
Taco NicolaiLe Mans University · Département de Chimie
Taco Nicolai
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Publications (349)
Water-in-water (W/W) emulsions, also called aqueous two-phase systems, are formed by mixing two incompatible polymers in water that phase separate into two distinct phases. They can be stabilized by addition...
The degradation of (micro)gels and fractal aggregates based on self-assembled amphiphilic triblock copolymers has been investigated in water by confocal microscopy and light scattering respectively. The triblock copolymer consisted of...
Nanocomposite hydrogels were elaborated that consisted of a physical network formed by an amphiphilic polymer in which C60 fullerene nanoplatelets were embedded. Characterization showed that the nanoplatelets within the polymer...
The possible presence of plastic particles with a size smaller than 1 μm in the aquatic environment raises widespread concern over their environmental impact. Therefore, it is important to understand whether and to what extent nanoplastics dispersed in water degrade under UV irradiation. To address this issue, we studied the effect of UV irradiatio...
The detection and quantification of micro(nano)plastics in the marine environment are essential requirements to understand the full impacts of plastic pollution on the ecosystem and human health. Here, static light scattering (SLS) and dynamic (DLS) light scattering techniques are assessed for their capacity to detect colloidal particles with diame...
Hypothesis:
Molecular surfactants are not able to stabilize water-in-water (W/W) emulsions, unlike nano or micro-particles, which can achieve this in some cases. However, the effect of electrostatic interactions between particles on the emulsion stability has rarely been investigated. We hypothesize that introducing charges modifies the stabilizat...
Hypothesis:
Water-in-water (W/W) emulsions formed by mixing incompatible polymers in aqueous solution can in some cases be stabilized by adding particles that adsorb spontaneously at the W/W interface. The importance of the contact angle of the particles with the interface on the stability of W/W emulsions is still an outstanding issue. We hypothe...
Macroporous hydrogels have great potential for biomedical applications. Liquid or gel-like pores were created in a photopolymerizable hydrogel by forming water-in-water emulsions upon mixing aqueous solutions of gelatin and a poly(ethylene oxide) (PEO)-based triblock copolymer. The copolymer constituted the continuous matrix, which dominated the me...
Polymerization‐induced self‐assembly (PISA) has established itself as a powerful and straightforward method to produce polymeric nano‐objects of various morphologies in (aqueous) solution. Generally, spheres are formed in the early stages of polymerization that may evolve to higher order morphologies (worms or vesicles), as the solvophobic block gr...
In the past protein microcapsules have been made using oil in water emulsions. Usage of such microcapsules in all aqueous systems requires removal of the oil which is difficult and tedious to do fully. Here we present two methods to obtain stable protein microcapsules directly in all aqueous systems, which in addition allows capturing of water solu...
Polymerization‐induced self‐assembly (PISA) has established itself as a powerful and straightforward method to produce polymeric nano‐objects of various morphologies in (aqueous) solution. Generally, spheres are formed in the early stages of polymerization that may evolve to higher order morphologies (worms or vesicles), as the solvophobic block gr...
Hypothesis: To disperse high concentration of C60 fullerene in water, we propose to use an emulsification-evaporation process in presence of an amphiphilic polymers whose chemical structure has been chosen for inducing specific interaction with fullerene The viscosity enhancement provided by self-assembly of the amphiphilic polymers in water should...
Hypothesis: Water in water (W/W) emulsions are formed by mixing aqueous solutions of incompatible polymers. It is possible to add a third polymer solution that forms at the right conditions a phase that completely covers the dispersed droplets as a thin layer. Our hypothesis is that by gelling the third phase, W/W emulsions can be stabilized and th...
Water in water emulsions were prepared by mixing aqueous solutions of amylopectin (AMP) and pullulan (PUL) in the presence of whey protein microgels (MG). Attractive interaction between the MG was introduced by decreasing the pH from neutral towards their isoelectric pH either by adding HCl while stirring or progressively in-situ by adding glucono-...
Hypothesis
Stabilization of water-in-water (W/W) emulsions resulting from the separation of polymeric phases such as dextran (DEX) and poly(ethyleneoxide) (PEO) is highly challenging, because of the very low interfacial tensions between the two phases and because of the interface thickness extending over several nanometers. In the present work, we...
Water in water emulsions were prepared by mixing aqueous solutions of dextran and poly(ethylene oxide) at three volume fractions. The xanthan was added to the emulsions up to 0.5 wt%. The stability of the emulsions was probed by measuring the time dependence of the transmission profiles at different centrifugal forces. At lower concentrations, xant...
