PEO Shell Research Articles

Revealing Phase Transitions in Poly(Ethylene Oxide)‐Based Electrolyte for Room‐Temperature Solid‐State Batteries

AbstractSolid‐state electrolytes (SSEs) offer enhanced safety, extended cycle life, and increased energy density when replacing flammable liquid electrolytes in lithium‐ion batteries. Poly(ethylene oxide) (PEO)‐based SSE is the only candidate that has been commercially implemented in electric vehicles. However, the equipped battery needs to operate at temperatures above 50 °C, and its phase transitions at room temperature are still unclear. Herein, the solidification of the PEO‐lithium bis(trifluoromethanesulfonyl)imide (PEOn‐LiTFSI) system is revisited. Contrary to the prevailing view of forming PEO(6)‐LiTFSI spherulites, the presence of crystalline PEO(8)‐LiTFSI complexes is quantitatively confirmed. The nucleation and growth processes of crystalline PEO and PEO(8)‐LiTFSI spherulites are also visually elucidated, and phase transitions with the impedance change are correlated. In addition, it is demonstrated that the crystalline PEO shell surrounding the PEO(8)‐LiTFSI spherulites hinders the kinetics of crystal growth, thereby enabling the highest ionic conductivity at n = 10. Importantly, it is pointed out that instead of the poor ionic conductivity of the electrolyte layer, the heterogeneous nucleation of PEO(8)‐LiTFSI within the electrodes is the limiting factor in constructing room‐temperature all‐solid‐state batteries.

Investigation of morphology and structure of drug-loaded PLA-b-PEO-b-PLA polymeric micelle: A dissipative particle dynamics simulations study.

The dissipative particle dynamics (DPD) simulation was used to study the morphologies and structures of the paclitaxel-loaded PLA-b-PEO-b-PLA polymeric micelle. We focused on the influences of PLA block length, PLA-b-PEO-b-PLA copolymer concentration, paclitaxel drug content on morphologies and structures of the micelle. Our simulations show that: (i) with the PLA block length increase, the self-assemble structure of PLA-b-PEO-b-PLA copolymers with paclitaxel vary between onion-like structure (core-middle layer-shell) to spherical core-shell structure. The PEO shell thins and the size of the PLA core increases. The onionlike structures are comprised of the PEO hydrophilic core, the PLA hydrophobic middle layer, and the PEO hydrophilic shell, the distribution of the paclitaxel drug predominantly occurs within the hydrophobic intermediate layer; (ii) The system forms a spherical core-shell structure when a small amount of the drug is added, and within a certain range, the size of the spherical structure increases as the drug amount increases. When the drug contents (volume fraction) cdrug = 10%, it can be observed that the PLA4-b-PEO19-b-PLA4 spherical structures connect to form rod-shaped structures. With the length of PLA block NPLA = 8, as the paclitaxel drug concentrations cdrug = 4%, PEO has been insufficient to completely encapsulate the PLA and paclitaxel drug beads. To enhance drug loading capacity while maintaining stability of the system in aqueous solution, the optimal composition for loading paclitaxel is PLA4-b-PEO19-b-PLA4; the drug content is not higher than 4%; (iii) The paclitaxel-loaded PLA4-b-PEO19-b-PLA4 micelle undergo the transition from onionlike (core-middle layer-shell) to spherical (core-shell) to rod-shaped and lamellar structure as the PLA4-b-PEO19-b-PLA4 copolymer concentration increases from ccp = 10% to 40%.

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).

Structure regulation for synergistically improving the permeation properties of the reverse osmosis membrane based on an amphiphilic hyperbranched polymer

The aromatic polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membrane has been widely used in the desalination processes to settle the global water crisis. To further decrease the desalination cost, in this work, an amphiphilic hyperbranched polymer of HBPO-star-PEO-COCl with abundant end groups of acyl chloride and core-shell hydrophilic/hydrophobic phase separation structure was synthesized and used as the functional nanomaterial to modify the conventional polyamide TFC RO membrane through interfacial crosslinking reaction. The modified RO membrane with 0.005% HBPO-star-PEO-COCl presents the optimal structure and permeation properties. Its PA layer becomes thinner and denser, and its water flux reaches 69.8LMH nearly double that of the original membrane (33.27LMH), at the same time, its NaCl rejection rate reaches 99.22% higher than that of the original membrane. It can attribute to the unique amphiphilic core-shell structure of HBPO-star-PEO-COCl. On the one hand, the PEO shell of HBPO-star-PEO-COCl is highly hydrophilic while the internal HBPO is highly hydrophobic and collapses easily in water to form a three-dimensional quasi-spherical structure, which leads to the formation of the core-shell two-phase interface, thereby facilitating the water molecules to rapidly pass through the PA layer along the hydrophobic wall surface. On the other hand, the end acly chloride groups of HBPO-star-PEO-COCl take part in the crosslinking reaction, which makes the PA layer have higher crosslinking degree and become denser, thereby enhancing the salt retention. Therefore, this study provides an effective way to fabricate a new reverse osmosis composite membrane with favorable comprehensive separation performance based on amphiphilic hyperbranched polymer.

