Honeycomb Porous Films Research Articles

Petal-Shaped Graphene Porous Films with Enhanced Absorption-Dominated Electromagnetic Shielding Performance and Mechanical Properties.

The absorption-dominated graphene porous materials, considered ideal for mitigating electromagnetic pollution, encounter challenges related to intricate structural design. Herein, petal-like graphene porous films with dendritic-like and honeycomb-like pores are prepared by controlling the phase inversion process. The theoretical simulation and experimental results show that PVP K30 modified on the graphene surface via van der Waals interactions promotes graphene to be uniformly enriched on the pore walls. Benefiting from the regulation of graphene distribution and the construction of honeycomb pore structure, when 15 wt % graphene is added, the porous film exhibits absorption-dominated electromagnetic shielding performance, compared with the absence of PVP K30 modification. The total electromagnetic shielding effectiveness is 24.1 dB, an increase of 170%; the electromagnetic reflection coefficient reduces to 2.82 dB; The thermal conductivity reaches 1.1 W/(m K), representing a 104% increase. In addition, the porous film exhibits improved mechanical properties, the tensile strength increases to 6.9 MPa, and the elongation at break increases by 131%. The method adopted in this paper to control the enrichment of graphene in the pore walls during the preparation of honeycomb porous films by the phase inversion method can avoid the agglomeration of graphene and improve the overall performance of the porous graphene porous films.

Raining-inspired method for construction of porous film material

The low-temperature environment caused by solvent evaporation leads to the condensation of water vapor into water droplets that remain on the surface of the film to form breath figure patterns. The conventional approach to regulate the pore morphology in the breath figure process is to optimize the ambient temperature, humidity, and solution concentration. However, realizing a wide adjustable window of pore size and uniform distribution of the pore are still challenges. Here, inspired by the rainfall phenomenon, we proposed a simple and efficient method called the “raining boxing method” (RBM) for preparing porous films based on exogenously given water droplets as templates. The RBM broadened the adjustable window of pore size (0.6–225 µm in this work) and solved the inherent problem of radial reduction of pore size from the film center to the edge caused by the significant difference in low-temperature duration at different locations accompanying the solvent evaporation process. Furthermore, this method could realize multi-types porous films, including surface porous films, spongy porous films, and honeycomb porous films, and could be universally applied in the casting process of various polymer solutions.

Construction of 3D Ordered Honeycomb Films with Controllable Pores as Efficient Catalytic Supports

AbstractThe facile construction of 3D porous film using the breath figure technique is critically important in diverse practical applications. However, the discovery of easy synthetic methods and preparation of stimuli‐responsive 3D ordered nano‐/micro‐architectures remain challenging. Herein, the promotive breath figure technique is presented to construct 3D honeycomb porous films on curved substrates using an azobenzene‐containing copolymer. The nanopore size of honeycomb structure decreases gradually with the increase of surface curvature, due to the different solvent drying speeds. Upon irradiation with directional linear polarization light, the round‐shaped nanopores are converted into rectangular‐ and rhombic‐shaped nanopores under different polarization directions. Moreover, these porous films are employed as substrates to load various metal nanoparticles, successfully preparing the nanocomposites. The catalytic capacity of both control and these nanocomposites are evaluated using the NaBH4‐mediated reduction reaction from 4‐nitrophenol to 4‐aminophenol. Compared to the control and nonporous films, the porous films with smaller nanopores exhibit larger catalytic activity. Additionally, UV irradiation upon the nanocomposites promotes the catalytic action, due to the change in surface hydrophilicity caused by the photoisomerization of azobenzene. Recyclable use of nanocomposites demonstrates the high stability. This research provides an innovative strategy to prepare 3D curved porous films for potential on catalysis.

