Tailoring Highly Ordered Honeycomb Films Based on Ionomer Macromolecules by the Bottom-Up Approach

Selectivity of a Copper Oxide CO2 Reduction Electrocatalyst Shifted by a Bioinspired pH-Sensitive Polymer

A bioinspired polymeric membrane capable of shifting the selectivity of a copper oxide electrocatalyst in the CO2 reduction reaction is described. The membrane is deposited on top of copper oxide thin films from wet deposition techniques under controlled conditions of humidity and self-assembles into an arranged network of micrometer-sized pores throughout the polymer cross-section. The membrane was composed of a block copolymer with a precisely controlled ratio of poly-4-vinylpyridine and poly(methyl methacrylate) blocks (PMMA-b-P4VP). The intrinsic hydrophobicity, together with the porous nature of the membrane's surface, induces a Cassie-Baxter wetting transition above neutral pH, resulting in water repulsion from the catalyst surface. As a consequence, the catalyst's surface is shielded from surrounding water molecules under CO2 electroreduction reaction conditions, and CO2 molecules are preferentially located in the vicinity of the catalytically active area. The CO2 reduction reaction is therefore kinetically favored over the hydrogen evolution reaction (HER).

Fabrication of Adsorption-Type Hierarchical Functional Films by Using a Facile Swollen Based Breath Figure Method

The morphology transition from primary to hierarchical adsorption-type microporous domains of amphiphilic block copolymer (BCP) honeycomb-structured films is demonstrated by a facile swollen based breath figure (BF) method. The characteristic parameters of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) hierarchical micro- and submicro-porous films can be controlled by changing the length of segments or subsequent swelling conditions. A plausible mechanism is demonstrated in this research. A typical amphiphilic BCP with very low volume content of hydrophilic blocks (f_P4VP ≤ 0.050) can efficiently stabilize water droplets and inherently assist in the formation of morphology transition. This BCP film can be used for Cr(VI) removal from wastewater, which additionally has enormous potential application in the field of novel optical devices, soft lithography, size-selective separation, etc. This article is protected by copyright. All rights reserved.

Direct formation of hydrophilic honeycomb film by self-assembly in breath figure templating of hydrophobic polylacticacid/ionic surfactant complexes

Honeycomb-patterned porous films with good surface wettability have great potential applications in various areas. However, hydrophilic honeycomb films are difficult to obtain using the direct self-assembly of pure (co)polymers. Thus, additional and special treatments are required to improve film wettability, which makes the procedure complicated and difficult to access. In this study, a facile way to prepare hydrophilic honeycomb-structured porous films is proposed that uses the direct self-assembly of complexes of biocompatible hydrophobic poly(l-lactic acid) and dodecyltrimethylammonium chloride by breath figure templating. The addition of ionic surfactant not only improves film quality but also confers good wettability. The obtained hydrophilic pore arrays were found to effectively promote cell attachment. Such a hydrophilic honeycomb-patterned porous film could find potential applications where pore wetting is required, including tissue engineering, lithography, and nanoparticle embedding.

Synthesis of novel guanidine-based ABA triblock copolymers and their antimicrobial honeycomb films

Novel antimicrobial poly(methacryl guanidine hydrochloride)-block-polystyrene-block-poly(methacryl guanidine hydrochloride) triblock copolymers were synthesizedviaRAFT polymerization and fabricated into antimicrobial honeycomb films.

Reactive nano-patterns in triple structured bio-inspired honeycomb films as a clickable platform

Towards unprecedented triple structured bio-inspired honeycomb film by selfassembly of a functional block copolymer during breath figure templating as a nano-patterned clickable platform.

Deterministic Reshaping of Breath Figure Arrays by Directional Photomanipulation

The fabrication of desired structures is one of the most urgent topics in current research on porous polymer films. Herein, directional photomanipulation in conjunction with breath figure processing has been demonstrated for the preparation of porous polymeric films with finely tunable pore shape and size. Because of the photoinduced directional mass migration of azobenzene units upon vertical incident linearly polarized light (LPL) irradiation, round pores on honeycomb films can be reshaped into multifarious shapes including rectangle, rhombus, dumbbell, line, and so forth. In addition, slantwise LPL irradiation produces unique asymmetrical structure inside the pores oriented along the polarized direction. On the other hand, circularly polarized light (CPL) irradiation affords manipulation of the wall thickness without changing the pore shape. This versatile directional photomanipulation method can be implemented to large-area and high-throughput reshaping processes, which paves the way to a number of promising applications such as a flexible etching mask for patterning.

