Static Breath Figure Research Articles

The microstructure and surface characteristics of fluorine‐based copolymer coatings deposited by the static breath method

We constructed a coating with controllable microstructure on the substrate by static breath figure (BF) method. In the atmosphere of water, when the fluorine‐containing 1H,1H,2H,2H‐perfluorooctyl polyacrylate‐block‐polystyrene copolymer (PTFOA‐b‐PS (4 h)) synthesized via atom transfer radical polymerization for 4 h was dissolved in carbon disulfide (CS2) and then coated on the silicon wafer, the concentrated pore size and uniform micro‐pore structure was successfully constructed on the surface. However, the hydrophobicity of the resulting microporous coating was not so good. An interesting result is that when the copolymer solution of PTFOA‐b‐PS (2 h) in tetrahydrofuran (THF) was used under the MeOH/H2O atmosphere (the methanol content was 60% or 80%), the microsphere coating can be produced on the substrate surface to obtain the excellent hydrophobicity. The water contact angles (WCAs) were 148.8 ± 1.8° and 150.3 ± 1.8°, respectively. Energy dispersive X‐ray spectrometer (EDS) results showed that the fluorine element was enriched in the outerfield of the microsphere coating. The low surface energy of fluorine combined with the rough and complex structure of the microspheres can effectively improve the hydrophobicity of the coating.

Facile preparation of super-hydrophobic fabrics composed of fibres with microporous or microspherical coatings using the static breath figure method

Fluorinated PTFOA-b-PS(2 h) and PTFOA-b-PS(4 h) block copolymers with controllable molecular weights were synthesised by atom transfer radical polymerisation (ATRP) and used to form microporous and microspherical coatings on fibres using the static breath figure (BF) method. The structures and properties of the coatings were examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and water contact angle (WCA) analysis. The fibre surface was complete coated with a microporous polymer in a water atmosphere using a 20 mg/mL PTFOA-b-PS(4 h) solution in CS2 as the finishing agent. The as-prepared fabric showed excellent hydrophobicity, with a WCA of 147.2 ± 1.6°. On the other hand, the fibre surfaces were coated with excellent polymer microspheres in a methanolic atmosphere using a 10 mg/mL PTFOA-b-PS(2 h) solution in THF; the WCA of the microsphere-coated fabric was 151.1 ± 0.1°. The WCA and EDS results reveal that synergism between the high roughness and low surface energy of the microspherical coating endows the fabric with super-hydrophobicity. At the same time, silanised block copolymers were synthesised by the silanisation of PTFOA-b-PS(2 h) and PTFOA-b-PS(4 h) and used to prepare microporous and microspherical coatings on fabrics. SEM showed that the silanised-PTFOA-b-PS(4 h)-coated fabric has a uniform and completely microporous morphology. A comparative study showed that both PTFOA-b-PS(2 h) and silanised-PTFOA-b-PS(2 h) form microspheres on fibre surfaces and that the latter exhibited hierarchical micro-nanostructures; the surface of fabric coated with this silanised polymer is super-hydrophobic, with a WCA of 152.2 ± 2.3°. Elemental distributions were determined by EDS, which revealed that the silanised-PTFOA-b-PS(2 h) microspheres contain more surface-migrating fluoropolymer segments, which produce hierarchical micro-nanostructures due to micro-phase separation. The air permeabilities and hardnesses of the silanised polymer-coated fabrics were also studied.

Ethyl cyanoacrylate ordered porous films prepared via in‐situ polymerization and static breath figures process

Ordered microporous films were fabricated via static breath figure process and in situ polymerization of ethyl cyanoacrylate (ECA) monomers. The influences of various parameters including solvent type (dichloromethane and chloroform), ECA concentration (0.2 and 1 wt%), temperature (17°C and 26°C), and substrate (glass, mica, PE, PP, and PET) were investigated on the structure of breath Figure (BF) films. Highly ordered porous films were generally formed at lower concentration of ECA and at 17°C for dichloromethane (DCM) and at 26°C for chloroform (CLF). The pores average diameter (D̅) of the films were in the range of 1 to 5 μm. The formation of regular porous structures were elucidated using the Marangoni (thermocapillary) convection flow and the rate of the polymer precipitation around the water droplets. There were an optimum ΔT (the temperature difference between the air and the solution surface) to create ordered BF film, regardless of solvent type. The prepared films have potential for templating applications.

