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.

International audienceHere we report on an all-in-one approach to prepare robust antimicrobial films on stainless steel. The strategy is based on the layer-by-layer deposition of polyelectrolytes. A polycationic copolymer bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) was synthesized and co-deposited with precursors of silver nanoparticles as the first layer. The presence of DOPA units ensures a strong anchoring on the stainless steel substrate, and the silver nanoparticles are sources of biocidal Ag+, providing stainless steel with antimicrobial activity. We show that multilayered films, obtained by alternating this nanoparticle-loaded polycationic copolymer with polystyrene sulfonate, a commercial polyanion, results in stainless steel with high antibacterial activity against Gram-negative E. coli bacteria. The polycationic layers are a reservoir of Ag+ that can be reactivated after depletion. The whole process of film formation, including the synthesis of the copolymer, is conducted in aqueous media under very mild conditions, which makes it very attractive for industrial scale-up and sustainable applications

Temporary networks were obtained from mixtures of two derivatized chitosans, one with -cyclodextrin (CD) cavities and the other with adamantyl (AD) moieties, randomly distributed along the chains. The viscoelastic response of these original systems in which cyclodextrin-adamantane complexes play a role of interchain junctions (sticky points) was investigated as a function of polymer concentration, degree of modification, ionic strength, temperature, and addition of competitive molecules. In the semidilute regime, an increase of the long relaxation times with the density of CD-AD complexes is observed, reflecting the hindrance of local flow processes due to reversible interchain bonds. The strong dependence of the apparent relaxation energy appears as a consequence of the temperature dependence of CD-AD interaction. However, contrary to the long time dynamics, the elastic plateau modulus of the transient network at short times does not seem to be much influenced by the density of stickers. The value of the plateau modulus is mainly dependent on polymer concentration.

New supramolecular assemblies based on hyaluronic acid stabilized by divalent -cyclodextrin/ adamantane ( -CD/AD) complexes were synthesized with the aim to compare their viscoelastic behavior in aqueous medium with systems resulting from monovalent complexes. For this purpose, dimers of AD and -CD to be coupled to hyaluronic acid were prepared by multistep chemical synthetic pathways. Investigation of the complexation properties of these dimers by isothermal titration calorimetry (ITC) experiments revealed a pronounced increase of the stability constant. These results can be attributed to divalency as suggested by the value of the complexation enthalpy (∆H 0 ) which is twice that of the monovalent complex, in agreement with literature data. Nevertheless, a decrease of the complexation properties of these dimers when fixed on the polysaccharide backbone was observed as a result of an unfavorable entropy of binding. The viscoelastic properties of the supramolecular assemblies were examined by dynamic rheological measurements, showing different behaviors related to the nature and the energy of the interchain physical junctions.

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.

The behavior in aqueous medium of new hyaluronic acid (HA) based supramolecular assemblies was fully investigated by rheological measurements. The physical networks studied are stabilized by specific interactions between (i) monomeric -cyclodextrin (CD) and adamantane (AD) molecules or (ii) dimeric CD and AD molecules, each randomly grafted along the polysaccharide chain. The viscoelastic properties of the resulting "mono-and bi-sticker systems", in which inclusion complexes play the role of sticky point, were analyzed as a function of polymer concentration, temperature and addition of host competitive molecules. These networks were shown to exhibit a marked non-Maxwellian behavior. The mono-and bi-interchain complexes considerably slow down the global dynamic and are believed to involve unusual viscoelastic properties that clearly differ from those of alkylated HA-based systems. These rheological features could be explained by a special mechanism of association leading to the formation of networks constituted by double-chain strands connected by fourfold junction points.

Novel H‐bond donor copolymers were designed by a versatile “click type” grafting reaction of unprotected mercaptoalcohols onto poly(2,3,4,5,6‐pentafluorostyrene) (PPFS). As demonstrated by 19F NMR and Fourier transform infrared spectroscopy (FTIR) analyses, the reaction appears to be chemoselective as the SH groups solely react onto the para‐fluoro position of the PFS units. The nucleophilic substitution was successfully performed with two mercaptoalcohols bearing either one or two hydroxyl groups. By carefully selecting the experimental conditions, a library of copolymers with various degree of substitution up to 95% was obtained in a reasonable timescale through kinetic control. By turbidity analysis, the ability of these functional polymers to form in solution interpolymer complexes with poly(4‐vinyl pyridine) was shown to be tunable by adjusting the molecular characteristics. FTIR, X‐ray photoelectron spectroscopy, and Differential scanning calorimetry evidence that different types of blends (immiscible, partially or totally miscible, and complex) can be achieved, and that the driving force of the interaction originates from H‐bond. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

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