Honeycomb-patterned Films Research Articles

PH-sensitive fractal structured polyaniline in the honeycomb-patterned porous polymer film for the detection of dopamine and glucose

Using highly pH-sensitive fractal structured polyaniline (f-PANI) inducing conductivity change in the honeycomb-patterned (HCP) porous polymer film, we have applied for the detection of dopamine and glucose. Fractal-structured PANI in the HCP porous polymer film is formed by the same method recently reported using solid–liquid interfacial reaction. For the interfacial reaction, the HCP polystyrene (PS) porous film containing benzoyl peroxide (BPO) was immersed into the aniline aqueous solution under conditions of non-stirring for the growing of fractal structure instead of aggregated PANI. The pH sensitivity of the conductivity of the HCP film functionalized with fractal structured PANI was so high compared to the HCP film functionalized with simple aggregated PANI (a-PANI) under stirring conditions for the solid–liquid interfacial reaction. By using the high pH sensitive fractal structured PANI functionalized HCP film, dopamine, and glucose were selectively detected. The film acts as a micro reactor for the effective detection of dopamine and glucose.

Novel Capturer-Catalyst Microreactor System with a Polypyrrole/Metal Nanoparticle Composite Incorporated in the Porous Honeycomb-Patterned Film.

A composite of polypyrrole/metal nanoparticles (PPy/MNPs) was selectively incorporated into the pores of a honeycomb-patterned porous polycaprolactone polymer film to fabricate a novel capturer-catalyst microreactor system. This fabrication involved a modified breath figure method, where the polymer solution containing metal ions as an oxidizing agent was cast under humid conditions along with the pyrrole monomer through an interfacial reaction in a one-step in situ process. The higher hydrophilicity of the metal ions compared to the polymer solution led to their self-assembly around the pore surface, resulting in the selective incorporation of the PPy/MNP composite into the porous film. Copper (Cu), silver (Ag), and gold (Au) were used for the PPy/MNP fabrication. Various methods characterized the fabricated film. Strong catalytic degradations of methylene blue and methyl orange were obtained with PCL-PPy/MNPs. Recycling experiments showed no loss of activity even after five cycles of recycling. Comparative analysis of PCL-PPy, PCL-MNP, and PCL-PPy/MNP results indicated the synergistic action of PPy and MNPs in dye degradation. High-performance liquid chromatography and mass spectroscopy analyses confirmed dye degradation after treatment with a fabricated microreactor. PPy might have acted as a capturer of the dye molecule and MNPs as a catalyst, thereby enhancing the efficiency of dye degradation. Additionally, the PCL-PPy/Cu composite exhibited strong antimicrobial properties against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) with no cytotoxicity as measured by the MTT assay. Therefore, the fabricated microreactor film has promising applications in various fields.

Bio-inspired hierarchical structure of polyaniline in the pore surface of polymer film through interfacial polymerization as a smart material sensitive to pH

The bio-inspired hierarchical structure of polyaniline (PANI) was fabricated in the pore surface of polymer film through interfacial polymerization. The porous polystyrene (PS) honey-comb patterned (HCP) film containing benzoyl peroxide (BPO) was first fabricated by the breath figure (BF) method under humid conditions, further, the film was immersed into aniline hydrochloride aqueous solution for the interfacial polymerization of PANI. The interfacial polymerization of the HCP porous film led to the biomimetic growth of PANI in fractal configuration for a bio-inspired snowflake or leaf-like pattern in the pore surface. The bio-inspired structure of PANI in the HCP porous film through interfacial polymerization is explained by the diffusion-leading aggregation (DLA) by the reaction of aniline monomer into an aqueous solution and self-assembled BPO in the pore surface. The morphology of the bio-inspired PANI structure in the HCP film was highly sensitive to pH, and revealed the conductivity variation over several orders of magnitude (10-3 to 10-1 S/cm) similar to a smart material. Due to the high pH sensitivity, the film can be applied in various biomedical sensing applications.

Antibacterial Activity of Polyaniline Coated in the Patterned Film Depending on the Surface Morphology and Acidic Dopant.

