Search Results (44)

Herein, we report the rational synthesis of porous g-C₃N₄ co-modified with oxygen (O) and fluorine (F) for the first time. Incorporating colloidal SiO₂ during thermal polymerization introduces lattice oxygen, forming C–O bonds, while post-treatment with NH₄·HF₂ establishes C–F bonds. The dual incorporation of O and F elements extends visible light absorption and effectively promotes the separation and transport of photoexcited charge carriers. Consequently, the co-modified g-C₃N₄ (O,F-g-C₃N₄) achieves a 13.2-fold increase in H₂ evolution rate compared to pristine g-C₃N₄. This synthesized O,F-g-C₃N₄ is then dispersed in waterborne polyurethane (WPU) to create an anti-corrosive coating for Q235 carbon steel substrates. Water resistance, mechanical property, and electrochemical characterization analyses reveal that the O,F-g-C₃N₄/WPU composite coating exhibits remarkable corrosion resistance with a high protection efficiency of 90.23%. This work offers a straightforward approach for developing highly efficient g-C₃N₄-based photocatalysts and corrosion-resistant coatings. Full article

A new nanodevice based on gold nanoparticles (AuNPs) capped with poly(diethylvinylphosphonate) (PDEVP) has been synthesized, showing interesting photophysical and thermoresponsive properties. The synthesis involves a properly designed Yttriocene catalyst coordinating the vinyl-lutidine (VL) initiator active in diethyl vinyl phosphonate polymerization. The unsaturated PDEVP chain ending was thioacetylated, deacetylated, and reacted with tetrachloroauric acid and sodium borohydride to form PDEVP-VL-capped AuNPs. The NMR, UV–Vis, and ESI-MS characterization of the metal nanoparticles confirmed the formation of the synthetic intermediates and the expected colloidal systems. AuNPs of subnanometric size were determined by WAXD and UV–Vis analysis. UV–Vis and fluorescence analysis confirmed the effective anchoring of the thiolated PDEVP to AuNPs. The formation of 50–200 nm globular structures was assessed by SEM and AFM microscopy in solid state and confirmed by DLS in aqueous dispersion. Hydrodynamic radius studies showed colloidal contraction with temperature, demonstrating thermoresponsive behavior. These properties suggest potential biomedical applications for the photoablation of malignant cells or controlled drug delivery induced by light or heat for the novel PDEVP-capped AuNP systems. Full article

Conductive polymers, such as polyaniline (PANI), have interesting applications, ranging from flexible electronics, energy storage devices, sensors, antistatic or anticorrosion coatings, etc. However, the full exploitation of conductive polymers still poses a challenge due to their low processability. The use of compatible stabilizers to obtain dispersible and stable colloids is among the possible solutions to overcome such drawbacks. In this work, potato starch was used as a steric stabilizer for the preparation of colloidal polyaniline (emeraldine salt, ES)/starch composites by exploiting the oxidative polymerization of aniline in aqueous solutions with various starch-to-aniline ratios. The polyaniline/starch bio-composites were subjected to structural, spectroscopic, thermal, morphological, and electrochemical analyses. The samples were then tested for their dispersibility/solubility in a range of organic solvents. The results demonstrated the formation of PANI/starch biocomposites with a smaller average size than starch particles, showing improved aqueous dispersion and enhanced solubility in organic solvents. With respect to previously reported PANI-EB (emeraldine base)/starch composites, the novel colloids displayed a lower overall crystallinity, but the conductive nature of PANI-ES enhanced its electrochemical properties, resulting in richer redox chemistry, particularly evident in its oxidation behavior, as observed through cyclic voltammetry. Finally, as proof of the improved processability, the colloids were successfully integrated into a thin polyether sulfone (PES) membrane. Full article

Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for producing colloidal dispersions of block copolymer particles with desired morphologies. Currently, PISA can be carried out in various media, over a wide range of temperatures, and using different mechanisms. This method enables the production of biodegradable objects and particles with various functionalities and stimuli sensitivity. Consequently, PISA offers a broad spectrum of potential commercial applications. The aim of this review is to provide an overview of the current state of rational synthesis of block copolymer particles with diverse morphologies using various PISA techniques and mechanisms. The discussion begins with an examination of the main thermodynamic, kinetic, and structural aspects of block copolymer micellization, followed by an exploration of the key principles of PISA in the formation of gradient and block copolymers. The review also delves into the main mechanisms of PISA implementation and the principles governing particle morphology. Finally, the potential future developments in PISA are considered. Full article