Hierarchical honeycomb-structured films by directed self-assembly in “breath figure” templating of ionizable “clicked” PH3T-b-PMMA diblock copolymers: an ionic group/counter-ion effect on porous polymer film morphology

Impact of the ionization of “clicked” rod–coil diblock copolymers on their directed self-assembly in “breath figure” templating for hierarchically honeycomb-structured films.

Hierarchically porous materials: synthesis strategies and structure design

This review addresses recent advances in synthesis strategies of hierarchically porous materials and their structural design from micro-, meso- to macro-length scale.

Amino-functionalized breath-figure cavities in polystyrene-alumina hybrid films: effect of particle concentration and dispersion

We report the formation of breath-figure (BF) patterns with amino-functionalized cavities in a BF incompatible polystyrene (PS) by incorporating functionalized alumina nanoparticles. The particles were amphiphilic-modified and the modifier ratio was regulated to achieve a specific hydrophobic/hydrophilic balance of the particles. The influence of the physical and chemical properties of the particles like particle concentration, the hydrophobic/hydrophilic balance, etc., on particle dispersion in solvents having different polarity and the corresponding changes in the BF patterns have been studied. The amphiphilic-modified alumina particles could successfully assist the BF mechanism, generating uniform patterns in polystyrene films with the cavity walls decorated with the functionalized alumina particles, even from water-miscible solvents like THF. The possibility of fabricating free-standing micropatterned films by casting and drying the suspension under ambient conditions was also demonstrated. The present method opens up a simple route for producing functionalized BF cavities, which can be post-modified by a chemical route for various biological applications.

The role of acrylonitrile in controlling the structure and properties of nanostructured ionomer films

Ionomers are polymers which contain ionic groups that are covalently bound to the main chain. The presence of a small percentage of ionic groups strongly affects the polymer's mechanical properties. Here, we examine a new family of nanostructured ionomer films prepared from core-shell polymer nanoparticles containing acrylonitrile (AN), 1,3-butadiene (Bd) and methacrylic acid (MAA). Three new AN-containing dispersions were investigated in this study. The core-shell nanoparticles contained a PBd core. The shells contained copolymerised Bd, AN and MAA, i.e., PBd-AN-MAA. Three types of crosslinking were present in these films: covalent crosslinks (from Bd); strong physical crosslinks (involving ionic bonding of RCOO(-) and Zn(2+)) and weaker physical crosslinks (from AN). We examined and compared the roles of AN and ionic crosslinking (from added Zn(2+)) on the structure and mechanical properties of the films. The FTIR spectroscopy data showed evidence for RCOOH-nitrile hydrogen bonding with tetrahedral geometry. DMTA studies showed that AN copolymerised within the PBd-AN-MAA phase uniformly. Tensile stress-strain data showed that inclusion of AN increased elasticity and toughness. Analysis showed that about 33 AN groups were required to provide an elastically-effective chain. However, only 1.5 to 2 ionically bonded RCOO(-) groups were required to generate an elastically-effective chain. By contrast to ionic bonding, AN inclusion increased the modulus without compromising ductility. Our results show that AN is an attractive, versatile, monomer for increasing the toughness of nanostructured ionomers and this should also be the case for other nanostructured polymer elastomers.

Formation of breath figure arrays in methanol vapor assisted by surface active agents

Breath figure (BF) process is a promising technique for fabricating honeycomb polymer films. It is usually conducted in water vapor. While, in organic vapors only unique polymer can be used to prepare BF arrays as reported in our previous article (Breath Figure in Nonaqueous Vapor. Soft Matter, 2013, 506-514), although new structure features are induced in the film. In this paper, a universal modified BF processing is devised for preparing porous films in methanol vapor with conventional polymers, by adding a small amount of surface active agent into the casting solution, such as siloxane- and fluorine-containing block copolymers. The pores in the PS films prepared with this method are of cylindrical shape with large depth-diameter aspect ratio, and the diameter and depth of pores can be well controlled by the experiment conditions. Based on these results, the formation mechanism of honeycomb structure in methanol vapor is discussed.

Butterfly effects: novel functional materials inspired from the wings scales

This review will provide a perspective overview of the research inspired from butterfly wing structures in recent years.

