PS Core Research Articles

Discrete element modelling and calibration of core-shell composite abrasives based on indentation experiments

PS@CeO2 is a novel abrasive used in the polishing process, consisting of an organic polymer core (polystyrene, PS) that is prone to elastic deformation and an outer shell made of inorganic abrasives (CeO2). Core-shell composite abrasives are susceptible to deformation or damage caused by impact during the polishing process, which presents challenges for damage analysis and assessment. This paper proposes a method for calibrating the micro-parameters of discrete element model with PS@CeO2 core-shell composite abrasives (CSCAP). The geometry parameters and the elasticity modulus of the core-shell composite abrasives were measured. The average elasticity modulus of the PS core, interface and total CSCAP in the specimens were 3.85 ± 0.2 MPa, 78.8 ± 0.9 MPa and 12.03 ± 0.9 MPa, respectively. Based on the principle of structural similarity, the core-shell composite abrasives with the core-to-shell ratio of 21.34 was established using the discrete element method (DEM). A serial of indentation experiments were conducted on the core, interface, and total core-shell composite abrasives, respectively. The elasticity modulus was used as an evaluation index to calibrate the micro-parameters of discrete element model of core-shell composite abrasives. The simulation results of elasticity modulus were 3.82 MPa and 12.26 MPa on the core PS, the interface, and the core-shell composite abrasives, respectively. Comparing the numerical simulation results with the experimental results, the elasticity modulus of the core-shell composite abrasives differs within 5 %. Finally, the discrete element simulation of core-shell composite abrasives impacted with workpieces was performed. The research results indicate that the established calibration method can accurately describe the damage and deformation of core-shell composite abrasives that occur in indentation experiments.

Fabrication of Polypyrrole Hollow Nanospheres by Hard-Template Method for Supercapacitor Electrode Material.

Conducting polymers like polypyrrole, polyaniline, and polythiophene with nanostructures offers several advantages, such as high conductivity, a conjugated structure, and a large surface area, making them highly desirable for energy storage applications. However, the direct synthesis of conducting polymers with nanostructures poses a challenge. In this study, we employed a hard template method to fabricate polystyrene@polypyrrole (PS@PPy) core-shell nanoparticles. It is important to note that PS itself is a nonconductive material that hinders electron and ion transport, compromising the desired electrochemical properties. To overcome this limitation, the PS cores were removed using organic solvents to create hollow PPy nanospheres. We investigated six different organic solvents (cyclohexane, toluene, tetrahydrofuran, chloroform, acetone, and N,N-dimethylformamide (DMF)) for etching the PS cores. The resulting hollow PPy nanospheres showed various nanostructures, including intact, hollow, buckling, and collapsed structures, depending on the thickness of the PPy shell and the organic solvent used. PPy nanospheres synthesized with DMF demonstrated superior electrochemical properties compared to those prepared with other solvents, attributed to their highly effective PS removal efficiency, increased specific surface area, and improved charge transport efficiency. The specific capacitances of PPy nanospheres treated with DMF were as high as 350 F/g at 1 A/g. And the corresponding symmetric supercapacitor demonstrated a maximum energy density of 40 Wh/kg at a power density of 490 W/kg. These findings provide new insights into the synthesis method and energy storage mechanisms of PPy nanoparticles.

Influence of hydrophilic block length on the aggregation properties of polyglycidol-polystyrene-polyglycidol copolymers.

Amphiphilic triblock copolymers, polyglycidol-polystyrene-polyglycidol (PGL-PS-PGL), were synthesised via anionic polymerization starting from the synthesis of a polystyrene macroinitiator with 60 styrene units in the block terminated by ethylene oxide. Poly(ethoxyethyl glycidyl ether) blocks of different lengths were created on both sides of the macroinitiator. By removing the ethoxyethyl blocking groups, PGL-PS-PGL copolymers containing polyglycidol blocks with DP 11, 23, 44 and 63 were received. Their structures were determined by NMR and FTIR. The hydrophilicity of PLG-PS-PGL films was studied upon exposure to water vapour. To perform the copolymers' aggregation in water, the samples were dialysed from DMF into water. The critical concentration of their micellisation (CMC) was determined by measuring the absorbance of the 1,6-diphenylhexa-1,3,5-triene (DPH) probe and the intensity of light scattered by the copolymers' solution as a function of concentration. CMC values increased with increasing the number of hydrophilic glycidol units in the copolymer chain. The sizes of aggregates formed slightly above the critical concentration were measured by dynamic light scattering (DLS), and particles were imaged by cryo-TEM. Cryo-TEM pictures showed the presence of regular micelles in copolymer dispersions. For copolymers with shorter PGL chains aggregated partices were detected. Moreover, cryo-TEM demonstrated that the copolymers with a polyglycidol block of DP = 63 formed regular spherical micelles that formed 2D ordered organisation on the surface. X-ray measurements showed the formation of a partially crystallised PS core in the micelle's interior. The aggregates of all copolymers were stable. Their sizes did not change after one year of storage. The particles did not disassociate even after diluting their dispersions to a concentration 10 times lower than the critical concentration.