ISO2‐PU Honeycomb Porous Films with a Peculiar Crystalline Structure by the Breath Figure Method Promote Osteogenic Differentiation of Stem Cells

AbstractThe breath figure (BF) method is a handy strategy to prepare porous films. Linear shape memory polyurethanes (SMPUs) are among the most promising polymers for bone repair or regeneration. However, little attention has been paid to the fabrication of SMPU films by using the BF method. In this work, an amorphous SMPU containing isosorbide (ISO) in the long‐chain hard segments (ISO2‐PU) is fabricated into honeycomb porous films. Strikingly, a peculiar crystalline structure with a “Z” configuration and highly regional orientation is formed on the hexagonal holes of the porous films, which results in significantly enhanced mechanical properties. Moreover, the ISO2‐PU honeycomb porous films can markedly accelerate the osteogenic differentiation of rat mesenchymal stem cells, indicating that the porous films have great potentials as bone repair materials. It is further speculated that the Marangoni effect in the condensed water droplets and the molecular assembly of ISO2‐PU due to the strong hydrogen bonds and the chiral center effect of ISO are key contributors. This work, to the best of authors’ knowledge, is the first time that this special crystalline structure on BF‐based porous films is observed and also the first speculation that combines Marangoni effect with the microstructure of BF‐based porous films.

Spiropyran-incorporated honeycomb porous films with reversible multistimuli-responsive properties

Spiropyran-modified honeycomb porous film with photo-, thermo- and acido-chromic properties.

Immobilization of Active Substances in Food Using Self‐Organized Patterned Porous Film via Breath Figure Approach

AbstractMicropattern of bioactive substances in food, such as functional protein and enzyme immobilization, play a crucial role in catalysis, proteomics, tissue engineering, nutrition transportation and biological detection. Currently, various techniques have been reported for the immobilization of bioactive substances on solid but the fabricated methods are often not facile and universal. In this study, we overcome these problems to localized capture ovalbumin (OVA) and trypsin (Try) efficiently by fabricating patterned porous film via simple breath figure approach. Upon optimization of preparation conditions, ordered honeycomb porous film were obtained. We confirmed the morphology and investigated thermostability and surface wettability of porous film. The immobilization of OVA and Try was confirmed by confocal laser scanning microscopy and SDS‐polyacrylamide gel electrophoresis, respectively. To our best knowledge, this work is the first report on patterning and trapping of food protein and enzyme via self‐organized patterned porous film. Our findings are essential for establishing a new convenient and efficient route to design food protein/enzyme‐trapped porous film materials, which opens a new sustainable way for food protein/enzyme immobilization and expected to used in the food industry, biological applications, and so on.

Honeycomb structured porous films from a platinum porphyrin-grafted poly(styrene-co-4-vinylpyridine) copolymer as an optical oxygen sensor

The rational design and realization of revolutionary sensing films for improving the sensitivity and photo-stability of oxygen sensors have been long-standing challenges. We presented a facile approach for the fabrication of honeycomb structured porous films for optical oxygen sensors using a platinum porphyrin-grafted poly(styrene-co-4-vinylpyridine) (PtTFPP-PSVP) copolymer. Honeycomb porous films were prepared by the “Breath figure method”, which provides an efficient and cost-effective method to produce highly ordered honeycomb patterns in PtTFPP-PSVP copolymer films at sub-micrometer dimensions. Importantly, the application of these ordered honeycomb structured porous films as oxygen sensors afford exceptional improvement in sensitivity performance and exhibited 200% higher sensitivity than the solid sensing film owing to the higher accessibility of gas molecules and larger specific surface area. Furthermore, the photo-bleaching of sensor molecules for PtTFPP grafted to PSVP copolymer films could also be effectively alleviated and the sensors’ photo-stability was significantly improved compared with the physically incorporated PtTFPP into the same PSVP copolymer. Interestingly, the remarkably light intensity-changing characteristic of the sensing film under lower O2 partial pressures facilitates convenient identification of O2 concentrations even with the naked eye. We believe that the proposed honeycomb structured porous film could be a promising candidate in various oxygen sensing fields such as nearly anoxic systems, unsteady pressure measurements and unsteady flow visualization, etc. Additionally, the “Breath figure method”, owing to its simplicity, high reproducibility and easy processability, is expected to be readily applicable to a rich variety of other high performance gas sensor devices.

