silicon and methacrylic-acid

The present work aims to show how the main properties of poly(methacrylic acid) (PMAA) hydrogels can be engineered by means of several silicon-based fillers (Laponite XLS/XLG, montmorillonite (Mt), pyrogenic silica (PS)) employed at 10 wt% concentration based on MAA. Various techniques (FT-IR, XRD, TGA, SEM, TEM, DLS, rheological measurements, UV-VIS) were used to comparatively study the effect of these fillers, in correlation with their characteristics, upon the structure and swelling, viscoelastic, and water decontamination properties of (nano)composite hydrogels. The experiments demonstrated that the nanocomposite hydrogel morphology was dictated by the way the filler particles dispersed in water. The equilibrium swelling degree (SDe) depended on both the pH of the environment and the filler nature. At pH 1.2, a slight crosslinking effect of the fillers was evidenced, increasing in the order Mt < Laponite < PS. At pH > pKaMAA (pH 5.4; 7.4; 9.5), the Laponite/Mt-containing hydrogels displayed a higher SDe as compared to the neat one, while at pH 7.4/9.5 the PS-filled hydrogels surprisingly displayed the highest SDe. Rheological measurements on as-prepared hydrogels showed that the filler addition improved the mechanical properties. After equilibrium swelling at pH 5.4, G’ and G” depended on the filler, the Laponite-reinforced hydrogels proving to be the strongest. The (nano)composite hydrogels synthesized displayed filler-dependent absorption properties of two cationic dyes used as model water pollutants, Laponite XLS-reinforced hydrogel demonstrating both the highest absorption rate and absorption capacity. Besides wastewater purification, the (nano)composite hydrogels described here may also find applications in the pharmaceutical field as devices for the controlled release of drugs.

Topics: Bentonite; Coloring Agents; Delayed-Action Preparations; Hydrogels; Methacrylates; Nanocomposites; Nanogels; Silicates; Silicon; Silicon Dioxide; Spectroscopy, Fourier Transform Infrared; Water; Water Pollutants

Europium(III)-imprinted polymer nanoparticles were synthesized using suspension polymerization in silicon oil. Vinyl pyridine and methacrylic acid were used either as the complexing ligand or functional monomer. Divinyl benzene was applied as cross-linker agent. Carbon paste electrodes, impregnated with the ion imprinted polymer (IIP), were incubated in the solutions containing Cu(2+) and different kinds of lanthanide ions. The oxidative stripping differential pulse voltammetry method was then utilized to measure the signal of adsorbed Cu(2+), after removal of the electrodes from the first solutions and immersion of them in the electrochemical cell. The response of the IIP-modified electrode to Cu(2+) decreased in the solution containing both Cu(2+) and Eu(3+); but, it was not influenced in the solutions of Cu(2+) and other lanthanides. This suggested that Eu(3+) could compete against Cu(2+) to capture the selective sites of the IIP; whereas, other lanthanide ions were not capable of replacement with Cu(2+) in the IIP sites. However, In the case of non-imprinted polymer (NIP)-modified electrode, no considerable signal difference was found between the pure Cu(2+) solution and the solution containing both Cu(2+) and Eu(3+). This indicated that the selective sites of the IIP were responsible for the observed phenomenon. The decrease in the response of IIP-based electrode to Cu(2+) was found to be reasonably proportional to Eu(3+) concentration. This finding was utilized for the indirect voltammetric determination of Eu(3+). The effect of different factors on the method was then investigated and the optimum conditions were chosen. The electrode showed high selectivity for Eu(3+), even in the presence of other lanthanide ions. The developed method exhibited concentration linear range of 5 × 10(-7)-3 × 10(-5)mol L(-1) and detection limit of 1.5 × 10(-7)mol L(-1) (signal/noise, S/N). Relative standard error percent of 5 separate determinations was found to be 2.91%. The developed method was successfully applied for the determination of Eu(3+) in the synthetic and spiked real samples.

Topics: Binding, Competitive; Carbon; Copper; Electrochemical Techniques; Electrodes; Europium; Humans; Hydrogen-Ion Concentration; Industrial Oils; Limit of Detection; Methacrylates; Molecular Imprinting; Polymers; Sensitivity and Specificity; Silicon; Vinyl Compounds; Water Pollutants, Chemical

We describe a pH responsive drug delivery system which was fabricated using a novel approach to functionalize biodegradeable porous silicon (pSi) by initiated chemical vapor deposition (iCVD). The assembly involved first loading a model drug (camptothecin, CPT) into the pores of the pSi matrix followed by capping the pores with a thin pH responsive copolymer film of poly(methacrylic acid-co-ethylene dimethacrylate) (p(MAA-co-EDMA)) via iCVD. Release of CPT from uncoated pSi was identical in two buffers at pH 1.8 and pH 7.4. In contrast, the linear release rate of CPT from the pSi matrix with the p(MAA-co-EDMA) coating was dependent on the pH; release of CPT was more than four times faster at pH 7.4 (13.1 nmol/(cm(2) h)) than at pH 1.8 (3.0 nmol/(cm(2) h)). The key advantage of this drug delivery approach over existing ones based on pSi is that the iCVD coating can be applied to the pSi matrix after drug loading without degradation of the drug because the process does not expose the drug to harmful solvents or high temperatures and is independent of the surface chemistry and pore size of the nanoporous matrix.

Topics: Camptothecin; Chemistry, Pharmaceutical; Coated Materials, Biocompatible; Delayed-Action Preparations; Drug Delivery Systems; Humans; Hydrogen-Ion Concentration; Methacrylates; Nanostructures; Polymers; Porosity; Silicon; Volatilization