Polymer-coated Silica Particles Research Articles

Competitive Distribution of Europium and Samarium Based on Reaction Rate-Limiting Process in Nitrilotriacetamide Extractant-Impregnated Polymer-Coated Silica Particles

Abstract Since in the nuclear fuel cycle, multiple lanthanide and actinide ions are separated by chromatography, understanding the mass transfer mechanism in the solution with multiple ions, which is generally difficult, is important for effective separation. In the present study, we have elucidated the mass transfer mechanism of Eu(III) and Sm(III) in a solution with these ions in single nitrilotriacetamide (NTA) extractant-impregnated polymer-coated silica particles. The rate-limiting process of mass transfer was the reaction of ions with NTA molecules, in which the NO3− ions were not involved, which was consistent with that obtained in a single ion distribution system. In a two-ion distribution system, the competitive reaction of Eu(III) and Sm(III) with NTA molecules was observed. The forward and backward reaction rate constants of Eu(III) and Sm(III) were determined to be $k_{1}^{\text{Eu}}$ = (1.8 ± 0.7) × 102 M−2 s−1 and $k_{ - 1}^{\text{Eu}}$ = (6.1 ± 5.3) × 10−4 s−1, and $k_{1}^{\text{Sm}}$ = (1.9 ± 0.5) × 102 M−2 s−1 and $k_{ - 1}^{\text{Sm}}$ = (5.8 ± 4.6) × 10−4 s−1. The obtained result indicates that in the near future the mass transfers of several ions in the particle can be analyzed with the present method.

Kinetic Mass Transfer Behavior of Eu(III) in Nitrilotriacetamide-Impregnated Polymer-Coated Silica Particles

Abstract We investigated the distribution mechanism of Eu(III) in a single polymer-coated silica particle including nitrilotriacetamide (NTA) extractants known as HONTA and TOD2EHNTA. We studied the kinetic rate constants of the distribution process at various concentrations of NO3− (CNO3−) that were prepared using HNO3 and NaNO3 solutions. The rate-determining process during the distribution of Eu(III) was identified as the reaction process of Eu(III) for both extractants, that is, the reaction process of Eu(III) and two NTA molecules in the polymer layer of the silica particle. Furthermore, the reaction of Eu(III) with NO3− ions was found not to be involved in the rate-determining process. The forward (k1) and backward (k−1) reaction kinetic constants for the reaction between Eu(III) and two NTA molecules were determined to be k1 = (5.7 ± 2.2) × 102 M−2 s−1 and k−1 = (2.3 ± 4.4) × 10−4 s−1 for HONTA, and k1 = (6.5 ± 3.0) × 102 M−2 s−1 in the NaNO3 system and k−1 = (2.0 ± 1.5) × 10−4 s−1 in both solutions for TOD2EHNTA. The present study provides a valuable approach for the evaluation and enhancement of the functionality of ‘single extractant-impregnated polymer-coated silica particles’.

Effect of polymer-coated silica particles in a Portland cement matrix via in-situ infrared spectroscopy

It is often of great importance in engineering to know precisely the properties of a material used with regard to its strength, its plasticity or its brittleness, its elasticity, and some other properties. For this purpose, material samples are tested in a tensile test by clamping the sample with a known starting cross-section in a tensile testing machine and loading it with a tensile force F. The force is then graphically displayed over the length change ΔL caused. This curve is called the force-extension diagram. In this study, a new measurement method enables for the first time, depending on the applied uniaxial stress, an insight at the atomic level into various energy dissipation processes at cement-based materials with the help of infrared spectroscopy. The samples are modified by adding SiO2 particles, which are coated by a polymer (PEG-MDI-DMPA) of different PEG molecular weights. Results show that elongating and breakage of [Formula: see text] and [Formula: see text] bonds play an essential role in the strain energy dissipation. Compared to the pure cement, the modified samples are affected more by elongating and breakage of [Formula: see text] as the admixture can effectively reduce the energy barrier of the hydrolytic reaction. The incorporating of particles into the cement matrix induces new mechanisms for energy dissipation by stretching of [Formula: see text] bending vibrations. Stretching vibration of the [Formula: see text] group indicates that part of the energy is dissipated by breakage of hydrogen bonding between the carboxyl group and PEG chains. Besides, a higher value of the ultimate fracture force following an increase in the molecular weight of PEG shows stronger bonding between particles and the cement matrix. As the chain-length of PEG is increased, less energy is absorbed through the other processes (especially at a higher level of strain). Thus, there is a balance between the whole deformation (toughness) and the strength of samples with the increase of the PEG molecular weight.