We have fabricated poly(ε-caprolactone) (PCL) films with flat and honeycomb-patterned (HCP) structures to coat polyaniline (PANI) on the film surface. In addition, the effect of chemical modification of PANI by sulfuric acid (H2SO4) was also studied for antibacterial activity. The flat and HCP PCL films were obtained by simple evaporation of the solvent and via the breath figure (BF) method, respectively. The morphology and chemical composition of PANI coated on the film surface were evaluated by scanning electron microscopy (SEM) and X-ray spectroscopy (EDX). Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analyses (TGA) were obtained to identify the PANI coating. The wettability and conductivity of the films were also measured. Applicational aspects were evaluated by assessing antibacterial and antibiofilm activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The EDX, TGA, and FT-IR findings indicated chemical modification of PCL film by PANI and H2SO4. The conductivity of the films was increased by the coating of PANI to the patterned surface and additionally increased by the chemically modified PANI. The antibacterial activity was 69.79%, 78.27%, and 88% against E. coli, and 32.73%, 62.65%, and 87.97% against S. aureus, for flat PANI, HCP PANI, and H2SO4-treated HCP films, respectively. Likewise, the PANI coated flat, HCP, and H2SO4-treated HCP films inhibited E. coli biofilm formation by around 41.62%, 63%, and 83.88% and S. aureus biofilm formation by 17.81%, 69.83%, and 96.57%, respectively. The antibacterial activity of the HCP film was higher than that of flat PANI films, probably due to the higher coating of PANI on the HCP surface. Moreover, sulfonation of the HCP film with H2SO4 might have improved the wettability, thereby enhancing the antibacterial and antibiofilm properties. Our results showed that topographical changes, as well as doping, offer simple and cost-effective ways to modify the structural and functional properties of films.

Modified Breath Figure Methods for the Pore-Selective Functionalization of Honeycomb-Patterned Porous Polymer Films.

Recent developments in the field of the breath figure (BF) method have led to renewed interest from researchers in the pore-selective functionalization of honeycomb-patterned (HCP) films. The pore-selective functionalization of the HCP film gives unique properties to the film which can be used for specific applications such as protein recognition, catalysis, selective cell culturing, and drug delivery. There are several comprehensive reviews available for the pore-selective functionalization by the self-assembly process. However, considerable progress in preparation technologies and incorporation of new materials inside the pore surface for exact applications have emerged, thus warranting a review. In this review, we have focused on the pore-selective functionalization of the HCP films by the modified BF method, in which the self-assembly process is accompanied by an interfacial reaction. We review the importance of pore-selective functionalization, its applications, present limitations, and future perspectives.

Fabrication and characterization of pore-selective silver-functionalized honeycomb-patterned porous film and its application for antibacterial activity

Pore-selective silver (Ag)-functionalized honeycomb-patterned (HCP) polystyrene (PS) films were fabricated via a modified breath figure method using an interfacial chemical reaction and its application for an antibacterial film using the role of micro-trapping pit was systematically studied. PS polymer solution containing ferrocene which acts as a reducing agent was cast under humid conditions containing silver nitrate (AgNO3) to induce an interfacial chemical reaction between ferrocene and AgNO3 at the water droplet/polymer solution interface. The confinement of Ag+ to the humidity is possible due to the formation of the water complex of Ag+ such as Ag+(H2O)n stabilized by the Lennard–Jones potential and electrostatic interactions. Ag+ may be carried to the polymer solution surface via the water humidity despite being a heavy metal. Scanning electron microscopy and elemental mapping analysis revealed that the pores of the obtained films were selectively coated by Ag. The contact angle of the HCP porous films was greatly decreased by the pore selective Ag functionalization, which acts as a micro-trapping pit for the antibacterial activity. The antibacterial activity of the film against Escherichia coli and Staphylococcus aureus was assessed by the micro-dilution method, selective fluorescence imaging, and crystal violet assay. The study of BF for a functional HCP film by accompanying an interfacial chemical reaction for the pore-selective Ag functionalization shows that specific metal or inorganic materials could be pore-selectively functionalized by a similar method under several conditions, thus potentially giving the HCP films various applications.

Nicotinic-Acid-Ornamented Tetrameric Rare-Earth-Substituted Phospho(III)tungstates with the Coexistence of Mixed Keggin/Dawson Building Blocks and Its Honeycomb Nanofilm for Detecting Toxins.

