We discovered that the free radical polymerization of N,N-dimethylacrylamide in water can lead, above a certain concentration, to gels without any added difunctional crosslinker. These so called ''selfcrosslinked'' hydrogels were prepared and their weak mechanical properties were improved by introducing silica nanoparticles. From swelling experiments performed at equilibrium in aqueous media, it was shown that silica particles behave as adhesive fillers and strongly interact with PDMA chains. These interactions are responsible for the reinforcement of mechanical properties. From initial elastic moduli, determined in the preparation state, we show that the elastic behaviour of these hydrogels mainly originates from entanglements and from physical crosslinks that can be controlled by the polymer concentration and the ratio between silica particles and polymer chains, respectively. The mechanical behaviour was characterized using: monotonic tensile tests, loading-unloading cycles at large strains and stress relaxation experiments in order to investigate long time behaviour. The introduction of silica highly increases the stiffness of the network without greatly reducing its extensibility, implying that strong interactions take place between PDMA chains and silica surfaces. Non-linear behavior was pointed out: softening at small deformations and hardening at high deformations which is related to finite chain extensibility. All these effects have been shown to strongly depend on the silica content. The analysis of hysteresis and residual strains induced by cycles, clearly indicate that contrary to chemical crosslinkers, hybrid interactions increase the dissipative process.Physico-chimie des Polym eres et des Milieux Dispers es, UMR 7615,

This paper presents the successful surface modification of a model cellulose substrate by the preparation and subsequent physical adsorption of cationic polymer latexes. The first part of the work introduces novel charged polymer nanoparticles constituted of amphiphilic block copolymers based on cationic poly(N,N-dimethylaminoethyl methacrylate-co-methacrylic acid) (P(DMAEMA-co-MAA)) as the hydrophilic segment, and poly(methyl methacrylate) (PMMA) as the hydrophobic segment. First, RAFT polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) in water was performed at pH 7, below its pK a. The simultaneous hydrolysis of DMAEMA led to the formation of a statistical copolymer incorporating mainly protonated DMAEMA units and some deprotonated methacrylic acid units at pH 7. The following step was the RAFT-mediated surfactant-free emulsion polymerization of methyl methacrylate (MMA) using P(DMAEMA-co-MAA) as a hydrophilic macromolecular RAFT agent. During the synthesis, the formed amphiphilic block copolymers self-assembled into cationic latex nanoparticles by polymerization-induced self-assembly (PISA). The nanoparticles were found to increase in size with increasing molar mass of the hydrophobic block. The cationic latexes were subsequently adsorbed to cellulose model surfaces in a quartz crystal microbalance equipment with dissipation (QCM-D). The adsorbed amount, in mg m −2 , increased with increasing size of the nanoparticles. This approach allows for physical surface modification of cellulose, utilizing a water suspension of particles for which both the surface chemistry and the surface structure can be altered in a well-defined way. † Electronic supplementary information (ESI) available: Determination of the degree of hydrolysis of DMAEMA during its RAFT polymerization in water by 1 H NMR and the molar mass of P(DMAEMA-co-MAA) by MALDI-ToF, determination of the glass transition temperatures of P(DMAEMA-co-MAA) and Latexes 1-4 by DSC and details of the adsorption measurements in the QCM-D. See