Porous Polymer Template Research Articles

Comparative evaluation of diffusion kinetics of arsenic adsorption on iron (oxy) hydroxides containing biopolymer nanocomposite beads

Exposure to arsenic-contaminated water poses great health risks to mankind. Nanocomposite beads have been proven to be an effective alternative for large-scale treatment of arsenic-loaded water. The larger size of the beads makes the adsorbent retrieval process less energy-intensive and prevents accidental leaching of nanoparticles into the surrounding environment. Adsorption using macroporous beads is predominantly a diffusion-controlled process. Therefore, in the present study, the shrinking core model (SCM) was used to compare and evaluate the diffusion kinetics of arsenic adsorption using in-situ precipitated iron (oxy)hydroxide alginate (IIAB) and chitosan beads (IICB). Simulated dynamic nondimensional liquid phase arsenic concentration profiles fit well with the experimental data (SSE = 0.018–0.025). External mass transfer coefficient (kf) and effective diffusivity coefficient (De) for both kinds of beads at different initial arsenic concentrations (C0 ∼ 1 mg.L−1 and 5 mg.L−1) were derived. By comparison of diffusivity values and the simulated concentration front profiles, it was observed that chitosan provided a better porous polymer template with more easily accessible adsorption sites covering up to 85 % of the beads’ volume. Comparison with progression conversion models has also been made to test the effectiveness of SCM fitting.

Accessibility and Mechanical Stability of Nanoporous Zinc Oxide and Aluminum Oxide Coatings Synthesized via Infiltration of Polymer Templates.

The conformal nanoporous inorganic coatings with accessible pores that are stable under applied thermal and mechanical stresses represent an important class of materials used in the design of sensors, optical coatings, and biomedical systems. Here, we synthesize porous AlOx and ZnO coatings by the sequential infiltration synthesis (SIS) of two types of polymers that enable the design of porous conformal coatings-polymers of intrinsic microporosity (PIM) and block co-polymer (BCP) templates. Using quartz crystal microbalance (QCM), we show that alumina precursors infiltrate both polymer templates four times more efficiently than zinc oxide precursors. Using the quartz crystal microbalance (QCM) technique, we provide a comprehensive study on the room temperature accessibility to water and ethanol of pores in block copolymers (BCPs) and porous polymer templates using polystyrene-block-poly-4-vinyl pyridine (PS75-b-P4VP25) and polymers of intrinsic microporosity (PIM-1), polymer templates modified by swelling, and porous inorganic coatings such as AlOx and ZnO synthesized by SIS using such templates. Importantly, we demonstrate that no structural damage occurs in inorganic nanoporous AlOx and ZnO coatings synthesized via infiltration of the polymer templates during the water freezing/melting cycling tests, suggesting excellent mechanical stability of the coatings, even though the hardness of the inorganic nanoporous coating is affected by the polymer and precursor selections. We show that the hardness of the coatings is further improved by their annealing at 900 °C for 1 h, though for all the cases except ZnO obtained using the BCP template, this annealing has a negligible effect on the porosity of the material, as is confirmed by the consistency in the optical characteristics. These findings unravel new potential for the materials being used across various environment and temperature conditions.

Macroscale Fabrication of Lightweight and Strong Porous Carbon Foams through Template-Coating Pair Design.

Manufacturing of low-density-high-strength carbon foams can benefit the construction, transportation, and packaging industries. One successful route to lightweight and mechanically strong carbon foams involves pyrolysis of polymeric architectures, which is inevitably accompanied by drastic volumetric shrinkage (usually >98%). As such, a challenge of these materials lies in maintaining bulk dimensions of building struts that span orders of magnitude difference in length scale from centimeters to nanometers. This work demonstrates fabrication of macroscale low-density-high-strength carbon foams that feature exceptional dimensional stability through pyrolysis of robust template-coating pairs. The template serves as the architectural blueprint and contains strength-imparting properties (e.g., high node density and small strut dimensions); it is composed of a low char-yielding porous polystyrene backbone with a high carbonization-onset temperature. The coating serves to imprint and transcribe the template architecture into pyrolytic carbon; it is composed of a high char-yielding conjugated polymer with a relatively low carbonization-onset temperature. The designed carbonization mismatch enables structural inheritance, while the decomposition mismatch affords hollow struts, minimizing density. The carbons synthesized through this new framework exhibit remarkable dimensional stability (≈80% dimension retention; ≈50% volume retention) and some of the highest specific strengths (≈0.13GPa g-1 cm3 ) among reported carbon foams derived from porous polymer templates.

