Polyethylene Oxide-polypropylene Oxide Research Articles

Hardly water-soluble pseudo-polyrotaxane nanosheets comprising polyethylene-oxide-modified polydimethylsiloxane and gamma-cyclodextrin

Abstract We have successfully prepared hardy water-soluble pseudo-polyrotaxane nanosheets composed of carboxy group-terminated polyethylene oxide (PEO)-modified polydimethylsiloxane and γ-cyclodextrin (CD). These pseudo-polyrotaxane nanosheets are more water-insoluble than previously reported pseudo-polyrotaxane nanosheets composed of pluronic—a triblock polymer comprising PEO, polypropylene oxide (PPO), and PEO—and β-CD, and have potential applications as surface treatment agents.

Inorganic-polymer composite electrolytes: basics, fabrications, challenges and future perspectives

Abstract This review covers the basics of, inorganic-polymer composite electrolyte materials that combine inorganic components with polymer matrices to enhance the ionic conductivity and mechanical properties of the electrolyte. These composite electrolytes are commonly employed in solid-state batteries, fuel cells, supercapacitors, and other electrochemical devices. The incorporation of inorganic components, such as ceramic nanoparticles or metal oxides, into a polymer matrix provides several advantages. The inorganic components can improve the overall ionic conductivity by providing pathways for ion transport, reducing the tortuosity of the polymer matrix, and facilitating ion hopping between polymer chains. Additionally, inorganic materials often exhibit higher thermal and chemical stability compared to pure polymers, which can enhance the safety and durability of composite electrolytes. Polymer matrices used in inorganic-polymer composite electrolytes can vary, but common choices include polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polyethylene oxide/polypropylene oxide (PEO/PPO) blends. These polymers offer good mechanical flexibility and processability, allowing for the fabrication of thin films or membranes. The fabrication methods for inorganic-polymer composite electrolytes depend on the specific application and desired properties. Common approaches include solution casting, in situ polymerization, melt blending, and electrospinning. During the fabrication process, the inorganic components are typically dispersed or mixed with the polymer matrix, and the resulting composite is processed into the desired form, such as films, membranes, or coatings. The performance of inorganic-polymer composite electrolytes is evaluated based on their ionic conductivity, mechanical strength, electrochemical stability, and compatibility with the electrode materials. Researchers continue to explore various combinations of inorganic and polymer components, as well as optimization strategies, to further improve the overall performance of these composite electrolytes for advanced energy storage and conversion applications.

Effects of suppressors on the incorporation of impurities and microstructural evolution of electrodeposited Cu solder joints

BackgroundCopper (Cu) electrodeposition is a cost-effective and scalable technology commonly used to fabricate interconnects and heat sinks in microelectronic devices. Adding organic functional additives, such as suppressors, to plating solutions is crucial to achieve conformal microvia filling by Cu electroplating. However, codeposition of organic additives is inevitable and leads to reliability concerns regarding impurity residues in the Cu electrodeposited layer. MethodsIn this study, polyethylene glycol (PEG) at 8,000 g mol−1 and a triblock copolymer EPE (polyethylene oxide-polypropylene oxide-polyethylene oxide) at 2,900 g mol−1 are applied as suppressors and individually added to plating solutions to compare their suppression strength toward Cu deposition using galvanostatic measurements. Their adsorption/desorption behaviors on the Cu surface are theoretically analyzed based on the electronic distribution properties of the two suppressor molecules calculated by quantum chemical calculations. The impurity residues in the Cu layers are measured by a time-of-flight secondary ion mass spectrometer, and their effects on the joining reactions between tin (Sn) solder and Cu are investigated by observing the microstructural evolution in the Sn/Cu joints subjected to isothermal aging. Significant findingsEPE2900 outperforms PEG8000 in the suppression strength toward Cu deposition. Unlike PEG8000, which causes a high level of impurity incorporation, the impurity residues in the Cu layer constructed by EPE2900 are negligible. As a result, the Sn/Cu solder joint constructed by EPE2900 exhibits high microstructural stability free of the propagation of detrimental voids during isothermal aging at 200 °C. The better suppression efficacy and negligible impurity residues of EPE2900 can be rationalized based on quantum chemical calculations.