A range of commercial chitosan samples with different molar masses and degrees of acetylation was tested for their capacity to stabilize water in water (W/W) emulsions formed by mixing aqueous solutions of dextran and poly (ethylene oxide). To further understand the effect of the acetylation degree, commercial samples were acetylated and deacetylat...
Hypothesis
Water-in-water (W/W) emulsions are formed by mixing aqueous solutions of incompatible polymers and can in some cases be stabilized by addition of particles. The adsorption of particles at the interface of W/W emulsions is dictated by the interfacial tension between the two aqueous phases and between the particles and each phase. It shoul...
Casein is the main protein component of milk where it is present in the form of colloidal complexes. Casein micelles are remarkably heat-stable in milk below the boiling point, but they aggregate when heated at lower temperatures after lowering the pH or adding calcium ions. Here the literature on gelation of casein micelle suspensions induced by h...
Water-in-water emulsions were formed by mixing aqueous solutions of the neutral polysaccharides guar and amylopectin. The effect of adding gelatin B on emulsions, both of a dispersed guar rich phase in a continuous amylopectin phase and the inverse, were investigated using confocal scanning laser microscopy as a function of the gelatin concentratio...
We report a straightforward process to produce well-defined dynamic networks of associative BAB triblock copolymers through two successive polymerization steps conducted in one-pot and exclusively in water. The copolymers are composed of a hydrophilic poly(N,N-dimethylacrylamide) A block extended in a typical RAFT-PISA dispersion formulation with t...
The viscosity (η) of dextran (Dex), methyl cellulose (MC), hydroxypropylmethyl cellulose (HPMC), κ-carrageenan (KC), alginate (Alg), and carboxymethyl cellulose (CMC) was measured as a function of the shear rate (γ̇) over a broad range of concentrations both in salt-free water and in 0.1 M NaCl. The concentration (C) dependence of the Newtonian vis...
Water in water (W/W) emulsions were prepared by mixing aqueous dextran and polyethylene oxide (PEO) solutions. Addition of different amounts of the polysaccharide chitosan inhibited coalescence of dispersed droplets of the dextran phase in the continuous PEO phase to different extents depending on the concentration and pH. Transmission profiles wer...
Childhood arterial ischemic stroke differs in essential aspects from adult stroke. It is rare, often relatively unknown among laypersons and physicians and the wide variety of age-specific differential diagnoses (stroke mimics) as well as less established care structures often lead to a considerable delay in the diagnosis of stroke. The possible tr...
Water-in-water (W/W) emulsions show a characteristic decrease of the viscosity with increasing shear rate that is well described by equations proposed in the literature. Confocal laser scanning microscopy images showed that the decrease of the viscosity was caused by deformation and alignment of the dispersed droplets followed by string formation....
The heat-induced gelation of aqueous micellar casein (MC) suspensions was studied as a function of the sodium polyphosphate concentration. The effect of replacing 30% of the casein with whey protein isolate (WP) was also investigated. Addition of less than 4 g L⁻¹ polyphosphate inhibited gelation of intact micelles, but adding more than 6 g L⁻¹ cau...
Static (SLS) and dynamic (DLS) light scattering techniques are assessed for their capacity to detect colloidal particles with diameters between d = 0.1 and 0.8 µm at very low concentrations in seawater. The detection limit of the apparatus was determined using model monodisperse spherical polystyrene latex particles with diameters 0.2 µm and 0.5 µm...
The influence of the salt concentration, pH, protein concentration and temperature was investigated on spontaneous reversible coacervation in soy protein isolate (SPI) solutions. Coacervation was characterized by formation of protein enriched micro-domains and was most significant at 0.1 M NaCl. It was predominant below 40 °C and favored by lowerin...
The influence of κ-carrageenan (KC) was investigated on the microstructure of gels formed by acid-induced gelation of whey protein aggregates (WPA). In part I of this two-part series we discussed results obtained by potentiometric titration, rheology and turbidimetry. Here we report on the microstructure of both the proteins and the polysaccharides...
Gelation of suspensions of whey protein aggregates (WPA) was induced by lowering the pH in-situ using GDL. The effect of adding κ-carrageenan (KC) on the relationship between the net charge density of the proteins (α) and the pH was determined by potentiometric titration. It showed that complexes were formed for α > −2. The effect of adding KC on t...
