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Gochev G.,Bulgarian Academy of Science | Gochev G.,Max Planck Institute of Colloids and Interfaces | Petkova H.,Bulgarian Academy of Science | Kolarov T.,Bulgarian Academy of Science | And 4 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

The interaction forces in foam and oil-in-water emulsion films stabilized by four inulin based graft copolymers with different degree of grafting of the dodecyl chains onto the inulin backbone were investigated. The adsorbing copolymers were found to form inulin-loops at the oil (air)/water interface, as the inulin-loop size decreased with increasing degree of grafting. Disjoining pressure isotherms (disjoining pressure, Π vs. equivalent film thickness, hw) were measured for the foam and emulsion films at sufficiently high NaCl concentration, whereby there is no electrostatic interaction in the films. Under these conditions, the stabilization of the films is due to interaction between the two layers of inulin-loops at oil (air)/water film interfaces. Transition to a stable Newton black film in the disjoining pressure isotherm for the emulsion films was observed for all the copolymers and the transition pressure significantly decreased for the films from the copolymer with the smallest inulin-loops. The stability against rupture of the foam films decreased with reducing inulin-loop size. The de Gennes' scaling theory for interaction between polymer 'brushes' was fitted to the experimental data for the foam films with the inulin-loops layer thickness as a fitting parameter. The results were interpreted on the basis of inulin-loop size induced changes of the steric forces in the foam and emulsion films. © 2011 Elsevier B.V. Source

Morros J.,IQAC | Levecke B.,BENEO Bio Based Chemicals | Infante M.R.,IQAC
Carbohydrate Polymers | Year: 2011

Medium and long chain esters of inulin have been prepared by reaction of alkenyl succinic anhydrides (ASA) such as 2-octen-1-ylsuccinic anhydride (OSA), and 2-dodecen-1-ylsuccinic anhydride (DDSA) in aqueous media and aqueous surfactant media, respectively. The design of the chemical process was based on the study of the influence of several reaction parameters on reaction efficiency (estimated by 1H NMR analysis of the pure end product) and reaction time. Inulin concentration, pH range, temperature, and the addition of a cationic surfactant such as dodecyltrimethylammonium bromide (DTAB) to the reaction media were evaluated for both OSA and DDSA anhydrides. Inulin slurry aqueous systems were found the best reaction media to carry out the esterification with OSA. In case of DDSA, the addition of a cationic surfactant such as DTAB was required to convert 65% of anhydride. Inulin precipitation was prevented at pH range 8.5-9.0 by the addition of DTAB. The reaction time for the synthesis of dodecenyl succinic esters of inulin, estimated as the total time required to consume all DDSA, was reduced dramatically from 24 h (without DTAB) to less than 1 h in presence of cationic surfactant. The use of micellar basic catalysis resulted in a useful way to obtain long chain alkenyl succinic esters of inulin. © 2011 Elsevier Ltd. All rights reserved. Source

Morros J.,CSIC - Institute of Advanced Chemistry of Catalonia | Levecke B.,BENEO Bio Based Chemicals | Infante M.R.,CSIC - Institute of Advanced Chemistry of Catalonia
Carbohydrate Polymers | Year: 2010

Neutral hydrophobic β-hydroxyalkyl ethers of inulin have been prepared with varying molecular features (the hydrophobic characteristics of the epoxide, length and nature, and the number of grafted groups per fructose units) in aqueous media under different conditions. The influence of several reaction parameters such as amount of solubilizer (isopropyl alcohol), basic catalysts, reaction time and temperature on the reaction efficiency has been studied through NMR analysis. We can state that the etherification of inulin in water is limited by the hydrophobic effect due to the alkyl chain of the epoxide, which can be avoided by adjusting the required amount of a solubilizer. On the other hand, the etherification rate appears to be strongly related to the temperature. Pure short and medium chain length β-hydroxyalkyl ethers of inulin can be obtained in KOH water media at 80 °C using 40% (w/w) of inulin concentration with reasonably good efficiencies and reaction times. © 2010 Elsevier Ltd. All rights reserved. Source

Morros J.,CSIC - Institute of Advanced Chemistry of Catalonia | Levecke B.,BENEO Bio Based Chemicals | Infante M.R.,CSIC - Institute of Advanced Chemistry of Catalonia
Carbohydrate Polymers | Year: 2010

The synthesis of long chain hydrophobic β-hydroxyalkyl ethers of inulin in aqueous surfactant media is described. β-hydroxyalkyl ethers of inulin were obtained in reaction media containing 40% inulin and 1 M KOH at 80 °C. Several parameters such as the amount and structure of two cationic surfactants (dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (CTAB)) and a non-ionic surfactant (β-hydroxydodecyl ether of inulin (EC12)) as well as the amount and epoxide chain length (C6-C18/26) on the reaction efficiency (RE) were examined through NMR analysis. We can state that the etherification of inulin in aqueous media with 1,2-dodecylepoxide was dependent on the surfactant used. The non-ionic surfactant, EC12, did not have any effect on the etherification reaction. On the contrary, adding a cationic surfactant such as CTAB or DTAB increased the RE significantly. The effect of DTAB micelles on this reaction could be attributed to both electrostatic (inulin/DTAB) and hydrophobic (epoxide/DTAB) interactions. A micellar catalysis mechanism is proposed to explain these interactions. Efficiencies did not increase more than 50% and were not related to variations in the epoxide alkyl chain. © 2010 Elsevier Ltd. Source

Obiols-Rabasa M.,CSIC - Institute of Advanced Chemistry of Catalonia | Obiols-Rabasa M.,CIBER ISCIII | Ramos J.,University of Granada | Forcada J.,University of the Basque Country | And 7 more authors.
Langmuir | Year: 2010

The seeded semicontinuous emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BuA) stabilized with a graft polymeric surfactant based on inulin, INUTEC SP1, as well as its mixture with sodium lauryl sulfate (SLS) is described. The mixture of SLS and Brij58 (alcohol ethoxylated) and the mixture of SLS and Pluronic P85 (block copolymer PEO-PPO-PEO) are also used as surfactant systems. The addition of methacrylic acid (MAA) or acrylic acid (AA) as comonomers is also studied. Previous results proved this inulin-derivative surfactant, INUTEC SP1, to be very effective on synthesizing latexes using a very low surfactant concentration. The kinetic features of the emulsion polymerization (instantaneous conversion and total conversion) were gravimetrically determined along the reactions. Latex dispersions were characterized by photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM) to obtain the average particle size, the particle size distributions (PSDs) as well as the polydispersity index (PdI). The stability was determined by turbidimetry measurements and expressed in terms of critical coagulation concentration. The results showed that the use of the graft polymeric surfactant allowed obtaining highly stable nanoparticles, at low surfactant concentrations and high solid contents (up to 37 wt %). This is an improvement with respect to previous works, in which a mixture of the graft polymeric surfactant with another surfactant was required to obtain stable nanoparticles with low polydispersity, at high solid content. In the present work, low polydispersity was achieved using INUTEC as the only emulsifier, which was related to the absence of secondary nucleations. When a mixture of INUTEC SP1 and SLS is used, a wider PSD is obtained due to secondary nucleations. Replacing INUTEC SP1 by other nonionic surfactants such as Brij58 or Pluronic P85 leads to an increase of average particle size and wider PSD. © 2010 American Chemical Society. Source

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