Carbon nanofibers with uniformly embedded silicon nanoparticles as self-standing anode for high-performance lithium-ion battery

Electrospinning has been used as a convenient technology to produce high-energy and self-standing anodes for lithium-ion batteries (LIBs) by encapsulating silicon nanoparticles (Si/NPs) into carbon nanofibers (CNF). However, the inhomogeneous distribution of Si/NPs in CNF results in low coulombic efficiency, rapid capacity decay and slow kinetics during cycling process which hinder the practical application of this promising composite anode. In this work, a principle of universal design is applied to the manufacture of Si-CNF composites, in this way, a self-standing electrode with homogeneous distribution of Si/NPs in CNF (Si//PCNF-15) is developed by introducing triblock copolymer Pluronic P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) as dispersant and pore directing agent. As anode of LIBs, the Si//PCNF-15 exhibits outstanding electrochemical performance and considerable flexibility due to the homogeneous dispersion of Si nanoparticles and high graphitization of the carbon network. As results, a specific capacity of 1074.8 mAh g−1 at 0.3 A g−1 and a rate capacity of 236.1 mAh g−1 at 10 A g−1 have been delivered when it is explored as a self-standing anode for LIBs. This work provides a universal approach for developing self-standing anodes of composite fibers with nanoparticles dispersed homogeneously in CNF.

Structural investigation and steric stabilisation of Guerbet glycolipid-based cubosomes and hexosomes using triblock polyethylene oxide-polypropylene oxide-polyethylene oxide copolymers

Aqueous dispersions of inverse nonlamellar liquid crystalline nanostructures namely cubosomes and hexosomes have been used as carriers for drug delivery. The large surface area and internal water channel networks in these nanocarriers make them useful to transport amphiphilic, hydrophilic and hydrophobic active ingredients. However, suitable stabilisers that can maintain the colloidal stability and preserving the internal structures of the complex cubosomes and hexosomes are integral. Herein, Guerbet glycolipids namely 2-hexyl-decyl-β-D-glucopyranoside (β-Glc-OC10C6) and 2-hexyl-decyl-β-D-xylopyranoside (β-Xyl-OC10C6) were investigated for their potential in forming cubosomes and hexosomes respectively using Pluronic copolymers as steric stabilisers. The performance of five different Pluronics was evaluated for stabilisation of the dispersions, with a view to establish a structure-property relationship between the lipids and the stabilisers. The dispersions were assessed through synchrotron small-angle X-ray scattering as a function of temperature and the concentration of stabilisers. The internal structure of dispersed particles of β-Glc-OC10C6 was susceptible to changes upon stabilisation by different Pluronics and with increasing temperature. The lowest molecular weight Pluronic studied, L64, had the greatest propensity to disrupt the structure, suggesting that it is able to penetrate the internal structure to a greater degree than the other Pluronic stabilisers. In contrast, the β-Xyl-OC10C6 counterpart formed a stable inverse hexagonal phase structure that was invariant with the Pluronic used or temperature. The stability of the structure of β-Xyl-OC10C6 suggests it has greater potential for use in drug delivery applications and the studies overall extend the current understanding around the structures formed upon dispersion of Guerbet lipids.

Tailoring Intermolecular Interactions Towards High-Performance Thermoelectric Ionogels at Low Humidity.