The effect was studied of adding both KCl and CaCl2 on gelation of solutions of -carrageenan, -carrageenan and mixtures of both types. The gel temperature (Tg) of -car was found to be determined by the CaCl2 concentration and Tg of -car by the KCl concentration. At a given salt concentration, -car was stiffest with pure CaCl2, but -car gels a...
The effect of adding a small quantity of linear polymers on the stability of water-in-water (W/W) emulsions was studied for emulsions of dextran rich droplets in a continuous poly(ethylene oxide) phase (D/P) and vice versa (P/D). It was found that out of 16 different polymers that were tested 3 had a significant effect: chitosan (Chit), diethylamin...
Small micellar casein particles were formed in aqueous solutions of native casein after addition of polyphosphate. These so-called submicelles aggregated and gelled with a rate that increased with increasing temperature. The evolution of the viscosity during this process was determined at constant shear rate or shear stress. When applying a small s...
Protein particles were complexed with polysaccharides and the effect on their capacity to stabilize water in water (W/W) emulsions was investigated. Protein microgels were formed by heating aqueous solutions of whey protein isolate. The-car) or chitosan, respectively. The molar mass and radius of the complexes formed in dilute microgel suspensions...
Hybrid protein-polysaccharide particles were formed by complexation of fractal whey protein aggregates (PA) and the
cationic polysaccharide chitosan. The fractal aggregates were preformed by heating native whey protein isolate at pH 7 and
subsequently mixed with chitosan at pH 3 where these proteins and polysaccharides don't interact with each othe...
κ-Carrageenan was extracted from three subspecies of Kappaphycus alvarezii—K. alvarezii, K. striatum, and K. malesianus—and ι-carrageenan was extracted from Eucheuma denticulatum. Mild water extraction was used in order to obtain carrageenan in the native form. The yield was higher for the raw extract from K. alvarezii (42%) than for the other spec...
Gelation of proteins is one of the principal means to give desirable texture to food products. Gelation of individual proteins in aqueous solution has been investigated intensively in the past, but in most food products the system contains mixtures of different types of proteins. Therefore one needs to consider interaction between different protein...
Gelation of dairy/plant protein mixed dispersions and emulsions was achieved upon heat or acid treatment. The presence of plant proteins is generally leading to a lowering of the gel strength compared to dairy proteins alone. This is mostly due to the formation of independent networks by the different protein sources, which do not often interact st...
Protein aggregates were generated by thermal denaturation of whey protein isolate. Depending on the heating conditions, fractal aggregates of various sizes or microgels were obtained. The osmotic compressibility and correlation length of mixtures of fractal aggregates of different sizes were found to be close to the weighted averages of the individ...
Globulins are one of the four major classes of plant proteins and are the main protein component in legumes such as soy and pea. An important functionality of globulins is that they can form gels when heated in aqueous solution. Thermal gelation of these plant proteins is reviewed and it is concluded that though the general features are similar to...
The heat-induced gelation of oil-in-water emulsions stabilised by mixtures of micellar caseins (MC) and plant proteins (PLP) was investigated in order to assess the potential of PLP to replace milk proteins for the development of novel food products. The aim of this work was to investigate how the heat-induced gelation of MC/PLP oil-in-water emulsi...
Microplastics are ubiquitous in the aquatic environment and polyethylene (PE) fragments are commonly identified in field samples. Studies are needed to evaluate the toxicity of microplastics, specially for the smallest ones that can be ingested by a wide range of organisms. However, due to a lack of preparation methods, small PE microplastics are n...
Aqueous pea protein isolate (PPI) solutions were investigated as a function of the pH (6–8) and the protein concentration (C = 1–4 wt%). Phase separation was observed below a critical pH and C-pH phase diagrams were determined at different temperatures between 5 and 40 °C. The morphology of the solutions after setting the pH was investigated with c...
Gels of kappa carrageenan (κ-car), iota carrageenan (ι-car) and their mixtures at a polysaccharide concentration of C = 10 g/L were prepared by cooling solutions in the presence of different concentrations of KCl or CaCl2. The mobility of carrageenan (Car) chains at 20 °C was determined using fluorescence recovery after photobleaching (FRAP). Slow...
The issue addressed here is whether kappa carrageenan (κ-car) and iota carrageenan (ι-car) mixed in aqueous solution microphase separate during gelation as has been claimed in the literature. Rheological properties and microstructure of individual κ-car and ι-car solutions as well as their mixtures were studied at different concentrations (5, 10, 2...
