Gels de polymères dopés par des nanoparticules de maghémite pour l'élaboration de matériaux magnétiques et thermosensibles

Nous sommes intéressés à un nouveau type de matière composite basé sur l'association d'un polymère thermosensible, le poly (N-isopropylacrylamide) noté (PNIPAM) et une dispersion colloïdale de nanoparticles magnétiques d'oxyde de fer appelés ferrofluide. Pour avoir des particules stabilisées vis-à-vis de l agrégation à pH 7, les nanoparticules sont fonctionnalisées avec des ions citrate. Le comportement des mélanges polymère/nanoparticules est ensuite étudié afin de comprendre les mécanismes d interactions mis en jeu lors de l association de ces deux composants. La concentration de citrate de sodium est un paramètre essentiel comme l atteste des mesures de gonflement. La transition en volume de ces gels nanocomposites peut être suivie à la fois à des échelles macroscopiques et nanoscopiques par des expériences de Diffusion de Neutrons aux Petits Angles en utilisant les nanoparticules comme sondes de structure interne.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Self-assembly of polymers or copolymers and ferrofluids leading to either 1-d, 2-d or 3-d aggregates decorated with magnetic nanoparticles

A novel type of hybrid colloids is presented, based on the association of several polymeric systems and ferrofluids. On the one hand, we use inorganic nanoparticles made of magnetic iron oxide prepared at the LI2C, which response to a magnetic field of low intensity. On the other hand the organic part is made either of long linear polyacrylamide chains or of mesoscopic structures (vesicles and micelles) self-assembled from amphiphile polybutadiene-b-poly(glutamic acid) di-block copolymers, which conformation is pH-sensitive

Interactions between polymer chains and magnetic nanoparticles in dilute solutions and ferrogel networks

Poste

Probing the internal structure of magnetic nanocomposites – thermo-sensitive gels and lamellar films – respectively by small angle neutron scattering and neutron reflectivity

In this poster we show two types of nanocomposite materials consisting of nanoparticles embedded in polymer matrices. On the one hand, a matrix with a high degree of organization is investigated for visible light optics and hyper-frequencies applications (reflectors, guides, antennae). On the other hand, a gel matrix with an isotropic loading of nanoparticles can exhibit a swelling transition triggered by an external field (electric or magnetic) or by temperature. The first system combines the self-assembly of a symmetrical diblock copolymer matrix poly(n-butylmethacrylate)-b–poly(styrene) (PBMA-b-PS) and the orientation properties under magnetic field of Γ-Fe2O3 nanoparticles. To confine the nanoparticles within the layers of PBMA-b-PS (Fig.1a), those were coated by a polymeric shell grown by surface initiation polymerization of PS ("grafting from"). Thin films obtained by spin-coating and annealing above the glass temperature Tg were doped with nanoparticles. The lamellar order was investigated by neutron reflectivity experiments (Fig.1b) which enable to fit the density profile of the films and to localize precisely the nanoparticles within the first PS blocs. The second system consists of the same iron oxide nanoparticles, which are confined this time within spherical clusters of PTEA-PAM (Fig.2a., cf. Pr. Perzynski), dispersed into a thermosensitive hydrogel of poly(N-isopropylacrylamide) PNIPAM. The deswelling of the matrix above the transition temperature causes the decrease of the average distance between those clusters, as shown by small angle neutron scattering experiment (Fig.2b)