41 research outputs found
How Tuning Interfaces Impacts the Dynamics and Structure of Polymer Nanocomposites Simultaneously
Fundamental understanding of macroscopic properties of polymer nanocomposites
(PNCs) remains difficult due to the complex interplay of microscopic dynamics
and structure, namely interfacial layer relaxations and three-dimensional
nanoparticle arrangements. The effect of surface modification by alkyl
methoxysilanes at different grafting densities has been studied in PNCs made of
poly(2-vinylpyridine) and spherical 20 nm silica nanoparticles (NPs). The
segmental dynamics has been probed by broadband dielectric spectroscopy, and
the filler structure by small-angle X-ray scattering and reverse Monte Carlo
simulations. By combining the particle configurations with the interfacial
layer properties, it is shown how surface modification tunes the attractive
polymer-particle interactions: bare NPs slow down the polymer interfacial layer
dynamics over a thickness of ca. 5 nm, while grafting screens these
interactions. Our analysis of interparticle spacing and segmental dynamics
provides unprecedented insight into the effect of surface modification on the
main characteristics of PNCs: particle interactions and polymer interfacial
layers
Toward a unified description of the electrostatic assembly of microgels and nanoparticles
The combination of soft responsive particles, such as microgels, with
nanoparticles (NPs) yields highly versatile complexes of great potential for
applications, from ad-hoc plasmonic sensors to controlled protocols for loading
and release. However, the assembly process between these microscale networks
and the co-dispersed nano-objects has not been investigated so far at the
microscopic level, preempting the possibility of designing such hybrid
complexes a priori. In this work, we combine state-of-the-art numerical
simulations with experiments, to elucidate the fundamental mechanisms taking
place when microgels-NPs assembly is controlled by electrostatic interactions.
We find a general behavior where, by increasing the number of interacting NPs,
the microgel deswells up to a minimum size, after which a plateau behavior
occurs. This occurs either when NPs are mainly adsorbed to the microgel corona
via the folding of the more external chains, or when NPs penetrate inside the
microgel, thereby inducing a collective reorganization of the polymer network.
By varying microgel properties, such as fraction of crosslinkers or charge, as
well as NPs size and charge, we further show that the microgel deswelling
curves can be rescaled onto a single master curve, for both experiments and
simulations, demonstrating that the process is entirely controlled by the
charge of the whole microgel-NPs complex. Our results thus have a direct
relevance in fundamental materials science and offer novel tools to tailor the
nanofabrication of hybrid devices of technological interest
Influence of drug/lipid interaction on the entrapment efficiency of isoniazid in liposomes for antitubercular therapy: a multi-faced investigation
Hypothesis. Isoniazid is one of the primary drugs used in tuberculosis
treatment. Isoniazid encapsulation in liposomal vesicles can improve drug
therapeutic index and minimize toxic and side effects. In this work, we
consider mixtures of hydrogenated soy phosphatidylcholine/phosphatidylglycerol
(HSPC/DPPG) to get novel biocompatible liposomes for isoniazid pulmonary
delivery. Our goal is to understand if the entrapped drug affects bilayer
structure.
Experiments. HSPC-DPPG unilamellar liposomes are prepared and characterized
by dynamic light scattering, -potential, fluorescence anisotropy and
Transmission Electron Microscopy. Isoniazid encapsulation is determined by UV
and Laser Transmission Spectroscopy. Calorimetry, light scattering and Surface
Pressure measurements are used to get insight on adsorption and thermodynamic
properties of lipid bilayers in the presence of the drug.
Findings. We find that INH-lipid interaction can increase the entrapment
capability of the carrier due to isoniazid adsorption. The preferential
INH-HSPC dipole-dipole interaction promotes modification of lipid packing and
ordering and favors the condensation of a HSPC-richer phase in molar excess of
DPPG. Our findings highlight the importance of fundamental investigations of
drug-lipid interactions for the optimal design of liposomal nanocarriers.Comment: 28 pages (main manuscript + supplementary information
Quantifying the performances of SU-8 microfluidic devices: high liquid water tightness, long-term stability, and vacuum compatibility
Despite several decades of development, microfluidics lacks a sealing
material that can be readily fabricated, leak-tight under high liquid water
pressure, stable over a long time, and vacuum compatible. In this paper, we
report the performances of a micro-scale processable sealing material for
nanofluidic/microfluidics chip fabrication, which enables us to achieve all
these requirements. We observed that micrometric walls made of SU-8
photoresist, whose thickness can be as low as 35 m, exhibit water pressure
leak-tightness from 1.5 bar up to 5.5 bar, no water porosity even after 2
months of aging, and are able to sustain under mbar vacuum. This
sealing material is therefore reliable and versatile for building microchips,
part of which must be isolated from liquid water under pressure or vacuum.
Moreover, the fabrication process we propose does not require the use of
aggressive chemicals or high-temperature or high-energy plasma treatment. It
thus opens a new perspective to seal microchips where delicate surfaces such as
nanomaterials are present
Etude numérique et analogique de la compaction des milieux géologiques
PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF
Microwave-assisted synthesis of tetrasubstituted aryl imidazole based polymers via cascade polycondensation process
International audiencePoly(Tetrasubstituted Aryl Imidazole)s (PTAIs), a new class of poly(heteroaromatic) polymers was prepared via a cascade polycondensation process, under microwave irradiation. These polymers were obtained by the tetrasubstituted aryl imidazole ring formation involving bis(aryl alpha-diketone)s, bis(arylaldehyde)s, mono(arylamine)s and ammonium acetate. The polymerization performed under microwave irradiation allowed to get high molecular weight PTAIs in very short reaction times. The chemical structure of these PTAIs was confirmed by NMR spectroscopy. Thermogravimetric analyses (TGA) showed a very good grade of thermal stability of these polymers. Glass transition temperatures (T-g) of PTAIs ranging from 155 degrees C to 265 degrees C were determined by Differential Scanning Calorimetry (DSC)
Microwave-assisted polymerization process: a way to design new, high molecular weight poly(arylimidazole)s
International audienc
Synthesis of 2,4,5-triarylimidazoles in aqueous solution, under microwave irradiation
International audienc
Poly(tetrasubstituted-aryl imidazole)s: A Way to Obtain Multi-Chromophore Materials with a Tunable Absorption/Emission Wavelength
International audienceSome original poly(tetrasubstituted imidazole)s incorporating different units were synthesized and characterized. These materials were obtained via a cascade polycondensation process assisted by microwave irradiation that was developed by our team. This time, we integrated two well-known chromophore structures into the macromolecular backbone, which were benzothiadiazole (BTD) and diketopyrrolopyrrole (DKPP). These new polymers were fully characterized: their chemical structures were confirmed using NMR spectroscopy and their thermal, optical and electrochemical properties were investigated and compared with a reference polymer containing a phenyl spacer instead of the mentioned chromophore units. These materials were found to exhibit a large Stokes shift of up to 350 nm. Furthermore, a polymer presenting large absorption on the UV–visible range and an emission close to the near-infrared region was obtained by coupling the mentioned moieties. According to the established properties of this latter polymer, it presents a potential for applications in biological imaging or optoelectronic devices