-carrageenan was extracted from three subspecies of Kappaphycus alvarezii: K. alvarezii, K. striatum, and K. malesianus, and -carrageenan was extracted from Eucheuma denticulatum. Mild water extraction was used in order to obtain carrageenan in the native form. The yield was higher for the raw extract from Kappaphycus alvarezii (42%) than for the...
We studied the efficiency of Aerosil® fumed silica particles to emulsify oils with water. Pickering emulsions were prepared using 1%wt of particles displaying different degrees of hydrophobicity. 0.1 Pa.s polydimethylsiloxane and paraffin oils were used to investigate the effect of the oil polarity and a 0.02 Pa.s polydimethylsiloxane was used to c...
Protein particles were complexed with polysaccharides and the effect on their capacity to stabilize water in water (W/W) emulsions was investigated. Protein microgels were formed by heating aqueous solutions of whey protein isolate. The microgels were subsequently mixed with anionic or cationic polysaccharides: -carrageenan (-car) or chitosan, re...
Transport properties of macromolecules in dense aggregate suspensions and gels of proteins are important for usage of these biomaterials in areas such as pharmaceutics, food and cosmetics. The mobility of polymers in protein gels has received some attention in the past, but the mobility in dense aggregate suspensions has not yet been investigated....
Homogeneous hydrogels were formed by self-assembly of triblock copolymers via association of small hydrophobic end blocks into micelles bridged by large poly(ethylene oxide) central blocks. A fraction of the end blocks were photo-cross-linkable and could be rapidly cross-linked covalently by in situ UV irradiation. In this manner networks were form...
Particle stabilized water-in-water emulsions were prepared by mixing dextran and poly(ethylene oxide) (PEO) in water and adding cellulose nanocrystals (CNC). The CNC formed a layer at the surface of the dispersed droplets formed by the PEO rich phase. Excess CNC partitioned to the continuous dextran phase. Aggregation of CNC at different rates was...
Hybrid protein-polysaccharide particles were formed by complexation of fractal whey protein aggregates and the cationic polysaccharide chitosan. The fractal aggregates were preformed by heating native whey protein isolate at pH 7 and subsequently mixed with chitosan at pH 3 where these proteins and polysaccharides don't interact with each other. St...
Hypothesis
The stability of particle stabilized water-in-water (W/W) emulsions depends on the position of the particles at the interface, which in turn depends on their preference for each phase. The surface properties of the particles determine their preference and it should therefore be possible to enhance the stability of W/W emulsions by modula...
Acid-induced gelation of fractal aggregates with different sizes formed by preheating whey protein isolate solutions has been investigated in the protein concentration range 10–60 g/L as a function of the net protein charge density (α). Homogeneous gels could be formed in a range of α that depended on the heating time and temperature. Decrease of t...
Aqueous suspensions of micellar casein (MC) gel when heated above a critical temperature that depends on the pH. The effect of adding CaCl2 and EDTA on thermal gelation was studied in order to assess the effect of increasing or decreasing the amount of bound Ca2+ on the process. The effect of adding NaCl was investigated in order to distinguish the...
Cold gelation of preformed whey protein aggregates was induced by adding CaCl2. The gels were
investigated using rheology and confocal laser scanning microscopy in order to study the evolution with
time of the elasticity and the microstructure as a function of the protein and calcium concentrations, the
size and shape of the aggregates and the temp...
Der arteriell ischämische Schlaganfall des Kindes – „childhood stroke“ – unterscheidet sich in wesentlichen Aspekten vom Schlaganfall des Erwachsenen. Er ist selten, bei Laien und Ärzten oft wenig bekannt und wird, aufgrund einer Fülle prozentual wahrscheinlicherer Differenzialdiagnosen („stroke mimics“) und in der Fläche noch wenig etablierter Ver...
Graft copolymers consisting of a poly(acrylic acid) (PAA) backbone and random grafts of n-butyl acrylate and acrylic acid, P(nBA50%-stat-AA50%)100, were synthesized by free radical polymerization of the backbone followed by ATRP polymerization of the grafts via a grafting-from approach. The rheological properties of their aqueous solutions were mea...
Soy protein aggregates with different sizes were prepared by heating soy protein isolate (SPI) in solution and characterized with light scattering. NaCl induced gelation of aqueous solutions of these aggregates was investigated as a function of protein concentration (10-75 g L⁻¹), NaCl concentration (0-0.5 M) and temperature (20-80 °C). The structu...
