Enhanced water barrier properties of surfactant-free polymer films obtained by macroRAFT-mediated emulsion polymerization

The presence of low-molar-mass surfactants in latex films results in detrimental effects on their water permeability, gloss, and adhesion. For applications such as coatings, there is a need to develop formulations that do not contain surfactants and have better water barrier properties. Having previously reported the synthesis of surfactant-free latex particles in water using low amounts ( < 2 wt %) of chains synthesized by controlled radical polymerization (Lesage de la Haye et al. Macromolecules 2017, 50, 9315-9328), here we study the water barrier properties of films made from these particles and their application in anticorrosion coatings. When films cast from aqueous dispersions of acrylate copolymer particles stabilized with poly(sodium 4-styrenesulfonate) (PSSNa) were immersed in water for 3 days, they sorbed only 4 wt % water. This uptake is only slightly higher than the value predicted for the pure copolymer, indicating that the negative effects of any particle boundaries and hydrophilic-stabilizing molecules are minimal. This sorption of liquid water is 5 times lower than what is found in films cast from particles stabilized with the same proportion of poly(methacrylic acid) (PMAA), which is more hydrophilic than PSSNa. In water vapor with 90% relative humidity, the PSSNa-based film had an equilibrium sorption of only 4 wt %. A small increase in the PMAA content has a strong and negative impact on the barrier properties. Nuclear magnetic resonance relaxometry on polymer films after immersion in water shows that water clusters have the smallest size in the films containing PSSNa. Furthermore, these films retain their optical clarity during immersion in liquid water for up to 90 min, whereas all other compositions quickly develop opacity ("water whitening") as a result of light scattering from sorbed water. This implies a remarkably complete coalescence and a very small density of defects, which yields properties matching those of some solvent-borne films. The latex stabilized with PSSNa is implemented as the binder in a paint formulation for application as an anticorrosive barrier coating on steel substrates and evaluated in accelerated weathering and corrosion tests. Our results demonstrate the potential of self-stabilized latex particles for the development of different applications, such as waterborne protective coatings and pressure-sensitive adhesives

Dynamic stratification in drying films of colloidal mixtures

In simulations and experiments, we study the drying of films containing mixtures of large and small colloidal particles in water. During drying, the mixture stratifies into a layer of the larger particles at the bottom with a layer of the smaller particles on top. We developed a model to show that a gradient in osmotic pressure, which develops dynamically during drying, is responsible for the segregation mechanism behind stratification

In situ monitoring of latex film formation by small-angle neutron scattering: Evolving distributions of hydrophilic stabilizers in drying colloidal films

The distribution of hydrophilic species, such as surfactants, in latex films is of critical importance for the performance of adhesives, coatings and inks, among others. However, the evolution of this distribution during the film formation process and in the resulting dried films remains insufficiently elucidated. Here, we present in situ (wet) and ex situ (dry) SANS experiments that follow the film formation of two types of latex particles, which differ in their stabilizer: either a covalently bonded poly(methacrylic acid) (PMAA) segment or a physically adsorbed surfactant (sodium dodecyl sulfate, SDS). By fitting the experimental SANS data and combining with gravimetry experiments, we have ascertained the hydrophilic species distribution within the drying film and followed its evolution by correlating the size and shape of stabilizer clusters with the drying time. The evolution of the SDS distribution over drying time is being driven by a reduction in the interfacial free energy. However, the PMAA-based stabilizer macromolecules are restricted by their covalent bonding to core polymer chains and hence form high surface-area disc-like phases at the common boundary between particles and PMAA micelles. Contrary to an idealized view of film formation, the PMAA does not remain in the walls of a continuous honeycomb structure. The results presented here shed new light on the nanoscale distribution of hydrophilic species in drying and ageing latex films. We provide valuable insights into the influence of the stabilizer mobility on the final structure of latex films

Anionic block copolymer vesicles act as Trojan horses to enable efficient occlusion of guest species into host calcite crystals

