Microporous Poly Research Articles

Tailored bifunctional polymer for plutonium monitoring.

Monitoring of actinides with sophisticated conventional methods is affected by matrix interferences, spectral interferences, isobaric interferences, polyatomic interferences, and abundance sensitivity problems. To circumvent these limitations, a self-supported disk and membrane-supported bifunctional polymer were tailored in the present work for acidity-dependent selectivity toward Pu(IV). The bifunctional polymer was found to be better than the polymer containing either a phosphate group or a sulfonic acid group in terms of (i) higher Pu(IV) sorption efficiency at 3-4 mol L(-1) HNO3, (ii) selective preconcentration of Pu(IV) in the presence of a trivalent actinide such as Am(III), and (iii) preferential sorption of Pu(IV) in the presence of a large excess of U(VI). The bifunctional polymer was formed as a self-supported matrix by bulk polymerization and also as a 1-2 μm thin layer anchored on a microporous poly(ether sulfone) by surface grafting. The proportions of sulfonic acid and phosphate groups in both the self-supported disk and membrane-supported bifunctional polymer were found to be the same as expected from the mole proportions of monomers in polymerizing solutions used for syntheses. α radiography by a solid-state nuclear track detector indicated fairly homogeneous anchoring of the bifunctional polymer on the surface of the membrane. Pu(IV) preconcentrated on a single bifunctional bead was used for determination of the Pu isotopic composition by thermal ionization mass spectrometry. The membrane-supported bifunctional polymer was used for preconcentration and subsequent quantification of Pu(IV) by α spectrometry using the absolute efficiency at a fixed counting geometry. The analytical performance of the membrane-supported-bifunctional-polymer-based α spectrometry method was found to be highly reproducible for assay of Pu(IV) in a variety of complex samples.

Multifunctional graphene incorporated conducting gel electrolytes in enhancing photovoltaic performances of quasi-solid-state dye-sensitized solar cells

Three-dimensional (3D) gel electrolytes are versatile in elevating encapsulation of liquid electrolyte in dye-sensitized solar cells (DSSCs), however, the poor contact at gel electrolyte/Pt counter electrode interface is unfavorable in electrocatalyzing triiodide ions. In the current work, we report the multifunctions of graphene, graphene oxide, or nanographite incorporated microporous poly(acrylic acid)-cetyltrimethylammonium bromide (PAA-CTAB) conducting gel electrolytes in both sealing liquid electrolyte and conducting refluxed electrons (electrons from external circuit to Pt counter electrode) into 3D framework of the conducting gel electrolyte, aiming at elevating liquid electrolyte content in per unit volume of gel electrolyte, increasing electrocatalytic area toward triiodide ions and diminishing charge-transfer resistance. The electrical and electrochemical performances of the resultant conducting gel electrolytes are thoroughly characterized. Light-to-electric power conversion efficiencies of 7.06%, 6.35%, and 6.17% are determined from DSSCs using graphene, graphene oxide, and nanographite incorporated PAA-CTAB conducting gel electrolytes in comparison with 6.07% from pure PAA-CTAB based DSSC.

Microporous Poly(Schiff Base) Constructed from Tetraphenyladamantane Units for Adsorption of Gases and Organic Vapors

A new microporous poly(Schiff base) (PSN-3) is constructed from 1,3,5,7-tetrakis(4-formylphenyl)adamantane and 1,3,5,7-tetrakis(4-aminophenyl)adamantane through an A4 -A4 ' reaction. The surface and internal morphologies of porous PSN-3 are examined by FE-SEM and HR-TEM. PSN-3 exhibits a BET surface area of 865 m(2) g(-1) with a major pore size around 0.6 nm. Moreover, PSN-3 can uptake 1.32 wt% H2 (77 K/1 bar), 13.6 wt% CO2 (273 K/1 bar), 80.5 wt% benzene, and 63.7 wt% cyclohexane (298 K/0.9 bar). The adsorption selectivities for CO2/N2, CO2/CH4, benzene/N2, and benzene/H2O are 88, 16, 267, and 19, respectively. The high adsorption capacities and selectivities for gases and vapors make PSN-3 a promising candidate for H2 storage, CO2 capture, and recovery of organic pollutants.