Development of ionic thermoelectric (iTE) materials is of immense interest for efficient heat‐to‐electricity conversion due to their giant ionic Seebeck coefficient (S i), but challenges remain in terms of relatively small S i at low humidity, poor stretchability, and ambiguous interaction mechanism in ionogels. Herein, a novel ionogel is reported consisting of polyethylene oxide (PEO), polyethylene oxide‐polypropylene oxide‐polyethylene oxide (P123), and 1‐ethyl‐3‐methylimidazolium acetate (Emim:OAC). By delicately designing the interactions between ions and polymers, the migration of anions is restricted due to their strong binding with the hydroxyl groups of polymers, while the transport of cations is facilitated through segmental motions due to the increased amorphous regions, thereby leading to enlarged diffusion difference between the cations and anions. Moreover, the plasticizing effect of P123 and Emim:OAC can increase the elongation at break. As a consequence, the ionogel exhibits excellent properties including high S i (18 mV K−1 at relative humidity of 60%), good ionic conductivity (1.1 mS cm−1), superior stretchability (787%), and high stability (over 80% retention after 600 h). These findings show a promising strategy to obtain multifunctional iTE materials by engineering the intermolecular interactions and demonstrate the great potential of ionogels for harvesting low‐grade heat in human‐comfortable humidity environments.

SDS triggered transformation of highly hydrophobic Pluronics® nanoaggregate into polymer-rich and surfactant-rich mixed micelles

This work reveals the role of sodium dodecylsulphate (SDS, anionic surfactant) in altering the phase behaviour and aggregation characteristics of five very hydrophobic polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymers containing 10% PEO but with different molecular weight. These copolymers are molecularly dissolved in water at ≤15–20 °C and exist as unstable vesicular structure at temperature close to cloud point (CP) >20 °C. SDS enhanced the aqueous solubility and CP of copolymers in water; progressive addition of SDS triggered the transformation of unstable vesicles into spherical mixed micelles. A correlation between the molecular orbital energy levels of Pluronics® and SDS is well comprehended using computational simulation approach where the perception of SDS stabilized Pluronics® micelles is predicted and correlated with optimized parameters. The size/ shape of copolymer-surfactant mixed nanoscale aggregates was evaluated using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The scattering studies showed the presence of spherical mixed aggregates, whose size expanded with increase in hydrophobicity of Pluronics®. In high SDS concentration regime, SANS analysis uncovered the diminishing size of vesicles into spherical mixed aggregates. The nanoscale Pluronics®-SDS mixed micelles remained stable in water where this investigation discloses the conceivable ability of orange-OT solubilization using UV–vis spectroscopy.

Study on the improvement of water resistance and water absorption of magnesium oxychloride cement using long-chain organosilane-nonionic surfactants

In this study, hexadecyltrimethoxysilane (HDTMS) and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) were added to magnesium oxychloride cement (MOC). Using the amphiphilicity of P123 to weaken the effect of HDTMS on the hydration reaction of MOC, the entire hydrophobic MOC material was prepared. Compared with the blank sample, the compressive strength can reach its 63% after 28 days. The softening coefficient can reach 0.90 and the mass water absorption is only 7.3% after 28 days of immersing.

Synthesis of NiS2/reduced graphene oxide nanocomposites as anodes materials for high-performance Sodium and Potassium ion batteries

Nickel sulfide (NiS2) has displayed a widely application prospect of rechargeable batteries, solar cells, and supercapacitors. NiS2/reduced graphene oxide nanocomposite are synthesized by a facile hydrothermal method, using polyethylene oxide-polypropylene oxide-polyethylene oxide as surfactant. Due to the synergistic effect from reduced graphene oxide and NiS2 nanoparticles, graphene nanocomposite structure can improve the electrode conductivity and efficient buffering the volume change. As an anode material, compared with the NiS2 sample, the NiS2/reduced graphene oxide electrode exhibit excellent sodium and potassium storage properties. A first discharge capacity is 821 mAh g–1, keep in 575 mAh g–1 after 100 cycles at 100 mA g–1, and an reversible capacity of 308 mAh g–1 after 500 cycles at 5000 mA g–1 for sodium ion battery. Moreover, a reversible capacities of 320 mAh g–1 after 100 cycles at 50 mA g–1 for potassium ion battery.