Multiple interfaces in self-assembled breath figures

Progress in the breath figure method is reviewed by emphasizing the role of the multiple interfaces and the applications of honeycomb films in separation, biocatalysis, biosensing, templating, stimuli-responsive surfaces and adhesive surfaces.

Polystyrene with hydrophobic end groups: synthesis, kinetics, interfacial activity, and self-assemblies templated by breath figures

Polystyrenes with hydrophobic end groups are synthesized from a series of alkyl or fluorinated ATRP initiators to fine-tune the surface morphologies of honeycomb films prepared by the breath figure method.

Synthesis of polystyrene with cyclic, ionized and neutralized end groups and the self-assemblies templated by breath figures

Polymers with functional end groups are synthesized using a cyclic lactone ATRP initiator for honeycomb-patterned porous films by the breath figure method.

Porous surface structure fabricated by breath figures that suppresses Pseudomonas aeruginosa biofilm formation

As colonizers of medical-device surfaces, Pseudomonas aeruginosa strains present a serious source of infection and are of major concern. In this study, we fabricated films with porous surfaces by breath figures that disturb mergence by bacterial attachment, thereby impeding biofilm development. Previous studies have shown that microtopography prevents the development of P. aeruginosa biofilms. Accordingly we indented surfaces with patterns of micrometer-sized pores using breath figures at ordinary temperatures and pressures. The antimicrobial effect of surface figures was experimentally investigated by controlling the surface structure. The results suggested that pores of 5-11 μm in diameter effectively inhibit bacterial activity. It appears that biofilm development is precluded by the decreased contact area between the films and bacteria.

Photoactive, porous honeycomb films prepared from Rose Bengal-grafted polystyrene

Honeycomb-structured porous polymer films based on photosensitizer-grafted polystyrene are prepared through the breath figure process. Rose Bengal (RB) photosensitizer is first attached to a well-defined poly(styrene-stat-4-vinylbenzyl chloride) statistical copolymer, synthesized by nitroxide-mediated radical polymerization. The RB grafted poly(styrene-stat-4-vinylbenzyl chloride) (ca. 20,000 g mol(-1) molar mass, 1.2 dispersity) leads to porous polymer films, with a hexagonal pore pattern, while a simple mixture of poly(styrene-stat-4-vinylbenzyl chloride) and the insoluble RB photosensitizer produced unstructured, nonporous films. The RB-grafted honeycomb films, compared with the corresponding nonporous flat films, are more efficient for oxidation of organic molecules via singlet oxygen production at a liquid/solid interface. The oxidations of 1,5-dihydroxynaphthalene to juglone and α-terpinene to ascaridole are followed in ethanol in the presence of both types of films. Oxidation of the organic molecules is a factor 5 greater with honeycomb compared to the nonporous films. This gain is ascribed to two factors: the specific location of the polar photosensitizer at the film interface and the greater exchange surface, as revealed by fluorescence and scanning electron microscopies.

Fabrication of structured porous films by breath figures and phase separation processes: tuning the chemistry and morphology inside the pores using click chemistry

Herein, a facile water-assisted templating technique, the so-called breath figures method, in combination with phase separation process, was employed to prepare multifunctional micropatterned films. Tetrahydrofuran solutions of incompatible ternary blends consisting of high-molecular-weight polystyrene, an amphiphilic block copolymer, polystyrene-b-poly[poly(ethylene glycol) methyl ether methacrylate] (PS40-b-P(PEGMA300)48), and a fluorinated homopolymer, poly(2,3,4,5,6-pentafluorostyrene) (P5FS21) were casted under humid atmosphere varying the proportion of the components. Two simultaneously occurring processes, i.e., the breath figures mechanism and the phase separation process, lead to unprecedented morphologies that could be tuned by simply varying the relative humidity or the composition of the blend. Confocal micro-Raman spectroscopy served to provide information about the location and distribution of the different functionalities in the films. As a result, both the amphiphilic block copolymer and the fluorinated polymer were mainly located in the cavities. Above a certain percentage of relative humidity, honeycomb structured films were obtained in which the block copolymer is distributed on the edge of the pore as a result of the affinity by the condensing water droplet and the coffee stain effect. The homopolymer is also preferentially situated at the pore edge, but forming spherical domains with narrow polydisperse sizes. Moreover, thiolated glucose molecules were specifically attached to the P5FS21 domains via thiol-para fluorine "click" reaction. Subsequently, the specific lectin (Concanavalin A, Canavalia ensiformis) was attached to the surface by conjugation with the glucose moieties. The successful binding of the Con A was demonstrated by the fluorescence, observed exclusively at the areas where P5FS21 domains are located. This nonlithographic method opens a new route to fabricate a huge variety of microstructured polymer films in terms of morphology not only for protein patterning, as illustrated in this manuscript, but also to produce a diversity of functional group arrangements.