Chromophoric Ion Receptor-Decorated Porous Monolithic Polymer for the Solid-State Naked Eye Sensing of Hg(II): An Experimental and Theoretical Approach.

The current work presents a perspective to obliterate toxic Hg(II) from an aqueous environment, a strategic environmental remediation and decontamination measure. We report a simple, efficient, and reusable solid-state visual sensing strategy for the selective detection and quantitative recovery of ultratrace Hg(II). The capture of Hg(II) ions was effectuated using a macro-/mesoporous polymer monolith uniformly decorated with an azo-based chromophoric ion receptor, i.e., 7-((1H-benzo[d]imidazol-2-yl)diazenyl)quinolin-8-ol (BIDQ). The porous polymer template was synthesized through free radical polymerization of gylcidylmethacrylate and ethylene glycol dimethacrylate, leading to distinct structural and surface properties that offer exclusive solid-state colorimetric selectivity for Hg(II) upon restricted spatial dispersion of the ion receptor. The sensor provides a broad linear response range of 1-200 μg/L, with an outstanding detection limit of 0.2 μg/L for Hg(II) ions, thus effectuating reliable and reproducible sensing. Optimizing analytical parameters such as solution pH, receptor concentration, sensor quantity, kinetics, temperature, and matrix interference proved to be promising for the real-time monitoring of toxic mercury ions from aqueous/industrial systems, with maximum response in the pH range of 7.5-8.0, with a response time of ≤80 s. Density functional theory (DFT) calculations were employed to study the electronic structure of BIDQ upon chelating with Hg(II) ions, using 6-311G and LAND2Z basis sets.

Template development for cellular Al 6xxx cast structure

Abstract Excellent heat transfer capacity of light weight Al 6xxx cellular structures have made them as a promising porous material for thermal applications. To develop these cellular structures, polymer templates are created using 3D printing. Several design optimizations have allowed us to achieve the desired porous polymer template that allow easy fluid flow. This template is later infilterated with NaCl slurry, to obtain the ceramic NaCl template, which is later used for Al 6xxx casting. NaCl slurry paste is obtained by mixing of NaCl powder in remixed solution of gelatin and NaCl saturated water. NaCl template prepared is heat treated up to 700 ℃ to remove gelatin, moisture and PLA along with strengthening of NaCl structure due to sintering and annealing. Studies to obtain NaCl template having good strength that can handle infiltration pressure are performed. Average compression strength of 1.10 GPa, yield strength 34 MPa and micro hardness 193 ± 4.53 HV is observed. This works shows that NaCl particle size and shape, mixing parameters and time, sinter and anneal time, cell/pore size plays a critical role in obtaining a good ceramic template.

Mixed-valence mesoporous manganese oxide spheres from waste manganese nitrate aqueous solution

Abstract The paper presents a novel simple and cost-effective approach to preparation of mixed-valence mesoporous manganese oxide in the form of easy to handle spheres. The synthesis relies on swelling of porous polymer templates (i.e. three selected resins Amberlite® XAD7 HP, XAD4 and XAD16) in a saturated Mn(NO3)2 solution and subsequent removal of the template via calcination in air. The products are porous with the specific surface area ( S B E T ) up to 100 m2 g−1. The detailed characteristic of the materials, thermogravimetric insight into its calcination in air, and the influence of porous polymer (template) on MnOx structure is provided. The final product can be of great significance for electrochemistry, catalysis and is of some importance to the environment protection.

Template‐assisted hydrophobic porous silica membrane: A purifier sieve for organic solvents

ABSTRACTSelf‐supporting, interconnected, porous inorganic (silicon/carbon) membranes were obtained by the calcination of composite membranes at 900 °C with a porous polymer template obtained by binary‐phase solid‐state photopolymerization at −60 °C with acrylate monomers followed by chemical vapor deposition. The physicochemical properties of all of the membranes were characterized by scanning electron microscopy, energy‐dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, X‐ray powder diffraction (XRD), thermogravimetric analysis (TGA), and the measurement of water contact angles, water uptake, and percentage of porosity. The membranes showed contact angles ranging from 127 to 130 ± 0.5°, which were close to those of superhydrophobicity. The EDS, FTIR spectroscopy, XRD, and TGA results confirmed the formation of the Si–C composite structure after calcination and an increase in the thermal stability. The polymer and composite membranes were found to be hydrophilic, whereas Si–C was hydrophobic. The poly(ethylene glycol) diacrylate derived Si–C membrane showed a good absorption efficiency for tinted toluene from water compared to the others. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45822.

Nanospace-Mediated Self-Organization of Nanoparticles in Flexible Porous Polymer Templates.