Recently, suitably sized polymer-based nanogels containing functional groups for the binding of biologically active substances and ultimately degradable to products that can be removed by glomerular filtration have become extensively studied systems in the field of drug delivery. Herein, we designed and tailored the synthesis of hydrophilic and biodegradable poly[N-(2-hydroxypropyl) methacrylamide-co-N,N′-bis(acryloyl) cystamine-co-6-methacrylamidohexanoyl hydrazine] (PHPMA-BAC-BMH) nanogels. The facile and versatile dispersion polymerization enabled the preparation of nanogels with a diameter below 50 nm, which is the key parameter for efficient and selective passive tumor targeting. The effects of the N,N′-bis(acryloyl) cystamine crosslinker, polymerization composition, and medium including H₂O/MetCel and H₂O/EtCel on the particle size, particle size distribution, morphology, and polymerization kinetics and copolymer composition were investigated in detail. We demonstrated the formation of a 38 nm colloidally stable PHPMA-BAC-BMH nanogel with a core–shell structure that can be rapidly degraded in the presence of 10 mM glutathione solution under physiologic conditions. The nanogels were stable in an aqueous solution modeling the bloodstream; thus, these nanogels have the potential to become highly important carriers in the drug delivery of various molecules. Full article

Polyaniline (PANI) is a conductive polymer easily converted into a conducting state. However, its limited mechanical properties have generated interest in fabricating PANI composites with other polymeric materials. In this study, a PANI–prevulcanized latex composite film was synthesized and fabricated in two phases following chronological steps. The first phase determined the following optimum parameters for synthesizing nanosized PANI, which were as follows: an initial molar ratio of 1, a stirring speed of 600 rpm, a synthesis temperature of 25 °C, purification via filtration, and washing using dopant acid, acetone, and distilled water. The use of a nonionic surfactant, Triton X-100, at 0.1% concentration favored PANI formation in a smaller particle size of approximately 600 nm and good dispersibility over seven days of observation compared to the use of anionic sodium dodecyl sulfate. Ultraviolet–visible spectroscopy (UV-Vis) showed that the PANI synthesized using a surfactant was in the emeraldine base form, as the washing process tends to decrease the doping level in the PANI backbone. Our scanning electron microscopy analysis showed that the optimized synthesis parameters produced colloidal PANI with an average particle size of 695 nm. This higher aspect ratio explained the higher conductivity of nanosized PANI compared to micron-sized PANI. Following the chronological steps to determine the optimal parameters produced a nanosized PANI powder. The nanosized PANI had higher conductivity than the micron-sized PANI because of its higher aspect ratio. When PANI is synthesized in smaller particle sizes, it has higher conductivity. Atomic force microscopy analysis showed that the current flow is higher across a 5 µm² scanned area of nanosized PANI because it has a larger surface area. Thus, more sites for the current to flow through were present on the nanosized PANI particles. Full article

In recent years, with the development of science and technology, the strategic position of germanium is becoming more and more important, and the global demand for germanium is also increasing. At present, there is no unified description of the existence form of germanium in solutions. Based on the current mainstream acid leaching process of germanium, this paper studies the existing form and properties of germanium in sulfuric acid solutions. Through the characterization and analysis of Raman, FTIR, and XPS of three concentrations of pure germanium solution, it is clear that germanium mainly exists in the form of H₂GeO₃ and some Ge⁴⁺ in sulfuric acid solution. Through the Tyndall effect and zeta potential, it is determined that H₂GeO₃ exists in the form of colloid in sulfuric acid solution. With the increase of germanium concentration, H₂GeO₃ will polymerize in a sulfuric acid solution to form polygermanic acid, and the H₂GeO₃ colloidal dispersion system becomes more stable. This study clarifies the existing form and properties of germanium in sulfuric acid solution, which is of great significance to the leaching extraction of germanium-containing materials and the development of the germanium industry. Full article

Different methods which could be used to produce colloidal dispersions of polyaniline (PANI) nano-objects without templates are described. While the methods are non-deterministic, different nano-objects (nanospheres, nanofibers, nanobelts, nanorice, nanotubes, nanorods, nanodisks, etc.) can be produced. Those most used are: (i) solution polymerization with steric stabilizers (SPS) to produce nanospheres, (ii) interfacial polymerization (IP) to produce nanofibers and (iii) solution polymerization in the presence of additives (SPA) to produce nanotubes. Oxidation of aniline in aqueous solution could produce nanotubes, nanofibers and other shapes by controlling mass transport/concentration of reactants, pH, and the presence of oligomers/additives. The different models proposed to explain the formation of various nano-objects are discussed. Mechanochemical polymerization (MCP) could produce nanofibers or nanospheres by controlling the aniline/oxidant ratio. PANI nanospheres of tunable sizes can also be produced by nanoprecipitation (NPT) of preformed PANI from its solutions using an antisolvent. The geometrical constraints to the small nano-objects made of high-molecular-weight rigid polymers are described. The conditions to produce nanostructures also affect the intrinsic properties of PANI (conductivity, crystallinity, and electroactivity). Selected technological applications of PANI nano-objects manufactured as colloidal dispersions without templates are discussed. Based on the reviewed work and models, future lines of work are proposed. Full article