We report a versatile ‘Trojan Horse’ strategy using highly anionic poly(methacrylic acid)–poly(benzyl methacrylate) vesicles to incorporate two types of model payloads, i.e. either silica nanoparticles or an organic dye (fluorescein), within CaCO3 (calcite). Uniform occlusion of silica-loaded vesicles was confirmed by scanning electron microscopy, while thermogravimetry studies indicated extents of vesicle occlusion of up to 9.4% by mass (∼33% by volume). Efficient dye-loaded vesicle occlusion produces highly fluorescent calcite crystals as judged by fluorescence microscopy. In control experiments, silica nanoparticles alone are barely occluded, while only very weakly fluorescent calcite crystals are obtained when using just the fluorescein dye. This new ‘Trojan Horse’ strategy opens up a generic route for the efficient occlusion of various nanoparticles and organic molecules within inorganic host crystals

Optimization of the high-throughput synthesis of multiblock copolymer nanoparticles in aqueous media: Via polymerization-induced self-assembly

Over the past fifteen years or so, polymerization-induced self-assembly (PISA) has become widely recognized as a powerful and versatile platform technology for the synthesis of a wide range of block copolymer nanoparticles of controlled size, shape and surface chemistry. In the present study, we report that PISA formulations are sufficiently robust to enable high-throughput experiments using a commercial synthesis robot (Chemspeed Autoplant A100). More specifically, we use reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerization of either n-butyl methacrylate and/or benzyl methacrylate to prepare various examples of methacrylic multiblock copolymer nanoparticles using a poly(methacrylic acid) stabilizer block. Adequate stirring is essential to generate sufficiently small monomer droplets for such heterogeneous polymerizations to proceed efficiently. Good reproducibility can be achieved under such conditions, with well-defined spherical morphologies being obtained at up to 45% w/w solids. GPC studies indicate high blocking efficiencies but relatively broad molecular weight distributions (Mw/Mn= 1.36-1.85), suggesting well-defined (albeit rather polydisperse) block copolymer chains. These preliminary studies provide a sound basis for high-throughput screening of RAFT-mediated PISA formulations, which is likely to be required for commercialization of this technology. Our results indicate that methacrylic PISA formulations enable the synthesis of diblock and triblock copolymer nanoparticles in high overall yield (94-99%) within 1-3 h at 70 °C. However, tetrablocks suffer from incomplete conversions (87-96% within 5 h) and hence most likely represent the upper limit for this approach

L'IMPACT DES FACTEURS MOTIVATIONNELS SUR L'INTEGRATION DES INFORMATIONS CATEGORIELLES ET INDIVIDUALISANTES

LE MODELE DE FISKE ET NEUBERG (1990) REPRESENTE LA FORMATION D'IMPRESSIONS SOUS LA FORME D'UN CONTINUUM OPPOSANT LES TRAITEMENTS CATEGORIELS AUX TRAITEMENTS INDIVIDUALISES. FACE A UNE CIBLE LE SUJET DISPOSE DE DEUX TYPES D'INFORMATIONS QU'IL DOIT INTEGRER : L'INFORMATION CATEGORIELLE ET LES INFORMATIONS INDIVIDUALISANTES. SI LE TRAITEMENT CATEGORIEL BASE SUR L'APPARTENANCE CATEGORIELLE DE LA CIBLE - EST PRIORITAIRE, LE SUJET PEUT PAR LE BIAIS DE L'ATTENTION PORTEE AUX ATTRIBUTS ALLER AU- DELA DES STEREOTYPES. EN PARTICULIER, LES AUTEURS METTENT EN AVANT LE ROLE DES FACTEURS MOTIVATIONNELS DANS LE GLISSEMENT VERS LES TRAITEMENTS CATEGORIELS OU VERS DES TRAITEMENTS PLUS INDIVIDUALISES. NOUS NOUS INTERESSONS PLUS PARTICULIEREMENT A LA JUSTIFICATION EN TANT QUE FACTEUR SITUATIONNEL QUI, SELONTETLOCK (1992), POURRAIT @AMENER LE SUJET PERCEVANT A ADOPTER UNE STRATEGIE D'AUTOCRITIQUE PREVENTIVE FACE A UN AUDITOIRE IMPARTIAL ; EN PRENANT EN COMPTE TOUTES LES INFORMATIONS DISPONIBLES, IL DEVRAIT PAR CONSEQUENT S'ORIENTER VERS UN TRAITEMENT INDIVIDUALISE. CEPENDANT, UNE MOTIVATION "INTERNE" TELLE QUE LA MENACE DE L'ESTIME DE SOI NOUS SEMBLE TENIR UN ROLE IMPORTANT DANS LES MECANISMES IMPLIQUES EN SITUATION DE JUSTIFICATION. LORSQUE LE SUJET S'ATTEND A EXPOSER SON JUGEMENT A UN TIERS, A COMPARER SES CRITERES DE JUGEMENTS A CEUX D'AUTRUI, CETTE SITUATION PEUT REPRESENTER UNE MENACE DE L'ESTIME DE SOI . CE TRAVAIL ENVISAGE LES LIENS COMPLEXES UNISSANT LA JUSTIFICATION, L'ESTIME DE SOI ET LE DEGRE DE STEREOTYPIE DES JUGEMENTS.PARIS5-BU Saints-Pères (751062109) / SudocSudocFranceF