Efficacy of Maintenance Therapies By Prognostic Subgroups in Post-Transplant Newly Diagnosed Multiple Myeloma Patients: A Systematic Review and Network Meta-Analysis

Introduction The optimal maintenance regimen by prognostic categories remains unclear in newly diagnosed multiple myeloma (NDMM) patients undergoing autologous stem cell transplant (ASCT). Therefore, we conducted a systematic review and network meta-analysis (NMA) to assess the comparative effectiveness of novel agents by different prognostic groups. Methods A comprehensive systematically structured literature search was conducted to identify phase II/III randomized controlled trials (RCTs) evaluating maintenance therapies in post-transplant NDMM patients and reporting data by subgroups including but not limited to international staging system (ISS), and cytogenetic risk. High cytogenetic risk (HCR) and standard cytogenetic risk (SCR) were defined in accordance with the eligible trials. Main outcomes of interest were overall survival (OS) and progression-free survival (PFS). Precomputed hazard ratios (HR) with 95% CI were pooled using an inverse variance approach. A frequentist network meta-analysis was conducted. P-score (PS) were used to assess relative rankings of the treatments and were interpreted in congruency with pairwise estimates. Higher ranks indicated better efficacy. Results This NMA included six RCTs with 4119 participants and six unique treatment arms. In patients with SCR, the combination of carfilzomib, lenalidomide, and dexamethasone (KRd) improved PFS when compared to lenalidomide (Len; HR: 0.44; 95% CI: 0.24-0.81), daratumumab (Dara; 0.27; 0.13-0.55), ixazomib (Ixa; 0.26; 0.13-0.53), and no maintenance therapy (0.17; 0.09-0.32). Similarly, KR improved PFS compared to lenalidomide (Len; 0.56; 0.33-0.96), daratumumab (Dara; 0.34; 0.18-0.65), ixazomib (Ixa; 0.33; 0.17-0.63), and no maintenance therapy (0.21; 0.12-0.38). There was no statistically significant difference between KRd and KR. KRd was ranked as potentially the most efficacious treatment (rank 1) followed by KR (rank 2), Len (rank 3), Dara (rank 4), and Ixa (rank 5) for improving PFS in SCR. In patients with HCR, KRd (0.35; 0.14-0.92), KR (0.32; 0.15-0.67), Dara (0.43; 0.25-0.73), and Len (0.48; 0.35-0.64) improved PFS when compared to no maintenance therapy. No other significant differences were observed in HCR patients. KR was ranked as potentially the most efficacious treatment followed by KRd (rank 2), Dara (rank 3), Len (rank 5), and Ixa (rank 5) for PFS in HCR patients. In patients with ISS-I/II, KRd and KR improved PFS when compared to Dara (KRd vs. Dara - 0.32; 0.16-0.65, KR vs Dara - 0.50; 0.26-0.94), and Ixa (KRd vs. Ixa - 0.22; 0.11-0.45, KR vs Ixa - 0.35; 0.18-0.65). KRd, not KR, improved PFS when compared to Len (0.41; 0.22-0.76). Rankings were consistent with those observed in SCR patients. No significant differences were observed among mixed treatment comparisons for ISS-III patients. Limited number of trials reporting OS precluded formal assessment. Conclusions The current data suggest that KRd and KR may delay disease progression regardless of risk category. Overall survival data is still emerging and, if consistent, may influence clinical practice. We maintain a living meta-analysis to incorporate new evidence constantly.