Poly (ionic liquid)-Based Breath Figure Films: A New Kind of Honeycomb Porous Films with Great Extendable Capability

In this work, we reported a new method for the convenient fabrication of various functional porous films, which cannot be directly generated using breath figures (BFs). A series of polystyrene-b-poly (ionic liquid) (PS-b-PIL) block copolymers were employed for BFs process for the first time. It was found that PS-b-PIL could form well-defined BFs porous structure. Remarkably, the described PS-b-PIL copolymers are prone to form hierarchical structure, and the formed pore structure is strongly dependent on the used experimental parameters. Importantly, we found that the anion exchange could provide as an effective means, by which the porous films could be further and facilely converted into other functional films. As a demonstration, in our case, porous films with different surface (hydrophilic and hydrophobic) property, porous polydopamine films decorated with Au nanoparticles or glutathione and porous SiO2 films were prepared by using different counteranions as well as further conversion. Due to the unlimited combination of cation and anion in ionic liquid moiety, all the results indicate that the BFs films generated by using PS-PIL could serve as a platform to access various functional porous films by a simple counteranion exchange, showing a great extendable capability.

Rhodamine B-decorated poly(hydroxypropyl acrylate) and their effects on the self-assembly of breath figure arrays

Novel poly(hydroxypropyl acrylate)-co-poly(hydroxypropyl acrylate)-rhodamine B (PHPA-co-PHPA-RhB) hydrophilic copolymers were synthesized via radical polymerization in this paper. And then the honeycomb-structured porous films were fabricated by dropping the (PHPA-co-PHPA-RhB) copolymers and PS solution on glass substrates by breath figure method (BFM). The effects of solvent, hydrophilic copolymers’ molecular weight, the proportion of hydrophilic copolymers and hydrophobic polymers on the formation of porous films were investigated. The porous films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), spectrofluorometer and confocal laser scanning microscope (CLSM). The results show that PHPA-co-PHPA-RhB and PS solutions can form regular honeycomb porous films; the average diameter of the films pore decreases with the proportion of hydrophobic polystyrene increased. Similar regular was also found when the molecular weight of PHPA-co-PHPA-RhB was enhanced. Furthermore, the fluorescence properties of the porous films were also investigated in this study.

Adhesive and repulsive properties of water droplet impact on honeycomb surfaces through breath figure method

ABSTRACTThe honeycomb porous films of tadpole‐shaped polyhedral oligomeric silsesquioxane fluorinated acrylates copolymers were fabricated through breath figure method. The static hydrophobic properties were studied through water contact angles (CAs) and the rim width/pore size (W/D) values. It was found that the low W/D value and high fluorine content generally indicated a high water CA. The properties such as morphology variations, energy conversion, contact diameter, adhesive, and repulsive forces were investigated on the porous and pincushion films. Furthermore, the kinetic energy of the droplet was converted into surface energy and internal energy dissipation after it impacted the surface. The residual energy made the droplet to recoil and influenced the bouncing height. The contact diameter and bouncing height characterized the energy level of the surface, and determined the surface energies of the copolymer/water/air system as well as the wettability. Finally, the adhesion and repulsion of water droplet on different surface at the times of establish contact, maximum contact diameter, and maximum bouncing height were compared. This work was helpful for us to further understand and control the adhesive force and the repulsive force on the porous and pincushion structure films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45476.

Langmuir-Schaefer film deposition onto honeycomb porous films for retinal tissue engineering.

Age-related macular degeneration (AMD) is a leading cause of central blindness in developed countries, associated with the degeneration of the retinal pigment epithelium (RPE), a specific cell layer at the back of the eye. Transplantation of RPE cells derived from stem cells is considered the best option to treat these patients. In this work, we developed a cell carrier for human embryonic stem cell-derived RPE that resembled the upper layers of the membrane that naturally supports the RPE cells in the retina. The new combination of technologies employed in this study resulted in very promising materials as confirmed by our studies on cell proliferation, morphology and function.

