Honeycomb Porous Films Research Articles

Functional Applications of Ordered Honeycomb-Patterned Porous Films Based on the Breath Figure Technique

The breath figure (BF) technique is regarded as a powerful tool for the fabrication of strictly ordered and closely packed nanoand micro-porous films. It is a facile, economical, and versatile approach in which condensed water droplets serve as a benign template by rearranging on the polymer solution surface. They direct the assembly of polymer molecules into ordered patterns. Furthermore, the morphology of the pores can be adjusted and optimized by controlling several critical experimental parameters such as the film-forming system of the materials and the circumstances. This technique has a vast range of potential and promising applications in relevant areas such as separations, templating, stimuli-responsive surfaces, biosensing and photoelectric materials. However, the possible interplay of general mechanisms for the formation of all breath figure systems is complex, because each casting system is unique. In some cases no definite conclusion on the effect of each variable could be drawn until now. We review investigations at home and abroad including our group over the last five years on the preparation of honeycomb porous films using the breath figure method. We summarize and analyze their formation, influencing factors, function technologies and the applications of these porous films, and attempt to reveal the principles behind the formation of holes and the control of pore morphology. This work is expected to lay the foundation for follow-up studies and applications.

Morphology and wettability control of honeycomb porous films of amphiphilic fluorinated pentablock copolymers via breath figure method

Amphiphilic pentablock copolymers of poly (trifluoroethyl methacrylate)-b-poly (methyl methacrylate)-b-poly (ethylene glycol)-b-poly (methyl methacrylate)-b-poly (trifluoroethyl methacrylate) (PTFEMA-b-PMMA-b-PEG-b-PMMA-b-PTFEMA) with three different block ratios as well as molecular weights were used to fabricate honeycomb structured porous films through the breath figure technique. Several critical influencing factors such as macromolecular structures, solvent properties, copolymer concentrations and the substrates were investigated to control the morphology of the pores. The results showed that chloroform utilized as a solvent with an appropriate concentration of 45 mg mL−1 on the substrate of silicon wafer offered the optimum condition. It could be evidenced that the pore sizes of the honeycomb films were increased by enhancing the molecular weight of the copolymer. In addition, an increase in the copolymer concentration leads to a decrease in the pore size, and even causes a few porous structures to disappear. The viscosity of the liquid substrates also affects the pore size, and it was found that a larger pore size was formed with an increase in the viscosity. The porous films possessed better hydrophobic and oleophobic properties than the flat films. In addition, the pincushion structure films exhibited the best hydrophobic and oleophobic properties and an excellent water-adhesion ability in the reverse state. This work may facilitate our understanding of the breath figure process and assist us in preparing films under different conditions, which show different perspectives as micro-suckers, hydrophobic and oleophobic membranes.

Synthesis of star-shaped polyhedral oligomeric silsesquioxane (POSS) fluorinated acrylates for hydrophobic honeycomb porous film application

Two different eight-arm star-shaped polyhedral oligomeric silsesquioxane (POSS) fluorinated acrylates were synthesized through atom transfer radical polymerization (ATRP) and applied for hydrophobic honeycomb-patterned porous films through the breath figure (BF) method. The structure of polymers was characterized by Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC), and surface analysis was featured by X-ray photoelectron spectroscopy (XPS). Depending on the influences of polymer architectures, solvents utilized, and solution concentrations, honeycomb-patterned porous films were obtained. It could be found that the introduction of fluorine components was a favorable condition for BF formation and chloroform (CHCl3) utilized as solvent with an appropriate concentration of 30 mg/mL was the best condition for these hydrophobic honeycomb-patterned porous films. Meanwhile, the obtained honeycomb films could be retained after long-time preservation in an acid-base condition, which shows a great potential in filtration, cell culture, tissue engineering, and marine antifouling applications.

Synthesis of amphiphilic diblock copolymers derived from renewable dextran by nitroxide mediated polymerization: towards hierarchically structured honeycomb porous films

A novel dextran-SG1 macro-alkoxyamine was designed to afford amphiphilic linear block copolymers synthesized by nitroxide mediated polymerization toward the formation of hierarchically structured bio-resourced honeycomb films.