Synthesis and characterization of polystyrene-b-poly(vinyldipicolinic acid) pH-responsive core-shell nanoparticles

The self-assembly of a new series of amphiphilic polystyrene-b-poly(4-vinyldipicolinic acid) PS-b-PVDPA diblock copolymers in aqueous solution is reported in order to obtain core–shell nanoparticles composed of a PS core and a PVDPA shell. Diblock copolymers were synthesized by Supplemental Activation Reducing Agent-Atom Transfer Radical Polymerization (SARA-ATRP) with a degree of polymerization (DP) of the PS block in the range 112–260 and a DP of PVDPA block of 10, 30 or 50. Anionic latex nanoparticles of PS-b-PVDPA were prepared by solvent displacement methods. All the nanoparticle suspensions had a narrow size distribution (0.014 ≤ PDI ≤ 0.144) with zeta potential in the range −27 mV to −38 mV indicating electrostatic repulsions due to carboxylate anions and therefore high colloidal stability. DLS was used to determine nanoparticle size, with SEM and TEM used to determine and confirm both size and spherical shape. All three methods found the size for these nanoparticles to be in the range 75–120 nm. Using fluorimetry and DLS methods, Critical Aggregation Concentration (CAC) for each type of nanoparticle was determined to be within the range of 33–69 mg/L. Micelles were pH-responsive with stability in aqueous conditions for pH > 3.5. Micelles were stable at pH 5.5 for up to 40 days and at temperature up to 60 °C.

Assembly of P2VP and PS-b-P2VP composite helical nanowire arrays at the liquid/liquid interface

The nanostructures based on polymers have attracted much research interest because of their rich morphologies, unique properties and potential applications in various fields. In particular, helical nanostructures have been research hotspots in recent years. In this work, composite non-helical and helical nanowire arrays of atactic poly(2-vinylpyridine) (P2VP), and block copolymers polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) were fabricated successfully with inorganic species such as HAuCl4 through a liquid/liquid interfacial adsorption and self-assembly approach without addition of any chiral inducers. The formation process of the helical nanowires of P2VP includes the following steps, i.e. adsorption of the polymer molecules and HAuCl4 at the interface, the following protonation of pyridine groups, straightening of the P2VP chains by mutual repulsion between the protonated pyridine groups, aggregation of the P2VP chains due to the hydrophobic interactions between the backbones, and ordered organization of the pyridine groups through π-π interactions. The helical nanowires of PS-b-P2VP are worm-like micelles with a PS core and a P2VP shell, which are formed through the self-assembly of the block copolymer molecules with HAuCl4 within the interfacial phase with the help of hydrophobic interaction between the PS blocks and orderly stacking of the P2VP blocks. The different formation mechanisms reflected the effects of molecular structure on the self-assembly of polymers. In addition, the formed nanowires further self-organize into ordered arrays due to the increasing interfacial pressure during the generation of the nanowires. The results of this study expand the scope of research on polymer self-assembly and the application of liquid/liquid interfacial self-assembly techniques to acquire highly ordered supramolecular nanostructures.

Micellar Nanoreactors Enabled Site-Selective Decoration of Pt Nanoparticles Functionalized Mesoporous SiO2 /WO3-x Composites for Improved CO Sensing.

Site-selective and partial decoration of supported metal nanoparticles (NPs) with transition metal oxides (e.g., FeOx ) can remarkably improve its catalytic performance and maintain the functions of the carrier. However, it is challenging to selectively deposit transition metal oxides on the metal NPs embedded in the mesopores of supporting matrix through conventional deposition method. Herein, a restricted in situ site-selective modification strategy utilizing poly(ethylene oxide)-block-polystyrene (PEO-b-PS) micellar nanoreactors is proposed to overcome such an obstacle. The PEO shell of PEO-b-PS micelles interacts with the hydrolyzed tungsten salts and silica precursors, while the hydrophobic organoplatinum complex and ferrocene are confined in the hydrophobic PS core. The thermal treatment leads to mesoporous SiO2 /WO3-x framework, and meanwhile FeOx nanolayers are in situ partially deposited on the supported Pt NPs due to the strong metal-support interaction between FeOx and Pt. The selective modification of Pt NPs with FeOx makes the Pt NPs present an electron-deficient state, which promotes the mobility of CO and activates the oxidation of CO. Therefore, mesoporous SiO2 /WO3-x -FeOx /Pt based gas sensors show a high sensitivity (31±2 in 50ppm of CO), excellent selectivity, and fast response time (3.6s to 25ppm) to CO gas at low operating temperature (66°C, 74% relative humidity).

