Pluronic Concentration Research Articles

Stable O/W emulsions by combining Pluronic L64 and Sodium Alginate

Emulsions play a pivotal role in many industrial fields, including food, pharmaceutics, and cosmetics. This paper explores the simultaneous effects of varying concentrations of Pluronic and Sodium Alginate (Alg), with particular attention to the resulting stability and the rheological properties of the incoming oil-in-water emulsions. Pluronics are used as amphiphilic molecules to stabilize the oil droplet interface, Alg is instead used to increase the viscosity of the suspending medium in a way to slow down droplet coalescence. High shear mixing is used to prepare the emulsions, and rheology and optical microscopy are employed to assess their microstructure. By optimizing both Alg and Pluronic concentrations, emulsions stable up to 90 days are achieved.

Solution-Phase Synthesis of KCl Nanocrystals Templated by PEO-PPO-PEO Triblock Copolymers Micelles.

The current work introduces the synthesis of inorganic salt nano/micro-crystals during the reduction of hydrogen tetrachloroaurate(III) by Pluronic triblock copolymers (P123, PEO20-PPO70-PEO20). The morphologies and component were confirmed using an electron microscope with an electronic differential system (EDS), and the crystal structures were determined with X-ray diffraction (XRD). The morphologies highly depend on the concentrations of Pluronic and pH values. The mean size of the nanocrystal and hollow micro-crystal were controlled typically in the range of 32-150 nm (side length) and 1.4 μm, respectively. Different from the electrospray-ionization (EI) method, a model in which KCl forms a supersaturated solution in the micellar core of Pluronic is used to explain the formation process. This work provides the new insight that inorganic salt nanocrystals could be synthesized with the template of micelles in pure aqueous solutions.

Self-assembling Organogels Loaded with Tenoxicam for Local Intensive Pain and Inflammation Cure: In Vitro and In Vivo Correlation.

Due to tenoxicam (TX)'s poor aqueous solubility (0.072 mg/ml), it is poorly absorbable in the GIT, and the long-term oral administration of TX may cause severe GIT disturbances. Topical administration of TX can help in bypassing the GIT adverse effects. Therefore, in the present work, we constructed different pluronic/lecithin organogels (PLOs) for topical delivery of TX. PLO was constructed simply via direct mixing of an aqueous pluronic solution with lecithin solution. The prepared PLO formulations were characterized for their physicochemical properties including pH, drug content, visual inspection, viscosity, and spreadability. Also, the in vitro release and kinetic studies were carried out to investigate the mechanism of drug release. Moreover, the in vivo studies were carried out by investigating the anti-inflammatory and analgesic activities using albino male rats. The results showed that the modified PLOs have good physicochemical properties. The viscosity of the modified gels is a direct proportionality with both lecithin and pluronic concentrations. Also, subsequently, the drug release rate is directly proportional to gel viscosity. Moreover, the in vivo studies showed that the modified PLOs (F19) showed a significant ( < 0.05%) paw edema inhibition and pain analgesia compared with other investigated groups. Also, the results indicated that the increase in dose is accompanied by higher activity and a longer duration of action which extended to 12 h. Hence, the modified PLOs are promising safe candidates or vehicles for effective TX loading with sustained delivery behavior.

Transforming layered 2D mats into multiphasic 3D nanofiber scaffolds with tailored gradient features for tissue regeneration.

Multiphasic scaffolds with tailored gradient features hold significant promise for tissue regeneration applications. Herein, this work reports the transformation of two-dimensional (2D) layered fiber mats into three dimensional (3D) multiphasic scaffolds using a 'solids-of-revolution' inspired gas-foaming expansion technology. These scaffolds feature precise control over fiber alignment, pore size, and regional structure. Manipulating nanofiber mat layers and Pluronic F127 concentrations allows further customization of pore size and fiber alignment within different scaffold regions. The cellular response to multiphasic scaffolds demonstrates the number of cells migrated and proliferated onto the scaffolds are mainly dependent on the pore size rather than fiber alignment. In vivo subcutaneous implantation of multiphasic scaffolds to rats reveals substantial cell infiltration, neo tissue formation, collagen deposition, and new vessel formation within scaffolds, greatly surpassing the capabilities of traditional nanofiber mats. Histological examination indicates the importance of optimizing pore size and fiber alignment for promotion of cell infiltration and tissue regeneration. Overall, these scaffolds have potential applications in tissue modeling, studying tissue-tissue interactions, interface tissue engineering, and high-throughput screening for optimized tissue regeneration.