Highly Enhanced Curcumin Delivery Applying Association Type Nanostructures of Block Copolymers, Cyclodextrins and Polycyclodextrins.

The limited bioavailability of the highly hydrophobic natural compound, curcumin with wide range of beneficial bioactivity is still a challenge. Self-association type systems of polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymers (Pluronic) were applied to enhance the aqueous solubility of curcumin. Comparison of four Pluronics (94, 105, 127,108) with different compositions led to the conclusion that solubilization capacity is maximum for Pluronic 105 with intermediate polarity (hydrophilic/lipophilic balance (HLB) = 15) possessing the optimum balance between capacity of hydrophobic core of the micelle and hydrophilic stabilizing shell of the associate. Curcumin concentration in aqueous solution was managed to increase 105 times up to 1–3 g/L applying Pluronic at 0.01 mol/L. Formation of a host–guest complex of cyclodextrin as another way of increasing the curcumin solubility was also tested. Comparing the(2-hydroxypropyl)-α, β and γ cyclodextrins (CD) with 6, 7 and 8 sugar units and their polymers (poly-α-CD, poly-β-CD, poly-γ-CD) the γ-CD with the largest cavity found to be the most effective in curcumin encapsulation approaching the g/L range of concentration. The polymer type of the CDs presented prolonged and pH dependent release of curcumin in the gastrointestinal (GI) system modelled by simulated liquids. This retarding effect of polyCD was also shown and can be used for tuning in the combined system of Pluronic micelle and polyCD where the curcumin release was slower than from the micelle.

Polypropylene oxide/polyethylene oxide‐cellulose hybrid nanocomposite hydrogels as drug delivery vehicle

AbstractThis article deals with the synthesis of hybrid nanocomposite hydrogels through the combination of cellulose (C), polypropylene oxide/poly ethylene oxide (PPO/PEO), and silver nanoparticles (AgNPs) by in situ polymerization technique for the in vitro release of ornidazole drugs. The structure of the resulted materials is identified using SEM, XRD, FTIR, XPS, and TGA spectroscopic techniques. The resulting structure, morphology, thermo responsive property, water retention, and swelling behavior of hydrogels are investigated. The rheological measurement is studied to establish the enhancement of the viscoelasticity and stiffness of hydrogels. The antibacterial activity of the biodegradable silver hybrid nanocomposite hydrogel is investigated by inhibition zone method against gram positive and negative bacteria. Maximum drug release of 96.4% is recorded at 7.4 pH in 5 h. The biocompatibility and cytotoxicity of the hybrid nanocomposite hydrogel are verified using mouse fibroblast cell line L‐929 (ATCC CCL‐1) cells for their possible use as controlled drug delivery vehicles. The nontoxic nature makes the materials more biocompatible and suitable to apply in the biological systems. Therefore, nontoxic and biocompatible natures of present materials with improved thermal and rheological properties support for their possible uses as drug delivery vehicles.

Polyethylene oxide-polypropylene oxide -polyethylene oxide derived porous carbon materials with different molecular weights as ORR catalyst in alkaline electrolytes

Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol−1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density，half-wave potential and initial potential are 5.23 mA cm−2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution.

Influence of surfactant's polar head group charge on the self-assembly of three PEO–PPO–PEO triblock copolymers of widely varying hydrophobicity