Single-Micelle-Templated Synthesis of Hollow Barium Carbonate Nanoparticle for Drug Delivery

A laboratory-synthesized triblock copolymer poly(ethylene oxide-b-acrylic acid-b-styrene) (PEG-PAA-PS) was used as a template to synthesize hollow BaCO3 nanoparticles (BC-NPs). The triblock copolymer was synthesized using reversible addition-fragmentation chain transfer radical polymerization. The triblock copolymer has a molecular weight of 1.88 × 104 g/mol. Transmission electron microscopy measurements confirm the formation of spherical micelles with a PEG corona, PAA shell, and PS core in an aqueous solution. Furthermore, the dynamic light scattering experiment revealed the electrostatic interaction of Ba2+ ions with an anionic poly(acrylic acid) block of the micelles. The controlled precipitation of BaCO3 around spherical polymeric micelles followed by calcination allows for the synthesis of hollow BC-NPs with cavity diameters of 15 nm and a shell thickness of 5 nm. The encapsulation and release of methotrexate from hollow BC-NPs at pH 7.4 was studied. The cell viability experiments indicate the possibility of BC-NPs maintaining biocompatibility for a prolonged time.

Preparation of Polystyrene/Polyacrylamide Core-Shell Microspheres via Microfluidizer-Assistant Emulsification Template Methods for Oil Recovery Enhancement

Polyacrylamide and its derivatives are commonly used functional polymers to enhance oil recovery in a water-flooding oilfield. By using its hydrophilic amide group to swell and gel in stratum water, it can plug the fractures and pore throats of underground. In order to improve the strength of polyacrylamide material, the polystyrene/polyacrylamide (PS/PAM) core-shell microspheres were successfully prepared by the microfluidizer-assistant emulsification template method. The influences of different preparation conditions, such as the different types and concentrations of surfactants, organic phase and oil/water ratios, on the morphology, diameter, and distribution of corresponding PS core have been systematically studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and laser light scattering analysis (LLS). Moreover, by the integration of porous meshes onto both inlet and outlet of the interaction chamber, the resultant polymer microspheres could be tuned larger due to the dual homogenization. Our procedure can provide a simple and general method to modulate the diameter of the polymer microspheres in the range of 30 nm to 3 μm with a narrow polydispersity index (PDI) of <0.2. The PS/PAM core-shell microspheres exhibited good water plugging performance.

Layer-by-layer development of chitosan/alginate-based platelet-mimicking nanocapsules for augmenting doxorubicin cytotoxicity against breast cancer

Breast carcinoma is considered one of the most invasive and life-threatening malignancies in females. Mastectomy, radiation therapy, hormone therapy and chemotherapy are the most common treatment choices for breast cancer. Doxorubicin (DOX) is one of the most regularly utilized medications in breast cancer protocols. However, DOX has showed numerous side effects including lethal cardiotoxicity. This study aims to fortify DOX cytotoxicity and lowering its side effects via its combining with the antidiabetic metformin (MET) as an adjuvant therapy, along with its effective delivery using natural platelet-rich plasma (PRP), and newly-developed PRP-mimicking nanocapsules (NCs). The PRP-mimicking NCs were fabricated via layer-by-layer (LBL) deposition of oppositely charged biodegradable and biocompatible chitosan (CS) and alginate (ALG) on a core of synthesized polystyrene nanoparticles (PS NPs) followed by removal of the PS core. Both natural PRP and PRP-mimicking NCs were loaded with DOX and MET adjuvant therapy, followed by their physicochemical characterizations including DLS, FTIR, DSC, and morphological evaluation using TEM. In-vitro drug release studies, cytotoxicity, apoptosis/necrosis, and cell cycle analysis were conducted using MCF-7 breast cancer cells. Also, an in-vivo assessment was carried out using EAC-bearing balb/c mice animal model to evaluate the effect of DOX/MET-loaded natural PRP and PRP-mimicked NCs on tumor weight, volume and growth biomarkers in addition to analyzing the immunohistopathology of the treated tissues. Results confirmed the development of CS/ALG-based PRP-mimicking NCs with a higher loading capacity of both drugs (DOX and MET) and smaller size (259.7 ± 19.3 nm) than natural PRP (489 ± 20.827 nm). Both in-vitro and in-vivo studies were in agreement and confirmed that MET synergized the anticancer activity of DOX against breast cancer. Besides, the developed LBL NCs successfully mimicked the PRP in improving the loaded drugs biological efficiency more than free drugs.