Adsorption of Mixed Dispersions of Silica Nanoparticles and an Amphiphilic Triblock Copolymer at the Water–Vapor Interface

This study investigates the surface modification of hydrophilic silica nanoparticles by non-chemical adsorption of an amphiphilic triblock copolymer, Pluronic F-127, and elucidates its influence on the interfacial dispersion properties. The interaction between Pluronic F-127 and silica nanoparticles drives the formation of copolymer-decorated particles with increased hydrodynamic diameter and reduced effective charge as the copolymer concentration increases, while the opposite effect occurs as the particle concentration increases at a fixed polymer concentration. This indicates that increasing the copolymer concentration leads to an increase in the coating density, whereas increasing the particle concentration leads to a decrease. This is of paramount importance for modulating the reorganization of the Pluronic F-127 shell upon adsorption at fluid–fluid interfaces and, thus, the adsorption of the decorated nanoparticles at the interface and the rheological properties of the obtained layers. In fact, the relationship between copolymer concentration and interfacial tension, as well as the mechanical response of the interface, mirrors the patterns observed in Pluronic F-127 solutions, and only a shift mediated by the Pluronic F-127 concentration is found. This suggests that the presence of particles limits the space available for Pluronic F-127 molecules to reorganize at the interface but does not significantly affect the interfacial behavior of the particle-laden interface.

Box Behnken optimization of cubosomes for enhancing the anticancer activity of metformin: Design, characterization, and in-vitro cell proliferation assay on MDA-MB-231 breast and LOVO colon cancer cell lines

This study aimed to formulate and statistically optimize cubosomal formulations of metformin (MTF) to enhance its breast anticancer activity. A Box Behnken design was employed using Design-Expert® software. The formulation variables were glyceryl monooleate concentration (GMO) w/w%, Pluronic F-127 concentration (PF127) w/w% and Tween 80 concentration w/w% whereas Entrapment efficiency (EE%), Vesicles' size (VS) and Zeta potential (ZP) were set as the dependent responses. The design expert software was used to perform the process of optimization numerically. X ray diffraction (XRD), Transmission electron microscope (TEM), in-vitro release study, short-term stability study, and in in-vitro cell proliferation assay on the MDA-MB-231 breast cancer and LOVO cancer cell lines were used to validate the optimized cubosomal formulation. The optimized formulation had a composition of 4.35616 (w/w%) GMO, 5 (w/w%) PF127 and 7.444E-6 (w/w%) Tween 80 with a desirability of 0.733. The predicted values for EE%, VS and ZP were 78.0592%, 307.273 nm and − 26.8275 mV, respectively. The validation process carried out on the optimized formula revealed that there were less than a 5% variance from the predicted responses. The XRD thermograms showed that MTF was encapsulated inside the cubosomal vesicles. TEM images of the optimized MTF cubosomal formulation showed spherical non-aggregated nanovesicles. Moreover, it revealed a sustained release profile of MTF in comparison to the MTF solution. Stability studies indicated that optimum cubosomal formulation was stable for thirty days. Cytotoxicity of the optimized cubosomal formulation was enhanced on the MDA-MB-231 breast and LOVO cancer cell lines compared to MTF solution even at lower concentrations. However, it showed superior cytotoxic effect on breast cancer cell line. So, cubosomes could be considered a promising carrier of MTF to treat breast and colon cancers.