The present study is based on the interaction between three polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymers namely Pluronics® L81, P84 and F88 (with same PPO Mol. Wt. but 10,40 and 80% PEO, respectively) and the ionic surfactants with 12-C chain but different polar head group charge viz. sodium dodecyl sulfate (SDS, anionic), dodecyl trimethylammonium bromide (DTAB, cationic) and N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (C12PS, zwitterionic) using plethora of techniques. The most hydrophobic Pluronic® L81 (cloud point, CP = 16.5 °C (5%w/w)) remains as molecularly dissolved below the CP and forms unstable vesicles close to CP, moderately hydrophobic, P84 (CP = 73.6 °C), remains molecularly dissolved below 15 °C and forms core-shell micelle above critical micelle temperature (CMT) and the highly hydrophilic F88 forms micelles at elevated temperatures. Micellization and dye solubilizing ability improved in the presence of salt (sodium chloride, NaCl). The presence of ionic surfactants leads to small sized surfactant rich micelles with progressive addition as confirmed by dynamic light scattering (DLS) and small angle neutron scattering (SANS). Amongst the three copolymers, P84 (Nagg ≈ 72) showed maximum solubility of dye and lowering power of CMC (CAC < 2 mM), hence SANS studies were limited to P84 and it was observed that SDS (Nagg ≈ 45) showed stronger interactions with P84 as compared to DTAB (Nagg ≈ 53) and C12PS (Nagg ≈ 83).

Dual-template strategy for electrocatalyst of cobalt nanoparticles encapsulated in nitrogen-doped carbon nanotubes for oxygen reduction reaction

Development of non-precious metal catalysts (NPMCs) with high performance and stability has important value for oxygen reduction reaction (ORR) of fuel cells. In this paper, a novel structure of nitrogen-doped carbon nanotubes-encapsulated cobalt nanoparticles (Co@NCNTs) is synthesized by a simple dual-template strategy using silica colloid and tri-block copolymer (polyethylene oxide-polypropylene oxide-polyethylene oxide, PEO-PPO-PEO, F127) as hard and soft templates, respectively. The Co@NCNTs-800 synthesized at 800 °C shows an excellent ORR performance, which can be attributed to the desirable combination of their unique one-dimensional carbon nanotube structure, the adequate nitrogen doping level, the large surface area created by the dual-template strategy, and the synergistic effect between graphitic carbon layer and cobalt nanoparticles. The doped N atoms can provide coordination sites for cobalt nanoparticles and form NC moieties as dominant active sites, which provide positive effect on catalytic ORR activity. The graphitic carbon layers can protect cobalt nanoparticles against agglomeration and electrolyte corrosion, while cobalt nanoparticles can activate the bordering graphitic carbon layers and further increase ORR activities. This dual-template synthetic strategy provides an opportunity to promote the catalytic performance of NPMCs for application of polymer electrolyte membrane fuel cells.

Characterization and application of mixed micellar assemblies of PEO-PPO star block copolymers for solubilization of hydrophobic anticancer drug and in vitro release

Over the past few decades, polymeric micelles have attracted enormous attention due to their beneficial properties such as (i) core-shell structure, capable to accommodate hydrophobic drugs, boosting the overall solubility in aqueous medium; (ii) appropriate size which favors accumulation within the tumor, displaying improved permeability and retention (EPR) effect and (iii) unimers that tune the activity of efflux pumps engaged in multidrug resistance (MDR). Taking this into consideration, the present study aims the optimization and application of mixed copolymeric system of polyethylene oxide-polypropylene oxide (PEO-PPO) star block copolymers, Tetronics® 901 and 904 (hereafter written as T901 and T904), with almost same molecular weight of PPO blocks but distinct PEO block lengths, for the solubilization and in vitro release of hydrophobic anticancer drug, curcumin (CN). The copolymer T901 being incorporated with a long PPO block (10% PEO, M. Wt. 4700) is highly unstable and has poor water solubility at ambient temperature. Thus, undergoes phase separation at temperatures below 25 °C. Tetronic® T904 (40% PEO, M. Wt. 6700) with relatively longer PEO blocks forms stable core-shell micelles (hydrodynamic diameter, Dh ~ 12.0 nm and aggregation number, Nagg ~ 24) in water. The inclusion of copolymer T901 in the micellar system of T904 is mutually beneficial for both the copolymers as the insertion of T901 in T904 extends its PPO core and consequently improves its drug solubilizing capacity. On the other hand, the solubility of T901, which otherwise remains insoluble in water (at ambient temperature) is increased. Hence, the assemblies so formed are more efficient for drug delivery and improve the carrier properties of both the copolymers. The solubility and release profiles of drug was also checked in the presence of commonly used pharmaceutical excipients viz. sodium chloride (NaCl) and glucose in isotonic conditions and it was witnessed that the presence of both the excipients promoted micellization and augmented the solubilization capacity of the mixed assemblies many folds. The in-vitro release profiles suggested release of drug through diffusion from the mixed assemblies.