Advances in Fabrication Materials of Honeycomb Structure Films by the Breath-Figure Method

Creatures in nature possess almost perfect structures and properties, and exhibit harmonization and unification between structure and function. Biomimetics, mimicking nature for engineering solutions, provides a model for the development of functional surfaces with special properties. Recently, honeycomb structure materials have attracted wide attention for both fundamental research and practical applications and have become an increasingly hot research topic. Though progress in the field of breath-figure formation has been reviewed, the advance in the fabrication materials of bio-inspired honeycomb structure films has not been discussed. Here we review the recent progress of honeycomb structure fabrication materials which were prepared by the breath-figure method. The application of breath figures for the generation of all kinds of honeycomb is discussed.

Functionalized and postfunctionalizable porous polymeric films through evaporation-induced phase separation using mixed solvents

Condensation of water droplets during rapid evaporation of a polymer solution, under humid conditions, has been known to generate uniformly porous polymer films. Similar porous films are also formed when a solution of the polymer in THF containing small amounts of water, is allowed to evaporate rapidly under air flow; this suggests that water droplets may be formed during the final stages of film formation. In the presence of added surfactants, the interface of water droplets could become lined with the surfactants and consequently the internal walls of the pores generated, upon removal of the water, could become decorated with the hydrophilic head groups of the surfactant molecules. In a series of carefully designed experiments, we have examined the effect of added surfactants, both anionic and cationic, on the formation of porous PMMA films; the films were prepared by evaporating a solution of the polymer in THF containing controlled amounts of aqueous surfactant solutions. We observed that the average size of the pores decreases with increasing surfactant concentration, while it increases with increasing amounts of added water. The size of the pores and their distribution were examined using AFM and IR imaging methods. Although IR imaging possessed inadequate resolution to confirm the presence of surfactants at the pore surface, exchange of the inorganic counterion, such as the sodium-ion of SDS, with suitable ionic organic dyes permitted the unequivocal demonstration of the presence of the surfactants at the interface by the use of confocal fluorescence microscopy.

Honeycomb-structured films by multifunctional amphiphilic biodegradable copolymers: surface morphology control and biomedical application as scaffolds for cell growth

Recently, fabrication of functional porous polymer films with patterned surface structures at the scale from nanometer to micrometer has been attracting increasing interests in material science and nanobiotechnology. In this work, we present new preparation of two series of multifunctional amphiphilic copolymers and preparation of their microporous thin films on solid substrates. First, diblock dendritic poly(l-lysine)-b-poly(l-lactide)s and triblock dendritic poly(l-lysine)-b-poly(l-lactide)-b-dendritic poly(l-lysine)s (C1-C6) were synthesized through 4-dimethylaminopyridine (DMAP)-catalyzed living ring-opening polymerization of (l-)-lactide with (l-)-lysine dendron initiators, and their structures were characterized by nuclear magnetic resonance spectrometer (NMR), gel permeation chromatography (GPC) and matrix-assisted laser desorption/ionization Fourier-transformed mass spectra (MALDI-FTMS). Employing the breath-figure (BF) fabrication strategy, thin films of the synthesized amphiphiles (C1-C6) were drop-cast, and their surface topologies were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the effects of new amphiphile structure and drop-casting parameters of amphiphile concentration, humidity and temperature on self-assembly of ordered porous surface were studied. Furthermore, the influence of surface energy of drop-casting substrates was additionally investigated. With a human cervical epithelial carcinoma cell line (HeLa), cytotoxicity of the prepared honeycomb-structured films by new amphiphile C6 was evaluated by thiazoyl-blue-tetrazolium-bromide (MTT) assay, and HeLa cell growth behavior with microporous amphiphile films as the scaffolds was also examined. It was found that tunable micropore diameter sizes and well ordered surface topologies of BF films could be achieved for the new prepared amphiphiles, and utilization of the honeycomb-like microporous films as scaffolds indicated favorable enhancement in cell proliferation. Therefore, the honeycomb-structured films by these biocompatible multifunctional amphiphiles may provide new materials as 3D-scaffold materials for potential application in tissue engineering and regeneration.