Efficient quasi-solid-state dye-sensitized solar cells employing polyaniline and polypyrrole incorporated microporous conducting gel electrolytes

With an aim of elevating liquid electrolyte loading, ionic conductivity, and electrocatalytic activity of gel electrolyte toward triiodides, freeze-dried microporous poly(acrylic acid)–poly(ethylene glycol) (PAA–PEG) matrix is employed to uptake conducting polymers, such as polyaniline (PANi) and polypyrrole (PPy). An ionic conductivity of 19.18 mS cm−1 at 65 °C is obtained from PAA–PEG/PANi conducting gel electrolyte which is nearly similar to 19.22 mS cm−1 from pure liquid electrolyte. The conducting polymers can form interconnected channels within insulating microporous PAA–PEG matrix, therefore, the reduction reaction of triiodide ions in the dye-sensitized solar cells (DSSCs) can be extended from Pt/gel electrolyte interface to both interface and three-dimensional framework of microporous conducting gel electrolyte. The resultant DSSCs from PAA–PEG/PANi and PAA–PEG/PPy conducting gel electrolytes display power conversion efficiencies of 7.12% and 6.53%, respectively, which are much higher than 5.02% from pure PAA–PEG-based DSSC. The new concept along with easy fabrication promises the microporous conducting gel electrolytes to be good alternatives in efficient quasi-solid-state DSSCs.

Study on microporous supported ionic liquid membranes for carbon dioxide capture

To capture carbon dioxide directly from ambient air, the fabrication of supported ionic liquid membranes (SILMs) on asymmetric and symmetric microporous poly(vinylidene fluoride) (PVDF) membranes were studied. The effect of support membrane structure on the IL loading, the stability of fabricated SILMs, and the carbon dioxide (CO2) capturing abilities of both SILMs were evaluated. The evaluations include the gas permeation of pure CO2 and nitrogen (N2), the mixed CO2–N2 gases containing 50%, 10% and 1% CO2, and the directly compressed ambient air. The results demonstrated that pure CO2 showed the highest permeance, followed by CO2–air and then N2. Compared with asymmetric SILMs which had higher gas permeance, the symmetric SILMs had better selectivity for CO2/N2, to more than 20 of CO2/N2 selectivity, for both single and mixed gases. The SILMs also were found to be capable of capturing CO2 from air from 2 to more than 5 of CO2/air selectivity for separation of air enriched with low CO2 concentrations (10%, 1% and zero) as the transmembrane pressure increased to 0.25MPa. Thus, this work might provide a potential method for sequestering CO2 directly from atmosphere to avoid the need for extensive CO2-transportation.

Surface Self-Assembled PEGylation of Fluoro-Based PVDF Membranes via Hydrophobic-Driven Copolymer Anchoring for Ultra-Stable Biofouling Resistance

Stable biofouling resistance is significant for general filtration requirements, especially for the improvement of membrane lifetime. A systematic group of hyper-brush PEGylated diblock copolymers containing poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) was synthesized using an atom transfer radical polymerization (ATRP) method and varying PEGMA lengths. This study demonstrates the antibiofouling membrane surfaces by self-assembled anchoring PEGylated diblock copolymers of PS-b-PEGMA on the microporous poly(vinylidene fluoride) (PVDF) membrane. Two types of copolymers are used to modify the PVDF surface, one with different PS/PEGMA molar ratios in a range from 0.3 to 2.7 but the same PS molecular weights (MWs, ∼5.7 kDa), the other with different copolymer MWs (∼11.4, 19.9, and 34.1 kDa) but the similar PS/PEGMA ratio (∼1.7 ± 0.2). It was found that the adsorption capacities of diblock copolymers on PVDF membranes decreased as molar mass ratios of PS/PEGMA ratio reduced or molecular weights of PS-b-PEGMA increased because of steric hindrance. The increase in styrene content in copolymer enhanced the stability of polymer anchoring on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be in the range between 1.5 and 2.0 with copolymer MWs above 20.0 kDa for the ultrastable resistance of protein adsorption on the PEGylated PVDF membranes. The PVDF membrane coated with such a diblock copolymer owned excellent biofouling resistance to proteins of BSA and lysozyme as well as bacterium of Escherichia coli and Staphylococcus epidermidis and high stable microfiltration operated with domestic wastewater solution in a membrane bioreactor.

