scanning calorimetry. Crystallizations were monitored at cooling rates of 3 and 1°C/ min from 60 to –10°C to determine the triacylglycerol organizations formed. Simultaneous thermal analysis permitted the correlation of the formation/melting of the different crystalline species monitored by XRDT to the thermal events recorded by differential scanning calorimetry. At intermediate cooling rates, milk fat triacylglycerols sequentially crystallize in 3 different lamellar structures with double-chain length of 46 and 38.5 Å and a triple-chain length of 72 Å stackings of {alpha} type, which are correlated to 2 exothermic peaks at 17.2 and 13.7°C, respectively. A time-dependent slow sub-{alpha} {leftrightarrow} {alpha} reversible transition is observed at –10°C. Subsequent heating at 2°C/min has shown numerous structural rearrangements of the {alpha} varieties into a single ß' form before final melting. This polymorphic evolution on heating, as well as the final melting point observed (~39°C), confirmed that cooling at 3°C/min leads to the formation of crystalline varieties that are not at equilibrium. An overall comparison of the thermal and structural properties of the crystalline species formed as a function of the cooling rate and stabilization time is presented. The influence on crystal size of the cooling rates applied in situ using temperature-controlled polarized microscopy is also determined for comparison