A fascinating class of nicotinic-acid-ornamented tetrameric rare-earth (RE)-substituted phospho(III)tungstates [NH2(CH3)2]10Na4H8[RE2(NA)(HNA)(H2O)6(W2O4)(β-H2P2IIIW13O49)(α-HPIIIW9O33)]2·22 H2O [RE = Nd3+ (1-Nd), Tb3+ (2-Tb), Dy3+ (3-Dy), Ho3+ (4-Ho), HNA = nicotinic acid] were isolated through a one-step reaction method of Na2WO4·2H2O, H3PO3, HNA, NH2(CH3)2·HCl, and RE(NO3)·6H2O. Of meticulous concern is that HPO32- was used as a template to construct tetrameric RE-substituted phospho(III)tungstates including mixed heteropolyoxotungstate building blocks. Their hybrid polyoxoanions are composed of two symmetrical [RE2(NA)(HNA)(H2O)6(W2O4)(β-H2P2IIIW13O49)(α-HPW9O33)]11- units linked by RE-O-W bonds. The symmetrical unit consists of one peculiar heterometal nicotinic-acid-ornamented [RE2(NA)(HNA)(W2O4)]9+ cluster connecting a pentavacant Dawson-like [β-H2P2W13O49]12- and a trivacant Keggin [α-HPW9O33]8- subunits. Furthermore, dimethyldioctadecylammonium chloride (DMDODA·Cl) was used to combine with 1-Nd in the CHCl3-H2O system through electrostatic interactions, leading to the 1-Nd@DMDODA composite material. The honeycomb-patterned film of the 1-Nd @DMDODA composite material was successfully constructed by using the breath figure method on a glassy carbon electrode, which can offer abundant binding sites to Au nanoparticles (nano-Au). Ulteriorly, Au-functionalized 1-Nd@DMDODA-modified electrode was utilized as an electrochemical sensor to detect ochratoxin A, showing a good detection limit of 1.19 pM.

Large-Scale and Low-Cost Preparation of Ordered Honeycomb-Patterned Film by Solvent Evaporation-Induced Phase Separation Method

A large-scale and low-cost method for producing highly ordered honeycomb-patterned film using commonly commercialized polymers was proposed. This method provides the ability to prepare honeycomb-pa...

A simple strategy for fabricating honeycomb patterns on commercially available polymer film under a wide humidity range

Abstract

Pore-selective modification of the honeycomb-patterned porous polystyrene film with poly(N-isopropylacrylamide) and application for thermo-responsive smart material

Porous honeycomb-patterned (HCP) polystyrene (PS) film was pore-selectively functionalized by carboxylic acid group and modified by thermo-responsive poly (N-isopropylacrylamide) (PNIPAAm) to extend the application of HCP polymer films. The carboxylic acid functionalized film was obtained by a reactive breath figure method by casting a formylated PS (PS-CHO) solution under aqueous humid conditions containing oxone, which oxidized aldehyde into carboxyl acid at the interface of a water droplet/polymer solution accompanying an interfacial reaction. The fabricated film was reacted with amine-terminated poly (N-isopropylacrylamide) in aqueous solution for the pore-selective PNIPAAm modified HCP film. Temperature-dependent pore-surface morphology and wettability of the film were observed by scanning electron microscopy and contact angle measurement analysis after immersing into the water at below and above the lower critical solution temperature of PNIPAAm. The increase of temperature induced the pore-surfaces of the film to a higher rugged surface morphology and more hydrophobicity. The temperature-dependent capture ability of Ag nanoparticles in the pore-selective PNIPAAm modified HCP film was studied by immersing the film in aqueous solution containing Ag nanoparticles at 25 °C and 40 °C, which resulted in a higher capturing at higher temperature.

The Effect of the Isomeric Chlorine Substitutions on the Honeycomb-Patterned Films of Poly(x-chlorostyrene)s/Polystyrene Blends and Copolymers via Static Breath Figure Technique.

Polymeric thin films patterned with honeycomb structures were prepared from poly(x-chlorostyrene) and statistical poly(x-chlorostyrene-co-styrene) copolymers by static breath figure method. Each polymeric sample was synthesized by free radical polymerization and its solution in tetrahydrofuran cast on glass wafers under 90% relative humidity (RH). The effect of the chorine substitution in the topography and conformational entropy was evaluated. The entropy of each sample was calculated by using Voronoi tessellation. The obtained results revealed that these materials could be a suitable toolbox to develop a honeycomb patterns with a wide range of pore sizes for a potential use in contact guidance induced culture.

