Tran Minh Duc - Academia.edu (original) (raw)

Papers by Tran Minh Duc

Langmuir, 1995

Atomic force microscopy (AFM) has been applied to investigate surface morphology of poly(buty1 ac... more Atomic force microscopy (AFM) has been applied to investigate surface morphology of poly(buty1 acrylate)/ poly(methy1 methacrylate) (PBAPMMA) core shell latex particles synthesized by a two-stage seeded emulsion polymerization. Imaging has been performed in air on ...

Surface and Interface Analysis, 1994

Static secondary ion mass spectrometry (SIMS) was applied for probing structural differences such... more Static secondary ion mass spectrometry (SIMS) was applied for probing structural differences such as unsaturation and branching in the case of simple aliphatic hydrocarbon polymers (polyethylene, polypropylene and their copolymers). The parameter introduced for quoting surface amounts of branching is the percentage of C6 to C8 cluster emission relative to the sum of all C2 to C8 clusters. The ratio of the total emission of hydrogen-deficient fragments to the sum of all C2 to C8 clusters is found to be a good pointer for unsaturation, especially for probing vinyl bonds. While applied successfully to polymers of the same family, these pointers cannot provide structural information on polyethylene/polypropylene copolymer surfaces in a straightforward way. The chemical surface composition of these copolymers is correlated to the percentage of the m/z 69 fragment.

Langmuir, 1996

In order to model biological membranes, DPPE (1, 2-dihexadecanoyl-sn-glycero-3-phosphoethanolamin... more In order to model biological membranes, DPPE (1, 2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine) and DPPC (1, 2-dihexadecanoyl-sn-glycero-3-phosphocholine) Langmuir-Blodgett (LB) films were deposited on hydrophilic mica and hydrophobic highly ...

Surface and Interface Analysis, 2000

Atomic force microscopy (AFM) is currently used to investigate polymer surface morphology, to obt... more Atomic force microscopy (AFM) is currently used to investigate polymer surface morphology, to obtain roughness parameters or to map the qualitative differences of surface properties. Some previous studies have attempted to determine quantitatively the elastic surface properties, but the difficulty with AFM is that the contact geometry is not very well known, due to the complexity of the mechanical system composed of the cantilever-tip set and the solid surface. We propose here a relative method for measuring the Young's modulus E of a polymer surface by AFM indentation, involving a calibration step obtained from a set of standards constituted by pure polymers with known modulus. Contact stiffness, indentation at peak load and shape of unloading curve are obtained for each reference polymer, leading to a linear relationship between E and a function of these parameters. This calibration curve allows the unknown Young's modulus values of the different phases at the surface of a biphase polymer system to be determined. The force volume mode was used to record force curves. Compared to classical indentation techniques, the force volume mode gives the advantage of imaging surface domains exhibiting elasticity differences. Thus, the elastic modulus can be quantified with a spatial resolution on a nanometric scale.

Biomaterials, 2000

Spoilage is a primary factor in the biocompatibility of soft contact lenses (SCL) within the lacr... more Spoilage is a primary factor in the biocompatibility of soft contact lenses (SCL) within the lacrimal #uid. Tears are a complex mixture of proteins, lipids, natural surfactants and salts. The spoilation process is due to a contribution of all these components and of the nature of SCL materials themselves. The aim of this study was to set up methods to observe and quantify lacrimal deposits and to select e$cient surfactants for preventing protein deposits. The present study was performed on PMMA-NVP SCL. The behaviour of SCL in presence of tears was studied by means of an in vitro arti"cial tear model consisting of the main tears components and quanti"ed by a colorimetric technique (BCA) performed directly on the lenses. The nature of the deposit was observed directly by atomic force microscopy (AFM) in a liquid medium showing the same adsorption trend noticed in the quantitative results and identifying speci"c adsorption sites. The assessment of surfactant adsorption was performed using Maron's method, as a mean to evaluate the a$nity of surfactant to the surface, while the action of selected surfactants on pre-treated SCL was assessed using the BCA method. Promising results were obtained with these two di!erent methods which can be used easily for the pre-selection of surfactants for further cleaning solution formulation studies.