Post Autologous Stem Cell Transplant Maintenance in Patients with Newly Diagnosed Multiple Myeloma: A Network Meta-Analysis

Introduction The therapeutic paradigm for newly diagnosed multiple myeloma (NDMM) patients undergoing autologous stem cell transplant (ASCT) is evolving. Emergence of newer maintenance therapies has prompted this network meta-analysis to assess the comparative effectiveness of available options using the most up-to-date evidence, and thereby informing optimal therapy in this setting. Methods MEDLINE and EMBASE were comprehensively searched using a systematically structured search strategy to identify phase II/III randomized controlled trials (RCTs) assessing contemporary maintenance therapies in NDMM patients undergoing ASCT. The main outcomes of interest included progression-free survival (PFS) and overall survival (OS). Precomputed hazard ratios (HR) with 95% CI were pooled using an inverse variance approach. Incidence rate ratios were computed for trials not reporting HR. Mixed treatment comparisons were made using a network meta-analytic approach within the frequentist framework. Relative treatment rankings were evaluated using P-scores (PS) and were interpreted in congruency with pairwise estimates. Higher ranks indicated better efficacy. Results As of 25th July 2022, 16 RCTs with 12 unique treatment arms, and 14 RCTs with 10 unique treatment arms, contributed to the network of PFS and OS outcomes, respectively. Mixed treatment comparisons showed that the combination of carfilzomib, lenalidomide, and dexamethasone (KRd) and KR were associated with significantly improved PFS when compared to lenalidomide (Len) maintenance (KRd vs. Len - HR: 0.56; 95% CI: 0.34-0.93, KR vs. Len - HR: 0.64; 0.44-0.94), daratumumab (Dara) (KRd vs. Dara - HR: 0.53; 0.30-0.93, KR vs. Dara - HR: 0.60; 0.38-0.96), thalidomide-steroid (Thal-Steroid) (KRd vs. Thal-Steroid: HR - 0.49; 0.28-0.84, KR vs. Thal-Steroid - HR: 0.56; 0.36-0.86), Thal (KRd vs. Thal - HR: 0.40; 0.23-0.69, KR vs. Thal - HR: 0.46; 0.30-0.71), and ixazomib (Ixa) maintenance (KRd vs. Ixa - HR: 0.39; 0.22-0.68, KR vs. Ixa - HR: 0.44; 0.28-0.69). Although there was a signal of potential PFS benefit with KRd and KR when compared to Ixa, lenalidomide, and dexamethasone (IRd), the difference was not statistically significant (KRd vs. IRd - HR: 0.68; 0.34-1.32, KR vs. IRd - HR: 0.77; 0.43-1.39). The results were consistent for KRd and KR as compared to Len-Steroid (KRd vs. Len-Steroid - HR: 0.67; 0.36-1.23, KR vs. Len-Steroid - HR: 0.76; 0.45-1.28). However, KRd and KR were not significantly different from each other. Ranking analysis showed KRd (PS: 0.95; rank 1) and KR (PS: 0.91; rank 2) were potentially the most efficacious with regards to PFS benefit followed by IRd and Len-Steroid (PS: 0.75, rank 3), Len (PS: 0.63; rank 5), Dara (PS: 0.57; rank 6), Thal-Steroid (PS: 0.49; rank:7), Thal (PS:0.30; rank: 8), and Ixa (PS: 0.28; rank: 9). Len maintenance was associated with significantly improved PFS compared to Ixa (HR: 0.69; 0.55-0.88), and Thal (HR: 0.72; 0.59-0.88) as shown in Figure 1A. Mixed treatment comparisons for OS outcomes showed a consistent pattern of benefit with KR when compared to Thal (HR: 0.40; 0.19-0.86), Thal-Steroid (HR: 0.46; 0.21-0.99), and Len-Steroid (HR: 0.35; 0.13-0.94). Although, there is a signal of OS benefit with KR when compared to Len, the effect is not statistically significant (HR: 0.54; 0.26-1.12). Similarly, while the direction of effect indicated potential OS benefit with KRd as compared to Thal, Thal-Steroid, and Len-Steroid, the difference was not statistically significant. No statistically significant associations were observed for other mixed treatment comparisons with regards to OS at the current follow up of the included trials as shown in Figure 1B. Sensitivity analyses limited to phase III RCTs showed consistent results. Conclusions Maintenance therapy with KRd and KR may prolong PFS compared to other therapies including Len, Thal, Ixa, and Dara maintenance but not when compared to Len-Steroid and IRd. Overall survival data is still emerging and results at longer-follow up with subgroup analyses by age, prior response status, and cytogenetic risk profiles are warranted and may offer additional insights. Thus, a living systematic review is being maintained and these results will be updated as soon as new data becomes available. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Der Rahmen von Ps 45 (V. 1–2; 17–18)

