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Publications (63)
It has been shown that the use of conformationally pH-switchable lipids can drastically enhance the cytosolic drug delivery of lipid vesicles. Understanding the process by which the pH-switchable lipids disturb the lipid assembly of nanoparticles and trigger the cargo release is crucial to optimize the rational design of pH-switchable lipids. Here,...
Nanoparticles or drug carriers which can selectively bind to cells expressing receptors above a certain threshold surface density are very promising for targeting cells overexpressing specific receptors under pathological conditions. Simulations and theoretical studies have suggested that such selectivity can be enhanced by functionalizing nanopart...
The stimuli-triggered cell attachment/detachment from responsive polymer-coated surfaces is influenced by several parameters including electrostatic interactions, wettability and swelling of the polymer coating. Herein, supported dual thermo- and pH-responsive cationic poly(N-isopropylacrylamide) microgels, surface-functionalized with polyethylene...
Unprecedented quantitative assessment of the swelling behavior of surface-immobilized photothermal responsive microgels (PTRM) is reported. The PTRM were prepared by incorporating plasmonic gold nanoparticles (AuNPs) in thermo-responsive cationic microgels based on poly(N-isopropylacrylamide) (BM). The stimuli-responsive behavior of the microgels w...
Normal and friction forces between immobilized two-dimensional (2D) homogeneous non-close packed colloidal arrays made of different particles are compared in aqueous media. Soft pH-responsive (microgels) and non-responsive hard (silica) particles of different sizes were used to create the 2D arrays. The results show that friction of soft responsive...
As double stranded, single stranded siRNA (ss-siRNA) has demonstrated gene silencing activity but still requires efficient carriers to reach its cytoplasmic target. To better understand the fundamental aspect driving the complexation of ss-siRNA with nanocarriers, the interactions between surfaces of various compositions across a ss-siRNA solution...
We report the first successful preparation of polyelectrolyte brushes using an ATRP initiator that was covalently grafted to silica and mica substrates via an organophosphonic acid. Covalent attachment of the initiator to silica and mica and the subsequent synthesis of polyacrylic acid (PAA) and poly(sulfopropyl methacrylic acid) brushes by water m...
We report the preparation, characterization and responsive behavior of polystyrene-block-poly(acrylic acid) (PS-b-PAA) copolymer brushes grafted from silica substrates using Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP). pH-dependent swelling behavior was investigated in situ by ellipsometry and it confirmed that PAA chains can b...
Current measurements of frictional forces are usually done parallel to the sliding direction. However, when the distances between the moving surfaces and the dimensions of the lubricant approach the nanometer scale, the molecular structure and surface asperities can induce significant frictional forces that are not parallel to the sliding direction...
We have studied the adsorption and lubricant properties of a multifunctional triblock copolymer poly(L-lysine)-b-polyacrylic acid-b-poly(L-lysine). In particular, we investigated the nature of the layer adsorbed under different conditions of polymer and salt concentration, and the lubricant properties of the polymer layer before and after its chemi...
The frictional properties of a thin hexadecane film confined between two atomically smooth surfaces of mica were studied using the surface forces apparatus equipped with a 3D actuator–sensor attachment specially designed to investigate static and dynamic forces in three orthogonal directions simultaneously. The use of this attachment allows the rel...
A new approach is presented that introduces interparticle forces induced by a change of temperature at which polymer coated particles are exposed. The particle cohesive flow behavior is shown for two different applications. The first one considers a dense granular flow that is typically observed for wet powder granulation using a modified spheroniz...
A new 3D sensor-actuator attachment for a Surface Forces Apparatus (SFA) allows measurements of friction forces between surfaces in all 3 orthogonal directions. The anisotropic friction forces when shearing two mica surfaces separated by a nanometer-thin film of hexadecane can induce complex transient and steady-state motions involving displacement...
Current measurements of frictional forces are usually done parallel to the sliding direction. However, when the distances between the moving surfaces and the dimensions of the lubricant approach the nanometer scale, the molecular structure and surface asperities can induce significant frictional forces that are not parallel to the sliding direction...
Poly(acrylic acid) (PAA) covalently immobilized on glass substrates was made fluorescent by grafting a BODIPY derivative (PMOH) via an ester linkage. Although only nanograms/square centimeter of polymer are understood to be immobilized onto the SiO2 substrate, the fluorophore-tagged polymer was readily visible to the naked eye and its fluorescence...
