The Effect of Clay Type on the Physicochemical Properties of New Hydrogel Clay Nanocomposites

This study focuses on the investigation of clay type effect on the final properties of semi-interpenetrated Salecan/poly(methacrylic acid)/clay hydrogel nanocomposites. Previous studies have indicated that the presence of clay in polymer composites leads to better swelling capacity and mechanical properties as functions of clay type. On the other hand, Salecan, which is a water soluble extracellular polysaccharide, was proved to assure greater flexibility to hydrogels. These properties recommend clay and Salecan for semi-interpenetrated hydrogels preparation with specific application in biomedicine. The purpose was to determine the most suitable type of clay as well as Salecan influence for developing the desired water retention/delivery ability and mechanically enhanced semi-interpenetrating polymer network (SIPN) nanocomposites. For our investigations, we have chosen commercially available montmorillonite (ClNa) and different commercial organomodified clay (Cl30B, Cl20A and Cl15A). Several analyses results (FTIR, TGA, DMA, XRD, microscopy and swelling studies) demonstrated that not only the presence of Salecan but also the clay type influenced the structure and properties of the final nanocomposites

The Effects of Monomer, Crosslinking Agent, and Filler Concentrations on the Viscoelastic and Swelling Properties of Poly(methacrylic acid) Hydrogels: A Comparison

The present work aims at comparatively studying the effects of the concentrations of a monomer (10–30 wt% based on the whole hydrogel composition), crosslinking agent (1–3 mol% based on the monomer), and reinforcing agent (montmorillonite-MMT, 1–3 wt.% based on the whole hydrogel composition) on the swelling and viscoelastic properties of the crosslinked hydrogels prepared from methacrylic acid (MAA) and N,N′-methylenebisacrylamide (BIS) in the presence of K2S2O8 in aqueous solution. The viscoelastic measurements, carried out on the as-prepared hydrogels, showed that the monomer concentration had the largest impact, its three-time enhancement causing a 30-fold increase in the storage modulus, as compared with only a fivefold increase in the case of the crosslinking agent and 1.5-fold increase for MMT in response to a similar threefold concentration increase. Swelling studies, performed at three pH values, revealed that the water absorption of the hydrogels decreased with increasing concentration of both the monomer and crosslinking agent, with the amplitude of the effect of concentration modification being similar at pH 5.4 and 7.4 in both cases, but very different at pH 1.2. Further, it was shown that the increased pH differently influenced the swelling degree in the case of the hydrogel series in which the concentrations of the monomer and crosslinking agent were varied. In contrast to the effect of the monomer and crosslinking agent concentrations, the increase in the MMT amount in the hydrogel resulted in an increased swelling degree at pH 5.4 and 7.4, while at pH 1.2, a slight decrease in the water absorption was noticed. The hydrogel crosslinking density determinations revealed that this parameter was most affected by the increase in the monomer concentration

Novel Formulations of PEG–Silica Phase-Changing Materials (PCMs) with Applications in Passive Storage of Thermal Energy

The aim of the present study is to design new PEG–silica hybrids (PEGx–Si) as phase changing [...

Synthesis of Zinc Oxide Nanomaterials via Sol-Gel Process with Anti-Corrosive Effect for Cu, Al and Zn Metallic Substrates

Nanosized zinc oxide (ZnO) particles modified with different silane coupling agents (octyltriethoxysilane (OTES), octadecyltriethoxysilane (ODTES) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS)) were synthesized in basic catalysis using the sol-gel method. The structure and morphology were characterized by dynamic light scattering (DLS), environmental scanning electron microscopy (ESEM) and Fourier transform infrared spectroscopy (FTIR) for bonding characteristics. The final hybrid materials were deposited on three types of metallic substrates (aluminum (Al), copper (Cu) and zinc (Zn)) in order to obtain coatings with ultrahydrophobic and anti-corrosion properties. Water wettability was studied revealing a contact angle of 145° for the surface covered with ZnO material modified with ODTES. The water contact angle increased with the length of the alkyl chain supplied by the silica precursor. The anti-corrosive behavior of ZnO/silane coupling agents particles deposited on metallic substrates was studied by the linear polarization technique in neutral medium

Rapid Microwave-Assisted Synthesis of Organo-Modified Nanostructured Silica Coatings with Tunable Water-Repellence Properties

A simple method to fabricate organo-modified silane coatings for water-repellent surface modification was proposed, by using a microwave sol-gel synthesis of hybrid materials. Low-cost fluorine-free tetraethoxysilane (TEOS) and dodecyltriethoxysilane (DDTES) were used as silane derivatives. The organo-modified silica coatings were prepared by the drop-casting method and were characterized by UV-VIS, FTIR spectroscopy, and AFM and SEM microscopy. The morphology of the film show the existence of submicrometer scale roughness due to the aggregation of modified silica nanoparticles. Contact angles of water and diiodomethane on surfaces modified with as prepared nanostructured film were determined in order to assess the hydrophobic and oleophobic properties. The TEOS/DDTES ratio was proved to be a crucial factor in tuning the wettability properties. The results suggest that significant increase of hydrophobicity could be achieved by using non-fluorinated cost-effective silica nanomaterials produced with a rapid ecofriendly method

