Bone cell viability on methacrylic acid grafted and collagen immobilized porous poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate)

Porous poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) (PHBV) film was prepared by solute leaching of salt/PHBV cast film. The surface chemistry of the PHBV membrane was modified by performing graft polymerization of methacrylic acid (MAA) on ozone treated porous PHBV film, followed by immobilization of type I collagen. The surface characteristics of the modified and nonmodified porous films were measured by water contact angle. The rat osteosarcoma cell line UMR‐106 osteoblast like cells were used as model cells to evaluate the cell viability on surfaces. The initial cell attachment, growth pattern, and proliferation as measured by MTT assay were used to evaluate the bone cell viability on the modified and nonmodified films. Among the PHBV films studied, the nonmodified porous PHBV and the porous PHBV film type I collagen dip coated showed no significant difference in cell attachment and proliferation, while the porous PHBV membrane that was collagen immobilized after MAA grafting showed considerable activity of osteoblast like cells. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1916–1921, 2005     

Superhydrophobic and Low‐k Polyimide Film with Porous Interior Structure and Hierarchical Surface Morphology

Porous interior structured polyimide (PI) films with a hierarchical surface are fabricated from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 4,4′‐oxydianiline by a water vapor induced phase separation process under a humid environment. Superhydrophobic properties with a water contact angle of 161° are obtained using the hierarchical surface morphology, which can be adjusted from flower‐like to wrinkle‐shape particles facilely by changing the relative humidity. The dielectric constant (k) of the PI film decreases sharply from 2.8 (film prepared under dry conditions) to ≈1.9 (film prepared under humid conditions) because of the interior porous structure and fluorine‐containing framework. Both a low‐k and superhydrophobicity are very important parameters for PI films in microelectronic and insulating applications.     

Inducing surface porosity in aqueous‐quenched,microporous Nylon 11 and Nylon 12 films

Nylon 11 and Nylon 12 have been studied for many years for the purpose of fabricating microporous films. Unfortunately, these polymers have somewhat unique properties that prevent the films from exhibiting porous surfaces when their solutions undergo thermally induced phase separation by quenching in water. Without surface pores, these films have limited utility as water purification membranes. In this work, application of high temperature diluent coatings to the surface prior to quenching is shown to enable the formation of surface porosity in Nylon 11 and Nylon 12 films. Furthermore, the pore sizes achieved are suitable for ultrafiltration applications. Following successful lab‐scale coating experiments, the effects of coating thickness, temperature, and solvent type on surface morphology are demonstrated over five film extrusion trials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44695.     

Fabrication of honeycomb‐structured porous films from poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) via the breath figures method

Formation of porous films from poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) using the breath figures (BF) method was investigated by evaporating solutions in chloroform in humid air and examining film structure using optical and scanning electron microscopy (SEM). BF films were successfully fabricated from PHB (M_w = 486,000 g/mol) and displayed hexagonal arrays of pores, which varied in diameter (D = 7–2 μm) with solution concentrations (0.5–2.00%). SEM of fractured films also showed subsurface closed nano‐pores (D = 500–700 nm). BF films cast from PHBV (5% HV) formed arrays with smaller pores and apparent surface defects. Differential scanning calorimetry showed that porous PHB and PHBV films produced using the BF method were more crystalline than nonporous solvent cast films of PHB and PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Surface differences and solute permeability in films of certain acrylic–methacrylic ester polymers

The influence of certain aspects of film surface on the diffusion of urea in aqueous solutions through films cast from two acrylic–methacrylic ester polymers has been investigated. Greater rate of permeation by urea occurred in films of both polymers when the lower surface (that in contact with the substrate during casting) was the entry surface for urea than when the upper surface (that in contact with the atmosphere during casting) was the entry surface. Furthermore, this difference between the upper and lower surfaces was more marked in film cast from one of the polymers; and scanning electron micrographs of films of the two polymers revealed differences in gross surface structure. Changes occurred in both upper and lower film surfaces during exposure to urea solution, the lower surface developing larger pores on exposure while smaller pores were observed on the upper side after exposure. The upper-lower surface differences occurred in films of both polymers. The less hydrophilic film (Eudragit RS100) was associated with lower overall permeation rate for urea and smaller postpermeation mean pore size on both upper and lower surfaces than the more hydrophilic film (Eudragit RL100). The relationship between permeability and changing microscopic appearance of the surfaces is discussed and pictorial evidence of porous structure presented.     