Recent studies have revealed that, in contrast to non-associating liquids such as oils or organic solvents, salt-free water retains a viscosity close to its bulk value even when confined to films thinner than some 3 nm, indeed down to only one or two monolayers thick [1,2]. For the case of high concentration aqueous salt solution compressed down to...
Unprecedented direct polymerization of sodium acrylate (NaA) on mica and silica substrates was undertaken using standard ATRP polymerization conditions at room temperature. The resulting thickness of the poly(sodium acrylate) (PNaA) grafted layer was determined using ellipsometry and AFM.
Poly(acrylic acid) (PAA) and poly(tert-butyl acrylate) (PBA) brushes of various grafting densities were prepared via surface-initiated polymerization of tert-butyl acrylate on mica. PAA was prepared by hydrolyzing the PBA brushes. The swelling behavior of PBA and PAA brushes was studied as a function of grafting density by AFM. The swelling of the...
Static and dynamic interaction forces between two thermosensitive polymeric nanoparticle monolayers grafted onto mica surfaces and immersed in water were studied using a surface forces apparatus. The polymeric nanoparticles (NPs) were made of N,N-diethylacrylamide and had a hydrodynamic diameter of ca. 780 nm at 20 degrees C in aqueous suspension....
Poly(acrylic acid) (PAA) brushes covalently linked to mica were prepared using the graft from approach in a two-step process: (i) poly(tert-butyl acrylate) (PtBA) brushes were first synthesized by atom transfer radical polymerization directly from an activated mica substrate (ii) followed by hydrolysis to generate PAA brushes. The hydrolysis reacti...
The controlled grafting density of poly(tert-butyl acrylate) was studied on OH-activated mica substrates via surface-initiated atom-transfer radical polymerization (ATRP). By properly adjusting parameters such as the immobilization reaction time and the concentration of an ATRP initiator, a wide range of initiator surface coverages and hence polyme...
Uptake and intracellular trafficking of hydrogel nanoparticles (NPs) of N,N-diethyl acrylamide and 2-hydroxyethyl methacrylate crosslinked with N,N 0 -methylene-bis-acrylamide were studied with a RAW 264.7 murine macrophage cell line. Results show that the uptake rate, the mechanism of internalization and the concentration of internalized NPs are c...
The behavior of adsorbed surface active molecules at mica surfaces from crude oil and from their extracted asphaltenes dissolved in different solvents was investigated. The interactions between mica surfaces across a crude oil and across asphaltene solutions using different solvents and humidity conditions were measured using the surface forces app...
Normal and lateral forces between two opposing monolayers of grafted polymer nanoparticles (NPs) were measured using the Surface Forces Apparatus in a humid atmosphere. The NPs made of N, N-diethylacrylamide and 2-hydroxyethyl methacrylate have a hydrodynamic diameter of ca. 660 nm at 25 degrees C. The effect of surface roughness was studied by cre...
New active particulate polymeric vectors based on branched polyester copolymers of hydroxy-acid and allyl glycidyl ether were developed to target drugs to the inflammatory endothelial cell surface. The hydroxyl and carboxyl derivatives of these polymers allow grafting of ligand molecules on the polyester backbones at different densities. A known po...
Normal and shear forces were measured as a function of surface separation, D, between hydrophobized mica surfaces bearing layers of a hydrophobic-polyelectrolytic diblock copolymer, poly(methyl methacrylate)- block-poly(sodium sulfonated glycidyl methacrylate) copolymer (PMMA- b-PSGMA). The copolymers were attached to each hydrophobized surface by...
We investigated the effect of physical and chemical modifications of mica surfaces induced by water vapor-based plasma treatments on the stability of silanols and grafted alkylsilane monolayers. The plasma-activated substrates were characterized using XPS, TOF-SIMS, and contact angle measurements. They revealed a large surface coverage of silanol g...
Polyelectrolyte brushes were built on mica by anchoring polystyrene-poly(acrylic acid) (PS-b-PAA) diblock copolymers at a controlled surface density in a polystyrene monolayer covalently attached to OH-activated mica surfaces. Compared to physisorbed polymer brushes, these irreversibly attached charged brushes allow the polymer grafting density to...
Mica substrates were activated by a plasma method leading to OH-functionalized surfaces to which an atom transfer radical polymerization (ATRP) radical initiator was covalently bound using standard siloxane protocols. The unprecedented covalently immobilized initiator underwent radical polymerization with tert-butyl acrylate, yielding for the first...