Porous polyurethane film fabricated via the breath figure approach for sustained drug release

ABSTRACTThe breath figure (BF) method is an effective process for fabricating porous polymeric films. In this study, we fabricated porous polymer films from thermoplastic polyurethane (PU) through static BF with CHCl3 as a solvent under 55–80% relative humidity. The porous PU films were prepared within various pore structures and sizes, which were adjustable, depending on the fabrication conditions. The humidity and exposure time were examined as variable parameters affecting the surface morphology, wettability, and cytotoxicity. Atorvastatin calcium, a hyperlipidemic agent, was loaded into the porous films during the casting process, and the drug‐loading and drug‐releasing behaviors of the porous PU membranes were evaluated. Approximately 60–80% of the drug was released in 14 days. The films exhibited sustained drug‐release performances because of the hydrophobicity and nonbiodegradable nature of PU for perivascular drug administration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47658.

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.

Static miscible vapor environment controlled honeycombed morphology in polystyrene–b–poly(methyl methacrylate) films

Breath figure (BF) technology involves a concise process to obtain large sized honeycombed morphology in polymer film. The vapor condensability and the affinity between the condensed vapor and the polymer play key roles in the film morphology. A static breath figure technology was introduced here to control the porous film morphologies of homo-polystyrene (homo-PS), homo-polymethyl methacrylate (homo-PMMA), and block copolymer polystyrene-block-polymethyl methacrylate (PS–b–PMMA) with different total molecular weights and PS contents by using miscible vapor consisting of ethanol/water or acetone/water as atmospheric environment. The results showed that the vapor including component with low evaporation enthalpy led to larger droplets and favored to form regular honeycombed morphologies. The pore size depended strongly on the total block copolymer molecular weights and PS contents: the larger the total molecular weight and the lower the hydrophobic PS content, the larger the pore size.

Crosslinking poly(acrylic glycidyl ether) honeycomb film by cationic photopolymerization and its converting to inorganic SiO2 film

Abstract Highly ordered hexagonal patterns of homopolymer poly(glycidyl methacrylate) (PGMA) thin film was successfully fabricated via a one-step static breath figure process. The regularity and pore size of the films can be modulated by changing solvent composition or polymer concentration. The stable PGMA honeycomb film were formed via cationic photopolymerization due to the epoxide group on the side chain of PGMA. After photo-crosslinked, not only the patterned structures were well preserved, but also the solvent resistance as well as thermal stability of the film was significantly improved. The obtained film could be used as template to assemble SiO 2 particles via chemical vapor deposition at mild condition. Under high temperature, the honeycomb film was burned up and the silica particles were sintered into SiO 2 microbowl arrays, which could be tunable by varying the structure of the obtained template.

Assembly of Ultrathin Gold Nanowires into Honeycomb Macroporous Pattern Films with High Transparency and Conductivity

Because of its promising properties, honeycomb macroporous pattern (HMP) film has attracted increasing attention. It has been realized in many artificial nanomaterials, but the formation of these HMPs was attributed to templates or polymer/supermolecule/surfactant assistant assembly. Pure metal HMP film has been difficult to produce using a convenient colloidal template-free method. In this report, a unique template-free approach for preparation of Au HMP film with high transparency and conductivity is presented. Ultrathin Au nanowires, considered a linear polymer analogue, are directly assembled into HMP film on various substrates using a traditional static breath figure method. Subsequent chemical cross-linking and oxygen plasma treatment greatly enhance the stability and conductivity of the HMP film. The resulting HMP film exhibits great potential as an ideal candidate for transparent flexible conductive nanodevices.