Collagen IV-Modified Scaffolds Improve Islet Survival and Function and Reduce Time to Euglycemia

Islet transplantation on extracellular matrix (ECM) protein-modified biodegradable microporous poly(lactide-co-glycolide) scaffolds is a potential curative treatment for type 1 diabetes mellitus (T1DM). Collagen IV-modified scaffolds, relative to control scaffolds, significantly decreased the time required to restore euglycemia from 17 to 3 days. We investigated the processes by which collagen IV-modified scaffolds enhanced islet function and mediated early restoration of euglycemia post-transplantation. We characterized the effect of collagen IV-modified scaffolds on islet survival, metabolism, and insulin secretion in vitro and early- and intermediate-term islet mass and vascular density post-transplantation and correlated these with early restoration of euglycemia in a syngeneic mouse model. Control scaffolds maintained native islet morphologies and architectures as well as collagen IV-modified scaffolds in vivo. The islet size and vascular density increased, while β-cell proliferation decreased from day 16 to 113 post-transplantation. Collagen IV-modified scaffolds promoted islet cell viability and decreased early-stage apoptosis in islet cells in vitro-phenomena that coincided with enhanced islet metabolic function and glucose-stimulated insulin secretion. These findings suggest that collagen IV-modified scaffolds promote the early restoration of euglycemia post-transplantation by enhancing islet metabolism and glucose-stimulated insulin secretion. These studies of ECM proteins, in particular collagen IV, and islet function provide key insights for the engineering of a microenvironment that would serve as a platform for enhancing islet transplantation as a viable clinical therapy for T1DM.

PLG Scaffold Delivered Antigen-Specific Regulatory T Cells Induce Systemic Tolerance in Autoimmune Diabetes

Islet transplantation is a promising treatment for human type 1 diabetes mellitus. Transplantation requires systemic immunosuppression, which has numerous deleterious side effects. Islet antigen-specific regulatory T cells (Tregs) have been shown to protect islet grafts from autoimmune destruction in the nonobese diabetic (NOD) model when co-localized in the kidney capsule. An extra-hepatic transplant site was established by transplanting islet-loaded microporous poly (lactide-co-glycolide) (PLG) scaffolds into abdominal fat. This study examined an autoimmune transplantation model and determined whether co-localized Tregs could protect islet grafts in an extra-hepatic and extra-renal transplant site. Normoglycemia was restored, and co-transplanted Tregs extended graft survival, including several instances of indefinite protection. Transplanted Tregs were replaced by recipient-derived Tregs over time, indicating that islet antigen-specific Tregs induce tolerance to islet grafts through host-derived Tregs. Thus, Tregs provided protection against a diverse repertoire of autoreactive T-cell-receptor specificities mediating diabetes in the NOD model, possibly through a phenomenon previously described as infectious tolerance. Interestingly, the infiltration by Tregs protected a second islet transplant, indicating systemic tolerance to islet antigens. In summary, PLG scaffolds can serve as an alternative delivery system for islet transplantation that allows for the co-localization of immunomodulatory cells within islet grafts and induces long-term graft survival in an autoimmune diabetes model. This method of co-localizing immunomodulatory cells with islets in a clinically translatable transplant site to affect the immune system on a local and systemic level has potential therapeutic implications for human islet transplantation.

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...

Surface Area Control and Photocatalytic Activity of Conjugated Microporous Poly(benzothiadiazole) Networks

Konjugierte mikroporöse Polymere (CMPs) wurden mithilfe einer Sonogashira-Hagihara-Kreuzkupplung in Gegenwart von Siliciumdioxid-Nanopartikeln als Template synthetisiert, wobei die spezifische Oberfläche kontrolliert werden konnte. Die CMPs sind heterogene Photosensibilisatoren für die Produktion von Singulettsauerstoff in einer kontinuierlichen Durchflusssynthese.

Surface Area Control and Photocatalytic Activity of Conjugated Microporous Poly(benzothiadiazole) Networks

Surface Area Control and Photocatalytic Activity of Conjugated Microporous Poly(benzothiadiazole) Networks

Immobilization of Acidithiobacillus ferrooxidans on sulfonated microporous poly(styrene–divinylbenzene) copolymer with granulated activated carbon and its use in bio-oxidation of ferrous iron