Breath Figure Micromolding Approach for Regulating the Microstructures of Polymeric Films for Triboelectric Nanogenerators

A triboelectric nanogenerator (TENG) is an innovative kind of energy harvester recently developed on the basis of organic materials for converting mechanical energy into electricity through the combined use of the triboelectric effect and electrostatic induction. Polymeric materials and their microstructures play key roles in the generation, accumulation, and retainment of triboelectric charges, which decisively determines the final electric performance of TENGs. Herein we report a simple and efficient breath figure (BF) micromolding approach to rapidly regulate the surface microstructures of polymeric films for the assembly of TENGs. Honeycomb porous films with adjustable pore size and dimensional architectures were first prepared by the BF technique through simply adjusting the concentration of the polymer solution. They were then used as negative molds for straightforward synthesis of polydimethylsiloxane (PDMS) films with different microlens arrays (MLAs) and lens sizes, which were further assembled for TENGs to investigate the influence of film microstructures. All MLA-based TENGs were found to have an obviously enhanced electric performance in comparison with a flat-PDMS-film-based TENG. Specifically, up to 3 times improvement in the electric performance can be achieved by the MLA-based TENG with optimal surface microstructures over flat-PDMS-film-based TENG under the same triggering conditions. A MLA-based TENG was further successfully used to harvest the waste mechanical energy generated by different human body motions, including finger tapping, hand clapping, and walking with a frequency ranging from 0.5 to 5.5 Hz.

Selective electroreduction of CO2 to formate on 3D [100] Pb dendrites with nanometer-sized needle-like tips

Honeycomb porous Pb films with a dendrite-like secondary structure growing along the [100]-axis were prepared by Dynamic Hydrogen Bubble Templating (DHBT) and used for the electroreduction of CO2.

Static and Dynamic Hydrophobic Properties of Honeycomb Structured Films via Breath Figure Method

This work reported the static and dynamic hydrophobic properties of the honeycomb porous and peeled films with pincushion structures by changing the concentrations of the copolymer solution. Honeycomb porous films were fabricated via breath figure technology employing a pentablock copolymer containing poly(ethylene glycol)/PEG, poly(methyl methacrylate)/PMMA, and poly(trifluoroethyl methacrylate)/PTFEMA. The relationship between the copolymer concentrations and the pore size (D) and rim width (W) was examined. Moreover, we studied the hydrophobic properties from different surfaces of flat, porous, and pincushion structures, and the contact angles, W/D ratios, and fraction of air on the porous and pincushion films were obtained. It was noteworthy that the W/D ratios and surface hydrophobic properties had a notable correlation. Finally, the dynamic behaviors of water droplets impacting on these porous and pincushion films were examined using a high speed camera. It examined the influence of the fraction of ...

Honeycomb porous films as permeable scaffold materials for human embryonic stem cell-derived retinal pigment epithelium.

Age-related macular degeneration (AMD) is a leading cause of blindness in developed countries, characterised by the degeneration of the retinal pigment epithelium (RPE), a pigmented cell monolayer that closely interacts with the photoreceptors. RPE transplantation is thus considered a very promising therapeutic option to treat this disease. In this work, porous honeycomb-like films are for the first time investigated as scaffold materials for human embryonic stem cell-derived retinal pigment epithelium (hESC-RPE). By changing the conditions during film preparation, it was possible to produce films with homogeneous pore distribution and adequate pore size (∼3-5 µm), that is large enough to ensure high permeability but small enough to enable cell adherence and spreading. A brief dip-coating procedure with collagen type IV enabled the homogeneous adsorption of the protein to the walls and bottom of pores, increasing the hydrophilicity of the surface. hESC-RPE adhered and proliferated on all the collagen-coated materials, regardless of small differences in pore size. The differentiation of hESC-RPE was confirmed by the detection of specific RPE protein markers. These results suggest that the porous honeycomb films can be promising candidates for hESC-RPE tissue engineering, importantly enabling the free flow of ions and molecules across the material. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1646-1656, 2016.