Preparation of N-doped nano-hollow capsule carbon nanocage as ORR catalyst in alkaline solution by PVP modified F127

In order to reduce the cost of oxygen reduction reaction (ORR) catalyst, a metal-free N-doped carbon nanocage as ORR catalysts is prepared by using Polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) three-block copolymer (F127), polyvinyl pyrrolidone (PVP) and Zn (OH)2 as a carbon source, nitrogen source and the morphology retaining agent, respectively, via a self-template method. The structure and microstructure of the N-doped carbon nanocage are characterized via physical characterization methods such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller method, and X-ray photoelectron spectroscopy. Electrochemical properties are evaluated in an O2-saturated alkaline solution. The obtained sample pyrolyzed at 800 °C with 10% content of PVP (C–N-800) presents nano-hollow carbon capsule with a diameter of 100 nm and shell thickness of 8 nm, and has the maximum surface area of 978 m2·g−1. In O2-saturated 0.1 M KOH solution, C–N-800's onset potential, limit current density, and half-wave potential, which are 0.87 V, 5.73 mA/cm2@0.45 V, and 0.77 V, respectively, are close to those of commercial 20% Pt/C catalysts. Meanwhile, its electrochemical performance only loss 11.75% after 5000 cycles, showing excellent ORR catalytic performance and stability. During self-assembly of F127, the added PVP participated into the process. Pyrolysis at 800 °C would result in the complete decomposition of F127 and PVP's lipophilic. So, the metal-free N-doped carbon nanocage was obtained and behaved excellent ORR catalytic activity and stability.

Solubilization, micellar transition and biocidal assay of loaded antioxidants in Tetronic® 1304 micelles

AbstractThe current study scrutinizes the solubilization behaviour of pharmaceutically active antioxidants, namely hydrocinnamic acid (HCA), cinnamic acid (CA) and phenyl propiolic acid (PPA), in the micelles of polyethylene oxide‐polypropylene oxide (PEO‐PPO) based star‐block copolymer: Tetronic® 1304 (T1304). A correlation between the molecular orbital energy levels of PEO‐PPO units of T1304 and the active parts of the antioxidants are well explained using a simulation study. The antioxidants modulate core–shell micelles of T1304 with enhanced solubilization dependent on their unsaturation and hydrophobicity, as depicted from UV–visible spectroscopy. Antioxidants as an additive induce micellization in 5% w/v T1304 thereby modulating the phase behaviour, as indicated by the decrease in the cloud point. The cloud point results are well complemented by steady state fluorescence spectroscopy findings, depicting a decrease in critical micelle temperature due to the solubilization of antioxidants into the T1304 micelles. A significant difference between the hydrodynamic diameter (Dh) of unloaded and loaded polymer micelles with antioxidants is observed from dynamic light scattering, ensuring the solubilization of the antioxidants in T1304 micelles. These results can apparently be attributed to the interaction and the charge induced by the antioxidants on non‐ionic T1304 micelles which increase the micellar size. Furthermore, the role of unsaturation and hydrophobicity of the employed antioxidants in 5% T1304 demonstrates the solution viscosity (η) change as a function of temperature. In addition, small‐angle neutron scattering depicts the shape transition (spherical to ellipsoidal to polymersomes) with temperature. The antioxidant loaded 5% T1304 micellar systems exhibit brilliant biocidal activity against the tested microbes, suggesting their antimicrobial application. © 2019 Society of Chemical Industry

Colloidal stability of graphene oxide nanosheets in association with triblock copolymers: A neutron scattering analysis.