The immobilization efficiencies of Acidithiobacillus ferrooxidans cells on different immobilization matrices were investigated for biooxidation of ferrous iron (Fe2+) to ferric iron (Fe3+). Six different matrices were used such as the polyurethane foam (PUF), granular activated carbon (GAC), raw poly(styrene–divinylbenzene) copolymer (rawSDVB), raw poly(styrene–divinylbenzene) copolymer with granular activated carbon (rawSDVB-GAC), sulfonated poly(styrene–divinylbenzene) copolymer (sulfSDVB) and sulfonated poly(styrene–divinylbenzene) copolymer with granular activated carbon (sulfSDVB-GAC). The sulfSDVB-GAC polymer showed the best performance for Fe2+ biooxidation. It was used at packed-bed bioreactor and the kinetic parameters were obtained. The highest Fe2+ biooxidation rate (R) was found to be 4.02g/Lh at the true dilution rate (Dt) of 2.47 1/h and hydraulic retention time (τ) of 0.4h. The sulfSDVB-GAC polymer was used for the first time as immobilization material for A. ferrooxidans for Fe2+ biooxidation.

Fabrication of Microporous PVDF Particles by an Emulsion Method and Control of Pore Structure

The Microporous Poly(vinylidene Fluoride) (PVDF) Materials Were Prepared by Emulsion in the Article, and through Appropriate Methods to Characterize Considerable Specific Surface Area and Excellent Pore Structure. with DMF as Solvent, Ethanol as a Diluent to Dissolve and Dilute PVDF, by Virtue of this Method to Destroy the Morphology of PVDF Structure, that Changed the Spherical Structure to Porous Structure, and to Get the Different Pore Size and Specific Surface Area through Controling the Speed of Dripping Water. the Structure Information, Surface Morphology and Specific Surface Area Were Determined by XRD, SEM (or Field Emission) and Specific Surface Area and Pore Size Analyzer, then Found the Regulation about Control of Pore Size and Specific Surface Area Preliminary.

Iron-complexed adsorptive membrane for As(V) species in water

Selective preconcentration of a target analyte in the solid phase is an effective route not only to enhance detection limit of the conventional analytical method but also for elimination of interfering matrix. An adsorptive membrane was developed for selective preconcentration and quantification of ultra-trace (ppb) amounts of As(V) present in a variety of aqueous samples. The precursor membrane was prepared by UV-initiator induced graft polymerization of sulphate and phosphate bearing monomers (1:1mol proportion) in pores of the host microporous poly(propylene) membrane. Fe3+ ions were loaded in the precursor membrane to make it selective for As(V) ions. The presence of phosphate functional groups prevent leaching of Fe3+ ions from the membrane when it comes in contact with solution like seawater having high ionic strength. The optimized membrane was characterized in terms of its physical structure, chemical structure and experimental conditions affecting As(V) uptake in the membrane. The possibility of quantifying total preconcentration of As content was also explored by converting As(III) to As(V). To quantify As(V), the membrane samples were subjected to instrumental neutron activation analysis (INAA). The studies carried in the present work showed that quantification of inorganic arsenic species in natural water samples is easily possible in 2–3ppb concentration range.

Development of intra-vaginal matrices from polycaprolactone for sustained release of antimicrobial agents

Microporous poly(ε-caprolactone) matrices were loaded with an antibacterial agent, ciprofloxacin and an antifungal agent, miconazole nitrate, respectively, for investigations of their potential as controlled vaginal delivery devices. Ciprofloxacin loadings up to 15% w/w could be obtained by increasing the drug content of the poly(ε-caprolactone) solution, while the actual loadings of miconazole were much lower (1-3% w/w) due to drug partition into methanol during the solvent extraction. The kinetics of ciprofloxacin release in simulated vaginal fluid at 37 were characterised by a small burst release phase in the first 24 h, low drug release up to 7 days (10%) and gradual release of up to 80% of the drug content by day 30. Meanwhile, the release kinetics of miconazole-loaded matrices could be effectively described by the Higuchi model with 100% drug release from the highest loaded matrices (3.2% w/w) in 13 days. Ciprofloxacin or miconazole released over 30 and 13 days, respectively, from poly(ε-caprolactone) matrices into simulated vaginal fluid retained high levels of antimicrobial activity in excess of 80% of the activity of the free drug. This study confirms the potential of poly(ε-caprolactone) matrices for delivering antimicrobial agents in the form of an intra-vaginal device.