Dissipative particle dynamics (DPD) was used to investigate the behavior of two opposing end-grafted charged polymer brushes in aqueous media under normal compression and lateral shear. The effect of polymer molecular weight, degree of ionization, grafting density, ionic strength, and compression on the polymer conformation and the resulting shear...
The purpose of this study was to develop oil-in-water emulsions (100-120 nm in diameter) and to correlate the surface properties of the emulsions with blood residence time and accumulation into neoplastic tissues by passive targeting. We investigated the effect of phospholipid and sphingolipid emulsifiers, hydrogenated soybean phosphatidylcholine (...
Homogeneous polystyrene monolayers covalently end-attached on mica and silica surfaces were obtained using a "graft to" methodology. The grafting was achieved via nucleophilic substitution between silanol groups (Si-OH) containing surface and monochlorosilyl terminated polystyrene (PS). Different parameters, such as surface activation, grafting rea...
Thermosensitive polymer nanospheres based on N,N-diethylacrylamide and 2-hydroxyethyl methacrylate (HEMA) have been prepared, characterized, and conjugated with biotin. The thermosensitivity of poly(N,N-diethylacrylamide) was enhanced by the incorporation of HEMA up to about 40 mol %. Atomic force microscopic images show that these particles can be...
The adhesive and mechanical properties of living cells assembled into a monolayer on two different substrates were investigated using the surface forces apparatus ( SFA) technique. The force measurements allowed elastic and bending moduli of the cells plated on substrates to be determined. The moduli are in good agreement with data reported in the...
The texture of food is considered related to its rheological behavior when confined within thin films between two shearing or squeezing surfaces. Such thin-film tribological properties may represent foods undergoing massive grinding and deformation during mastication. The thin-film tribological properties rather than the bulk rheological properties...
The behavior of three copolymers of N-isopropylacrylamide (NIPAM), methacrylic acid (MAA), and hydrophobic moiety was studied at phospholipid monolayer/subphase interfaces. The hydrophobic moieties, N-terminal dioctadecylamine (DODA) and random octadecylacrylate (ODA), were used as anchoring groups. The interactions between a 1,2-distearoyl-sn-glyc...
In contrast to non-associating liquids such as oils or organic solvents, whose viscosity diverges when they are confined by solid surfaces to films thinner than about ten molecular diameters, recent studies reveal that salt-free water remains fluid, with a viscosity close to its bulk value, even when confined to films down to only one or two monola...
Dynamic shear oscillation measurements at small strains are used to characterize the polymerization process in situ and the viscoelastic properties of cross-linked polyacrylamide hydrogels. Hydrogels are synthesized by free-radical redox polymerization of acrylamide (8 wt %) for different concentrations of cross-linker, N,N′-methylenebis(acrylamide...
Molecular interactions between a terminally alkylated pH-sensitive N-isopropylacrylamide copolymer DODA-poly(NIPAM-co-MAA) and a monolayer of distearoylphosphatidylcholine (DSPC) at the air/water interface are investigated using the Langmuir balance technique. The compression isotherms ofthe copolymer monolayer at the air-water interface confirm th...
Long-ranged forces between surfaces in a liquid control effects from colloid stability to biolubrication, and can be modified either by steric factors due to flexible polymers, or by surface charge effects. In particular, neutral polymer 'brushes' may lead to a massive reduction in sliding friction between the surfaces to which they are attached, w...
A surface force balance has been used to investigate the viscosity of salt-free (conductivity) water confined between hydrophilic and between hydrophobic surfaces. We examine the process of jump-in, across the last few nanometres of thin water films, to adhesive contact between the surfaces. We analyse the flow of water out of the gap under slip an...
The aim of this study was to characterize a pH-sensitive liposome formulation bearing a terminally alkylated N-isopropylacrylamide (NIPAM) copolymer with regard to its pH responsiveness, surface properties, and pharmacokinetics. The interacting forces between two lipid bilayers bearing the anchored NIPAM copolymer were measured with a surface force...
We studied the association of hydrophobically anchored polyelectrolyte layers with a free oppositely charged surfactant at a hydrophobized solid–liquid interface under partially screened conditions using the surface forces and ellipsometry techniques. Combining results from both measurements, we conclude that the association of surfactant (from sol...