ATRP Synthesis of PS-b-PtBMA and Preparation of Porous Film

The polystyrene with end group of Br was synthesized by using MBrP as the initiator, CuBr/ PMDETA as the catalyst system according to atom transfer radical polymerization (ATRP). The effect of reaction temperature was studied and the system was confirmed as the active polymerization. Then PS-Br and CuBr/ PMDETA were respectively used as macroinitiator and catalyst to polymerize tBMA according to atom transfer radical polymerization (ATRP). The structure of the product was characterized by GPCFTIR1H-NMR. The amphiphilic block copolymer was obtained after hydrolysis. And the honeycomb porous film was prepared by PS-b-PMAA through using breath figure method.

Honeycomb Porous Films Prepared from Porphyrin-Cored Star Polymers: Submicrometer Pores Induced by Transition of Monolayer into Multilayer Structures

Honeycomb porous films prepared by the breath figure method show great potential in fields such as templating, separation, microanalysis, and superhydrophobic materials. This method is of significant simplicity but generally generates films with pores larger than 1 μm. Here we report an approach to formation of films with pore diameter as small as about 240 nm, which is based on the transition of monolayer into multilayer structures. Porphyrin-cored star polymers poly(styrene-block-2-hydroxyethyl methacrylate) having on average only 1–2 hydrophilic monomer units were synthesized by atom transfer radical polymerization (ATRP) and used for preparing honeycomb films. We investigated the effects of polymer structure and concentration on the pore diameter and film morphology. A tentative mechanism for the formation of multilayer structures was proposed and experimentally verified by in situ observing the breath figure process and measuring the glass transition temperature of the stars using differential scanning calorimetry (DSC). This work is helpful in understanding the mechanism of the breath figure method and preparing honeycomb films with submicrometer-sized pores which show perspectives as advanced microfiltration membranes.

Hierarchically structured hybrid honeycomb films via micro to nanosized building blocks

Metal oxide nanoparticles were chemically modified by surface initiated polymerization to core@shell building blocks (CSBBs). These CSBBs were then self-assembled using the bottom up breath figure (BF) method to design honeycomb (HC) porous hybrid films exhibiting hexagonal pore arrays. Depending on the nature, the size and the shape of the building blocks, honeycomb hybrid films with tunable pore sizes can be achieved.

Synthetic Route Effect on Macromolecular Architecture: From Block to Gradient Copolymers Based on Acryloyl Galactose Monomer Using RAFT Polymerization

Statistical, gradient, and block copolymer containing 2-(2′,3′,4′,6′-tetra-O-acetyl-β-d-galactosyloxy)ethyl acrylate (AcGalEA) glycomonomer and styrene (S) were synthesized by RAFT polymerization using S-methoxycarbonylphenylmethyl dodecyltrithiocarbonate (MCPDT) as control agent. The block copolymer was synthesized by a two-stage experiment, whereas the statistical and gradient copolymers were obtained in one-pot synthesis. Results obtained from the size exclusion chromatography (SEC) and the nuclear magnetic resonance (NMR) reveal that the polymers synthesized by RAFT were controlled. The kinetic of each synthetic route was investigated, and the reactivity ratio of both monomers was estimated by in situ NMR experiments: rAcGalEA = 0.07 ± 0.01 and rS = 0.7 ± 0.1. Moreover the AcGalEA moieties were deacetylated to achieve potential amphiphilic bioactive copolymer. The preparation of three different macromolecular architectures to form honeycomb porous films by breath figure process was investigated using ...

PH Sensitive Hierarchically Self‐Organized Bioinspired Films

In the present manuscript, we have demonstrated that hierarchically structured smart porous polymer films based on honeycomb-patterned surface can be elaborated from PS-b-P4VP pH-responsive block copolymer using the breath figure process. Despite the fast film formation by a bottom-up process, the copolymer nanostructuration was observed inside the walls of the honeycomb porous film. Atomic force microscopy (AFM), small angle X-ray and neutron scattering (SAXS and SANS) measurements were used to reveal both the hexagonal arrays formed by the pores at the micrometer length scale and the hexagonal copolymer self-assembly at the nanometer length scale. Contact angle (CA) measurements were used to point out the reversible pH-responsive wettability character of the surface. The PS-b-P4VP honeycomb film shows a contact angle variation of 20° between pH 9 and pH 3. An increase of the roughness was obtained with the pincushions hexagonal array enhancing the pH responsiveness of the polymer film with a switching CA gap of 75° when pH tuned from pH 9 to pH 3. This work presents the first report on honeycomb porous and pincushion films exhibiting a reversible pH-responsive character.

