Preparation of organic/inorganic hybrid and hollow particles by catalytic deposition of silica onto core/shell heterocoagulates modified with poly[2-(N,N-dimethylamino)ethyl methacrylate]

Application of nanosilica in the construction industry: A bibliometric analysis using Methodi Ordinatio

The number of publications related to the implementation of nanotechnology in the construction industry, and specifically to the application of nanosilica (SiO2), has had a constant increase in recent years. Based on this, in the present work, an analysis was carried out using bibliometric techniques, with the aim at characterizing the development of specialized literature and identifying the largest areas of growth in the field, maintaining hydrophobic nanosilica as the research guideline. This analysis acquired information from the Scopus and Web of Science (WoS) databases to compare bibliometric indicators of the publications. It should be noted that, even though bibliometric analysis is useful to identify the study areas of greatest interest, to complement this work, the implementation of a method that helped in the research process to obtain the most important bibliography was required. This study implemented Methodi Ordinatio, which helped to take a new direction. Therefore, based on this method, a list of articles cataloged and ranked is obtained, which is the basis for integrating the final bibliographic portfolio. •The study applies the Methodi Ordinatio to obtain a portfolio of the most relevant articles to guide the researchers' work.•Insightful information can be obtained using VOSviewer to analyze and visualize metadata of the bibliographic portfolio.•The study demonstrates how the alpha value in the InOrdinatio formula modifies the resulting portfolio.

Cationic polymeric template-mediated preparation of silica nanocomposites

Biosilicification allows the formation of complex and delicate biogenic silica in near-neutral solutions under ambient conditions. Studies have revealed that, during biosilicification, basic amino acid residues and long-chain polyamines of organic substrates interact electrostatically with negatively charged silicate precursors in solution, catalyzing the polycondensation of silicic acid and accelerating the formation of silica. This mechanism has inspired researchers to explore polymers bearing chemical similarity with these organic matrices as cationic templates for biomimetic silicification. Such templates can be classified into two general categories based on the physical forms applied. One is a solution of water-soluble cationic polymers, either natural or synthetic, used as is for silicification. The other category includes various microscopically shaped entities made of cationic polymer-containing molecules, in the form of micelles, vesicles, crystalline aggregates, latex particles, and microgels. Combined with controlled polymerization and other techniques, these preorganized templates can be tailor designed in terms of sizes and morphologies to allow further expansion of properties and functions. In this review, notable research progress for both categories of silicification under biomimetic conditions is discussed. With the merits of silica and cationic polymers seamlessly integrated, the potential of such versatile nanocomposites in biomedical as well as energy and environmental applications is also briefly highlighted.

Silicification of Amine-Epoxide Cationic Microgels: An In Vitro Investigation

Herein, the applicability of an unconventional, non-vinylic type of amine-epoxide microgels (MGs) to promote silica deposition from tetraethyl orthosilicate (TEOS) was investigated. Simply mixing MGs with TEOS in water at 25 °C resulted in the formation of hybrid silica-MG particles (sMGs) as a function of silicification time. The sMGs were cationic with thermal-sensitive swelling capability. Extending silicification time to 24 h was shown to increase silica content to 43%. Besides, the sMGs became structurally more rigid to resist drying-induced deformation and exhibited a rugged surface texture. Mechanistically, the aminated nature of the MGs was proved beneficial for the success of their silicification, fulfilling dual functions of the catalyst for TEOS hydrolysis and template for silica deposition. Through electrostatic adsorption, the sMGs provided a facile yet robust option for surface modifications toward bone-related applications. Surface-induced mineralization in simulated biological fluids was observed with sMG-immobilized surfaces, where the presence of hydroxyapatite was characterized in the deposited apatite. In vitro MC3T3-E1 pre-osteoblast cell studies showed that cell adhesion, morphology, and proliferation could be influenced by both sMG types and their adsorption density. Of particular interest is the finding of cells exhibiting elongated and greatly polarized morphology on the surface with high adsorption density of sMGs of 43% silica. It was postulated that the rugged appearance of such sMGs could have presented a hierarchically structured surface toward cells, an interesting aspect to be further exploited for the engineering of cell-surface interactions.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Imprinting Dimples on Narrowly Dispersed Polymeric Spheres by Heterocoagulation between Hard Polymer Particles and Soft Oil Droplets

Golf ball-like particles having a number of dimples on their spherical surfaces were prepared by a combined method of heterocoagulation between hard polymer particles and soft silicone oil droplets, polymerization of the oil droplets, and dissolution of the polymer particles with tetrahydrofuran. In the heterocoagulation, polystyrene (PSt) particles of three different sizes were employed as hard particles. Distribution of dimples formed with small-sized PSt particles was less homogeneous than that with middle-sized PSt particles (MPS). Narrowly dispersed golf ball-like particles with homogeneously distributed dimples were successfully prepared with a high number ratio of MPS to oil droplets. The employment of large-sized PSt particles in the heterocoagulation decreased the number of PSt particles required for the stabilization of the oil droplets, which created polyhedron-like particles having dimples on their surface. Additional experiments in which polymer particles with different surface affinities to the oil droplets were heterocoagulated with the droplets revealed that a high surface affinity of particles to the droplets could deeply embed the polymer particles into the droplets and form dimples with a low contact angle.