Solvent and relative humidity effect on highly ordered polystyrene honeycomb patterns analyzed by Voronoi tesselation

ABSTRACTHighly ordered honeycomb‐patterned polystyrene surfaces are efficiently prepared by static breath figure method. The structured arrays can be obtained by casting a dilute solution polymer on glass substrates under various conditions. Tetrahydrofuran and chloroform are used as solvent to form cavities of several micrometers. The analysis of the surfaces indicates nonlinear relation between concentration and pore size in this system. Voronoi tessellations of the polystyrene surfaces at different relative humidity (RH) are achieved, and each conformational entropy determined. Optimum parameters of concentration and RH are obtained for both solvents. Analysis of hole size distribution and conformational entropy demonstrates the high order of the films obtained. This is a promising method for the fabrication of homogeneous and highly porous films from polystyrene. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44004.

Multi-length scale porous polymer films from hypercrosslinked breath figure arrays

Multi-length scale porous polymer (MLSPP) films were fabricated using commercially available polystyrene (PS) via static breath figure (BF) process and sequent hypercrosslinking reaction. One level of ordered pores in microscale were introduced using static BF process, and the other level in nanoscale were produced by the sequent Friedel–Crafts hypercrosslinking reaction. The chemical structure of the PS MLSPP film was investigated by Fourier transformation infrared spectrometry and solid state nuclear magnetic resonance, and the morphology of the film was observed with electron microscopes. The MLSPP films showed large specific surface areas and excellent chemical and thermal stabilities, owing to the micropores and the crosslinked chemical structure produced by the Friedel–Crafts reaction. The methodology reported in this paper is a template-free, low cost and general strategy for the preparation of MLSPP films, which has potential applications in the areas of environment and energy.

Well-defined monocarboxyl-terminated polystyrene with low molecular weight: A candidate for the fabrication of highly ordered microporous films and microspheres via a static breath-figure process

Aiming at the fabrication of highly ordered microporous films, a series of well-defined monocarboxyl-terminated polystyrenes (PSCOOH) with low molecular weight (PS13KCOOH: Mn=13kgmol−1, Mw/Mn=1.04; PS10KCOOH: Mn=10kgmol−1, Mw/Mn=1.05; PS4.4KCOOH: Mn=4.4kgmol−1, Mw/Mn=1.05 and PS2.1KCOOH: Mn=2.1kgmol−1, Mw/Mn=1.08) were synthesized firstly via reversible addition-fragmentation chain transfer (RAFT) polymerization using S-1-dodecyl-S’-(α, α’-dimethyl-α’’-acetic acid) trithiocarbonate as chain transfer agent. Then, a facile static breath-figure (BF) process was employed to fabricate microporous films of PSCOOHs. The influencing factors on the morphology of such microporous films, such as relative humidity, temperature, solvent, polymer concentration and molecular weight of polymer were investigated. Highly ordered microporous film with average pore size of 1.33μm and better regularity was fabricated through a static BF process using PS10KCOOH solution in CS2 (40mgmL−1) at 22°C in relative humidity of 95%. It was noteworthy that highly ordered microporous film (the average pore sizes from 0.77μm to 0.83μm) can be successfully fabricated using PSCOOH with very low Mn of 2.1kgmol−1 for the first time. Moreover, microsphere pattern of PSCOOH with the average diameters from 0.85μm to 5.40μm was formed when replacing water with methanol as environmental vapor in the chamber for the static BF process.