The solute mechanical properties impact on the drying of dairy and model colloidal systems.

The evaporation of colloidal solutions is frequently observed in nature and in everyday life. The investigation of the mechanisms taking place during the desiccation of biological fluids is currently a scientific challenge with potential biomedical and industrial applications. In the last few decades, seminal works have been performed mostly on dried droplets of saliva, urine and plasma. However, the full understanding of the drying process in biocolloids is far from being achieved and, notably, the impact of solute properties on the morphological characteristics of the evaporating droplets, such as colloid segregation, skin formation and crack pattern development, is still to be elucidated. For this purpose, the use of model colloidal solutions, whose rheological behavior is more easily deducible, could represent a significant boost. In this work, we compare the drying of droplets of whey proteins and casein micelles, the two main milk protein classes, to that of dispersions of silica particles and polymer-coated silica particles, respectively. The mechanical behavior of such biological colloids and model silica dispersions was investigated through the analysis of crack formation, and the measurements of their mechanical properties using indentation testing. The study reveals numerous analogies between dairy and the corresponding model systems, thus confirming the latter as a plausible powerful tool to highlight the signature of the matter at the molecular scale during the drying process.

Targeting Ability of Affibody-Functionalized Particles Is Enhanced by Albumin but Inhibited by Serum Coronas

Protein coronas formed on engineered particles can alter their targeting ability as they enter biological environments. Here, we engineer polymer-coated silica particles and investigate the influence of protein coronas derived from various sources. The particles were functionalized with a small antibody-mimetic ligand (affibody), and their targeting ability to cancer cells in the presence of protein coronas was determined. Protein coronas derived from human serum showed a dramatic inhibition of specific particle-cell association (from ∼70 to ∼7%), whereas the most abundant protein in human serum-human serum albumin-enhanced the specific association of functionalized particles to SK-OV-3 human ovary cancer cells (to ∼90%). This study shows how protein coronas can both facilitate and impede targeting and provides key insights into the importance of challenging engineered particles with multicomponent biologically relevant environments.

Application of guanidine-containing polymers for preparation of pH responsive silica-based particles for drug delivery systems

Abstract Guanidine containing polymers were applied to prepare polymer coated silica particles via a sol–gel method as potential candidates for drug encapsulation. Here, we used four types of grafted polymers for surface modification. The grafting amount was evaluated by thermogravimetric and elemental analysis and was in 18–34% range. Also polymer coated silica particles were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry and high resolution electron microscopy. The effect of grafted polymers on particle properties and pH-response has been reported. Anionic (sulfasalazine) and cationic (doxorubicin) drugs were effectively loaded into polymer coated silicas. The drug loading and drug release were pH dependent and affected by the nature of grafted polymer and its content. The properties revealed for investigated system have shown promising results for drug delivery with pH controllable drug release.

Tuning the hydrophobicity of plasma polymer coated silica particles

The modification of particle hydrophobicity has been conventionally carried out using wet chemistry methods. This investigation has however applied plasma polymerisation as a novel approach to produce silica particles with tailored hydrophobicity. Deposition of plasma polymerised 1,7-octadiene (ppOD) was carried out using a radio frequency inductively coupled reactor fitted with a rotating chamber. Plasma polymerisation parameters were varied to study the hydrophobicity of hydrocarbon functionalised particles. The surface chemistry of the ppOD coated particles was analysed via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Deposition of ppOD coatings under low specific energy plasma conditions resulted in both chemically and hydrophobically heterogeneous ensemble of particles. Whereas optimised plasma conditions resulted in homogeneous ppOD coatings. Development of hydrophobicity in ppOD coated particles was confirmed by Washburn capillary rise measurements, film flotation tests and environmental scanning electron microscopy observations. Silica particles with a range of water contact angles from 36° to more than 90° were obtained by controlled deposition of ppOD films. Plasma polymerisation using a rotating reactor has shown to be an efficient approach in the surface modification of silica particles to obtain surfaces with controlled hydrophobicity, which are of direct interest in a diverse range of practical applications as well as fundamental studies.