MICRONEEDLES ASSISTED ENHANCEMENT OF TRANSDERMAL DELIVERY OF CURCUMIN THROUGH ORGANOGEL FORMULATION

Curcumin is a natural compound found in turmeric and has been shown to have anti-inflammatory and antioxidant properties. Topical delivery of curcumin through an organic emulsion-based gel can effectively target inflammation at specific sites on the body. The current study aims to formulate Pluronic based organogel of curcumin, whose absorption is further assisted by microneedles technology. Nine organogel formulations were prepared and optimized by 32 full factorization model to fix the ratio of lecithin[A] and Pluronic[B] concentration in order to get optimum drug release after 2 hours (Q2) and maximum release of drug after 8 hours (Q8). The in-vitro study through the Franz diffusion cell indicated a significant impact of Pluronic F-127 concentration on the release of drug. As increased concentration of Pluronic increased the viscosity of formulations which ultimately retarded the release of drug. Based on Design of Experiment (DoE) study, optimized batch containing 6.5% lecithin and 20.6% Pluronic was further studied for microneedle assisted ex-vivo skin permeation through rat skin. Permeation without microneedle poration was around 70.26% after 8 hours, which was significantly increased (around 25%) after microneedle treatment of the skin. The results indicated promising application microneedle assisted skin permeation as a non-invasive and controlled delivery of curcumin through the transdermal route. Further, in-vivo studies are recommended to further establish this promising concept, targeting a variety of inflammatory conditions, including arthritis, psoriasis, and eczema, etc., through non-invasive transdermal drug delivery systems.

Dapsone-Loaded Mixed Micellar Gel for Treatment OF Acne Vulgaris

Mixed polymeric micelles are potential nanocarriers for topical drug delivery. Dapsone (DAP) is an antibacterial used as anti-acne agent, but challenged by low water solubility and poor skin permeability. In the present study, DAP-loaded mixed micellar gel was developed comprising Pluronics F-68 and F-127. Micelles were prepared by solvent evaporation method and particle size, ex vivo permeation, drug loading, and entrapment efficiency were determined. Central Composite Design was used to optimize formulation. Independent variables were concentration of Pluronics at three levels while micelle size and drug loading capacities were dependent variables. Droplet size ranged from 400 to 500 nm. Transmission electron microscopy revealed spherical morphology of micelles. Optimized micelles were incorporated into gel base using HPMC K100M, Sodium CMC, and Carbopol 980 as gelling agents. Gels were evaluated for pH, drug content, spreadability, rheology, syneresis, ex vivo permeation, and subacute dermal toxicity. Compared with solubility of free DAP (0.24+0.056 µg/ml), solubility in mixed micelles was 18.42±3.4 µg/ml in water at room temperature. Order of spreadability of gels was Na CMC < HPMC < Carbopol 980. Carbopol gels displayed thixotropy with index of 3.17. Syneresis for all gels from day 0 to day 30 was found to be in range of 4.2 to 15.6% w/w. Subacute dermal toxicity studies showed no signs of erythema and edema on rat skin until 21 days. These results suggest that mixed micelles can significantly increase solubility and permeability and sustain release of DAP and are suitable carriers for topical DAP delivery in anti-acne therapies.

Different effects of two Poloxamers (L61 and F68) on the conductance of bilayer lipid membranes.

The integral conductance of planar lipid bilayer membranes in the presence of two Poloxamers (Pluronics) L61 and F68 with the same lengths of hydrophobic poly(propylene oxide) blocks and the different lengths of hydrophilic poly(ethylene oxide) blocks increases with an increase in the concentration of both Pluronics; however, the shape of the conductance-concentration curves is super linear for L61 and sublinear for F68. In the presence of both Pluronics, rare discrete current jumps are observed against the background of continuous current. At high concentrations, the I-V curves of membranes with both L61 and F68 became nonlinear at sufficiently low voltages but differed significantly. At voltages greater than 50mV, the conductance of membranes with L61 increased sharply and quantized jumps were observed toward higher conductance, which could be interpreted as the appearance of additional pores. On the contrary, the conductance of membranes with F68 decreased and quantized jumps to lower conductance were observed, which could be interpreted as blocking of already existing pores. We attributed the differences in the conductance-concentration and I-V curves of these two Pluronics to their different effects on the dynamics of membrane hydration and, accordingly, on the probability of formation of conducting pores.

