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(60) Production(s) de l'année 2019
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Swelling behaviour of core-shell microgels in H2O, analysed by temperature-dependent FTIR spectroscopy
Auteur(s): Wiehemeier Lars, Cors M., Wrede Oliver, Oberdisse J., Hellweg Thomas, Kottke Tilman
(Article) Publié:
Physical Chemistry Chemical Physics, vol. 21 p.572-580 (2019)
Ref HAL: hal-01985848_v1
DOI: 10.1039/c8cp05911j
WoS: WOS:000454922300002
Exporter : BibTex | endNote
10 Citations
Résumé: Stimuli-responsive microgels are colloidal particles and promising candidates for applications such as targeted drug delivery, matrices for catalysts, nanoactuators and smart surface coatings. To tailor the response, the architecture of microgels is of paramount importance with respect to these applications. Statistical copolymer microgels based on N-isopropylmethacrylamide (NiPMAM) and N-n-propylacrylamide (NnPAM) show a cooperative phase transition leading to a collapse at a specific temperature. Interestingly, some core-shell microgel particles reveal a linear response of the hydrodynamic radius with temperature. Such observations were made by photon correlation spectroscopy (PCS), which is limited to the diffusion properties dominated by the particle shell. In this work we investigate the molecular hydration within the network of microgels in H2O by temperature-dependent FTIR spectroscopy. The phase transition temperature wasdetermined by the shift in frequency of the NH bending vibration in homopolymer and statistical copolymer microgels and the results are in accordance with those from PCS. In contrast, experiments on core-shell particles show a broadening and shift of the respective phase transition temperatures of core and shell indicating an interaction of core and shell polymers on a molecular level that extends far into the core. In conclusion, temperature-dependent FTIR spectroscopy is a convenient approach to elucidate the internal architecture of complex microgel particles in H2O.
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Probing shear-induced rearrangements in Fourier space. I. Dynamic light scattering
Auteur(s): Aime S., Cipelletti L.
(Article) Publié:
Soft Matter, vol. 15 p.200-212 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-01982836_v1
DOI: 10.1039/c8sm01563e
WoS: WOS:000454947400016
Exporter : BibTex | endNote
5 Citations
Résumé: Understanding the microscopic origin of the rheological behavior of soft matter is a long-lastingendeavour. While early efforts concentrated mainly on the relationship between rheology and structure,current research focuses on the role of microscopic dynamics. We present in two companion papers athorough discussion of how Fourier space-based methods may be coupled to rheology to shed light onthe relationship between the microscopic dynamics and the mechanical response of soft systems. In thisfirst companion paper, we report a theoretical, numerical and experimental investigation of dynamiclight scattering coupled to rheology. While in ideal solids and simple viscous fluids the displacement fieldunder a shear deformation is purely affine, additional non-affine displacements arise in many situationsof great interest, for example in elastically heterogeneous materials or due to plastic rearrangements.We show how affine and non-affine displacements can be separately resolved by dynamic lightscattering, and discuss in detail the effect of several non-idealities in typical experiments.
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Probing shear-induced rearrangements in Fourier space. II. Differential dynamic microscopy
Auteur(s): Aime S., Cipelletti L.
(Article) Publié:
Soft Matter, vol. 15 p.213-226 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-01982835_v1
DOI: 10.1039/c8sm01564c
WoS: WOS:000454947400017
Exporter : BibTex | endNote
3 Citations
Résumé: We discuss in two companion papers how Fourier-space measurements may be coupled to rheologicaltests in order to elucidate the relationship between mechanical properties and microscopic dynamics insoft matter. In this second companion paper, we focus on Differential Dynamic Microscopy (DDM)under shear. We highlight the analogies and the differences with dynamic light scattering coupled torheology, providing a theoretical approach and practical guidelines to separate the contributions toDDM arising from the affine and the non-affine part of the microscopic displacement field. We showthat in DDM under shear the coherence of the illuminating source plays a key role, determining theeffective sample thickness that is probed. Our theoretical analysis is validated by experiments on 2Dsamples and 3D gels.
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Physico-chemical properties and surface characterization of renewable hybrid nanofilms interacting with model proteins
Auteur(s): Theodoratou A., Costa Luca, Bonnet L., Blanc C., Lapinte Vincent, Etienne P., Milhiet Pierre-Emmanuel, Robin Jean-Jacques, Oberdisse J., Chopineau Joel, Aubert-Pouessel Anne
(Article) Publié:
European Polymer Journal, vol. 111 p.161-169 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-01974331_v1
DOI: 10.1016/j.eurpolymj.2018.12.018
WoS: 000458597600018
Exporter : BibTex | endNote
2 Citations
Résumé: A comprehensive characterization of physical-chemical properties and biological interactions of ca. 200-nm-thick hybrid films based on silylated (inorganic part) castor oil (organic part) is proposed. A series of such nanofilms was fabricated and cross-linked by a sol-gel procedure, and their properties such as hydrophilicity, hardness and water vapour transmission rate were systematically studied as a function of the ratio of silylated agent to castor oil. It was found that the nanofilms have contact angles always below 90°, tunable Young modulus and hardness in the MPa range. Moreover, their water vapour transmission rates are increased by decreasing the silica ratio. The protein adsorption and cytocompatibility were evaluated using model proteins and cells. The adsorption of the proteins bovine serum albumin (BSA) and lysozyme was characterized using a quartz crystal microbalance in energy dissipation mode (QCM-D), and atomic force microscopy (AFM). The combination of the latter provided evidence for the different affinities of the proteins with the films. It was found that BSA and lysozyme form rigid layers on the surface with surface coverage close to 30%, and that both protein layers decrease their thickness after their dehydration. Finally, cell culture experiments exhibited a good viability of the fibroblasts compared to ultra-low adhesion surfaces, which makes them potential candidates for biomedical applications.
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