Nanoporous Poly Research Articles

Electrocatalytic oxidation of NADH at low overpotential using nanoporous poly(3,4)-ethylenedioxythiophene modified glassy carbon electrode

Nanoporous-poly(3,4)ethylenedioxythiophene (PEDOT) modified glassy carbon electrode (GCE) significantly lowers the overpotential and shows high resistance against fouling while oxidizing β-nicotinamide adenine dinucleotide (NADH). The electrocatalytic behaviour of nanoporous-PEDOT modified GCE was studied using cyclic voltammetry in 0.1M phosphate buffer solution (pH 7.0) containing 5mM NADH. Studies revealed that nanoporous-PEDOT/GCE exhibited strong electrocatalytic activity on the oxidation of NADH with a decreased overpotential of about 0.318V as compared to a bare GCE. In addition, chronoamperometric measurements were studied to understand the electron transfer kinetics of nanoporous-PEDOT/GCE which revealed an average diffusion co-efficient (D) and apparent rate constant (k) of 1.56×10−6cm2s−1 and 1.09×102M−1s−1, respectively. Sensitivity of nanoporous-PEDOT/GCE is measured by amperometric method which showed linear variation in the concentration range between 5 and 45μM at an applied overpotential of 0.5V. Limit of detection (LOD) and sensitivity are found to be 3.8μM and 0.026μA/μM, respectively. While quantifying the sensitivity of the electrode, it is found that the electrode surface fouling towards NADH oxidation decreased to an extent of 85%. Interference study is examined in the presence of ascorbic acid (AA) where a peak separation of more than 0.370V is observed between AA and NADH. Thus, nanoporous-PEDOT/GCE provides a simple platform for the oxidation of NADH at low overpotential with high resistance against fouling and without AA interference.

Utilization of geothermal water as irrigation water after boron removal by monodisperse nanoporous polymers containing NMDG in sorption–ultrafiltration hybrid process

A relatively new method of polymerization, ‘modified seeded polymerization’ has been used for the synthesis of monodisperse nanoporous poly(glycidyl methacrylate-co-ethylene dimethacrylate) and poly(vinylbenzyl chloride-co-divinylbenzene) beads. The synthesized polymer beads were then functionalized with N-methyl-D-glucamine (NMDG) to obtain boron selective resins. The efficiency of these particles for boron removal from geothermal water was investigated by using the hybrid process coupling sorption with ultrafiltration (UF) method where a submerged hollow fiber type UF membrane module was employed for filtration. It was possible to reduce the boron concentration from 11.0mg/L to ≤1mg/L in 20min with hybrid method using poly(glycidyl methacrylate-co-ethylene dimethacrylate)-NMDG beads with 4g-resin/L-geothermal water. The respective period for poly(vinylbenzyl chloride-co-divinylbenzene) beads with the same resin dosage was 30min. In the case of commercially available boron selective ion exchange resin Dowex-XUS 43594.00 ground to an average particle size of 20μm, the target boron concentration which is ≤1mg/L was reached in 20min by using 2g-resin/L-geothermal water.

Nanoporous Poly(Melamine Formaldehyde) Networks by Aqueous Dispersion Polycondensation—Synthesis and Adsorption Properties

The preparation of nanoporous melamine‐formaldehyde resins by aqueous dispersion polycondensation under oxalic acid catalysis is presented. Multimodal porosity, including micro‐, meso‐, and macropores, is achieved by an interplay of hard‐templating of 12 nm sized silica nanoparticles and phase separation processes, resulting in materials with high potential for adsorption applications, as exemplified by investigation of the CO2 adsorption properties. The materials are characterized by a set of methods, including electron microscopy, gas adsorption, and small‐angle X‐ray scattering. The influence of the synthesis conditions (e.g. stirring speed) on the properties of the obtained products is also discussed and a suggestion is made for the formation mechanism of the materials. Finally, the properties are compared to materials obtained by bulk polycondensation.