Pore‐Selective SnS Functionalization in Honeycomb‐Patterned Films by a Breath Figure Process Accompanied by Chemical Reaction

AbstractA new fabrication process for the pore‐selective functionalization of honeycomb‐patterned porous (HCP) films is demonstrated by a modified breath figure method accompanied by an in situ chemical reaction. A polymer solution containing one reactant is cast under humid conditions containing counter reactant to facilitate a chemical reaction at condensed droplet/polymer solution interface, which results in the pore‐selective functionalization of HCP films. Polystyrene (PS) solution containing tin(II) chloride is cast under humid conditions containing aqueous hydrogen sulfide for the formation of tin sulfide (SnS)‐functionalized PS HCP films. H2S humidity is generated by pumping ambient air through the aqueous sodium sulfide solution. Scanning electron microscopy, transmission electron microscopy, and elemental mapping analyses indicate the formation of SnS as thin layers selectively in the pores of PS HCP films.

A supramolecular hyperbranched polymer with multi-responsiveness constructed by pillar[5]arene-based host–guest recognition and its application in the breath figure method

A supramolecular gel with multi-responsiveness or honeycomb-patterned film was constructed by pillararene-based host–guest recognition.

Honeycomb-patterned hybrid films of surfactant-encapsulated polyoxometalates by a breath figure method and its electrocatalysis for BrO3.

In this paper, a sandwich type of polyoxophosphotungstate K7Na3[Cu4(H2O)2(PW9O34)2]·20H2O (abbr. Cu4(PW9)2) was selected as an active unit to construct inorganic/organic hybrid materials. The ordered honeycomb structure of the surfactant-encapsulated polyoxometalate (SEP) complex was successfully obtained by using a famous breath figure method. Cu4(PW9)2 maintains typical features as confirmed by IR spectra, magnetization hysteresis studies and UV-vis spectra. An investigation of the effects of the relative humidity on the morphology of the honeycomb structures demonstrated a wide generality and high reproducibility of the formation of self-organized honeycomb-patterned films. In the present experiment, this magnetically ordered honeycomb was successfully deposited on indium tin oxide (ITO) substrates by directly casting the SEP chloroform solution. The cyclic voltammetric responses showed the redox couples of Cu4(PW9)2. The electrochemical behavior of the electrode was studied. In addition, the modified electrode exhibited high electrocatalytic activity for the reduction of BrO3-, which offered a new POM-based film material for the electrochemical fields.

Fabrication of honeycomb-patterned film using hyperbranched polyethylene-based copolymer

Branched polymers were considered as one of the ideal materials to prepare patterned honeycomb film because of their strong ability to stabilize water droplets. In this work, we reported the first example of preparing patterned honeycomb films via breath figure method using hyperbranched polyethylene-based copolymer (HBPE-g-PtBMA). A systematic research was conducted to study the effect of solution concentration, relative humidity and substrate on the micro-structure of HBPE-g-PtBMA honeycomb film. It was found that the pore diameter (varied from 1.25 to 2.18μm) and pore height (varied from 61 to 820nm) could be controlled by adjusting solution concentration and relative humidity respectively. Besides, we verified that substrate with lower heat conductivity contributed to the formation of more regular honeycomb films. This work paved the way of fabricating patterned honeycomb films employing other hyperbranched polyethylene-based polymers and pointed to a new direction for the development of next-generation honeycomb patterned materials.

Uphill Water Transport on a Wettability-Patterned Surface: Experimental and Theoretical Results.

In nature, there exist many functional water-controlling surfaces, such as the water-repellent surface of lotus leaves, the superhydrophobic water-adhesive surface of rose petals, the water-harvesting surface of a beetle's back, and the water-transporting surface of the legs of Ligia exotica. These natural surfaces suggest that surface chemistry and hierarchical structures are essential for controlling the water behavior. We have reported the preparation of superhydrophobic and antireflection silicon nanospike-array structures using self-organized honeycomb-patterned films as three-dimensional dry-etching masks. Moreover, the surface wettability of the silicon nanospike-array structures can be easily transformed from superhydrophobic to superhydrophilic by changes in the surface chemistry. In this report, we show the preparation of water-controlling surfaces, such as water-harvesting and water-transporting surfaces, by the wettability patterning of silicon nanostructured surfaces. We prepared honeycomb-patterned films for dry-etching masks made from polystyrene and an amphiphilic polymer by casting a chloroform solution. After the fixation of the top layer of the honeycomb-patterned films on a single-crystal silicon substrate, reactive ion etching was performed. The as-prepared silicon nanospike-array structure showed superhydrophobicity, and the water contact angles were over 170°. After UV-O3 treatment with photomasks, only the UV-irradiated surfaces showed superhydrophilicity, suggesting that we can obtain superhydrophobic- and superhydrophilic-patterned surfaces for which the patterns are the same as those of the photomasks. On the basis of these wettability-patterned surfaces, we demonstrated water harvesting by superhydrophilic dot-patterned surfaces and water transportation against gravity by superhydrophilic triangular-patterned surfaces. In particular, we investigated uphill water transport through the motion of droplets on tilting slopes based on the equation of motion. These results suggested that we can obtain superior microfluidic devices suitable for various applications through the use of optional wettability patterns.

