Fructose/glycerol/water as a biosourced LTTM solvent to design a variety of sodium alginate-based soft materials with enhanced rheological properties.

Sodium alginate was associated to a ternary solvent composed of fructose, glycerol, and water in a 1:1:5 M ratio (FGW), classified as a natural Low Transition Temperature Mixture (LTTM), to generate various soft materials. The rheological properties of mixtures composed of sodium alginate and FGW were thoroughly analyzed and compared to their aqueous analogues. FGW-based solutions present a pronounced shear-thinning character combined to high viscosity, up to 8000 Pa.s. The overlap concentrations and intrinsic viscosities values evidence a good solvent character of FGW for alginate polymer chains. The increase of alginate concentration in FGW leads to materials with enhanced elasticity (up to 6000 Pa) and high energy of activation (55 kJ/mol). Interestingly, the addition of divalent calcium cations in FGW according to two optimized experimental protocols, allows for the generation of never described ionotropic gels in FGW under various shapes as bulk gels or beads of gels able to encapsulate extracted vegetal actives that are used in the cosmetic industry. Thus, FGW appears as a well-suited solvent of alginate to design a broad range of new biobased soft materials.

α-Substituted ketones as reagent for Passerini modification of carboxymethyl cellulose: Toward dually functionalized derivatives and thermo-sensitive chemical hydrogels.

The present works describes the Passerini modification of carboxymethyl cellulose (CMC) by using a library of nine α-substituted ketones derivatives, differing in their hydrophobicity and reactivity, conjointly with cyclohexyl isocyanide. The Passerini ligation, achieved in aqueous and mild conditions, was shown to be successful, leading to a large panel of dually functionalized CMC derivatives, in an eco-friendly manner. A particular attention was dedicated to the influence of the experimental parameters such as the stoichiometry, the nature of a co-solvent or the temperature, which allowed to tune the extent of modification. The reactivity of the ketone was proven to be governed by its i) compatibility with water, ii) sterical accessibility, and by iii) the presence of neighboring electron-withdrawing group. The resulting Passerini CMC products modified by methacrylate moieties (CMC-MA) were used as reactive macromonomer under a "grafting through" approach. The copolymerization of CMC-MA with oligoethylene glycol methacrylate (OEGMA) and diethylene glycol methacrylate (DEGMA) upon thermal radical reaction conditions enabled to generate tightly cross-linked chemical hydrogels, with a thermo-sensitive and thermo-reversible behavior, reflected by a macroscopical shrinkage/swelling response, and confirmed by SAXS analysis. Such chemical strategy paves the way toward multifunctional polysaccharide-based networks with potential utilizations as drug delivery devices, dye removals or actuators.

Solvent-Free Synthesis of Amidated Carboxymethyl Cellulose Derivatives: Effect on the Thermal Properties.

The present work explores the possibility of chemically modifying carboxymethyl cellulose (CMC), a widely diffused commercial cellulose ether, by grafting of hydrophobic moieties. Amidation of CMC, at high temperature and in heterogeneous conditions, was selected as synthetic tool for grafting on CMC a panel of commercially available amines (bearing long aliphatic chains, alkyl aromatic and heteroaromatic groups, more or less spaced from the cellulose backbone). The reaction was successfully carried out in absence of solvents, catalysts and coupling agents, providing a promising and more sustainable alternative to conventional amidation procedures. Relationships between the chemical structure of the obtained CMC derivatives and their thermal properties were carefully studied, with a particular attention to the thermal behavior. Grafting of aromatic and heteroaromatic alkyl amines, presenting a linear alkyl chain between CMC backbone and a terminal bulky moiety, allowed for efficiently separating the polysaccharide chains, improving their mobility and resulting in a consequent lowering of the glass transition temperature (Tg). The Tg values obtained (90-147 °C) were found to be closely dependent on both the size of the aliphatic spacer, the structure of the aromatic ring and the extent of amidation.

Homogeneous acylation of Cellulose diacetate: Towards bioplastics with tuneable thermal and water transport properties.