Nanoporous polymer scaffold-embedded nonwoven composite separator membranes for high-rate lithium-ion batteries

The never-ceasing pursuit of high-energy/high-power lithium-ion batteries, which have garnered a great deal of attention particularly in (hybrid) electric vehicle and grid-scale energy storage system applications, is having with serious issues related to the performance deterioration and safety failures of cells. Herein, to overcome these challenges, we demonstrate a new class of three-dimensionally interconnected, nanoporous poly(vinylidene fluoride–hexafluoropropylene) (PVdF–HFP) scaffold-embedded polyethylene terephthalate (PET) nonwoven composite separators (referred to as “SF-NW separators”) as a microporous membrane-based approach. Motivated by unique porous structure based on inverse replicas of densely-packed nanoparticle arrays, sacrificial colloidal silica (SiO2) template-mediated nanoarchitecturing is exploited to fabricate SF-NW separators. The selective removal of SiO2 nanoparticles dispersed in PVdF–HFP matrix allows for the formation of a nanoporous PVdF–HFP scaffold in a PET nonwoven, where the PET nonwoven acts as a compliant porous substrate providing mechanical/thermal stability. The nanoporous structure of SF-NW separators is fine-tuned by varying the SiO2/PVdF-HFP composition ratio. Owing to the highly-developed nanoporous PVdF–HFP scaffold, the SF-NW separator shows facile ionic transport and excellent electrolyte wettability; thus, contributing to the superior cell performance (particularly at high charge/discharge current densities) in comparison to conventional polyolefin separators.

Facile and scalable synthesis of nanoporous materials based on poly(ionic liquid)s.

A simple, fast, sustainable, and scalable strategy to prepare nanoporous materials based on poly(ionic liquid)s (PILs) is presented. The synthetic strategy relies on the radical polymerization of crosslinker-type ionic liquid (IL) monomers in the presence of an analogous IL, which acts as a porogenic solvent. This IL can be extracted easily after polymerization and recycled for further use. The great advantages of this synthetic approach are the atom-efficiency and lack of waste. The effects of different monomer/porogen ratios on the specific surface area, porosity, and pore size have been investigated. Finally, the potential of the materials as CO2 sorbents has been evaluated.

Photopatterning of poly(N-isopropylacrylamide) membranes for a high level of enrichment and cleanup of nucleic acids in microfluidic chips.

An ideal nanoporous poly(N-isopropylacrylamide) membrane has been fabricated in glass microchannels by means of spatially controlled photopatterning technology for a high level of enrichment and cleanup of nucleic acids.

High-sensitivity hydrogen gas sensors based on Pd-decorated nanoporous poly(aniline-co-aniline-2-sulfonic acid):poly(4-styrenesulfonic acid)

We report a novel method for fabricating Pd-decorated nanoporous poly(aniline-co-aniline-2-sulfonic acid):poly(4-styrenesulfonic acid) (P(ANI-co-ASA):PSS) nanostructures and demonstrate their use as sensing elements for hydrogen (H2) gas sensors. Both co-monomers and PSS provide sufficient –SO3H groups to effectively anchor palladium nanoparticles and lead to enhanced interactions with H2 gas, while retaining the charge transport properties of the P(ANI-co-ASA):PSS. The pores were 10–30 nm in diameter and were readily formed on the Pd-decorated P(ANI-co-ASA):PSS surfaces by introducing water-soluble porogen agents. The pores enlarged the surface area available for interaction with the H2 gas molecules, resulting in much higher sensitivity compared with both the non-porous Pd-decorated P(ANI-co-ASA):PSS and the pristine P(ANI-co-ASA):PSS. We achieved a detection limit of 5 ppm for H2 gas using a conducting polymer at room temperature.

Nanoporous Poly(lactide) by Olefin Metathesis Degradation

We describe an approach to ordered nanoporous poly(lactide) that relies on self-assembly of poly(butadiene)-poly(lactide) (PB-PLA) diblock copolymers followed by selective degradation of PB using olefin metathesis. The block copolymers were obtained by a combination of anionic and ring-opening transesterification polymerizations. The molar mass of each block was tailored to target materials with either a lamellar or cylindrical microphase-separated morphology. Orientation of these nanoscale domains was induced in thin films and monolithic samples through solvent annealing and mechanical deformation, respectively. Selective degradation of PB was achieved by immersing the samples in a solution of Grubbs first-generation catalyst in cyclohexane, a nonsolvent for PLA. Successful elimination of PB was confirmed by size-exclusion chromatography and (1)H NMR spectroscopy. Direct imaging of the resulting nanoporous PLA was obtained by scanning electron microscopy.