Thermosensitive Pluronic® F127-Based in situ gel formulation containing nanoparticles for the sustained delivery of paclitaxel

Bone metastasis is one of the most encountered complications among cancer patients and majority of cancer types has led to bone metastasis. Paclitaxel (PCX) is an anticancer agent commonly used in cancer treatment. However, its clinical use is restricted owing to poor water solubility. PCL NPs were investigated to cope with solubility problem of PCX. The size, polydispersity index and zeta potential of PCL were 383.8±2.4 nm, 0.253±0.122 and +51.3±6.1 mV, respectively. The PCX encapsulation efficiency was 77.2±2.1%. Subsequently, in situ gellling system was prepared by using different Pluronic F-127 concentration in order to determine the optimum ratio. İn situ gel formulation containing 20% Pluronic F-127 was selected as the optimum formulation and subjected to characterization tests. The viscosity of in situ gelling system with CS/PCX-PCL NPs at room temperature (25 °C±0.1) and at body temperature (37 °C±0.1) were found 137.00 ±3.05 cP and 890.30 ±89.61 cP at 100 rpm, respectively. According to the release results, in situ gel provided prolonged release profile compared to PCL NPs alone. Consequently, in situ gel containing CS/PCX-PCL NP elucidated in detail is a promising approach for locally applicable injectable systems.

Non-Ionic Surfactant Effects on Innate Pluronic 188 Behavior: Interactions, and Physicochemical and Biocompatibility Studies.

The aim of this research was to prepare novel block copolymer-surfactant hybrid nanosystems using the triblock copolymer Pluronic 188, along with surfactants of different hydrophilic to lipophilic balance (HLB ratio-which indicates the degree to which a surfactant is hydrophilic or hydrophobic) and thermotropic behavior. The surfactants used were of non-ionic nature, of which Tween 80® and Brij 58® were more hydrophilic, while Span 40® and Span 60® were more hydrophobic. Each surfactant has unique innate thermal properties and an affinity towards Pluronic 188. The nanosystems were formulated through mixing the pluronic with the surfactants at three different ratios, namely 90:10, 80:20, and 50:50, using the thin-film hydration technique and keeping the pluronic concentration constant. The physicochemical characteristics of the prepared nanosystems were evaluated using various light scattering techniques, while their thermotropic behavior was characterized via microDSC and high-resolution ultrasound spectroscopy. Microenvironmental parameters were attained through the use of fluorescence spectroscopy, while the cytotoxicity of the nanocarriers was studied in vitro. The results indicate that the combination of Pluronic 188 with the above surfactants was able to produce hybrid homogeneous nanoparticle populations of adequately small diameters. The different surfactants had a clear effect on physicochemical parameters such as the size, hydrodynamic diameter, and polydispersity index of the final formulation. The mixing of surfactants with the pluronic clearly changed its thermotropic behavior and thermal transition temperature (Tm) and highlighted the specific interactions that occurred between the different materials, as well as the effect of increasing the surfactant concentration on inherent polymer characteristics and behavior. The formulated nanosystems were found to be mostly of minimal toxicity. The obtained results demonstrate that the thin-film hydration method can be used for the formulation of pluronic-surfactant hybrid nanoparticles, which in turn exhibit favorable characteristics in terms of their possible use in drug delivery applications. This investigation can be used as a road map for the selection of an appropriate nanosystem as a novel vehicle for drug delivery.