Abstract While the core of Ps 45 (vv. 3–16) clearly bears the stamp of a Phoenician royal court, the beginning and end highlight features that elucidate the psalm’s main body. V. 1 f. present an author who has assumed an Aramaic title (סוֹפֵר מׇהִיר): he reflects on his works, puts his poetry indirectly on a par with a Greek poem by adopting the Greek concept of ποίημα (= מַעֲשֶׂה), and through the superscription »a love song« secondarily reads this idea into the psalm, even though love is nowhere mentioned. V. 17 f. link up organically with the psalm’s main body, but no longer deal with the king alone; the focus is now on his dynasty, whose impact is international, unbounded by time or place.

Ag Nanoparticle-Coated Polystyrene Microspheres for Electromagnetic Interference Shielding Films with Low Metal Content

The fabrication of thin composite films incorporating metal-based fillers with a delicate structure to achieve high electromagnetic interference shielding effectiveness (EMI SE) at low metal content remains a great challenge. In this work, benefiting from the excellent electrical conductivity of Ag nanoparticles, Ag nanoparticle-coated polystyrene (PS@Ag) microspheres with a large PS core were selected as electrically conductive fillers, and the volume exclusion effect guaranteed the construction of an electrically conductive network with low silver loading. A spontaneous process to construct a segregated laminar structure with a three-dimensional electrically conductive network happened with the assistance of a gravity-driven effect. The flexible thin films with a low amount of silver exhibited outstanding EMI SE per unit thickness (SE/d). To further investigate the effect of the structure on the EMI SE efficiency, it is found that the alternate interfaces play a critical role in enhancing shielding performance by stacking multiple films compared to the bulk films obtained by casting. The EMI SE for an only 0.3 mm triple-piece stacking film with 6.3 wt % Ag loading could reach 55.3 dB compared to 37.2 dB for the triple-thickness casting film. Using the stacking process results in easy accessibility for tailored composites with the desired EMI SE, which supplies a new strategy for the design of shielding materials in the next-generation electronics.

Morphology Control of Multicompartment Micelles in Water through Hierarchical Self-Assembly of Amphiphilic Terpolymers

Multicompartment micelles (MCMs) allow the simultaneous storage of multiple cargoes such as dyes, catalysts, or drugs, and have therefore gained attention in catalysis, nanotechnology, and nanomedicine. In the present work, we describe design rules to control the morphology of MCMs in water including spheres, cylinders, sheets, and vesicles. For that, we synthesized a series of poly(ethylene oxide) (PEO)-b-polystyrene (PS)-b-poly(methyl acrylate) (PMA) triblock terpolymers and systematically varied the length of the PS and PMA block. Using a stepwise hierarchical assembly process, we first form patchy precursor micelles in organic solvent with PS core and mixed PEO/PMA corona. In the second step, these micelles act as subunits, which assemble (or cluster) in water into MCMs, where PEO forms the stabilizing corona, PS the compartment, and PMA the inner core. We find that the shape of the final MCM can be predicted by ascribing a Janus balance to precursor micelles as the molar ratio of PEO to PMA, which provides a synthetic handle to target specific MCM morphologies.