New Insight into Cluster Aggregation Mechanism during Polymerization-Induced Self-Assembly by Molecular Dynamics Simulation

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Synthesis of Well-Defined Dawson-Type Poly(N,N-diethylacrylamide) Organopolyoxometalates

International audienceAn organotin-substituted Dawson-type phosphotungstate was covalently linked to a trithiocarbonate group by postfunctionalization methods. This organopolyoxometalate led to a series of polyoxometalate (POM)–poly(N,N-diethylacrylamide) hybrids in a controlled way through reversible addition–fragmentation chain transfer (RAFT) polymerization. Detailed comparison with and without the presence of POMs revealed that they do not profoundly disturb the RAFT mechanism, despite their oxidative power. The molar masses of the polymers were in the range of 10 to 100 kg mol−1 and molar mass dispersities of the composites were low (Mw/Mn<1.5). The POM building block in the hybrids retained the photocatalytic reactivity of the parent Dawson polyanion [P2W18O62]6−. Smaller, more homogeneous, and colloidally more stable silver nanoparticles were formed with the covalently linked POM–polymer compound than with its single unbound component

Amphiphilic Polyoxometalates for the Controlled Synthesis of Hybrid Polystyrene Particles with Surface Reactivity

International audienceAmphiphilic organo-polyoxometalates (POMs) used in the radical emulsion polymerization of styrene allowed the preparation in aqueous medium of stable 50-100 nm polystyrene-POM composite latexes. Thanks to the presence of a trithiocarbonate group in the POM amphiphile, POMs could be covalently linked to the polymer particle surface. The chemical and catalytic integrity of the POMs was confirmed, and the POM-mediated surface photoactivity of the latexes was demonstrated by the spatially controlled nucleation of silver nanoparticles at the periphery of the composites

Study of the temperature-induced aggregation of polyoxometalate-poly(N,N-diethylacrylamide) hybrids in water

International audienceIn this article, we study the temperature-induced phase transition of aqueous solutions of tailor-made Dawson polyoxometalate-poly(N,N-diethylacrylamide) hybrids (POM-PDEAAm) by means of differential scanning calorimetry, dynamic light scattering and cryo-TEM microscopy. Generally, the typical thermoresponsive aggregation of the PDEAAm in water was transferred to the hybrids. The organization of the compounds in solution below and above the transition temperature was studied, and precious insights in the aggregation mechanisms were obtained. The impact of the polymer chain-ends, the nature of the counterions of the negatively charged POM subunits and the weight fraction of the POM was elucidated, revealing a strong influence of the POM's counter-ions. Temperature and nature of the cations are thus two external factors that can be used to control the properties of the conjugates