Structural transitions in mixed Phosphatidylcholine/Pluronic micellar systems and their in vitro therapeutic evaluation for poorly water-soluble drug

The self-assemblies of phosphatidylcholine (PC) liposomes and Pluronic polymers with varying compositions have been studied. The micellar transition formed in the mixed PC and Pluronics (F127, P123, and mixed F127/P123) systems was investigated through dynamic light scattering (DLS), small-angle neutron scattering (SANS), rheology, and transmission electron microscopy (TEM) measurements.Results indicated that the PC appeared to be perfectly large bilayer vesicles. With an increasing concentration of Pluronics, the PC vesicle is also transformed intospherical micelles. The transitions from large lamellar vesicles to spherical micelles have been found with all the mixed systems, in which mixed F127/P123 performed better. The mixed PC/Pluronic micellar systems (PCFP) are being investigated for the problems associated with curcumin delivery, such as poor solubility and stability. The solubilization of curcumin in the PCFP systems has been examined and found to be better. The curcumin-loaded PCFP micellar system was synthesized through the thin-film method and evaluated in-vitro. Nuclear magnetic resonance(NMR) analysis indicated location of curcumin has found in the core of the PCFP micelles. The curcumin-loaded PCFP showed a slower and more sustained drug release under physiological conditions. The resistance to the oxidation of curcumin-loaded PCFP micelles is considerably higher than that of pure curcumin. Results also revealed that the curcumin-loaded PCFP effectively inhibits the cell proliferation of human breast adenocarcinoma cells (MCF-7) and induces cell death. This study suggests that the curcumin-loaded mixed PC/Pluronic micellar system enhances the bioavailability of curcumin.

Interaction of triblock copolymers (Pluronic®) with DMPC vesicles: a photophysical and computational study

Pluronic/lipid mix promises stealth liposomes with long circulation time and long-term stability for pharmaceutical applications. However, the influence of Pluronics on several aspects of lipid membranes has not been fully elucidated. Herein it was described the effect of Pluronics on the structured water, alkyl chain conformation, and kinetic stability of dimyristoylphosphatidylcholine (DMPC) liposomes using interfacial and deeper fluorescent probes along with computational molecular modeling data. Interfacial water changed as a function of Pluronics’ hydrophobicity with polypropylene oxide (PPO) anchoring the copolymers in the lipid bilayer. Pluronics with more than 30–40 PO units had facilitated penetration at the bilayer while shorter PPO favored a more interfacial interaction. Low Pluronic concentrations provided long-term stability of vesicles by steric effects of polyethylene oxide (PEO), but high amounts destabilized the vesicles as a sum of water-bridge cleavage at the polar head group and the reduced alkyl-alkyl interactions among the lipids. The high kinetic stability of Pluronic/DMPC vesicles is a proof-of-concept of its advantages and applicability in nanotechnology over conventional liposome-based pharmaceutical products for future biomedical applications.

Effect of Pluronic P103 Concentration on the Simple Synthesis of Ag and Au Nanoparticles and Their Application in Anatase-TiO2 Decoration for Its Use in Photocatalysis.

Silver and gold nanoparticles were synthesized under environmentally-friendly reaction conditions by using a biodegradable copolymer and water as a solvent. The triblock copolymer Pluronic P103 was utilized as a stabilizing agent or soft template to produce Ag and Au nanoparticles (NPs) of different sizes. Moreover, in the synthesis of Au NPs, the polymer acted as a reducing agent, decreasing the number of reagents used and consequently the residues produced, hence, rendering the procedure less complicated. It was observed that as the concentration of the polymer increased, the size of the metallic NPs augmented as well. However, AgNPs and AuNPs prepared with 1 and 10 wt% Pluronic P103, respectively, showed a significant decrease in particle size due to the presence of polymeric soft templates. The hybrid materials (metal/polymer) were characterized by UV-Vis spectroscopy, DLS, and TEM. The pre-synthesized nanoparticles were employed to decorate anatase-TiO2, and the composites were characterized by DRS, XRD, BET surface area measurements, the TEM technique with the EDS spectrum, and XPS spectroscopy to demonstrate NPs superficial incorporation. Finally, methylene blue was used as a probe molecule to evidence the effect of NPs decoration in its photocatalytic degradation. The results showed that the presence of the NPs positively affected methylene blue degradation, achieving 96% and 97% removal by utilizing TAg0.1 and TAu10, respectively, in comparison to bare anatase-TiO2 (77%).