Coordinated single-molecule micelles: a self-template approach for preparing mesoporous doped carbons.

Porous carbons prepared using a self-template approach inherit the pore features of template, but they exhibit almost no evenly dispersed mesopores, which is significant for diffusion-limited applications. Herein, N-doped hierarchically porous carbons (NHPCs) with uniform mesopores are prepared using a self-template method. The spherical single-molecule micelle of polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) is turned into a Zn2+-coordinated PS-b-P4VP micelle (CPM) by coordination of Zn2+ with the P4VP shell. Then, the self-template of the CPM is carbonized into a hollow carbon nanosphere. During carbonization, the PS core is decomposed to generate the central mesopore, whereas the Zn2+-coordinated P4VP shell is transformed into a carbonaceous shell. These even hollow carbon nanospheres aggregate to form uniformly mesoporous carbon lumps. Simultaneously, the coordinated Zn2+ of the CPM is reduced to metal zinc at high temperatures and then it is evaporated, thus creating numerous micropores in the carbonaceous shell. These NHPCs with uniform mesopores display a high specific surface area. As a demonstration in diffusion-limited applications, their catalytic performances for the oxygen reduction reaction (ORR) are investigated. Strikingly, NHPCs exhibit outstanding catalytic performances for the ORR. This self-template method paves a facile approach for preparing mesoporous carbons with high performances.

Silica particles with dynamic Janus surfaces in Pickering emulsion

In Pickering emulsions, solid particles are adsorbed to the oil/water interface, and the dispersed oil or water droplets are stabilized by the particles. The adsorption and wettability of the particles at the liquid-liquid interface play key roles in Pickering emulsion. In this research, the application of the silica particles with responsive surface nanostructures in Pickering emulsion is investigated. Amphiphilic surface micelles (s-micelles) on the silica particles are prepared by polymerization induced surface self-assembly approach. In water, spherical s-micelles with PS cores and quaternized poly(2-(dimethylamino) ethyl methacrylate) (q-PDMAEMA) shells are formed on the silica particles. In toluene, layered surface structures with PS at the top surfaces and q-PDMAEMA embedded in the inner layers, are formed. The silica particles with amphiphilic s-micelles (SiO2-ASM) can be used as stabilizers in Pickering emulsion. Upon addition of SiO2-ASM into O/W emulsion, the interfacial tension decreases significantly, due to the residence of the silica particles at the liquid-liquid interfaces. At the interfaces, the silica particles present dynamic Janus surfaces. On the sides immersed in aqueous phase, hydrophilic surfaces are produced; on the other sides immersed in toluene phase, lipophilic surface structures are formed. Both of confocal laser scanning microscopy and scanning electron microscopy results demonstrate the formation of the silica particles armored liquid-liquid interfaces.

PH-Switchable Latexes Based on the Nonionic Amphiphilic Diblock Copolymer with a Chargeable End-Group on the Core-Forming Block

Reversible addition-fragmentation transfer (RAFT) dispersion polymerization of styrene was performed in an ethanol-water mixture using a Z-group carboxylated poly(N-acryloylmorpholine) (PNAM) macro-RAFT agent, and dialysis was performed against water to produce the PNAMx-PSy-COOH (PS = polystyrene) diblock copolymer latexes. This new formula is developed for the fabrication of pH-switchable copolymer latexes through an end-group response approach. The PNAM44-PS134-COOH latex is unstable at suitably low pH values (pH ≤ 4), and these aggregated spherical nanoparticles are redispersed successfully by adding base as determined by analysis of their dynamic light scattering (DLS) diameters and transmission electron microscopy (TEM) data. Negative zeta potential (-19.4 mV at 0.02% w/w) of the original latex indicated that carboxylic acid end-groups were anchored on the surface of the PS core via the polymerization-induced self-assembly (PISA) process and exposed to the solvent. Protonation of carboxylate groups reduces the degree of hydration of the PS core with a great impact on the free energy of the core/solvent interface, inducing the aggregation of PNAM44-PS134-COOH latex particles. A comparative experiment where the carboxylic acid end-group is designed on the PNAM stabilizer block proves that no pH-switchable behavior occurs in this case. Moreover, the vesicle-like nanoparticles composed of PNAM44-PS428-COOH copolymers have an apparently anionic character (zeta potential ≈ -33.5 mV at 0.02% w/w) and are still pH-switchable with a lower critical flocculation point (pH 2-3). More importantly, the latex composed of PNAM118-PS151-COOH diblock copolymers is insensitive to the solution pH.

