Radovan Toth

Sodium montmorillonite silylation: Unexpected effect of the aminosilane chain length

In this work, the silylation of sodium montmorillonite (Na-MMT) was performed in glycerol using 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]-propyl-trimethoxysilane. The effects on the d-spacing of sodium montmorillonite (Na-MMT) upon reaction with three aminosilanes of different chain length were studied in details by combining experimental and computational techniques. Infrared spectroscopy was used to monitor the grafting process, while the degree of grafting was calculated using thermogravimetric analysis. X-ray diffraction experiments were carried out to evaluate the shift of the (0 0 1) basal spacing. It was found that the degree of silylation of Na-MMT increases with increasing the length of the aminosilane organic moieties, the overall aminosilane concentration, and temperature. The same beneficial effects were observed on the silicate d-spacing, as its value increases with increasing silane concentration and reaction temperature. Remarkably, however, increasing the length of the organic chains in the silane modifiers resulted in decreasing values of the Na-MMT interlayer distance. A rationale for this behavior is proposed on the basis of atomistic molecular dynamics simulation evidences.

MULTISCALE MODELING OF POLYMER/CLAY NANOCOMPOSITES

Multiscale molecular modeling (M3) is applied in many fields of material science, but it is particularly important in the polymer science, due to the wide range of phenomena occurring at different scales which influence the ultimate properties of the materials. In this context, M3 plays a crucial role in the design of new materials whose properties are infiuenced by the structure at nanoscale. In this work we present the application of a multiscale molecular modeling procedure to characterize polymer/clay nanocomposites obtained with full/partial dispersion of nanofillers in a polymer. This approach relies on a step-by step message-passing technique from atomistic to mesoscale to finite element level; thus, computer simulations at all scales are completely integrated and the calculated results are compared to available experimental evidences. In details, nine polymer nanocomposite systems have been studied by different molecular modeling methods, such as atomistic Molecular Mechanics and Molecular Dynamics, the mesoscale Dissipative Particles Dynamics and the macroscale Finite Element Method. The entire computational procedure has been applied to a number of diverse polymer nanocomposite systems based on montmorillonite as clay and different clay surface modifiers, and their mechanical, thermal and barrier properties have been predicted in agreement with the available experimental data.

Simple, Fast, and Accurate In silico Estimations of Contact Angle, Surface Tension, and Work of Adhesion of Water and Oil Nanodroplets on Amorphous Polypropylene Surfaces

In this work, two computational recipes based on atomistic molecular dynamics simulations are developed and compared to quickly and accurately quantify the interactions of amorphous polypropylene surface with water and oil. Fundamental quantities such as contact angle and surface tension are estimated in excellent agreement with the corresponding experimental values, wheras the comparable values of the work of adhesion obtained using both computational recipes confirm the internal consistency in the presented methodologies.

Experimental validation of specificity of the squamous cell carcinoma antigen-immunoglobulin M (SCCA-IgM) assay in patients with cirrhosis

Abstract Background: Squamous cell carcinoma antigen-immunoglobulin M (SCCA-IgM) is a useful biomarker for the risk of development of hepatocellular carcinoma (HCC) in patients with cirrhosis due to its progressive increase associated to HCC evolution. In patients with cirrhosis, other assays have been affected by interfering reactivities of IgM. In this study, the analytical specificity of the SCCA-IgM assay was assessed by evaluating SCCA-IgM measurement dependence on different capture phases, and by measuring the recovery of SCCA-IgM reactivity following serum fractionation. Methods: Serum samples from 82 patients with cirrhosis were analyzed. SCCA-IgM was measured using the reference test (Hepa-IC, Xeptagen, Italy) that is based on rabbit oligoclonal anti-squamous cell carcinoma antigen (SCCA) and a dedicated ELISA with a mouse monoclonal anti-SCCA as the capture antibody. Results: SCCA-IgM concentrations measured with the reference assay (median value=87 AU/mL) were higher than those measured with the mouse monoclonal test (median value=78 AU/mL). However, the differences in the SCCA-IgM distribution were not statistically significant (p>0.05). When SCCA-IgM concentrations measured with both tests were compared, a linear correlation was found (r=0.77, p<0.05). Fractionation of the most reactive sera by gel-filtration chromatography showed that total recovery of SCCA-IgM reactivity was seen only in the fractions corresponding to components with a molecular weight higher than IgM and SCCA (>2000 kDa) with both tests. Conclusions: The equivalence of both SCCA-IgM assays and the absence of reactivity not related to immune complexes support the analytical specificity of SCCA-IgM measurements. The results validate the assessment of SCCA-IgM for prognostic purposes in patients with cirrhosis. Clin Chem Lab Med 2010;48:217–23.