Pluronic F-68 Reduces the Endothelial Adherence and Improves the Rheology of Liganded Sickle Erythrocytes

A perfluorochemical blood substitute emulsified with Pluronic F-68 has been shown to improve the filterability of deoxygenated sickle red cells. We questioned whether some of the effect was independent of oxygen loading and studied the influence of Fluosol DA (Green Cross, Osaka, Japan) and Pluronic on the rheology and adhesion of sickle red cells saturated with oxygen and carbon monoxide. A 5-vol/vol% concentration of Fluosol or equivalent concentration of Pluronic was equally effective at improving the filtration of washed sickle cells through 5-micron-diameter pores at wall shear stresses approximating 1,000 dyne/cm2. The same concentration of Pluronic reduced the extensional static rigidity of irreversibly sickled cells (ISC) by 25% and also abolished the adherence of gravity-sedimented sickle cells to endothelial monolayers in the presence of saline or plasma. The inhibition of adherence was not reversible by washing and was accomplished with equal ease by isolated treatment of sickle cells or endothelium. Pluronic had no effect on the rheology or adhesion of normal adult red cells. Neither Fluosol nor Pluronic changed sickle or normal cell shape, mean cell volume, mean cell density, or cell density distribution. A lubricating effect of Pluronic on cell surfaces could explain all of the rheological observations and offers another direction of inquiry in the search for therapy for sickle cell disease.

Exploring high pressure nebulization of Pluronic F127 hydrogels for intraperitoneal drug delivery

Peritoneal metastasis is an advanced cancer type which can be treated with pressurized intraperitoneal aerosol chemotherapy (PIPAC). Here, chemotherapeutics are nebulized under high pressure in the intraperitoneal (IP) cavity to obtain a better biodistribution and tumor penetration. To prevent the fast leakage of chemotherapeutics from the IP cavity, however, nebulization of controlled release formulations is of interest.In this study, the potential of the thermosensitive hydrogel Pluronic F127 to be applied by high pressure nebulization is evaluated. Therefore, aerosol formation is experimentally examined by laser diffraction and theoretically simulated by computational fluid dynamics (CFD) modelling. Furthermore, Pluronic F127 hydrogels are subjected to rheological characterization after which the release of fluorescent model nanoparticles from the hydrogels is determined.A delicate equilibrium is observed between controlled release properties and suitability for aerosolization, where denser hydrogels (20% and 25% w/v Pluronic F127) are able to sustain nanoparticle release up to 30 h, but cannot effectively be nebulized and vice versa. This is demonstrated by a growing aerosol droplet size and exponentially decreasing aerosol cone angle when Pluronic F127 concentration and viscosity increase. Novel nozzle designs or alternative controlled release formulations could move intraperitoneal drug delivery by high pressure nebulization forward.

Magnetic Characterization by Scanning Microscopy of Functionalized Iron Oxide Nanoparticles.

This study aimed to systematically understand the magnetic properties of magnetite (Fe3O4) nanoparticles functionalized with different Pluronic F-127 surfactant concentrations (Fe3O4@Pluronic F-127) obtained by using an improved magnetic characterization method based on three-dimensional magnetic maps generated by scanning magnetic microscopy. Additionally, these Fe3O4 and Fe3O4@Pluronic F-127 nanoparticles, as promising systems for biomedical applications, were prepared by a wet chemical reaction. The magnetization curve was obtained through these three-dimensional maps, confirming that both Fe3O4 and Fe3O4@Pluronic F-127 nanoparticles have a superparamagnetic behavior. The as-prepared samples, stored at approximately 20 °C, showed no change in the magnetization curve even months after their generation, resulting in no nanoparticles free from oxidation, as Raman measurements have confirmed. Furthermore, by applying this magnetic technique, it was possible to estimate that the nanoparticles’ magnetic core diameter was about 5 nm. Our results were confirmed by comparison with other techniques, namely as transmission electron microscopy imaging and diffraction together with Raman spectroscopy. Finally, these results, in addition to validating scanning magnetic microscopy, also highlight its potential for a detailed magnetic characterization of nanoparticles.