Self-organization is a fundamental process for the construction of complex hierarchically ordered nanostructures, which are widespread in biological systems. However, precise control of size, shape, and surface properties is required for self-organization of nanoparticles. Here, we demonstrate a novel self-organization phenomenon mediated by flexible nanospaces in templates. Inorganic nanoparticles (e.g., silica, zirconia, and titania) are deposited in porous polymer thin films with randomly distributed pores on the surface, leaving a partially filled nanospace in each pore. Heating at temperatures beyond the glass transition temperature of the template leads to self-organization of the inorganic nanoparticles into one-dimensional chainlike networks. The self-organization is mediated by the deformation and fusion of the residual nanospaces, and it can be rationally controlled by sequential heat treatments. These results show that a nanospace, defined by the nonexistence of matter, interacts indirectly with matter and can be used as a component of self-organization systems.

Ti scaffolds with tailored porosities and mechanical properties using porous polymer templates

This study proposes a simple, useful approach to produce three-dimensionally macrochanneled titanium (Ti) scaffolds with tailored porosities and mechanical properties using porous polylactic acid (PLA) templates that can be prepared by conventional solid freeform fabrication (SFF) technique. Specifically, methylcellulose (MC) polymer was used as a binder since it could effectively bind coarse Ti particles and remain chemically stable inert in organic solvents used to dissolve PLA polymer. A Ti slurry-filled PLA was immersed in chloroform to remove the PLA template, followed by sintering at 1300°C for 3h in a vacuum. The use of a relatively small amount of a MC binder and removal of the PLA template in solvent enabled the construction of straight Ti frameworks and macrochannels in a 3-D periodic pattern without severe impurity contamination. This tightly controlled porous structure enabled the achievement of high compressive strengths without a catastrophic failure, while the compressive strength increased from ~72MPa to 121MPa with a decrease in overall porosity from ~75vol% to ~67vol%. In addition, the porous Ti scaffolds showed good biocompatibility, which was assessed by in vitro cell tests in terms of attachment, proliferation, and differentiation of MC3T3-E1 cells.

In situ SERS interrogation of catalytic reaction on three-dimensional gold nanowire carpeted polycarbonate membranes

Direct monitoring of a catalytic process is essential to elucidate the underlying chemical principles and to expedite the design of next generation catalysts. The in situ SERS approach on three-dimensional gold nanowire ensembles was investigated in this study, which have a double role as an optical enhancer for Raman scattering and as a catalytic active center over many chemical reactions. The nanowire cluster was first electrolessly deposited using a porous polymer template, producing a SERS-active substrate with massive optical enhancement with an average factor of ∼105. This established system, integrating a heterogeneous catalysis and real-time SERS detection, is assessed by monitoring the catalytic reduction of 4-nitrophenol in the presence of excessive amount of NaBH4, during which the gradual increase of Raman intensity from the signature peak of 4-aminophenol is clearly recorded, implying the successful chemical transformation of gold nanowires. Therefore, this integrated system, synchronizing reaction and detection, is an ideal candidate for the in situ study of catalytic reactions on a relatively large scale as it balances technological and economical advantages.

Green plating of high aspect ratio gold nanotubes and their morphology-dependent performance in enzyme-free peroxide sensing

The development of a green electroless plating protocol allowing the homogeneous deposition of nanoscale gold films on complex shaped substrates is presented. It is based on the environmentally benign reducing agent ascorbic acid and was used for the fabrication of gold nanotubes in porous polymer templates. The key action to achieve well-defined nanotubes of high aspect ratio (>100) was to reduce the reaction rate in order to ensure homogeneous metal deposition within the extended inner surface of the template. Depending on the plating time, nanotubes with porous as well as closed walls could be synthesized, which were characterized by SEM and EDX. Both nanostructure types were successfully implemented in the amperometric detection of hydrogen peroxide. The generally improved performance of the porous nanotubes compared to their closed counterparts was attributed to their better accessible and higher surface area (limit of detection: 2.3 μM vs. 8.2 μM; maximum of linear range: 11.7 mM vs. 8.0 mM; response time: 3.6 s vs. 5.5 s; sensitivity: 770 μA mM cm−2 vs. 360 μA mM cm−2). These excellent performance parameters surpass comparable, conventionally synthesized Au nanotube arrays as well as enzyme-modified one-dimensional Au catalysts, proving the high potential of adapted electroless plating reactions for green nanotechnology.