Polymethylene‐b‐polystyrene diblock copolymer: Synthesis, property, and application

AbstractThe design and synthesis of well‐defined polymethylene‐b‐polystyrene (PM‐b‐PS, Mn = 1.3 × 104–3.0 × 104 g/mol; Mw/Mn (GPC) = 1.08–1.18) diblock copolymers by the combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) was successfully achieved. The 1H NMR spectrum and GPC traces of PM‐b‐PS indicated the successful extension of PS segment on the PM macroinitiator. The micellization behavior of such diblock copolymers in tetrahydrofuran were characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM) techniques. The average aggregate sizes of PM‐b‐PS diblock copolymers with the same length of PM segment in tetrahydrofuran solution (1.0 mg mL−1) increases from 104.2 nm to 167.7 nm when the molecular weight of PS segment increases. The spherical precipitated aggregates of PM‐b‐PS diblock copolymers with an average diameter of 600 nm were observed by AFM. Honeycomb porous films with the average diameter of 3.0 μm and 6.0 μm, respectively, were successfully fabricated using the solution of PM‐b‐PS diblock copolymers in carbon disulfide via the breath‐figure (BF) method under a static humid condition. The cross‐sections of low density polyethylene (LDPE)/polystyrene (PS)/PM‐b‐PS and LDPE/polycarbonate (PC)/PM‐b‐PS blends were observed by scanning electron microscope and reveal that the PM‐b‐PS diblock copolymers are effective compatilizers for LDPE/PS and LDPE/PC blends. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1894–1900, 2010

Highly ordered microporous films containing a polyolefin segment fabricated by the breath-figure method using well-defined polymethylene-b-polystyrenecopolymers

Highly ordered microporous films containing polyolefin segment were successfully fabricated via the breath-figure (BF) method using well-defined polymethylene-b-polystyrene (PM-b-PS) diblock copolymers in CS2 under a static humid condition. The effects of molecular weight of diblock copolymers, relative humid, fabrication method and temperature on the morphology of film are investigated. The honeycomb porous films with different pore size (1.2–2.5 μm) were obtained by using PM-b-PS with different PM : PS ratio. The thick (7 μm) and thin (2 μm) films were fabricated via a different process. The film with a pothole-like structure was fabricated when using PM-b-PS with the shortest PS segment. Smaller satellite pores were found to surround the regular micropores of honeycomb films when the BF process was carried out at 28 °C.

Microsphere Pattern Prepared by a “Reverse” Breath Figure Method

We have reported an interesting method, named reverse breath figure, for the preparation of polymeric microsphere patterns. By the same procedure as breath figure, instead of under a humid atmosphere, linear and star-shaped poly(styrene-block-butadiene) copolymers dissolved in solvents such as toluene, trichloroform, and dichloromethane were cast onto the surface of a glass substrate in methanol or ethanol vapor. After the complete evaporation of the solvent, microspheres with the diameters ranging from hundreds of nanometers to several micrometers were prepared. The microsphere patterns are the reverse of the honeycomb porous structure of breath figure. The mechanism of the microsphere formation has been studied to show that when the surface tension of the polymer solution is 1.5 mN/m higher than that of the condensed liquid, microsphere patterns can be prepared, whereas a honeycomb porous film of breath figure can be obtained when the surface tension of the polymer solution is lower than that of the condensed liquid. The viscosity of the polymer solution is also an important factor to influence the fabrication of the microsphere patterns.

Regular honeycomb porous polymer films based on amphiphilic block copolymer

The design of highly ordered microporousmembranes has attracted considerable attentionsin the past decade because of their great interestsin basic research and industrial applications.Among many methods for fabricating microporouspolymeric film, the “breath figure” method [1–3]has attracted much attention due to the simple pro-cess. It employs solvent evaporative cooling onthe surface under humid conditions and waterdroplets are formed at the interface of the solutionand water vapor. Then, water droplets interactwith one another and are finally ordered in a hex-agonal lattice. In this paper, we prepared a seriesof amphiphilic diblock copolymer poly(vinyl phe-nol-