Tuning the surface hydrophobicity of honeycomb porous films fabricated by star-shaped POSS-fluorinated acrylates polymer via breath-figure-templated self-assembly

Porous films with tunable surface morphology and hydrophobicity were prepared via breath figure employing star-shaped polyhedral oligomeric silsesquioxane (POSS)-fluorinated polyacrylates, which were synthesized by atom transfer radical polymerization (ATRP) to ensure controlled polymer structure and molar mass. The influence of polymer architecture, solution concentration and the type of solvent on the surface morphology of the resulted porous films were evaluated. The optimized porous films with a broad range of pore diameter (D) and rim width (W) were characterized revealing in significant increasing of the surface hydrophobicity. Moreover, the surface morphology of the porous films, characterized by the D/W values (defined as fa), and surface hydrophobicity were found to have a notable positive correlation. Furthermore, the stripped films from above mentioned porous films were investigated revealing superhydrophobic surface due to the pincushion-like structure. Higher fa values for stripped films than the related porous film was found.

Fabrication of honeycomb films from highly functional dendritic structures: electrostatic force driven immobilization of biomolecules

Herein we report the preparation of honeycomb porous films for selective immobilization of biomolecules via the breath figure technique, a water-assisted micropatterning method.

Fabrication of polyurushiol/Ag composite porous films using an in situ photoreduction method

In this work, polyurushiol (PUS) was synthesized through a Friedel–Crafts reaction using bronsted acid as a catalyst. The product was then utilized in the fabrication of honeycomb porous films by breath figures (BFs). The PUS porous films were subsequently exposed to a high pressure mercury lamp for several seconds (5–30 s). An AgNO3 solution was then dripped onto the surface of films to form PUS/Ag composite porous films through the in situ photoreduction method, avoiding the use of harmful reducing agents. Key preparation factors, including solvent type, UV irradiation time and AgNO3 concentration, were systematically investigated. The composite films were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Ag particles (approximate size of 50 nm) were formed on the surface of PUS porous films when water was used as a solvent. In addition, increased AgNO3 concentration or UV irradiation time facilitated a change in the conductivity state of PUS/Ag porous films from insulator to semiconductor. The as-prepared PUS/Ag composite porous films provided excellent electronic properties and thus provided significant potential for future application in various fields.

Mussel-Inspired Modification of Honeycomb Structured Films for Superhydrophobic Surfaces with Tunable Water Adhesion

In this paper, we report novel superhydrophobic surfaces with tunable water adhesion by combining mussel-inspired surface chemistry and bioinspired multiscale surface structures. Highly ordered honeycomb porous films were prepared from a diblock copolymer polystyrene-block-poly(N,N-dimethylaminoethyl methacrylate) by the breath figure method. Removing the top surface layer of the honeycomb films leads to pincushion-like surfaces. The films were coated with polydopamine after completely prewetting by ethanol, followed by the reaction with 1H,1H,2H,2H-perfluorodecanethiol for fluorination. As a result of the surface modification, both the honeycomb and the pincushion-like surfaces are superhydrophobic with a water contact angle higher than 150°. Interestingly, the former is highly adhesive, on which water droplets are pinned at any tilted angles, whereas the latter is relatively low adhesive. Calculations indicate that the honeycomb films are in the Cassie state, whereas the pincushion-like surfaces are in ...

Honeycomb porous films of pentablock copolymer on liquid substrates via breath figure method and their hydrophobic properties with static and dynamic behaviour

The peeled film obtained on the isopropanol substrate through breath figure method exhibits the best hydrophobic properties, and the water droplet impact behavior shows an obvious rebound tendency and a weak maximum spreading diameter.