Polymer hydrogel supported Pd–Ni–B nanoclusters as robust catalysts for hydrogen production from hydrolysis of sodium borohydride

Catalyzed sodium borohydride hydrolysis is a highly valuable method to produce clean hydrogen energy for portable applications. This study provides a new and fast route to preparation of reusable hybrid materials composed of nickel-boron based nanoclusters dispersed in nanoporous poly(acrylamide) hydrogels for catalyzed hydrogen production. Palladium was added to the Ni–B catalysts during chemical reduction under the protection of poly(N-vinylpyrrolidone). The resulting nanoclusters immobilized in the hydrogels were essentially alloy particles with uni-modal size distributions and average diameters ranging from ca. 4–8 nm. Pd exerted significant promoting effects on the activities of the Ni–B catalysts. The highest activity was achieved for Pd–Ni–B nanoclusters with a charge ratio of Pd/Ni = 1/20 in moles, which exhibited activity nearly twice that of a Ni–B catalyst and good recyclability for consecutive uses. The hydrogen production rates also increased with the decreasing particle sizes. The activation energy, enthalpy and entropy for the reaction were determined to be 31.10 kJ mol−1, 28.39 kJ mol−1 and -45.22 J mol−1 K−1, respectively. The activation energy is lower than that of previously reported polymer-stabilized Co(0), Fe(0), or Ni(0) nanoparticle catalysts.

Tailoring the photocatalytic reaction rate of a nanostructured TiO2 matrix using additional gas phase oxygen

Nanostructured TiO2 was synthesized by the sol–gel method. The titania was supported on nanoporous poly (styrene-co-divinylbenzene) (PS). The samples were characterized by several techniques (scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and ultraviolet–visible spectroscopy). Three types of TiO2 samples were prepared using various temperatures and were studied for the photocatalytic degradation of methylene blue. The photocatalytic efficiency of TiO2 was observed to increase by activating the TiO2 surface using nanoporous PS. The photocatalytic performance of the synthesized samples showed a higher performance using molecular O2, which was purged through the reactor.

ABAC Tetrablock Terpolymers for Tough Nanoporous Filtration Membranes

Nanoporous poly(styrene)-b-poly(isoprene)-b-poly(styrene) (PS–PI–PS) was prepared from PS–PI–PS–PLA (PLA = poly(d,l-lactide)) tetrablock terpolymer precursors. Hydroxy end-functionalized PS–PI–PS was synthesized by sequential anionic polymerizations and used to initiate the ring-opening polymerization of d,l-lactide. A combination of small-angle X-ray scattering, transmission electron microscopy and scanning electron microscopy data supports a core–shell cylinder morphology with PLA as the core component. The inherently robust mechanical properties associated with PS–PI–PS block copolymers provide the materials with enhanced flexibility and toughness compared to analogous nanoporous polystyrene samples prepared by etching of PS–PLA diblocks. Composite membranes containing nanoporous PS–PI–PS on top of microporous poly(ether sulfone) (PES) were prepared by direct spin-coating and also by a salt-plate coating/film-transfer strategy. Nanopores (dpore ≈ 15 nm) were created by a combination of reactive ion etc...

Configuration-controlled Au nanocluster arrays on inverse micelle nano-patterns: versatile platforms for SERS and SPR sensors

Nanopatterned 2-dimensional Au nanocluster arrays with controlled configuration are fabricated onto reconstructed nanoporous poly(styrene-block-vinylpyridine) inverse micelle monolayer films. Near-field coupling of localized surface plasmons is studied and compared for disordered and ordered core-centered Au NC arrays. Differences in evolution of the absorption band and field enhancement upon Au nanoparticle adsorption are shown. The experimental results are found to be in good agreement with theoretical studies based on the finite-difference time-domain method and rigorous coupled-wave analysis. The realized Au nanopatterns are exploited as substrates for surface-enhanced Raman scattering and integrated into Kretschmann-type SPR sensors, based on which unprecedented SPR-coupling-type sensors are demonstrated.

Poly(vinylidene fluoride)/nickel nanocomposites from semicrystalline block copolymer precursors

The fabrication of nanoporous poly(vinylidene fluoride) (PVDF) and PVDF/nickel nanocomposites from semicrystalline block copolymer precursors is reported. Polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PS-b-PVDF-b-PS) is prepared through functional benzoyl peroxide initiated polymerization of VDF, followed by atom transfer radical polymerization (ATRP) of styrene. The crystallization of PVDF plays a dominant role in the formation of the block copolymer structure, resulting in a spherulitic superstructure with an internal crystalline-amorphous lamellar nanostructure. The block copolymer promotes the formation of the ferroelectric β-polymorph of PVDF. Selective etching of the amorphous regions with nitric acid leads to nanoporous PVDF, which functions as a template for the generation of PVDF/Ni nanocomposites. The lamellar nanostructure and the β-crystalline phase are conserved during the etching procedure and electroless nickel deposition.