Constructing honeycomb micropatterns on nonplanar substrates with high glass transition temperature polymers

In Qiao’s previous report, only star polymers with Tg (glass transition temperature) below 48°C were found forming homogeneous honeycomb coatings on the nonplanar substrates. The polymers with high Tg are believed not able to duplicate nonplanar substrate due to their brittleness. This article presents a comprehensive study on the construction of macroporous polymeric films on various nonplanar substrates with static breath figure (BF) technique, using linear polymers with high Tg. Two kinds of linear polymers with high Tg, polystyrene-b-poly(acrylic acid) and polystyrene without polar end groups, are employed to prepare 3-dimensional macroporous films on different nonplanar substrates. Scanning electronic microscopy views on the side wall in addition to views in-plane prove that polymer films with BF array perfectly replicated the surface features of these substrates. The formation processes of macropores on these substrates are analyzed in detail, and it demonstrates that neither molecular topography nor Tg of polymers is the critical factor contouring nonplanar substrate. A new hypothesis involving polymer plasticization and conformation during the solvent evaporation is formulated.

Adjustable supramolecular polymer microstructures fabricated by the breath figure method

Highly ordered supramolecular polymer honeycomb-patterned films were fabricated successfully via the static breath figure method. The supramolecular polymer that was used to prepare these intriguing films was obtained from the self-organization of a heteroditopic monomer based on the benzo-21-crown-7/secondary ammonium salt recognition motif. The morphologies of these microstructures were observed by scanning electron microscopy, optical microscopy and atomic force microscopy techniques. The monomer concentration plays an important role in the fabrication of these supramolecular polymer microstructures. The pore size of honeycomb-patterned films decreases with the increase of the monomer concentration from 4 wt% to 30 wt%. A microsphere (900 nm) pattern and a highly-ordered honeycomb-patterned film (2.0 μm) were obtained via the static breath figure method using acetonitrile as the solvent at concentrations of 2 wt% and 30 wt%, respectively.

Constructing robust 3-dimensionally conformal micropatterns: vulcanization of honeycomb structured polymeric films

Here, we present the static breath figure process for constructing 3-dimensionally conformal microporous films on nonplanar substrates, with a commercially available triblock polymer, polystyrene-b-polyisoprene-b-polystyrene. The polymer can cover the surface of nonplanar substrates with ordered porous morphology despite the sharp corners and irregular shapes, which was ascribed to the fluid-like character of the matrix. In the subsequent vulcanization, the micro-patterned polymer films were effectively crosslinked and became self-supported even after removing the sacrificial templates. The 3D structures became resistant to a wide range of organic solvents and thermally stable up to 350 °C, an increase of more than 300 K as compared to the un-crosslinked films. The surface features on the 3D structures along the direction of the descending solvent level were investigated in detail by scanning electron microscopy. Furthermore, the versatility of this patterning method was also demonstrated by forming hierarchical micro-structures on bas-relief Si substrates with different patterns. Particularly, hydroxy groups were introduced into another commercially available triblock polymer, polystyrene-b-polybutadiene-b-polystyrene by hydroboration. The functionalized 3D micro-patterns feasible for site-directed grafting were created by the hydroxyl-containing polymers.

A Novel Path to Patterning Based on the Static Breath Figure Technique

National Natural Science Foundation of China [50703032, 20974089]; Outstanding Young Scientists Foundation of Fujian Province, China [2009106029]; Program for New Century Excellent Talents of Ministry of Education of China

Formation of ceramic microstructures: honeycomb patterned polymer films as structure-directing agent

Here, we show a facile and versatile method preparing highly ordered ceramic microstructures on solid substrates by pyrolyzing UV cross-linked copolymer films to circumvent the expensive lithographic technique. The employed block copolymer, poly(dimethylsiloxane)-block-polystyrene (PDMS-b-PS), in this study was synthesized by controlling radical polymerization. The highly ordered microporous polymer films were formed using a static breath figure process. After 4 h UV irradiation, the PS composition was effectively cross-linked. The cross-linked microporous polymer matrix served as a structure-directing agent in the following pyrolysis process, in which the PDMS composition was converted into silica to form honeycomb structured micropatterns on the substrate. The chemical components of the ceramic microstructures were adjusted by simply mixing different functional precursors. Moreover, the ceramic microstructures on substrate could be replicated to prepare textured PDMS stamps. This simple technique offers new prospects in the fields of micropatterns, soft lithography and templates.