Dual templating using aqueous cetyltrimethylammonium chloride/hydroxide (CTMA Cl/OH) and latex spheres was performed to prepare powders of bimodal silica molecular sieves with mesopore and macropore systems. The CTMA/Si ratio was chosen to generate a cubic mesopore of MCM-48 structure. According to high Brunauer–Emmett–Teller surface area, narrow p...
Recent Surface Forces Apparatus (SFA) experiments have shed new light on the roles of surface roughness and surface deformations, both at the molecular and microscopic scales, in determining adhesion and friction. Depending on the roughness, but also on other factors such as the stiffness and viscoelasticity of surfaces, these effects can cause the...
The adsorption kinetics of a diblock copolymer poly(tert-butyl methacrylate)-b-poly(glycidyl methacrylate sodium sulfonate) on hydrophobic substrate from aqueous solution under different added monovalent salt (NaCl) concentrations was investigated using an ellipsometric technique. The effect of monovalent counterion size on adsorption kinetics of t...
New surfactants derived from crown ethers were synthesized and used as templates in the preparation of inorganic mesostructures. These surfactants having a crown ether group as hydrophilic head yielded silica mesoporous molecular sieves of the M41S family which were transformed with subsequent thermal treatment into a material of particular unprece...
We investigated the nature and the range of interactions between negatively charged polyelectrolyte-coated surfaces as a function of salt concentration using the surface forces apparatus. The measured force profiles (interaction forces versus separation distance) are purely repulsive and show long-range electrostatic and short-range steric interact...
Lyotropic liquid crystalline phases are currently exploited as templates for the synthesis of inorganic mesostructures. Using this approach, micellar associations of a series of new surfactants having crown-ethers groups as their polar heads were used to prepare mesoporous materials of the M41S family. In this study, the influences of aliphatic cha...
The forces and viscosity between calcium benzene sulfonate surfactant-coated mica surfaces in various hydrocarbon liquids containing a polyamine-functionalized hydrocarbon polymer (M
W≈8000) have been measured using the surface forces apparatus technique. The polymer is found to adsorb to the substrate surfaces by displacing the surfactant layer, a...
In this study, micellar associations of cetyltrimethylammonium chloride/hydroxide with different Cl/OH exchange ratios and new surfactants having crown-ethers groups as their polar head were used to prepare mesoporous materials of M41S family, with subsequent calcination or CO2 supercritical fluid extraction to remove the template.The influences of...
The interactions between surfaces across a nonionic surfactant (tetraoxyethylene dodecyl ether, C12E4) solution and its microemulsion in the dilute regime have been directly measured using the surface force apparatus. The results show that the structure of the adsorbed surfactant layer depends dramatically on the size and shape of the self-assemble...
This paper deals with the study of deposit and friction films of overbased calcium sulphonate diluted in mineral oil, on metal surfaces.
The technique used for this work is Infrared Reflection Absorption Spectroscopy by Fourier Transform and Polarisation Modulation (PM‐IRRAS or PM FTIR). The spectra obtained from this method contain only informatio...
Overbased calcium sulfonates can be used to prevent wear occurring during friction phenomenon by forming a boundary film on friction surfaces. The formation mechanism of the boundary film was investigated using polarization modulated infrared reflection absorption spectroscopy. It appears that the film mainly consists of CaCO3 crystallites and that...
Colloidal dispersions of calcium carbonate stabilised by calcium alkylaryl sulphonates are detergent additives used in lubricant oils, and have particular effects on wear processes. In the present work, such additives were investigated using Small Angle X-ray Scattering technique (SAXS). Different scattering intensity simulation and curve-fitting p...
Overbased calcium sulfonates were investigated using small angle X-ray scattering (SAXS). Different scattering intensity simulation and curve fitting programs were used to determine the sizes of the micelles and to characterize the interactions between them. SAXS results for diluted solutions were compared to electronic microscopy observations. The...
The shear behaviour of a thin hexadecane confined film has been studied at 17°C thanks to a new "3D device" mounted in a surface force apparatus. This device has the particularity of allowing the measurements of both normal and lateral forces independently in three orthogonal directions. Periodic sliding was performed either in one or two direction...
Mica substrates were activated by a plasma method leading to OH-functionalized surfaces to which an ATRP radical initiator was covalently bound using standard siloxane protocols. The initiator grafting on the mica substrate was confirmed by TOF-SIMS, while the change in water contact angle of the OH-activated mica surface was used to follow the cha...
Thèse (M.Sc.) - Université Laval, 1989. Bibliogr. : f. 136-138.