Nanoporous fibers of type-I collagen coated poly(l-lactic acid) for enhancing primary hepatocyte growth and function.

Advanced scaffold materials are required for liver tissue engineering, to improve primary hepatocyte activity and hepatic function in vitro. The nanotopography of the scaffold material plays an important role in the regulation of cell growth and function. Therefore, in the current study, we developed a novel scaffold composed of type-I collagen coated nanoporous poly(l-lactic acid) (PLLA) fibers (nPFs) to provide a nanotopography with a combination of fibrous and porous features for the culture of primary hepatocytes. The interaction between the nanotopography and the hepatocytes was described by testing cell morphology, retention, activity and hepatic function over a 15 day culture period. Primary hepatocytes cultured on the nPFs formed large-area stable immobilized monolayers after 3 days of culture, and displayed excellent cell bioactivity with higher levels of liver-specific function maintenance, in terms of albumin secretion, urea synthesis, and CYP1A and UGT enzymatic activity, than those cultured on type-I collagen coated non-porous PLLA fibers (Fs). These results indicate that the combined fibrous and porous nanotopography of nPFs has a superior promoting effect on primary hepatocyte culture compared to the non-porous fibrous nanotopography of Fs. The nPFs may be a suitable material for liver tissue engineering research and potential therapeutic applications, such as in bioartificial liver devices, and as a substrate for primary hepatocyte culture.

Network Nano-Porous Poly(vinylidene fluoride-co-hexafluoropropene) Membranes by Nano-Gelation Assisted phase Separation of Poly(vinylidene fluoride-co-hexafluoropropene)/Poly(methyl methacrylate) Blend Precursor in Toluene

Network nanoporous poly(vinylidene fluoride-co-hexafluoropropene (PVDF–HFP) membrane formation mechanism via poly(methyl methacrylate) (PMMA) leaching from PVDF–HFP/PMMA blend film was studied. The blends of PVDF–HFP with PMMA comprise miscible amorphous phase much larger in quantity than those of poly(vinylidene fluoride) (PVDF) with PMMA. The residual PVDF–HFP crystalline phase which may present in very small fraction was characterized by SAXS, which permitted estimation of the critical composition of phase boundary of blend. The FESEM micrograph revealed the network morphology of the membranes being composed of interconnected tiny sheaves of recrystallized PVDF–HFP. Nanogelation mechanism is proposed to describe the crystallization of disentangled PVDF–HFP chain segments under spatial confinement during PMMA leaching from amorphous solution phase in blend film. The crystallinities of membranes determined by DSC are found to be consistent with the theoretically calculated values. Present research suggested a novel approach for the formation of network nanoporous membranes from semicrystalline polymers.

Alignment of Organic Crystals under Nanoscale Confinement

Nanocrystals of α,ω-alkanedicarboxylic acids (HO2C(CH2)n−2CO2H, n = 3–13, odd) grown in aligned nanometer-scale cylindrical pores of nanoporous poly(cyclohexylethylene) monoliths (p-PCHE) adopt preferred orientations relative to the pore direction. X-ray diffraction reveals that nanocrystals of malonic acid (n = 3) grown in 14, 30, and 40 nm diameter pores adopted two preferred mutually perpendicular orientations simultaneously, each orientation coinciding with the direction of hydrogen-bonded chains in the solid state. Nanocrystals of glutaric acid (n = 5) embedded within 30 and 40 nm pores adopted orientations with hydrogen-bonded chains coincident with the pore direction, but the chains were perpendicular to the pore direction in 14 nm pores. Pimelic acid (n = 7) nanocrystals were oriented with their hydrogen-bonded chains parallel to the pore direction, but nanocrystals of longer alkane dicarboxylic acids (n = 9, 11, or 13) adopted orientations in which the their hydrogen-bonded chains progressively tilted away from the pore direction as the alkane length was increased. This behavior can be attributed to increasingly strong dispersive interactions between the alkane chains, which alter the ranking of the fast growing crystal directions. The appearance of preferred orientations for embedded nanocrystals argues that critical size effects and surface energy considerations favor precritical nuclei that are oriented with their fast growth axis aligned with the pore direction. This condition permits the nuclei to achieve critical size more readily while minimizing the area of planes with high surface energies, thereby providing a competitive advantage over other orientations during nucleation. The observation in some cases of two orientations simultaneously and size-dependent orientations reveals the delicate balance of free energies among differently oriented nuclei. Collectively, these observations demonstrate the utility of nanoscale confinement for investigating the earliest stages of crystal growth.