Encapsulation of Curcumin in Polystyrene-Based Nanoparticles-Drug Loading Capacity and Cytotoxicity.

Nanoparticles made of amphiphilic block copolymers are commonly used in the preparation of nano-sized drug delivery systems. Poly(styrene)–block–poly(acrylic acid) (PS–PAA) copolymers have been proposed for drug delivery purposes; however, the drug loading capacity and cytotoxicity of PS–PAA nanoparticles are still not fully recognized. Herein, we investigated the accumulation of a model hydrophobic drug, curcumin, and its spatial distribution inside the PS–PAA nanoparticles. Experimental methods and atomistic molecular dynamics simulations were used to understand the molecular structure of the PS core and how curcumin molecules interact and organize within the PS matrix. The hydrophobic core of the PS–PAA nanoparticles consists of adhering individually coiled polymeric chains and is compact enough to prevent post-incorporation of curcumin. However, the drug has a good affinity for the PS matrix and can be efficiently enclosed in the PS–PAA nanoparticles at the formation stage. At low concentrations, curcumin is evenly distributed in the PS core, while its aggregates were observed above ca. 2 wt %. The nanoparticles were found to have relatively low cytotoxicity to human skin fibroblasts, and the presence of curcumin further increased their biocompatibility. Our work provides a detailed description of the interactions between a hydrophobic drug and PS–PAA nanoparticles and information on the biocompatibility of these anionic nanostructures which may be relevant to the development of amphiphilic copolymer-based drug delivery systems.

Comparison between Various Adsorbents for Direct Blue Dye 14 Removal from Aqueous Solution

In this work, the adsorption potential of various adsorbents was investigated in batch mode study. Polyaniline (PAn) and its nanocomposites were prepared using a novel synthesis method and then used as an adsorbent for removal of direct blue dye 14 (DB14). The results were compared with frequently used adsorbents granular activated carbon (GAC) and powder activated carbon (PAC). Furthermore, the combination of PAn and porous carbon adsorbents was examined. Adsorbents that stand out for high removal efficiency are PAn, polyaniline/hydroxypropylcellulose (PAn-HPC), and polyaniline/polystyrene (PAn-PS). The results indicate that PAn-PS was an attractive candidate for direct blue dye removal. Therefore, present work focuses on utilization of PAn-PS nanocomposite as an efficient adsorbent for DB14 removal in a batch adsorption system. PS core particles were prepared in microemulsion system and further coated with PAn by in situ polymerization method. The core-shell structure of PAn-PS was confirmed with a field emission scanning electron microscope (FESEM). Experiments were carried out as a function of pH, contact time, initial dye concentration, and adsorbent dosage. The adsorption kinetics was found to follow the pseudo-second-order model. The applicability of the Freundlich and Langmuir models was investigated and the equilibrium data were fitted well with the Langmuir model. Design of experiment was used in order to evaluate the interaction effects of all the parameters and analysis of variance (ANOVA) test was used to check the significance of the model. The results demonstrated that PAn-PS can act as an appropriate adsorbent for DB14 removal from aqueous solution.

Kinetic Control of Length and Morphology of Segmented Polymeric Nanofibers in Microfluidic Chips.

In this work, we report an approach to prepare segmented polymer nanofibers (SPNFs) composed of rodlike subunits by kinetically controlled self-assembly of polystyrene-b-poly(4-vinylpyridine)-based supramolecules in microfluidic chips. The length and morphology of the SPNFs could be effectively adjusted by changing the total flow rate (Vtotal) and the molar ratio (x) of 4-vinylpyridine (4VP) unit to a hydrogen-bonding molecule, 3-n-pentadecyphenol. Moreover, the subunits of SPNFs could transform from short rods to spheres when the interfacial tension between PS core and solvent increased. On the contrary, the SPNFs elongated along the major axis when the interfacial tension decreased. This work not only offers mechanism insights into the hierarchical self-assembly of block copolymer-based supramolecules but also provides a versatile and effective method for kinetically controlling the hierarchical structures of assemblies.