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.

Aqueous interfaces are ubiquitous in Nature and play a fundamental role in environmental or biological processes or modern nanotechnologies. These interfaces are negatively charged, and despite several decades of research, the rationale behind this phenomenon is still under debate. Two main controversial schools of thought argue on this issue; the first relies on the adsorption of hydroxide anions on hydrophobic surfaces, whereas the second one supports a self-rearrangement of water molecules at the interface bearing hydronium ions. Here, we report on two series of independent experimental studies (nanoprecipitation and interfacial tension measurements) that demonstrate that in the pH 5–10 range the negative interfacial charge of the colloids mostly stems from bicarbonate ions, whereas at lower and higher pH, protons and hydroxide ions contribute, with bicarbonate ions, to the interfacial charging. This new interpretation complies with previous studies and opens new perspectives to this striking physical chemical issue.

The internal structure of nanometric microgels in water has been studied as a function of temperature, crosslinker content, and level of deuteration. Small-angle neutron scattering from poly(N isopropylmethacrylamide) (pNIPMAM, volume phase transition ≈ 44 °C) microgel particles of radius well below 100 nm in D2O has been measured. The intensities have been analyzed with a combination of polymer chain scattering and form-free radial monomer volume fraction profiles defined over spherical shells, taking polydispersity in size of the particles determined by AFM into account. A reverse Monte Carlo optimization using a limited number of parameters was developed to obtain smoothly decaying profiles in agreement with the experimentally scattered intensities. Result are compared to the swelling curve of microgel particles in the temperature range from 15 to 55 °C obtained from photon correlation spectroscopy (PCS). In addition to hydrodynamic radii measured by PCS, our analysis provides direct information about internal water content and gradients, the strongly varying steepness of the density profile at the particle-water interface, the total spatial extension of the particles, and the visibility of chains. The model has also been applied to a variation of the crosslinker content, N,N′ methylenebisacrylamide (BIS), from 5 to 15 mol%, providing insight in the impact of chain architecture and crosslinking on water uptake and on the definition of the polymer-water interface. The model can easily be generalized to arbitrary monomer contents and types, in particular mixtures of hydrogenated and deuterated species, paving the way to detailed studies of monomer distributions inside more complex microgels, in particular core-shell particles.

Red blood cells under shear flow present a specific swinging motion superimposed to a fluid-like tanktreading motion. Swinging is hypothesized to originate from periodic storage of shear energy in the cell membrane. Here we designed giant unilamellar vesicles with two lipid phases separated by a contact line, which swing and tanktread like red cells. We propose a model that quantitatively fits our data, finds the value of the contact-line tension and shows that swinging is due to the storage of elastic energy associated with the periodic modulation of the contact-line length during tanktreading.

The addition of nanoparticles to a polymermatrix is a well-known process to improve the mechanicalproperties of polymers. Many studies of mechanical reinforcementin polymer nanocomposites (PNCs) focus on rubberymatrices; however, much less effort concentrates on thefactors controlling the mechanical performance of thetechnologically important glassy PNCs. This paper presentsa study of the effect of the polymer molecular weight (MW)on the overall mechanical properties of glassy PNCs withattractive interaction by using Brillouin light scattering. Wefound that the mechanical moduli (bulk and shear) have anonmonotonic dependence on MW that cannot be predictedby simple rule of mixtures. The moduli increase with increasing MW up to 100 kg/mol followed by a drop at higher MW. Wedemonstrate that the change in the mechanical properties of PNCs can be associated with the properties of the interfacialpolymer layer. The latter depend on the interfacial chain packing and stretching, as well as polymer bridging,which vary differently with the MW of the polymer. These competing contributions lead to the observed nonmonotonicvariations of the glassy PNC moduli with MW. Our work provides a simple, cost-effective, and efficient way to control themechanical properties of glassy PNCs by tuning the polymer chain length. Our finding can be beneficial for the rational designof PNCs with desired mechanical performance.