DPD Study on the Interfacial Properties of PEO/PEO-PPO-PEO/PPO Ternary Blends: Effects of Pluronic Structure and Concentration.

Using the method of dissipative particle dynamics (DPD) simulations, we investigated the interfacial properties of PEO/PEO-PPO-PEO/PPO ternary blends composed of the Pluronics L64(EO13PO30EO13), F68(EO76PO29EO76), F88(EO104PO39EO104), or F127(EO106PO70EO106) triblock copolymers. Our simulations show that: (i) The interfacial tensions () of the ternary blends obey the relationship < < < , which indicates that triblock copolymer F68 is most effective in reducing the interfacial tension, compared to L64, F88, and F127; (ii) For the blends of PEO/L64/PPO and the F64 copolymer concentration ranging from ccp = 0.2 to 0.4, the interface exhibits a saturation state, which results in the aggregation and micelle formation of F64 copolymers added to the blends, and a lowered efficiency of the L64 copolymers as a compatibilizer, thus, the interfacial tension decreases slightly; (iii) For the blends of PEO/F68/PPO, elevating the Pluronic copolymer concentration can promote Pluronic copolymer enrichment at the interfaces without forming the micelles, which reduces the interfacial tension significantly. The interfacial properties of the blends contained the PEO-PPO-PEO triblock copolymer compatibilizers are, thus, controlled by the triblock copolymer structure and the concentration. This work provides important insights into the use of the PEO-PPO-PEO triblock copolymer as compatibilizers in the PEO and PPO homopolymer blend systems.

Direct ink writing of boron carbide monoliths

Direct ink writing – an extrusion-based additive manufacturing process – followed by pressureless sintering was investigated to produce boron carbide monoliths. The effects of ceramic powder loading and Pluronic binder concentration on the rheology of boron carbide pastes were studied and linked to both processing behaviour and final outcome in terms of sintered density and hardness. The effects of printing parameters, in particular orifice diameter and printing speed, were also investigated. Reducing the size of the extrusion nozzle from 584 μm to 406 μm led to significantly better shape retention, lower surface roughness, as well as higher density and hardness. A 203 μm printing orifice was also trialled but was unsuccessful due to faster drying kinetics that occurred with smaller ceramic struts resulting in rapid warping and nozzle clogging. Carbon-black – 8 wt% relative to B4C – acted as an effective sintering aid to increase both density and hardness. After optimisation of feedstock and printing parameters, few-layer samples (3–5 layers) had a density as high as ∼ 97 % TD and a hardness of ∼ 30 GPa. On the other hand, 18-layer specimens had a sintered density of ∼ 87 % TD, despite a fully dense microstructure, due to the formation of a 3D array of inter-strut pores. Nevertheless, several issues that arose during manufacturing and post-processing were detrimental to the density and structural integrity of printed specimens; these issues were identified, discussed, and suggestions for future work are provided.

Simulated synthesis of silica nanowires by lyotropic liquid crystal template method

ABSTRACT Dissipative particle dynamics simulations were adopted to study the mechanism of lyotropic liquid crystal (LLC) formation and the synthesis process of silica nanowires by LLC template method. Simulation results show that the one-dimensional (1D) LLC channel can be formed at the Pluronic F127 concentration range of 61 ∼ 67%. With the increase of Pluronic F127 concentration, the diameter of LLC channel decreases and the deformation degree increases. The effect of PEO: PPO ratio on the diameter of LLC channel is slight. The appropriate PEO: PPO ratio of Pluronic is 40:70 for the formation of 1D LLC channel, as the deformation degree of channel is the smallest in this case. The effect of polymerisation degree on the diameter and deformation degree of LLC channel is both little. With the increase of TEOS concentration, the nanowire diameter increases rapidly at first, and then increases quite slowly. This work can provide guidance for silica nanowires synthesis by LLC template method.