Surface-Initiated Controlled Radical Polymerization from Silica Nanoparticles with High Initiator Density

The surface of silica nanoparticles is modified using the “grafting from” technique. A multi-step reaction is conducted to modify their surface properties. (3-glycidoxypropyl) trimethoxysilane (GPS) is used as the coupling agent for the fixation of atom transfer radical polymerization (ATRP) initiator. The grafting efficiency of GPS mixed with aqueous suspension of silica nanoparticles is studied, followed by the coupling efficiency towards ATRP initiator. The bromide concentration of ATRP initiator is kept constant for comparative kinetic studies of styrene and MMA polymerizations. The consequences at high conversions and the particle size distribution are studied. The behaviour of the glass transition temperature of either polymer-modified particles and the nature of dispersion of polymer-coated silica particles are analyzed.

Microstructure evolution in Stöber-type silica nanoparticles and their in vitro apatite deposition

Prepared via Stober-type sol–gel routes were three types of silica particles of Si–OH as well as hydrogen bonding interactions among them. In addition, the Ca–silica and core-shell silica deposited apatite in Kokubo’s simulated body fluid. Thus, the present Ca–silica and polymer-coated silica particles were suggested to be applicable to injectable bone fillers for bone generation.

Silica reinforced triblock copolymer gels

The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene–poly(ethylene/butylene)–polystyrene (PS–PEB–PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order to evaluate the influence of the compatibility between gel and filler. Time-resolved SANS and small-angle X-ray scattering (SAXS) shows that the presence of silica particles affects the ordering of the polystyrene domains during gelsetting. The scattering pattern of silica-reinforced gels reveals strong scattering at very low q, but no structure and formfactor information. However, on heating above the viscoelastic to plastic transition, the ‘typical’ scattering pattern of the copolymer gel builds-up. All reinforced gels are strengthened by the addition of the reinforcing agent. The transitions from a viscoelastic rubber to a plastic fluid and from a plastic fluid to a viscoelastic liquid are shifted to more elevated temperatures when silica is added to the triblock copolymer gel.

Electrochemical preparation of chiral polyaniline nanocomposites

Optically active polyaniline colloids have been generated in high yield via the electrohydrodynamic polymerisation of aniline in the presence of 1.0 mol dm −3 (+)- or (−)-camphorsulfonic acid as dopant using colloidal silica (5% w/w) as dispersant and an applied potential of +0.8 V (vs. Ag/AgCl). Both the rate of polymer formation and the degree of chiral induction in the polyaniline chains were enhanced compared to colloid formation using polystyrenesulfonate (PSS) as steric stabiliser. Higher chiral induction was achieved using 10% w/w silica as dispersant, while lower silica concentrations (e.g., 2.5% w/w) led to over-oxidation. Lower (+)-HCSA concentrations (≤0.5 mol dm −3) also caused over-oxidation. The dispersions using 5 and 10% w/w silica were very stable, showing unchanged chiroptical properties after 3–4 months. The particle size (300–600 nm) increased with increasing polymerisation time. Transmission electron micrographs (TEM) studies on the dried PAn.(+)-HCSA/silica colloid also showed large (200–600 nm diameter) particles, which on high magnification were seen to be nanocomposites consisting of individual polymer-coated silica particles (ca. 20 nm) fused together to give a raspberry-like morphology.

Synthesis of Polymer-Coated Silica Particles with Specific Recognition Sites for Glucose Oxidase by the Molecular Imprinting Technique

Abstract A polymer layer around silica beads, composed of acrylamide, acrylic acid, and crosslinkers, was able to preferentially recognize glucose oxidase (GOD) from a mixture of proteins. Matching between the ζ-potential of GOD and that of its imprinted polymer is suggested to be important in enhancing the recognition effect.

Characterization of polymer-coated silica particles by microelectrophoresis

Electrophoretic mobility measurements have been used to characterize monodispersed colloidal particles of silica, silica coated with alumina (cores), of these cores incorporating a dye (pigments), and finally of pigments coated with polymers. The latter consisted of poly(divinylbenzene), of poly(vinylbenzyl chloride), and of their copolymers, synthesized directly on the core or pigment particles, with and without subsequent sulfonation.

Packed Column Development in Supercritical Fluid Chromatography

Having been categorically dismissed as inapplicable for supercritical fluid chromatography during the mid-1980s, packed columns are rapidly regaining much of their lost popularity. Much of the renewed interest stems from the introduction of more deactivated polymer-coated silica particles, which enable the separation of highly polar analytes to be carried out with nonmodified carbon dioxide. Furthermore, the employment of packed capillary columns makes it possible to utilize both GC-like and LC-like detectors. Major findings in the evolution of packed columns, specifically for supercritical fluid chromatography, are discussed.