Fabrication and infrared-transmission properties of monolayer hexagonal-close-packed metallic nanoshells

This paper presents a novel method for fabricating a monolayer of hexagonal-close-packed metallic nanoshells with a small opening, based on a combination of a porous polymer template and a nanocrystal-seeded electroless plating technique. Light transmission spectra of the metallic nanoshell arrays are measured, which show that light can transmit through the dense particle assemblies via excitations of a variety of surface-plasmons (SPs). Further numerical simulations confirm these transmission resonances and reveal that they are attributed to the excitations of localized quadrupolar spherelike and Fano-type hybridized SP modes supported by the specific structure. The present metallic microstructure could find applications in plasmonics.

High-Resolution Direct Patterning of Gold Nanoparticles by the Microfluidic Molding Process

A novel microfluidic molding process was used to form microscale features of gold nanoparticles on polyimide, glass, and silicon substrates. This technique uses permeation pumping to pattern and concentrate a nanoparticle ink inside microfluidic channels created in a porous polymer template in contact with a substrate. The nanoparticle ink is self-concentrated in the microchannels, resulting in dense, close-packed nanoparticle features. The method allows for better control over the structure of printed features at a resolution that is comparable to inkjet printing, and is purely additive with no residual layers or etching required. The process uses low temperatures and pressures and takes place in an ambient environment. After patterning, the gold nanoparticles were sintered into continuous and conductive gold traces.

Ferromagnetic nanowire-loaded membranes for microwave electronics

In this article, we show how the microwave properties of ferromagnetic nanowires electrodeposited into a porous polymer template depend on various parameters such as the geometrical parameters of the nanowires array and elaboration conditions. Our nanowires behave as strong uniaxial nanomagnets and exhibit zero-field resonance frequencies tunable up to 36 GHz. Novel microwave devices such as circulators and filters, using a porous polymer template loaded with metallic nanowires, are discussed. An accurate knowledge of magnetic and dielectric properties of the loaded polymer template is mandatory for the design of such devices.

Preparation of Unsintering Calcium Phosphate Macroporous Materials with Hydroxyapatite Nanowhisker In Situ Growth

Unsintering macroporous calcium phosphate scaffolds with macropore sizes of 200∼400μm and hydroxyapatite nanofiber of in-situ growth were prepared by coating porous polyurethane templates with α-tricalcium phosphate bone cement (CPC) slurry, and their subsequent hydrolysis to calcium deficient hydroxyapatite (HAp) during the self-setting processes are presented. The effects of Sr2+ (SrNO3) on the nucleation, growth of the hydroxyapatite nanofiber and phase constitution were studied. The results show that the main component of the coating is HA after hydrolysis for 72h and the Sr2+ added could depress the growth of block or sheet HA crystal and promote the nanowhisker growth. This new processing technique can be used to improve the bioactivity of porous polymer template while maintaining its macroporous structure.

Morphology-controllable fabrication of ordered platinum nanoshells with reducedsymmetry

This paper presents a novel method for fabricating an ordered array of metallic nanoshellswith a controllable shape by a combination of a porous polymer template and ananocrystal-seeded electroless plating technique. The morphology of hollow particles has astrong dependence on the seed-deposition time onto the surfaces of the original colloidaltemplate. Using this method, ordered Pt nanobowls (bowl-shaped shells) and, alternatively,nanocups (cup-shaped shells) are prepared. These materials show some intriguingproperties: (i) reduced symmetry of the building blocks; (ii) a well-ordered structure; and(iii) a high ratio of surface area to volume, all of which are useful in many areas such ascatalysts, sensors, and photonic crystals.

Nanoindentation on Porous Bioceramic Scaffolds for Bone Tissue Engineering

We report nanoindentation mechanical properties measurements on porous ceramic scaffolds made for tissue engineering applications. The scaffolds have been made from tricalcium phosphate (TCP), hydroxyapatite (HA) nanopowder and mixed powders of HA (50 wt%) and TCP (50 wt%) using the polyurethane sponge method, which produces open porous ceramic scaffolds through replication of a porous polymer template. The scaffolds prepared by this method have a controllable pore size and interconnected pore structure. The crystal structures and morphology of porous scaffolds were determined by X-ray diffraction (XRD) and atomic force microscopy (AFM) respectively. Nanoindentation measurements to a depth of 600 nm showed a Young's modulus value of 10.3 GPa for HA+TCP composite scaffolds and 1.5 GPa for TCP scaffolds. The hardness values were 240 MPa for HA+TCP composites and 21 MPa for TCP sample respectively. The results showed that the mechanical properties of the biodegradable scaffolds can be considerably enhanced with the addition of HA while maintaining the interconnected open pores and pore geometry desirable for bone tissue engineering.