In this paper, the aqueous copolymer dispersions of methyl (meth)acrylate-grafted poly(vinyl alcohol) are in situ synthesized and studied as a promising platform for the deposition of thin films with advanced applications. A series of dispersions of the varied copolymer structure and composition are obtained at mild reaction conditions by carrying out a redox polymerization at a different monomer-to-PVA ratio and initiator concentration. The obtained colloidal particles are characterized by Fourier transformed infrared spectroscopy, nuclear magnetic resonance, dynamic light scattering, and transmission electron microscopy. The copolymer dispersions are further used for deposition of thin films on silicon substrates. The films are characterized optically through reflectance measurements and non-linear curve fitting. Their suitability for the optical sensing of acetone vapors is confirmed by reflectance measurements before and during their exposure to analyte vapors. The cross sensitivity, sensing repeatability, and recovery of the sensitive films are discussed. Full article

Scientific research based on the self-assembly behavior of block copolymers (BCs) comprising charged-neutral segments has emerged as a novel strategy mainly looking for the optimization of efficiency in the generation and storage of electrical energy. The sulfonation reaction re- presents one of the most commonly employed methodologies by scientific investigations to reach the desired amphiphilic character, leading to enough ion concentration to modify and control the entire self-assembly behavior of the BCs. Recently, several works have studied and exploited these changes, inducing improvement on the mechanical properties, ionic conduction capabilities, colloidal solubility, interface activity, and stabilization of dispersed particles, among others. This review aims to present a description of recent works focused on obtaining amphiphilic block copolymers, specifically those that were synthesized by a living/controlled polymerization method and that have introduced the amphiphilic character by the sulfonation of one of the segments. Additionally, relevant works that have evidenced morphological and/or structural changes regarding the pristine BC as a result of the chemical modification are discussed. Finally, several emerging practical applications are analyzed to highlight the main drawbacks and challenges that should be addressed to overcome the development and understanding of these complex systems. Full article

Colloidal microspheres could be used as raw materials to construct the photonic crystal modification layers on wood surfaces, and the wood would produce gorgeous structural color effect. The diameter, monodispersity and self-assembly of colloidal microspheres directly affect the well-structure order of photonic crystals. Therefore, poly(styrene-acrylic acid) (P(St-AA)) shell-core microspheres were prepared by emulsion polymerization. The effects of the reaction time, amount of initiator and emulsifier and reaction temperature on the particle size and dispersity of colloidal microspheres during polymerization were analyzed by single-factor experiments. The P(St-AA) colloidal microspheres self-assembled on wood surfaces and formed photonic crystals with structural color through thermally-assisted gravity deposition. The effects of the amount of emulsion coating per unit surface area and ambient temperature on the optical properties of the photonic crystals were investigated. It was found that the particle size of the synthesized microspheres increased with the increase of initiator amount and reaction temperature and the decrease of emulsifier; however, the effect of reaction time on microspheres was less regular. The best optical properties of the photonic crystals on wood surfaces were obtained using 0.408 μL/mm² emulsion coating at a temperature of 50 °C. The photonic crystals were composed of both ordered and disordered layers. Full article

Hollow TiO₂ nanoparticles (HNPs) capped with conducting polymers, such as polythiophene (PT), polypyrrole (PPy), and polyaniline (PANI), have been studied to be used as polarizability-tunable electrorheological (ER) fluids. The hollow shape of TiO₂ nanoparticles, achieved by the removal of the SiO₂ template, offers colloidal dispersion stability in silicone oil owing to the high number density. Conducting polymer shells, introduced on the nanoparticle surface using vapor deposition polymerization method, improve the yield stress of the corresponding ER fluids in the order of PANI < PPy < PT. PT-HNPs exhibited the highest yield stress of ca. 94.2 Pa, which is 5.0-, 1.5-, and 9.6-times higher than that of PANI-, PPy-, and bare HNPs, respectively. The improved ER response upon tuning with polymer shells is attributed to the space charge contribution arising from the movement of the charge carriers trapped by the heterogeneous interface. The ER response of studied ER fluids is consistent with the corresponding polarizability results as indicated by the permittivity and electrophoretic mobility measurements. In conclusion, the synergistic effect of hollow nanostructures and conducting polymer capping effectively enhanced the ER performance. Full article