In this study, we report a simple, non-degrading and efficient homogeneous acylation of cellulose diacetate (CDA) by using a large panel of commercially available acylating aliphatic moieties, differing in their structure (fatty, ramified, bulky, cycloaliphatic, aromatic, more or less spaced from the cellulose backbone), in view of generating a library of well-defined cellulose mixed esters with enhanced thermoplasticity. As reflected by a lowering of the glass temperature (Tg), the covalent grafting confers an improved mobility to the cellulose chains, by disrupting the initial H-bonds. In particular, it appears that the gain in free volume is tailored by the substituent structure and that acylating reagents consisting in a terminal bulky moieties spaced from CDA chains by a linear chain efficiently separate macromolecular chains without generating detrimental stiffening interactions (low Tg around 125 °C). Moreover, free-standing films easily prepared by solvent casting exhibit relevant water transport properties, which are closely dictated and tuned by the water solubility of the cellulose mixed ester.

Biohybrid cellulose fibers: Toward paper materials with wet strength properties.

Herein, we report on the preparation of novel cellulose-PEG biohybrid papers with wet strength properties. The biohybrid paper sheets are obtained using a two-step procedure where ω- or α, ω-azide functionalized PEG chains are anchored onto alkyne-functionalized wood fibers through CuAAC ligation in mild and aqueous conditions. The incorporation of the PEG grafts mostly occurs at the periphery of the cellulose fibers and degrees of substitution up to 0.028 are obtained. The presence of PEG grafts significantly increases the tensile, burst and tear strength properties in the wet state, the reinforcement being more pronounced for fibers grafted with α,ω-azide PEG. This reinforcement is consistent with a relatively sparse hetero-crosslink reaction creating inter-fiber covalent bonds and forming a cellulose network within the cell wall.

Guar gum as biosourced building block to generate highly conductive and elastic ionogels with poly(ionic liquid) and ionic liquid.

In this study, we report on the simple and straightforward preparation of ionogels arising from the addition of guar gum (a plant-based polysaccharide) in a solution of precisely-defined poly(ionic liquid) chains (PIL) in imidazolium-based ionic liquid (IL). The development of intermolecular polar interactions (mainly hydrogen bonds) and topologic chain entanglements induces the formation of physical biohybrid ionogels, whose elastic properties can be easily tuned by varying the composition (up to 30000Pa). The combined presence of guar gum and PIL confers excellent dimensional stability to the ionogels with no IL exudation combined with high thermal properties (up to 310°C). The resulting materials are shown to exhibit gel scattering profiles and high conductivities (> 10-4S/cm at 30°C). The benefit linked to the formation of guar/PIL associations in IL medium enables to find a good compromise between the mechanical cohesion and the mobility ensuring the ionic transport.

Aqueous RAFT Polymerization of Imidazolium-Type Ionic Liquid Monomers: En Route to Poly(ionic liquid)-Based Nanoparticles through RAFT Polymerization-Induced Self-Assembly.

The synthesis by aqueous RAFT polymerization of hydrophilic narrowly dispersed imidazolium-based poly(ionic liquid)s (D typically below 1.20) is reported. Full monomer conversion is achieved within hours and high end-group fidelity of the living end groups affords the preparation of well-defined block copolymers. The resulting poly(ionic liquid) macroRAFT agents are finally exploited to polymerize 2-vinylpyridine in water and generate PIL-based nanoparticles of various morphologies (spheres, vesicles, or worms) in a one-pot surfactant-free process.

Layer by layer H-bonded assembly of P4VP with various hydroxylated PPFS: impact of the donor strength on growth mechanism and surface features.

Hydrogen bond mediated films made by step by step deposition of poly(4-vinylpyridine) (P4VP) and hydroxylated poly(2,3,4,5,6-pentafluorostyrene) (PPFS) copolymers prepared by thiol para-fluoro coupling, bearing either one (PPFSME) or two (PPFSMPD) hydrogenated hydroxyl groups or a (poly)fluorinated hydroxyl (PPFSOH), respectively, were successfully constructed. The influence of the structural parameters, such as the hydroxyl environment (which dictates the H-bond strength) was in-depth investigated in terms of their impact on (i) growth mechanism, (ii) internal organization, and (iii) surface features. The use of the weaker H-bond donor partner (PPFSME) leads to low quality films composed of irregularly distributed aggregates. While [PPFSMPD/P4VP] multilayer films are comparatively thick and composed of stratified layers with smooth topology, the use of PPFSOH with P4VP yields thin films made of mixed and interpenetrated polymer layers. Playing on the interaction strength appears as a powerful tool to elaborate tailored multilayer films with molecularly tunable properties.

Dual guar/ionic liquid gels and biohybrid material thereof: rheological investigation.