Neck-size distributions of through-pores in polymer membranes

Abstract Capillary flow porometry (CFP) is used for measuring the most constricted part (bottleneck) of through-pores in synthetic membranes. In present work, a systematic study has been carried out to evaluate influence of membrane properties like tortuosity, intersecting pores and thickness on CFP. For evaluating CFP, the track-etched membranes were used as these membranes have cylindrical pores. The average, maximum and minimum pore diameters and pore-diameter distributions in the track-etched membranes were obtained by CFP, and compared with the values obtained by different techniques like atomic force microscopy (AFM), scanning electron microscopy (SEM) and molecular weight cut-off (MWCO). The internal architecture of pore in the track-etched membranes was studied by growing gold nano-rods in the pores. The gold nano-rods were grown in the membrane by electrodeposition using removable electrode (Hg). The transmission electron microscopy (TEM) of nano-gold rods were carried out after dissolution of the membranes in dichloromethane. The studies carried out in the present work showed that: (i) the CFP data remained practically independent of the membrane thickness and tortuosity, (ii) it measured the most constricted diameter of a pore independent of pore-architecture, and (iii) mean flow pore-diameters data were highly reproducible (±5%). The capability of CFP for assessing quality of the membrane was demonstrated using the pore-filled membrane samples having different amounts of the crosslinked poly- N -isopropylacrylamide (poly-NIPA). These samples were prepared by UV-initiator induced in situ photo-polymerization of NIPA in pores of the host microporous poly(propylene) membrane.

Study on the Process of Preparing Microporous Polyvinyl Chloride

Microporous Poly (vinyl chloride) (PVC) was prepared by foaming of PVC powders using the solution of 2, 2’-azo-bis-iso-butyronitrile (AIBN) in co-solvent of butanone and cyclohexanone when heated. The effect of composition of solvent and quantity fraction of AIBN also preferred dioctyl phthalate (DOP) on the structure of microporous PVC is discussed. The results indicated that much microporosity with average size of 0.2-2μm can be generated when acetone is selected as solvent, 2% DOP and 10% AIBN are used. The microporous PVC is a potential desirable reactor to prepare CaCO3 nanoparticle.

Poly(L‐lactide‐co‐glycolide) microporous membranes for medical applications produced with the use of polyethylene glycol as a pore former

AbstractThe aim of this study was to prepare microporous poly(L‐lactide‐co‐glycolide) (PLGA) membranes by mixing PLGA previously dissolved in methylene chloride with polyethylene glycol (PEG) as a pore former. PEGs with different molecular weights of 300, 400, 600, 1000, and 3400 kDa were used. The PEG concentration was fixed at 20–80%, resulting in membranes with increased porosity. The properties of the membranes were characterized by tensile testing, and by SEM, AFM, and FTIR. Solvent evaporation rate from PEG/PLGA blends and PEG solutions was also estimated. Cytocompatibility of the materials in contact with osteoblast‐like MG 63 cells was studied and cell viability and morphology were assessed. SEM evaluation demonstrated that porosity of the membranes can be easily controlled by addition of a defined amount of PEG. The membranes produced with 60% PEG have the most favorable mechanical properties from the point of view of medical applications: tensile strength of 12.6 ± 2.3 MPa, Young's modulus of 0.53 ± 0.08 GPa, and total elongation at break of 56.4% ± 12.3%. The size and distribution of pores in the membranes depend on PEG molecular weight: low‐molecular weight PEG resulted in more homogenous distribution of pores, while high‐molecular weight PEG resulted in asymmetric membranes with the skin on the air‐cured surface. The obtained membranes support cell growth and are promising materials for biological applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Microporous Poly(Vinylidene Fluoride – Trifluoroethylene)/Zeolite Membranes for Lithium-Ion Battery Applications

Microporous Poly(Vinylidene Fluoride – Trifluoroethylene)/Zeolite Membranes for Lithium-Ion Battery Applications

Preparation and characterization of triptycene-based microporous poly(benzimidazole) networks

We demonstrate the synthesis of two triptycene-based microporous poly(benzimidazole) networks through condensation of triptycene-hexone with dialdehyde in refluxing glacial acetic acid containing ammonium acetate. The benzimidazole-linkage in the resulting polymers is confirmed by Fourier transform infrared and solid-state 13C CP/MAS NMR spectroscopy. The spindle-shaped morphology of the obtained polymers was also observed through scanning electron microscopy. The materials, with Brunauer–Emmet–Teller (BET) specific surface area over 600 m2 g−1, possess a good hydrogen storage capacity (up to 1.57 wt% at 77 K and 1.0 bar) and a high carbon dioxide uptake (up to 14.0 wt% at 273 K and 1.0 bar). These excellent performances would probably make them promising candidates for gas-selective adsorption, heterogeneous catalysis, and proton-exchange membrane fuel cells.