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

Scalable synthesis of fluorescent organic nanodots by block copolymer templating

Salt-assisted microstructure evaluation of hydrophilic block copolymer F98: A thermal and scattering study

The temperature- and salt induced micellization and phase behavior of a very hydrophilic ethylene oxide (EO)-propylene oxide (PO) triblock copolymer Pluronic® F98 (EO118-PO46-EO118, 80% PEO) in aqueous solutions has been investigated by high sensitivity differential scanning calorimetry (HSDSC), viscosity, dynamic light scattering (DLS) and small-angle neutron scattering (SANS) measurements. Data on critical micellization temperature (CMT), cloud point (CP) and thermodynamic parameters for aggregation of F98 in water and salt solution are reported. Both CMT and CP decrease with an increase either in F98 concentration or NaCl concentration. The enthalpy and entropy change of micellization decreased with increasing F98 concentration. The process is related to dehydration of PEO blocks which is dominating factor for positive heat capacity. The solution viscosity of these Newtonian fluids shows significant increase at higher F98 concentration/higher temperature/presence of salt due to intermicellar interaction and is followed by a decrease due to progressive dehydration of PEO shell. SANS and DLS results show that micelles remain spherical with slight increase in size at all temperatures and in the presence of NaCl.

Quest for Thermoresponsive Block Copolymer Nanoparticles with Liquid-Crystalline Surfactant Cores.

This work reports on the preparation and characterization of anisotropic composition nanoparticles based on the electrostatic binding of dodecyltrimethylammonium surfactant to poly(acrylic acid) blocks of diblock copolymers with poly(ethylene oxide) (PEO) and poly(N-isopropyl acrylamide) (PNIPAm). These nanoparticles form kinetically stable dispersions and display liquid–crystalline cores with a micellar cubic structure, as determined by small-angle X-ray scattering. Mixtures with different proportions of the two block copolymers and stoichiometric amounts of C12TA+ were prepared and their behavior was compared with that of the parent nanoparticles. Upon heating, dilute dispersions (0.01 and 0.1 wt %) analyzed by dynamic light scattering display a slight decrease in the hydrodynamic radius, consistent with the dehydration of PNIPAm and mixed PNIPAm–PEO blocks at the shell. At higher concentrations, 2 wt %, the nanoparticles with pure PNIPAm shell undergo macroscopic phase separation above 32 °C. Nanoparticles with a pure PEO shell do not display temperature sensitivity. For the mixtures, no visual change is observed, but the dynamic light scattering results evidence the formation of clusters, whose size and reversibility depend on the PEO/PNIPAm proportion. This indicates the formation of mixed nanoparticles containing both PEO and PNIPAm blocks. Nuclear Overhauser enhancement spectroscopy NMR analyses of the mixtures do not show the correlation peak expected for PEO and PNIPAm blocks in close proximity, suggesting their segregation at the nanoparticle shell. On the basis of these results, we discuss the possibilities of the neutral blocks distribution on the shell of mixed nanoparticles. Overall, we have confirmed that these nanoparticles may display a temperature-controlled reversible aggregation while preserving their internal liquid–crystalline structures.

Surface-initiated RAFT polymerization of pseudo-superhydrophilic polymer brush as intraocular lens coating for reduced after cataract

We describe here a straightforward strategy towards the high yield preparation of raspberry-like all-organic particles. Poly(acrylic acid)-b-poly(butyl acrylate) core–shell nanoparticles (D ∼ 80 nm) and larger poly(ethylene oxide)-b-poly(butyl acrylate) core–shell (D ∼ 230 nm), synthesized by RAFT emulsion polymerization, were mixed at high solids content (23 wt%) at room temperature without any particular precaution (no dropwise addition, no pH adjustment). Raspberry-like particles constituted of one central PEO-b-PBA particle surrounded by about thirty PAA-b-PBA particles were successfully obtained, with no coagulum formation. The heteroaggregation process is probably driven by the hydrogen-bond interactions between the PAA and the PEO shells of the particles. The raspberry-like particles were characterized using electron microscopy (TEM and cryo-TEM), dynamic light scattering (DLS), chromatography (HDC) and calorimetry (ITC), demonstrating the selectivity of the process.