Polysaccharide-based ion gels were prepared by mixing biosourced guar gums with imidazolium ionic liquid (IL) molecules that act as crosslinking agents. The in-depth investigation of the rheological properties of the guar/IL solutions emphasized that the shear viscoelastic properties can be finely tuned by IL chemical structure, concentration and molecular weight of guar chains as well as by temperature changes. Under suited conditions, highly elastic physical ion gels were formed as a result of multiple guar/IL, guar/guar and IL/IL interactions. Such synergistic associations were usefully exploited to elaborate films dually composed of guar chains and entrapped IL molecules. Their thermomechanical properties, which revealed a solid-state behavior, were closely controlled by the structural parameters of the constituents. This straightforward approach, which requires no chemical derivatization step, provides a facile way to design physical gels with a large applicative potential.

Green nondegrading approach to alkyne-functionalized cellulose fibers and biohybrids thereof: synthesis and mapping of the derivatization.

Alkyne-functionalized cellulose fibers have been generated through etherification under basic water or hydroalcoholic conditions (NaOH/H(2)O/isopropanol). For a given NaOH content, the medium of reaction and, more particularly, the water/IPA ratio, were shown to be of crucial importance to derivatize the fibers without altering their integrity and their crystalline nature. It was shown that the degree of substitution (DS) of the fibers increases concomitantly with isopropanol weight ratio and that, contrary to water or water-rich conditions, derivatization of fibers under isopropanol-rich conditions induces an alteration of the fibers. Optimization of etherification conditions in aqueous media afforded functionalized cellulose materials with DS up to 0.20. Raman confocal microscopy on derivatized fibers cross sections stressed that alkyne moieties are incorporated all over the fibers. The resulting fibers were postfunctionalized by molecular probes and macromolecules in aqueous or water-rich conditions. The effectiveness of the grafting was strongly impacted by the nature of the coupling agents.

Modification of polysaccharides through controlled/living radical polymerization grafting-towards the generation of high performance hybrids.

This review covers the literature concerning the modification of polysaccharides through controlled radical polymerizations (NMP, ATRP and RAFT). The different routes to well-defined polysaccharide-based macromolecules (block and graft copolymers) and graft-functionalized polysaccharide surfaces as well as the applications of these polysaccharide-based hybrids are extensively discussed.

Combination of electrografting and layer-by-layer deposition: an efficient way to tailor polymer coatings of (semi)-conductors.

This communication reports on a novel, simple and highly versatile concept, which consists in combining the advantages of two complementary and relevant techniques (i) electrografting and (ii) layer-by-layer deposition process with the goal to tailor strongly adhering coatings to (semi)-conducting surfaces imparting them with tunable specific properties.

Controlled synthesis and inclusion ability of a hyaluronic acid derivative bearing beta-cyclodextrin molecules.

A new synthetic route to beta-cyclodextrin-linked hyaluronic acid (HA-CD) was developed. This was based on the preparation of a HA derivative selectively modified with adipic dihydrazide (HA-ADH) and a beta-cyclodextrin derivative possessing an aldehyde function on the primary face, followed by their coupling by a reductive amination-type reaction. The CD-polysaccharide was fully characterized in terms of chemical integrity and purity by high-resolution NMR spectroscopy. The complexation ability of the grafted CD was further demonstrated by isothermal titration calorimetry using sodium adamantane acetate (ADAc) and Ibuprofen as model guest molecules. The thermodynamic parameters for the complexation of these negatively charged guest molecules by the beta-CD grafted on negatively charged HA were shown to be largely influenced by the ionic strength of the aqueous medium.

Investigation of the complexation of (+)-catechin by beta-cyclodextrin by a combination of NMR, microcalorimetry and molecular modeling techniques.

(+)-Catechin is a polyphenolic compound of natural origin that presents anti-oxidant properties of interest for therapeutics or cosmetics uses. Preliminary studies on inclusion into cyclodextrin cavities yielded contradictory results both for the quantitative (affinity constant) and qualitative description of the interaction. By a combination of several experimental and theoretical methods, the present study resolved the previous ambiguities about the interaction between (+)-catechin and beta-cyclodextrin. Thermodynamic data measured by isothermal titration calorimetry demonstrate that the binding is enthalpy driven. Excellent agreement has been obtained for the measurement of the association constant by NMR and microcalorimetry. The several docking modes obtained by systematic docking studies have been compared to intermolecular contacts measured by NMR and the overall geometry of the complex can be proposed.