Polyethylene Oxide-polypropylene Oxide-polyethylene Oxide Triblock Research Articles

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.

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.

Coarse-Grained Simulations of Aqueous Thermoresponsive Polyethers.

Thermoresponsive polymers can change structure or solubility as a function of temperature. Block co-polymers of polyethers have a response that depends on polymer molecular weight and co-polymer composition. A coarse-grained model for aqueous polyethers is developed and applied to polyethylene oxide and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock co-polymers. In this model, no interaction sites on hydrogen atoms are included, no Coulombic interactions are present, and all interactions are short-ranged, treated with a combination of two- and three-body terms. Our simulations find that The triblock co-polymers tend to associate at temperatures above 350 K. The aggregation is stabilized by contact between The hydrophobic methyl groups on The propylene oxide monomers and involves a large, favorable change in entropy.

Nanoarmoring of Proteins by Conjugation to Block Copolymer Micelles.

The creation of polymer nanoparticles with protein functionality is of great interest to many applications such as targeted drug or gene delivery, diagnostic imaging, cancer theranostics, delivery of protein therapeutics, sensing chemical and biomolecular analytes in complex environments, and design of protective clothing resembling a second skin. Many approaches to achieving this goal are being explored in the current literature. In this chapter, we describe a relatively simple and flexible approach of conjugating the protein to an amphiphilic block copolymer and creating polymer nanoparticles with protein functionality by taking advantage of the intrinsic self-assembly behavior of the amphiphilic block copolymer. The commercially available and biocompatible polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is used as the polymer building block. For demonstrative purposes, bovine serum albumin was chosen as the protein. We determine the molecular weight of the protein-polymer conjugate and thereby the degree of conjugation using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry measurements. Retention of protein secondary structure in the conjugate was determined by circular dichroism spectroscopy, and the biological activity of the protein in the conjugated state has been evaluated by kinetic assay involving hydrolysis of an organophosphate compound. Dynamic light scattering and zeta potential measurements were used to characterize the size and charge of the protein-polymer conjugate micelle. Precise control of the size of the micelle and surface number density of the proteins on the micelle surface by coassembling with a second block copolymer have been demonstrated. These studies document a rational approach to armor the protein by conjugation with a block copolymer micelle, as a general approach.

Silica capsules enclosing P123 triblock copolymer micelles for flurbiprofen storage and release.

Flurbiprofen was incorporated in 200-400 nm silica capsules filled with Pluronic P123 polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer. The assembly process of the capsules and the molecular organization of drug molecule, surfactant and silica were investigated using SAXS, TGA, SEM, DLS, DSC, 13C single-pulse, CPMAS and 1H-1H two-dimensional NMR. Flurbiprofen molecules are molecularly dispersed inside polypropylene cores of P123 surfactant micelles occluded in a 20-30 nm thick silica shell. Flurbiprofen molecules in polypropylene cores of P123 micelles exhibit high mobility and are easily released after introduction in simulated gastrointestinal fluid and the solubility limit is reached within minutes. Release rates are favored at high pH due to acid dissociation of the carboxylic acid group of the flurbiprofen molecule. The molecular environment of flurbiprofen in these P123 filled silica capsules is different from ordered mesoporous silica materials synthesized using P123 as sacrificial template having the drug molecules adsorbed on the silica surface of pore walls. These findings uncover a new concept of storage and release of hydrophobic bioactive molecules.

Controlled design and construction of multifunctional nanoparticles by molecular self-assembly

Controlled design of nanoparticles (NPs) displaying multiple functionalities is of great interest to many applications such as targeted drug or gene delivery, diagnostic imaging, cancer theranostics, delivery of protein therapeutics, sensing chemical and biomolecular analytes in complex environments, and design of future soldier protective clothing resembling a second skin. Current methods of synthesizing multifunctional nanoparticles (MNPs) typically involve sequential chemical processing of NPs; for example, drug-encapsulated NPs are first formed, followed by surface modifications involving the sequential conjugation of ligands to provide other functionalities such as targeting, responsiveness to stimuli, etc. We describe an alternate flexible approach to constructing MNPs employing the machinery of molecular self-assembly, starting with individually functionalized amphiphilic block copolymers. The commercially available polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is used as the building block for illustrative purposes and functionalities are provided by other chemical moieties conjugated to it via degradable linkers. For demonstrative purposes, we have chosen folic acid (a targeting ligand), bovine serum albumin (resembling a therapeutic protein), and gadolinium (a MRI contrast agent) as the functionalities, but the choice of functionalities is not limited. The self-assembly of the conjugated block copolymers is induced by solvent polarity control, resulting in the production of MNPs. Quantitative determination of the amount of each conjugated functionality is done using spectrophotometry, which shows that the composition of the MNP is controlled by the composition of the precursor functionalized block copolymers and that self-assembly preserves the compositional control. The size of the MNP can be controlled by adding a second block copolymer. The combination of the ability to introduce multiple functionalities, vary the relative proportion of functionalities, and control the nanoparticle size, all independent of one another, renders the self-assembly approach uniquely efficient for producing interesting multifunctional nanoparticles for numerous applications.

Preparation and Performance of Antifouling PVC/CPVC Blend Ultrafiltration Membranes

Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) were used as membrane materials to fabricate blend ultrafiltration membranes. Polyethylene glycol (PEG2000) and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (Pluronic F127) were used as both pore forming agent and surface modifier to improve the permeability. The advantage of amphiphilic Pluronic F127 is that it enables higher −CH2–CH2–O– segment coverage on the membrane surfaces. The increase of CPVC proportion in membrane materials could improve the water fluxes of PVC/CPVC blend membranes with the slight change of protein rejection ratios. All the PVC/CPVC blend membranes with an additive of Pluronic F127 have excellent antifouling property. The blend method is an appropriate way to prepare new antifouling PVC/CPVC ultrafiltration membranes which have lower cost and better performance.

Mesoporous Silicates as Nanoreactors for Carbon Nanotube Production in the Absence of Transition Metal Catalysts

Carbon nanotubes were produced from either a template or the polymer-filled pore systems of mesoporous silicates of various structures and dimensions by heat treatment in the absence of air. Successful synthesis was done when the template molecules contained little or no oxygen. For SBA-15 material, where the structure-directing molecule used for synthesis of mesoporous silicate was polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, no carbon nanostructures were formed. A peculiar carbon nanostructure was generated from the template for pore expanded MCM-41. To demonstrate carbon nanotube formation from polymer in the mesoporous silicates, the mesopores of MCM-41, MCM-48, and SBA-15 silicates were filled with divinyl-benzene polymer and then graphitized at 1300 K. The polymer was successfully transformed into carbon nanotubes for the MCM class silicate but not the SBA-15 silicate.

Prevention of protein adsorption on surfaces by polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymers in capillary electrophoresis

Protein adsorption to untreated fused-silica capillaries in capillary electrophoresis was prevented by a chemical modification of the capillary surface. This was achieved through the coating of Pluronic polymers onto capillaries which were pre-derivatised with silylating agents. The polymers were made up of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymers. The coatings prevent protein adsorption and provide high-efficiency separations. Two different types of silylating agents were used and the effects of the concentrations on the stability and efficiency of the columns were examined. The application of these columns for capillary electrophoretic separation of protein samples was demonstrated.