Influence of PVDF concentration on the morphology, surface roughness, crystalline structure, and filtration separation properties of semicrystalline phase inversion polymeric membranes

This study was focused on the fabrication of nanoporous poly(vinylidene fluoride) (PVDF) membranes at different polymer concentration (14, 17, and 20 wt%) via phase inversion method. The morphology and surface roughness of the resulting membranes were investigated by scanning electron microscopy (SEM) and atomic force microscope, respectively. SEM results showed that with the increase of polymer concentration, the pore size of membranes and the overall porosity decrease. Also, the results showed that varying concentration results in significant changes on the surface roughness. Analysis of the crystalline structures of PVDF membranes by X-ray diffraction showed that the membranes, which precipitated in the higher concentration of polymer (20 wt%) had a typical “β” form of the crystalline phase, whereas those membranes that formed at lower concentration (14 wt%) showed crystallites of the “α + β” form of the crystalline phase. Furthermore, the filtration separation experiments of Acid Yellow 23 (AY23) were conducted to examine the effects of concentration parameter on the performance of nanoporous PVDF membranes. Results showed that the retention of AY23 increases as the polymer concentration increases and an efficiency of 89.72% was achieved in polymer concentration of 20 wt%.

Nanoporous peptide particles for encapsulating and releasing neurotrophic factors in an animal model of neurodegeneration.

Neurotrophin-BDNF can be effectively encapsulated in nanoporous poly(L-glutamic acid) particles prepared via mesoporous silica templating. The loaded BDNF can be released in a sustained manner with retained biological activity. Animal experiments demonstrate the released BDNF can efficiently rescue the auditory neurons (as indicated by the arrows) in the cochlea of guinea pigs with sensorineural hearing loss.

Gas Sorption and Diffusion in Amorphous and Semicrystalline Nanoporous Poly(2,6-dimethyl-1,4-phenylene)oxide

In this contribution is presented an analysis of mass transport properties of low molecular weight compounds in amorphous PPO and in two semicrystalline PPOs obtained by treating with benzene and carbon tetrachloride the amorphous sample. It is found that semicrystalline samples are endowed with larger gas sorption capacity and diffusivity as compared to the amorphous ones: this behavior has been attributed prevalently to the nanoporous nature of the crystalline phases induced by treatment with solvents. In particular, sorption experiments, carried out at 30 °C with methane, carbon dioxide, propane and propylene, have shown that both semicrystalline PPOs display rather interesting features which make them suitable for use as membrane materials in gas separation processes, in view of the relatively high values of solubility and diffusivity. Moreover, these peculiar sorption and mass transport properties have been found to be virtually unaffected by thermal aging: in fact, sorption experiments conducted on ...

Nanoporous multilayer poly(l-glutamic acid)/chitosan microcapsules for drug delivery

Nanoporous poly(l-glutamic acid)/chitosan (PLGA/CS) multilayer microcapsules were fabricated by layer-by-layer (LbL) assembly using the porous silica particles as sacrificial templates. The LbL assembled nanoporous PLGA/CS microcapsules were characterized by Zeta-potential analyzer, FTIR, TGA, SEM, TEM and CLSM. 5-Fluorouracil (5-FU) was chosen as model drug. The drug loading content of PLGA/CS microcapsules depends on loading time, loading temperature, pH value and NaCl concentration. High loading capacity of microcapsules can be achieved by simply adjusting pH value and salt concentration. Moreover, 5-Fu loaded microcapsules take on a sustained release behavior, especially in an acid solution, in contrast to burst release of bare 5-Fu. The kinetics of 5-Fu release from PLGA/CS microcapsules conforms to Korsmeyer-Peppas and Baker-Lonsdale models, the mechanism of which can be ascribed to priority of drug diffusion and subordination of polymer degradation. The MTT cytotoxicity assay in vitro reveals the satisfactory anticancer activity of the drug-loaded PLGA/CS microcapsules. Therefore, the novel nanoporous PLGA/CS microcapsules is expected to find application in drug delivery systems.