Ultrafine Co-based Nanoparticle@Mesoporous Carbon Nanospheres toward High-Performance Supercapacitors.

A general synthetic methodology is reported to grow ultrafine cobalt-based nanoparticles (NPs, 2-7 nm) within high-surface-area mesoporous carbon (MC) frameworks. Our design strategy is based on colloidal amphiphile (CAM) templated oxidative self-polymerization of dopamine. The CAM templates consisting of a hydrophobic silica-like core and a hydrophilic PEO shell can coassemble with dopamine and template its self-polymerization to form polydopamine (PDA) nanospheres. Given that PDA has rich binding sites such as catechol and amine to coordinate metal ions (e.g., Co2+), PDA nanospheres containing Co2+ ions can be converted into hierarchical porous carbon frameworks containing ultrafine metallic Co NPs (Co@MC) using high-temperature pyrolysis. The CAM templates offer strong "nanoconfinements" to prevent the overgrowth of Co NPs within carbon frameworks. The yielded ultrafine Co NPs have an average size of <7 nm even at a very high loading of 65 wt %. Co@MC can be further converted into various oxides and sulfides, e.g., CoO, Co3O4, CoS2 and transition-metal doped bimetallic CoxM1-xS2, without significantly changing the size of NPs. As a proof-of-concept application, the porous Co-based NPs@MC hybrids were used as electrode materials for supercapacitors, which exhibit excellent supercapacitive performance with outstanding long-term cycling stability, due to the features such as ultrafine size, controllable chemical compositions, hierarchical porous structures, and full coverage of conductive carbons.

DNA Island Formation on Binary Block Copolymer Vesicles.

Here, we report DNA-induced polymer segregation and DNA island formation in binary block copolymer assemblies. A DNA diblock copolymer of polymethyl acrylate-block-DNA (PMA-b-DNA) and a triblock copolymer of poly(butadiene)-block-poly(ethylene oxide)-block-DNA (PBD-b-PEO-b-DNA) were synthesized, and each was coassembled with a prototypical amphiphilic polymer of poly(butadiene)-block-poly(ethylene oxide) (PBD-b-PEO). The binary self-assembly of PMA-b-DNA and PBD-b-PEO resulted in giant polymersomes with DNA uniformly distributed in the hydrophilic PEO shell. When giant polymersomes were connected through specific DNA interactions, DNA block copolymers migrated to the junction area, forming DNA islands within polymersomes. These results indicate that DNA hybridization can induce effective lateral polymer segregation in mixed polymer assemblies. The polymer segregation and local DNA enrichment have important implications in DNA melting properties, as mixed block copolymer assemblies with low DNA block copolymer contents can still exhibit useful DNA melting properties that are characteristic of DNA nanostructures with high DNA density.

Novel Microstructured SiCNO Films Based on Polyvinylsilazane‐Swelled F127 Micelles

We report a facile route to synthesize novel microstructured SiCNO films via a block copolymer micellar‐templating approach, in which polyvinylsilazane (PVSZ)‐swelled F127 micelles are used as a precursor and the crystallization of the PEO shell of PVSZ‐swelled F127 micelles is used to control the microstructure of SiCNO films. By changing the evaporation temperature of multistep thermal treatments, SiCNO films containing nanospheres, rods, crosses, cuboids, and microspheres can be formed. We find that these microstructures have a significant effect on the dielectric loss of SiCNO films, which can be explained by the Maxwell–Wagner effects and impurities at interfaces.

Aqueous Solutions of Poly(ethylene oxide)-Poly(N-isopropylacrylamide): Thermosensitive Behavior and Distinct Multiple Assembly Processes

Detailed phase transition and conformational changes taking place as a function of temperature in poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEO-b-PNIPAM) semidiluted aqueous solutions are elucidated in the present study. By the use of elaborate vibrational spectroscopy techniques in combination with two-dimensional correlation spectroscopy (2Dcos), three transition regions including respective rich domains (<29 °C), loose aggregations (30-36 °C), and dense sphere micelles (>37 °C) are depicted. In particular, subtle variations of hydrogen bonds are detected even under the lower critical solution temperature (LCST), and the respective rich domain regime is marked with strong participation from hydrogen bonding at different concentrations and compositions. Both the formation of intermolecular hydrogen bonds and the less hydration degrees of PNIPAM segments compared with PNIPAM homopolymer at elevated temperatures verify the evolution of PNIPAM from their own domains to loose aggregations with PEO shells. Dense micelles are formed beyond the LCST of PNIPAM, while the outmost PEOs act as buffer layers and postpone the shrinkage of PNIPAM chains. Due to the existence of a buffer layer, higher phase transition temperatures compared with PNIPAM homopolymer are observed.