Usnic acid (UA) is one of the most abundant and common metabolites of lichens, known for its numerous pharmacological properties. Nevertheless, it presents some criticalities that severely limit its use in therapy: poor solubility in water and significant hepatotoxicity. Soluplus and Solutol HS15 and D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) were employed to develop polymeric micelles (UA–PM). The chemical and physical properties of the system were characterized, including the size, homogeneity, zeta potential, critical micellar concentration (CMC), encapsulation efficiency (EE%), and in vitro release. The freeze-drying process was considered to prevent agglomeration and improve the stability of the formulation. The stability of the micelles and the freeze-dried product (UA–PML) was also evaluated. The anti-migratory activity of UA and UA–PM was evaluated in human neuroblastoma SH-SY5Y cells using the wound healing assay. Their effect on the activity of metalloproteinases (MMP)-2/9 involved in the migration process of cells was verified by gelatin zymography. The optimized UA–PM contained Soluplus, Solutol HS15, and TPGS in a 1:4:0.5 weight ratio and increased the aqueous solubility to about 150-fold solubilized, solubilizing 0.5 mg/mL of UA. UA–PM has a small size (45.39 ± 0.31 nm), a polydispersity index (PDI) of 0.26 ± 0.01, and an EE% of 82.13 ± 5.57%. The colloidal dispersion was stable only for 9 days at 4 °C, while the freeze-drying process improved the stability for up to 30 days. UA was released for a prolonged period during the in vitro release study. The in vitro cell-based experiments showed that UA–PM (0.2 µg/mL) inhibited SH-SY5Y cell migration and the gelatinolytic activity of MMP-2/9 in culture media, while free UA at the same concentration exerted no biological activity. This study demonstrates that polymeric micelles are an excellent formulation for UA to manifest inhibitory action on neuroblastoma cell migration. Full article

The utilization of vegetable oil in the production of polymeric material has gained interest due to its proven ability to replace nonrenewable petroleum sources, as it is readily modified via chemical reaction to produce polyol and subsequently for polyurethane production. Jatropha oil (JO), a second-generation feedstock, is one of the suitable candidates for polyester polyol synthesis because it contains a high percentage of unsaturated fatty acids. In this study, jatropha-based polyester polyols (JOLs) with different hydroxyl values were successfully synthesized via a two-step method: epoxidation followed by oxirane ring-opening reaction. Ring-opening reagents; methanol, ethanol, and isopropanol were used to produce polyol with hydroxyl number of 166, 180, and 189 mg/KOH, respectively. All the synthesized JOLs exhibited a Newtonian to shear thinning behavior in the measured shear rate ranges from 10 to 1000 s⁻¹ at 25 °C. The viscosity of a JOL ring-opened with methanol, isopropanol, and ethanol was 202, 213, and 666 mPa·s, respectively, at 20 °C and 100 s⁻¹, which is within the range of commercially available polyols. Successively, the JOLs were reacted with isophorone diisocyanate (IPDI) to produce polyurethane prepolymer by utilizing 2,2-dimethylol propionic acid (DMPA) as an emulsifier. The prepolymer was then dispersed in water to produce a waterborne polyurethane dispersion. Colloidal stability of the jatropha-based polyurethane dispersions (JPUDs) were investigated by particle size analysis. A JPUD with a small particle size in the range of 6.39 to 43.83 nm was obtained, and the trend was associated with the soft segment of the polyol in the formulation. The zeta potentials of the JPUs ranged from −47.01 to −88.9 mV, indicating that all synthesized JPUs had high dispersity and stability. The efficient synthesis procedure, low cost, and excellent properties of the resulting product are thought to offer an opportunity to use jatropha oil as a sustainable resource for polyester polyol preparation. Full article

We investigate the use of an ionic liquid (IL) as a surfactant in emulsion polymerization (EP) reactions. ILs have been proposed as surfactants for micellar dispersions, emulsions, micro-emulsions and suspensions. Thus, it is important to acquire knowledge of the application of ILs in heterogeneous polymerizations. We selected the amphiphile cationic oligoether IoLiLyte C1EG™ as an IL for this purpose and compared its performance to that of the conventional surfactant dodecyl trimethyl ammonium bromide (DTAB) in the EP of methyl methacrylate and styrene. After we found the proper concentration range of the IL, this amphiphile showed similar polymerization rates to those observed with DTAB for both monomers. The evolution of monomer conversion and the final average diameter of formed polymeric particles were similar for both evaluated surfactants, demonstrating their capability to stabilize the EPs of the investigated monomers. We simulated the evolution of monomer conversion and particle size using a conventional model for emulsion polymerization, which showed good agreement with the experimental data, suggesting that the EP with this IL follows Smith-Ewart kinetics. Full article