Photonic properties of hybrid colloidal crystals fabricated by a rapid dip-coating process

The enhancement of the capillarity fabrication of well-ordered two-dimensional (2D) and three-dimensional (3D) opal photonic crystal is described herein. The quality enhancement and the reduction of the fabrication time are improved by using core@soft adhesive shell (Silica@PolyButylAcrylate) particles dispersed in an organic solvent with a high boiling point. The hybridization by an elastomeric corona polymer, grafted from the SiO(2) surface, has offered adhesive properties naturally tunable by changing the polymer state from a solvated to a dry one. Such properties involve drastic changes of the self-assembly behavior and qualities. Their use, as elementary building blocks, for colloidal crystal fabrication have required a high withdrawal rate (up to 4000 μm s(-1)), i.e. involving a three order of magnitude reduction in time compared to a classic vertical deposition method (1 to 10 μm s(-1)) and a good control/prediction of the coating thickness can be tuned by varying the withdrawal rate and the particle concentration. In addition, an analysis of the 2D synthetic iridescence of the hybrid photonic crystal was performed under white light, revealing the adhesive shell bridge influence on the dissipation energy of cracks linked to the crystal quality and the photonic properties.

Nanogels based on poly(vinyl acetate) for the preparation of patterned porous films

The use of poly(vinyl acetate) (PVAc) nanogels for the fabrication of patterned porous surfaces is described. These nanogels were synthesized by controlled radical cross-linking copolymerization (CRCC) involving a xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) mechanism. This synthesis methodology allowed for the preparation of nanogels based on PVAc with a controlled constitutive chain length and average numbers of chains and cross-links. Solutions of these branched polymers were prepared in THF with a fixed amount of water and spin coated onto a surface of graphite. The surface porosity of corresponding films was observed by atomic force microscopy (AFM). Compared with linear PVAc homologues with a degree of polymerization (DP) sufficiently high to favor the formation of porous structures (DP = 50), a sharper and better defined porosity was observed with nanogels, the constitutive chains of which had the same DP. For nanogels differing only in their cross-link density, the pores were smaller and better defined in the case of the higher cross-link density, suggesting an enhanced stabilization of the water droplets during film formation. To explain these observations, it is postulated that PVAc nanogels can behave as compact particles providing steric stabilization of water droplets, which is referred to as a Pickering effect. The coalescence of water droplets would be better prevented as the cross-link density of the nanogels increases, resulting in a smaller size pore.

Bioinspired material based on femtosecond laser machining of cast sheet micromolding as a pattern transfer process

We present herein a simple, fast, and easy-to-use process to replicate poly(methyl methacrylate) (PMMA) plates generating surface effects. First, a femtosecond laser has been used to fabricate, with sufficient accuracy, a periodic pattern on a glass plate at the microscale. This glass plate, used as a master, can be structured on a large distance with a good control of its roughness. Then, the polymer plates were obtained by bulk polymerization without any solvents with a good replication from the cast sheet process, which has been industrially performed for years. Thus, the modification of this process, environmentally friendly, lets us foresee new applications for commodity polymers by introducing visual iridescent properties and hydrophobicity exaltation.

Aggregation behaviour of peptide-polymer conjugates containing linear peptide backbones and multiple polymer side chains prepared by nitroxide-mediated radical polymerization

A series of peptides with an alternating sequence of alkoxyamine conjugated lysine and glycine residues were synthesized by classical solution phase peptide coupling. The resulting peptides containing up to eight alkoxyamine moieties were used as initiators in nitroxide-mediated polymerization (NMP) to obtain peptide-polymer conjugates with well defined linear peptide backbones and a defined number of polymeric side chains. Polymerization of styrene and N-isopropylacrylamide (NIPAM) occurred in a highly controlled fashion. Molecular weight and polydispersity index (PDI) were determined by gel permeation chromatography (GPC). Aggregation behaviour of these hybrid materials was investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM). Depending on composition, number and length of the polymer side chains, the conjugates aggregate to different topologies. Whereas peptide-polystyrene conjugates may aggregate to so called honeycomb structures, peptide-poly-N-isopropylacrylamide conjugates show differentiated aggregation behaviour.