Emulsion gels, also called emulgels, were formed by heating homogenized suspensions of micellar casein (MC) mixed with sunflower oil at pH < 6.5. The shear moduli of the emulgels were determined during heating and their microstructure was investigated by confocal laser scanning microscopy. The gel stiffness was studied as a function of the MC conce...
Gelation kinetics of aqueous solutions of xyloglucan (XG) extracted from H. courbaril seeds was investigated, in-situ, during enzymatic removal of galactose units by oscillatory shear rheological measurements, at different XG and enzyme (β-galactosidase) concentrations. Increasing the enzyme concentration (Cenz) led to an increase of the gelation r...
Self-assembly of native glycinin at room temperature was investigated as a function of the pH and the NaCl concentration. Microphase separation leading to the formation of dense protein microdomains was observed by confocal laser scanning microscopy. Depending on the conditions, the microdomains coalesced into a continuous protein rich phase or ass...
Model water in water (W/W) emulsions were formed by mixing polyethylene oxide (PEO) and dextran in aqueous solution. The emulsions were stabilized by addition of 5 g/L fractal aggregates or microgels of proteins that accumulated at the interface between the two polymer phases. Excess protein particles partitioned to the dextran phase for pH > 4.0....
Thermal aggregation and gelation of soy protein isolate (SPI) was studied at fixed charge density over a wide range of protein concentrations (1–95 g/L), NaCl concentrations (0–0.5 M) and temperatures (30–85 °C). Gelation was studied with oscillatory shear measurements and aggregation with light scattering. At all conditions, self-similar aggregate...
Transient hydrogels formed by cationic BAB triblock copolymers consisting of a hydrophilic poly(dimethylaminoethyl methacrylate) (P(DMAEMA)) A block and amphiphilic B blocks composed of randomly distributed DMAEMA and n-butyl methacrylate (nBMA) units were investigated. Oscillatory shear measurements revealed formation of dynamic networks with term...
Aqueous mixtures of pH-sensitive block random BAB triblock copolymers with different hydrophobic B blocks connected to the same hydrophilic A block were studied in order to investigate comicellization and the impact on the dynamic mechanical properties. The B blocks were statistical copolymers of acrylic acid (AA) and n-butyl acrylate (nBA) with va...
Heat-induced aggregation and gelation of aqueous solutions of whey protein isolate (WPI) in the presence of sodium caseinate (SC) and CaCl2 was studied at pH 6.6. The effect of adding SC (0-100 g/L) on the structure of the aggregates and the gels was investigated by light scattering and confocal laser scanning microscopy at different CaCl2 concentr...
The self-assembly of polymeric worm-like micelles in water was studied by rheology, light scattering and small angle neutron scattering. The polymer was synthesized by randomly grafting pendant quaternized alkylamine moieties to a polystyrene chain. The rheological properties of the gels evolve greatly over time: the elastic modulus G′ increases up...
The data presented in this article are related to the research article entitled Structure of Self-assembled Native Soy Globulin in Aqueous Solution as a Function of the Concentration and the pH by N. Chen, M. Zhao C. Chassenieux, T. Nicolai (2016) [1]. Please refer to this article for interpretation of the data. The protein composition of soy prote...
Hydrogels with average pore sizes ranging from 10⁻²–10³ μm were prepared using photo-cross-linkable self-assembling amphiphilic triblock copolymers based on poly(ethylene oxide) (PEO) mixed with homopolymers of dextran or PEO. Above a critical concentration, the triblock copolymers self-assembled into a transient network, which could be rendered pe...
Begrenzte Zeit für den Patienten und allgegenwärtige administrative Verpflichtungen kennzeichnen das Arbeitsprofil von klinisch tätigen ÄrztInnen in der Erwachsenenmedizin.
The rheological properties of viscoelastic aqueous solutions of wormlike micelles formed by the self-assembly of comblike copolyelectrolytes have been investigated by flow and dynamic measurements. The comblike polymers consisted of a polystyrene backbone grafted with a fixed amount of pendant N,N-dimethyl quaternary ammonium alkyl groups of variou...
Cellulose nanocrystals (CNC) are rod-like bio-sourced nano-particles that are widely used in a range of applications. Charged CNC was obtained by acid extraction from cotton and dispersed in aqueous solution using ultrasound and characterized by light scattering. Aggregation and gelation of CNC induced by addition of NaCl was investigated by light...