Mesoporous Silica Nanoreservoirs Loaded with 1-H Benzotriazole for Active Anticorrosion Protection

In recent years, scientists are paying increased attention to the development of intelligent nanocontainers in applications such as biomedical, catalysis, and anticorrosion [1]. Preparation of anticorrosion coatings containing smart nanocontainers loaded with corrosion inhibitors, which can be initiated when the barrier coatings are damaged, favor the long-term function, as uncontrolled loss by leaching is inhibited [2]. The aim of the present study is to optimize the amount of an organic inhibitor (1-H benzotriazole (BTA)) that can be in situ encapsulated in a mesoporous silica nanocontainer, prepared by an original sol-gel formulation. Materials and methods: For the synthesis of silica mesoporous, nanoparticles loaded with BTA were used with three silica co-precursors: tetraethylorthosilicate (TEOS), phenyltriethoxysilane (PTES), and octyltriethoxysilane (OTES), at a 5/1/1 gravimetric ratio. The synthesis was carried out in the presence of a solvent (ethanol) and of a surfactant (Igepal CA-630). The pH of the sol–gel system was adjusted to ~9 by dripping an aqueous solution of NH4OH (25%). Prior to the addition to the sol–gel reaction system, BTA was completely dissolved in ethanol. Various amounts of BTA were loaded to the sol–gel systems: 0.25; 0.5; 0.75; 1; 1.25; 1.5; and 2 g (corresponding to 0.09; 0.18; 0.27; 0.35; 0.44; 0.53; and 0.70% grav. of the total amount of sol–gel mixture, respectively). Furthermore, a similar set of samples was prepared in the presence of a constant amount of rhodamine B, dissolved in ethanol. This second set was obtained in order to perform a visual evaluation of the encapsulation efficiency. Particles dimensions, size distributions, and particles charging in the final dispersions were evaluated by the dynamic light scattering (DLS) technique and Zeta potential measurements. Surface morphology was observed by SEM. The structural characteristics of the silica mesoporous particles were investigated by N2 adsorption–desorption analysis on the calcined samples. Results: During the in situ synthesis of silica nanoparticles, the aromatic molecules of the corrosion inhibitor BTA were linked via a hydrophobic interaction with the phenyl groups from the silica pores formed by the hydrophobic functions of silica co-precursors, i.e., PTES and OTES. In addition, the corrosion inhibitor was trapped inside the surfactant micelles of Igepal and encapsulated together inside the silica pores formed by the surfactant. Moreover, it was observed that only a small amount of BTA can be encapsulated in the absence of the surfactant. Conclusions: An optimized method was developed to obtain mesoporous silica nanoparticles loaded with 1-H Benzotriazole (BTA) as a corrosion inhibitor. The optimal range of the BTA concentration was found to be between 0.18 and 0.35%

Mixed Pluronic—Cremophor Polymeric Micelles as Nanocarriers for Poorly Soluble Antibiotics—The Influence on the Antibacterial Activity

In this work, novel polymeric mixed micelles from Pluronic F127 and Cremophor EL were investigated as drug delivery systems for Norfloxacin as model antibiotic drug. The optimal molar ratio of surfactants was determined, in order to decrease critical micellar concentration (CMC) and prepare carriers with minimal surfactant concentrations. The particle size, zeta potential, and encapsulation efficiency were determined for both pure and mixed micelles with selected composition. In vitro release kinetics of Norfloxacin from micelles show that the composition of surfactant mixture generates tunable extended release. The mixed micelles exhibit good biocompatibility against normal fibroblasts MRC-5 cells, while some cytotoxicity was found in all micellar systems at high concentrations. The influence of the surfactant components in the carrier on the antibacterial properties of Norfloxacin was investigated. The drug loaded mixed micellar formulation exhibit good activity against clinical isolated strains, compared with the CLSI recommended standard strains (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922). P. aeruginosa 5399 clinical strain shows low sensitivity to Norfloxacin in all tested micelle systems. The results suggest that Cremophor EL-Pluronic F127 mixed micelles can be considered as novel controlled release delivery systems for hydrophobic antimicrobial drugs

Use of Bacterial Carbonatogenesis for Construction Materials

Concrete is the most used construction material, but its industrial production from lime consumes 2–3% of the global energy demand, generating 0 [...

Use of Bacterial Carbonatogenesis for Construction Materials

Concrete is the most used construction material, but its industrial production from lime consumes 2–3% of the global energy demand, generating 0 [...

Adjusting Some Properties of Poly(methacrylic acid) (Nano)Composite Hydrogels by Means of Silicon-Containing Inorganic Fillers

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 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