Graphene oxide incorporated poly(ε-caprolactone) honeycomb-patterned porous polymer films by the breath figure method

Poly(e-caprolactone)-graphene oxide (PCL-GO) honeycomb-patterned films were successfully fabricated by breath figure method for the first time by the simple blending of individual components in a water miscible solvent, tetrahydrofuran. PCL-GO films were reduced using sodium borohydride to obtain PCL-reduced graphene oxide (PCL-rGO) films. The films were characterized by their color, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). TGA result shows the improvement of the thermal properties of PCL by the incorporation of GO. The SEM image shows the formation of monodispersed porous honeycomb-patterned PCL-GO films, and these patterns are retained after the reduction of GO to PCL-rGO without any wreckage. The reduction of GO to rGO was confirmed from the color of the films and from the XPS analysis. The present methodology is expected to widen the use of breath figure technique to achieve a wide variety of functionalized films by simple blending using water miscible solvents, which would otherwise not be possible using water immiscible solvents.

Reversible change of wettability in poly(ɛ-caprolactone/azobenzene) honeycomb-patterned films by UV and visible light illumination

A new type of photosensitive poly(ɛ-caprolactone) (PCL) composites containing 4-dimethylamino-4′-(6-hydroxy hexyloxy) azobenzene (Azo) was synthesized by in situ ring-opening polymerization of ɛ-caprolactone in the presence of different Azo amounts. The PCL-Azo composites were characterized using Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and UV–vis spectroscopy. Honeycomb-patterned porous polymer films were fabricated by casting the polymer solution under humid conditions: and for comparison, flat films were also prepared by drying the polymer solution at ambient conditions. Water contact angle was compared between porous and flat films, and was reversely changed by UV and visible light illuminations. The contact angle of PCL-Azo composite films was decreased by UV illumination and was recovered with visible light illumination both on the patterned and flat films. Reversibility in contact angles by UV and visible light can be interpreted by photo-switched isomerization of the Azo component in the polymer composite films due to isomeric structural changes between trans and cis isomers inducing the changes in dipole moment of the films.

Effect of UV illumination on the fabrication of honeycomb-patterned film in the photo-responsive poly(methylmethacrylate/azobenzene) copolymer

A photoresponsive poly(methylmethacrylate/azobenzene) copolymer was synthesized through the copolymerization of methylmethacrylate (MMA) with 6-[4-(4-dimethylaminophenylazo)phenoxy]-hexyl methacrylate (Azo-monomer) to see the effect of UV illumination on the formation of honeycomb-patterned films fabricated by casting the copolymer solution under humid conditions. The synthesized copolymer was characterized by Fourier transform infrared, UV-vis, and nuclear magnetic resonance spectroscopy. The honeycomb-patterned films obtained by UV illumination showed more highly ordered films. It is due to a photo-switched isomerization of the azobenzene component in the PMMA-Azo copolymer from trans- to cis-isomer, which induces the amphiphilicity of the copolymer solution by increased dipole moment.

Electron transport and photoelectrical behavior of poly(N-vinylcarbazole)/Poly(3,4-ethylenedioxythiophene) composite honeycomb-patterned films

New type of poly(N-vinylcarbazole) (PVK) polymer nanocomposites were prepared by a solid-state polymerization of N-vinylcarbazole in the presence of different concentration (wt%) of poly(3,4-ethylenedioxythiophene) (PEDOT). The prepared PVK/PEDOT nanocomposites were characterized by using Fourier transform infrared (FTIR) and UV-vis spectra. The transmission electron microscopy (TEM) and X-diffraction studies were performed to understand the surface morphology and nature of the polymer composites. The characterization and morphological studies suggest that there is a conjugation between PVK and PEDOT. Furthermore, the honeycomb-patterned films were obtained by dissolving the PVK/PEDOT nanocomposites into the chloroform solvent under humid conditions. The temperature-dependent DC electrical conductivity and room temperature photo-electrical conductivity of the honeycomb-patterned films were measured. Results showed that the incorporation of PEDOT in PVK polymer has greatly improved the electrical conductivity and photo-electrical behavior of the PVK/PEDOT nanocomposites.