Water-Dispersible Silica-Polyelectrolyte Nanocomposites Prepared via Acid-Triggered Polycondensation of Silicic Acid and Directed by Polycations

The present work describes the acid-triggered condensation of silicic acid, Si(OH)₄, as directed by selected polycations in aqueous solution in the pH range of 6.5⁻8.0 at room temperature, without the use of additional solvents or surfactants. This process results in the formation of silica-polyelectrolyte (S-PE) nanocomposites in the form of precipitate or water-dispersible particles. The mean hydrodynamic diameter (d_h) of size distributions of the prepared water-dispersible S-PE composites is presented as a function of the solution pH at which the composite formation was achieved. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and block copolymers of DMAEMA and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) were used as weak polyelectrolytes in S-PE composite formation. The activity of the strong polyelectrolytes poly(methacryloxyethyl trimethylammonium iodide) (PMOTAI) and PMOTAI-b-POEGMA in S-PE formation is also examined. The effect of polyelectrolyte strength and the OEGMA block on the formation of the S-PE composites is assessed with respect to the S-PE composites prepared using the PDMAEMA homopolymer. In the presence of the PDMAEMA₆₀ homopolymer (M_w = 9400 g/mol), the size of the dispersible S-PE composites increases with solution pH in the range pH 6.6⁻8.1, from d_h = 30 nm to d_h = 800 nm. S-PDMAEMA₆₀ prepared at pH 7.8 contained 66% silica by mass (TGA). The increase in dispersible S-PE particle size is diminished when directed by PDMAEMA₃₀₀ (M_w = 47,000 g/mol), reaching a maximum of d_h = 75 nm. S-PE composites formed using PDMAEMA-b-POEGMA remain in the range d_h = 20⁻30 nm across this same pH regime. Precipitated S-PE composites were obtained as spheres of up to 200 nm in diameter (SEM) and up to 65% mass content of silica (TGA). The conditions of pH for the preparation of dispersible and precipitate S-PE nanocomposites, as directed by the five selected polyelectrolytes PDMAEMA₆₀, PDMAEMA₃₀₀, PMOTAI₆₀, PDMAEMA₆₀-b-POEGMA₃₈ and PMOTAI₆₀-b-POEGMA₃₈ is summarized.

Preparation of aliphatic–aromatic polyimide particles by polycondensation of diethyl hexafluoroisopropylidenediphthalate and diaminooctane in ethylene glycol

Polycondensation of nylon salt-type monomer composed of diethyl hexafluoroisopropylidenediphthalate and diaminooctane was performed at 130°C in ethylene glycol to form confetti-shaped particles. Before the polycondensation, the salt monomer solution was homogeneous. As the polycondensation proceeded, the solution became turbid and polyimide particles grew to around 7 μm for 8 h. After the polycondensation, small particles precipitated and got deposited onto large particles to form confetti-shaped particles. Rod-shaped particles were also formed by the polycondensation at low monomer concentration in a long reaction time. They were found to be crystalline in form.

Mesopore-free hollow silica particles with controllable diameter and shell thickness via additive-free synthesis

Mesopore-free hollow silica particles with a spherical shape, smooth surface, and controllable diameter (from 80 to 300 nm) and shell thickness (from 2 to 25 nm) were successfully prepared using an additive-free synthesis method. Different from other hollow particle developments, a mesopore-free shell was produced because of the absence of additive. Although common reports pointed out the importance of the additional additive in pasting and growing silica on the surface of a template, here we preferred to exploit the effect of the template charge in gaining the silica coating process. To form the silica, basic amino acid (i.e., lysine) was used as a catalyst to replace ammonia or hydrazine, which is harmless and able to control the silica growth and produce hollow particles with smooth surfaces. Control of the particle diameter was drastically achieved by altering the size of the template. The flexibility of the process in controlling the shell thickness was predominantly attained by varying the compositions of the reactants (i.e., silica source and catalyst). The present mesopore-free hollow particles could be efficiently used for various applications, especially for thermal insulator and optical devices because of their tendency not to adsorb large molecules, as confirmed by adsorption analysis.