This study investigates stabilization of graphene oxide (GO) nanosheets in polyethylene oxide-polypropylene oxide (PEO-PPO) block copolymers (P103, P123 and F127). Changes in micellization of copolymers upon GO addition were monitored using dynamic light (DLS) and small angle neutron scattering (SANS). Structural developments at sheet surface were studied with two possibilities; (i) adsorption of PPO block over hydrophobic basal plane allowing the engagement of hydrophilic PEO with aqueous bulk, and (ii) adsorption of micelles mediated via carboxylated groups. Insignificant changes in micellar parameters for P123 and P127 were indicative of their inferior interaction with GO. On the other hand, P103 micelles exhibited high affinity for sheets, noticeable as emergence of mass fractals and more than two-fold enhancement in micelle number density. The latter allowed coverage of entire surface with P103 micelles. Existence of mass fractals was verified by extracting the form and structure factors from the fitted SANS data. Spectroscopic and thermogravimetric analyses illustrated non-covalent adsorption of copolymer aggregates. It was interesting to note that the dispersion remained stable against protein and electrolyte addition. A comprehensive understanding on colloidal stability can be valuable for drug delivery applications of GO sheets.

Fabricating carbon nanocages as ORR catalysts in alkaline electrolyte from F127 self-assemble core-shell micelle

In order to reduce the cost of oxygen reduction reaction (ORR) catalyst in fuel cell, polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) three-block copolymer (F127) and Zn(OH)2 were used as carbon resource and morphology retaining agent to prepare porous nanocages for ORR catalyst in alkaline solution. Its composition and microstructure were characterized by X-ray diffraction Raman spectroscopy (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) method. Electrochemical properties were evaluated in O2 saturated alkaline solution. Results showed the sample obtained at 700 °C (C-700) was composed of porous carbon nanocages with diameter of 50 nm and shell thickness of 4 nm. C-700 had the maximum surface area (1011 m2 g−1) and the best ORR catalytic performance. The main reason is that polypropylene oxide (PPO) group at the lipophilic end begins to decompose at 500 °C, and the polyethylene oxide (PEO) group at the lipophilic end at 700 °C decomposes completely. In O2 saturated 0.1 M KOH solution, C-700's oneset potential, limit current density and half-wave potential, which were 0.89 V, 5.59 mA/cm2@0.45 V and 0.71 V, respectively, were close to that of commercial 20% Pt/C catalyst. It was noted that the oneset potential and half-wave potential of C-700 had barely change, and limit current density attenuated about 87.8% after 2000 CV cycle. The obtained catalyst behaved good catalytic activity and stability for ORR in alkaline solution and a potential application prospect in fuel cells.

Influence of surfactant assisted exfoliation of hexagonal boron nitride nanosheets on mechanical, thermal and dielectric properties of epoxy Nanocomposites

ABSTRACTIn Present decade, polymer nanocomposites are extensively used for manufacturing of automotive, aircraft structural components. The polymer nanocomposites properties enhancement depends upon dispersion quality of nanofiller. Recently, hexagonal boron nitride (hBN) nanosheets is one of the most attractive nanofiller; a white solid with a layered structure, physically or structurally similar to graphite, also known as White graphene. In the present work, the hBN nanosheets are prepared by surfactant assisted liquid-phase exfoliation method using ethanol as solvent. The surfactant used is a block copolymer of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO). Although ethanol is a poor solvent, but it is a green solvent. A highly concentrated and stable dispersion of hBN nanosheets (~0.45 mg/ml) is obtained by probe sonication followed by centrifugation. The surfactant modified hBN nanosheets reinforced epoxy nanocomposites are prepared by an open casting method and characterized by various characterization techniques. At 0.08 wt% of surfactant modified hBN nanosheets incorporation in epoxy matrix show enhancement in flexural modulus and strength is by 3.6% and 5.7%. There is a multilayer dispersion of surfactant modified hBN nanosheets in epoxy matrix facilitating the dampening of cracks for flexural properties enhancement.