Polymeric micelles based on poly(ethylene oxide) and α-carbon substituted poly(ɛ-caprolactone): An in vitro study on the effect of core forming block on polymeric micellar stability, biocompatibility, and immunogenicity

A series of block copolymers based on methoxy poly(ethylene oxide)-block-poly(ɛ-caprolactone) (PEO-b-PCL), PEO-b-PCL bearing side groups of benzyl carboxylate (PEO-b-PBCL), or free carboxyl (PEO-b-PCCL) on the PCL backbone with increasing degrees of polymerization of the PCL backbone were synthesized. Prepared block copolymers assembled to polymeric micelles by co-solvent evaporation. The physical stability of prepared micelles was assessed by measuring their tendency toward aggregation over time using dynamic light scattering (DLS). The resistance of micelles against dissociation in the presence of a micelle destabilizing agent, i.e., sodium dodecyl sulfate (SDS), was also investigated using DLS. The rate of micellar core degradation was determined using 1H NMR for polymer molecular weight measurement upon incubation of micelles in PBS (pH=7.4) at 37°C followed by dialysis of the remaining polymer at different time intervals. The effect of pendent group chemistry in the micellar core on the adsorption of serum proteins to micellar structure was then evaluated using Bradford Protein assay kit. Finally, the effect of micellar core structure on the induction of bone marrow derived dendritic cell (BMDC) maturation and secretion of IL-12 was studied as a measure of micellar immunogenicity. The results showed micelle structures from polymers with higher degree of polymerization in the hydrophobic block and/or those with more hydrophobic substituents on the core-forming block, to be more stable. This was reflected by a decreased tendency for micellar aggregation, reduced dissociation of micelles in the presence of SDS, and diminished core degradation. All micelles were shown to have insignificant adsorption of serum protein suggesting that the hydrophilic PEO shell provided sufficient protection of the core. However, the protein adsorption increased with increase in the hydrophobicity and molecular weight of the core-forming block. Irrespective of the micellar core structure, all tested micelles were found to be non-immunogenic in BMDCs.

Synthesis and unimolecular micelles of amphiphilic copolymer with dendritic poly(l-lactide) core and poly(ethylene oxide) shell for drug delivery

A novel type of amphiphilic copolymer POSS-(G3-PLLA-b-PEO-COOH)8 with a hydrophobic third-generation dendritic PLLA core and a functionalized hydrophilic PEO shell with surface carboxylic groups was synthesized as a carrier for drug delivery.

High yield preparation of all-organic raspberry-like particles by heterocoagulation via hydrogen bonding interaction

We describe here a straightforward strategy towards the high yield preparation of raspberry-like all-organic particles. Poly(acrylic acid)-b-poly(butyl acrylate) core–shell nanoparticles (D ∼ 80 nm) and larger poly(ethylene oxide)-b-poly(butyl acrylate) core–shell (D ∼ 230 nm), synthesized by RAFT emulsion polymerization, were mixed at high solids content (23 wt%) at room temperature without any particular precaution (no dropwise addition, no pH adjustment). Raspberry-like particles constituted of one central PEO-b-PBA particle surrounded by about thirty PAA-b-PBA particles were successfully obtained, with no coagulum formation. The heteroaggregation process is probably driven by the hydrogen-bond interactions between the PAA and the PEO shells of the particles. The raspberry-like particles were characterized using electron microscopy (TEM and cryo-TEM), dynamic light scattering (DLS), chromatography (HDC) and calorimetry (ITC), demonstrating the selectivity of the process.

Formation–dissociation of glucose, pH and redox triply responsive micelles and controlled release of insulin

An amphiphilic copolymer containing PEO and PAPBA linked by a disulfide bond (PEO–SS–PAPBA) was synthesized by RAFT. The micelles with a PEO shell and a PAPBA core presented glucose, pH and redox triple responses. The controlled release of insulin could be achieved through adding glucose or GSH.

Polyelectrolyte–Surfactant Complexes of Poly[3,5-bis(dimethylaminomethyl)-4-hydroxystyrene]-block-poly(ethylene oxide) and Sodium Dodecyl Sulfate: Anomalous Self-Assembly Behavior

Polyelectrolyte-surfactant complexes (PE-S) formed by double hydrophilic cationic polyelectrolyte poly[3,5-bis(dimethylaminomethyl)-4-hydroxystyrene]-block-poly(ethylene oxide) (NPHOS-PEO) and anionic surfactant sodium dodecyl sulfate (SDS) in acidic aqueous solutions were studied by light scattering, SAXS, and scanning transmission electron microcopy in the environmental mode (wet-STEM) for various stoichiometric ratios between the numbers of SDS anions and dimethylaminomethyl groups of NPHOS in the complex. The obtained results show that the NPHOS-PEO/SDS system behaves differently from other systems of double hydrophilic block polyelectrolyte and oppositely charged ionic surfactant because it forms water-insoluble PE-S for compositions close to the zero net charge of the complex. This phase separation occurs, instead of the PE-S rearrangement to core-shell particles, which is hindered due to conformational rigidity of the NPHOS blocks. For the surfactant amounts below and above the precipitation region, large spherical aggregates and their clusters are present in the solution. SAXS measurements indicate that although the NPHOS-PEO/SDS system does not form the core-shell particles with the NPHOS/SDS core and the PEO shell as other PE-S of double hydrophilic polyelectrolytes, the aggregates contain domains of closely packed surfactant micelles which bind to both NPHOS polyelectrolyte blocks and PEO blocks.

Easy and effective method to produce functionalized particles for cellular uptake

In this contribution, a versatile approach for the synthesis of functionalized particles for drug delivery is presented, using two nonaggressive standardized procedures. The first procedure considered is the functionalization of an azido-terminated α-norbornenyl poly(ethylene oxide) (PEO) macromonomer with an alkyne-containing active molecule via the copper catalyzed azide alkyne cycloaddition, click type reaction. The functionalized macromonomer is then polymerized by Ring-Opening Metathesis Polymerization (ROMP) in dispersion to form functionalized particles. The second procedure consists in synthesizing particles by ROMP in dispersed media of norbornene with azido-terminated α-norbornenyl PEO macromonomer. The ROMP was initiated by the first generation Grubbs catalyst. Such functionalized core-shell particles have stealthy properties due to their PEO shell and can be viewed as universal nanocarriers on which any alkyne-modified active molecule can be grafted by click chemistry. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

A Facile Method to Form a Densely Grafted PEO‐b‐P4VP Brush on Gold Surface

AbstractHere we report a facile method for the preparation of a PEO113‐b‐P4VP93 brush on gold surface with a grafting density as high as 1.32 chains/nm2; the P4VP blocks were physically adsorbed on gold surface forming an inner layer while the PEO blocks stretched towards the solution forming PEO brush. PEO113‐b‐P4VP93 micelles with P4VP core and PEO shell formed in methanol/water mixed solvents were used as the precursor. By adsorbing PEO113‐b‐P4VP93 micelles from pure water, in which the density of the micelles is the largest, maximum amount of the micelles was adsorbed onto gold surface, and the adsorbed micelles existed as individual domains on the surface. To prepare the polymer brush with a density as high as possible, we annealed the adsorbed micelles by methanol/water mixed solvent at the volume fraction of methanol (VF) of 20%, which was the proper proportion at which the core‐forming P4VP chains began to be flexible but the integrity of the micelles was remained. At this volume fraction, almost all the adsorbed micelles originally existing as individual domains were transformed into a dense polymer brush.

Molecular Nanoworm with PCL Core and PEO Shell as a Non‐spherical Carrier for Drug Delivery

Core/shell wormlike polymer brushes with densely grafted poly(ϵ-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) are synthesized via grafting an alkynyl terminated PCL-b-PEO (ay-PCL(17) -b-PEO(113) ) onto a well-defined azido functionalized polymethacrylate (PGA(940) ) and are evaluated preliminarily as a single molecular cylindrical vehicle for drug delivery. Water soluble molecular worms of ca. 230 nm are obtained and then the anticancer drug doxorubicin (DOX) is loaded into its PCL core by hydrophobic interaction. Compared with spherical micelles from linear PCL(17) -b-PEO(113) , the brushes demonstrate a lower loading efficiency but a faster release rate of DOX. Confocal laser scanning microscopy measurements show that DOX-loaded cylindrical molecular brushes can easily enter into HeLa and HepG2 cells in 1 h.