Surface of poly(ethylene terephthalate/isophthalate) copolyesters studied by atomic force microscopy

An atomic force microscope (AFM) operating in Tapping™ and contact modes has been used to study the surface topography and the molecular organization of poly(ethylene terephthalate) (PET) films containing 2% (PET‐2I) and 10% (PET‐10I) isophthalate, and of injection/blow molded bottles containing 2.6% (PET‐2.6I) and 10% isophthalate. Large‐scale (15‐μm × 15‐μm) AFM images have shown that both surfaces are fairly flat and heterogeneous in nature, often containing inclusions. Whereas the PET surface appears to be formed mainly by microfibrils, isophthalic acid (IPA) incorporation at the 2–10 mol % level gives the surface a granular appearance. The IPA‐containing PET surfaces are frequently coated by a lacelike film consisting of submicron “beads” joined together by filaments. These “strings of beads” form bundles and can also connect bundles. AFM images of PET‐2I closely resemble those generated for PET films. By contrast, the lacelike structure becomes a dominant feature of the PET‐10I surface. The level of inclusions observed on film surfaces appears to correlate with the levels of extractable oligomers present in the polymers. Nanometer‐scale AFM images of PET‐10I exhibit surfaces composed of short stacks of plates or rods, with 30–50‐nm voids or pores between these stacks. Whereas surface deposits of what we suggest is most likely an oligomer correlates with isophthalate concentration, we see no gross structural features in PET‐2I and PET‐10I that explain the observed improvement in gas diffusion barrier in these polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 750–762, 2001     

Fabrication of super water repellent silver flake/copolymer blend films and their potential as smart fabrics

A facile technique is demonstrated for the fabrication of super water repellent co‐polymer blend‐silver composite films from fatty acid surface functionalized fine silver flakes. Initially, high concentrations of surface functionalized silver flakes were dispersed in poly(vinyl chloride‐co‐vinyl acetate‐co‐vinyl alcohol) copolymer in solution to form electrically conducting adhesives/paints (ECAs) with a bulk resistivity of ∼3 × 10⁻⁵ Ω cm. The solvent‐borne ECAs were then blended with a water‐dispersed perfluoromethacrylate copolymer (Zonyl 8740) using a simple solvent‐inversion process to obtain super water‐repellent colloidal copolymer blend‐silver emulsions. The colloidal emulsions could be spray‐deposited on a number of fibrous substrates including fabrics and paper. A particular example is demonstrated herein by spray‐depositing these emulsions onto molten paraffin wax‐based laminates (60°C), which were partially impregnated into fabrics to fabricate highly water repellent, flexible, and thermoresponsive fabrics. A paraffin wax/polyolefin blend base film was used for the purpose. The surface topology of the superhydrophobic copolymer/silver composite films displayed fractal‐like hierarchical structures ideal for self‐cleaning hydrophobicity. On relatively low‐absorbent permeable porous surfaces such as cellulosic films (paper) impregnated with wax/polyolefin films, self‐cleaning ability of the coatings was maintained even for temperatures at which paraffin wax component of the laminated film was molten indicated by low‐water roll‐off angles. Hence, the composites have excellent compatibility with organic phase change materials such as paraffin wax and wax/polyolefin blends, and they can be used to fabricate nonwetting, thermoregulated, and electroactive fabrics. Antimicrobial properties of silver offer additional advantages for potential biomedical applications. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Breath figure templated semifluorinated block copolymers with tunable surface properties and binding capabilities

Patterning of functionalized polymeric surfaces enables the adjustment of their characteristics and use in novel applications. We prepared breath figure (BF) films from three semifluorinated diblock copolymers, which all are composed of a polystyrene block and a semifluorinated one to compare their surface properties. “Click” chemistry was employed to one of the polymers, containing a poly(pentafluorostyrene) block to incorporate hydrophilic sugar or carboxylic acid moieties. The structure of the polymer alters the obtained porous morphology of the films. Contact angle (CA) analyses of the BF films reveals that the surface porosity increases water CAs compared with solvent cast films, and, in the case of hydrophobic polymers, leads to significant increase in the CAs of dodecane. The hydrophobicity of the BF films is further amplified by the removal of the topmost layer which leads in some cases to superhydrophobic surfaces. BF films containing glucose units are hydrophilic exhibiting water CAs below 90°. These glycosylated porous surfaces are shown to bind lectin Con A‐FITC or can be labelled with isothiocyanate marker. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41225.     

Effect of water saturation on gas slippage in circular and angular pores

A unified model for gas slip flow through circular and angular pores in both single phase flow and two‐phase flow conditions is developed, and the effect of water saturation on gas slippage factors in different pore shapes are revealed. For circular pores, the water saturation retains as thin film binding on pore surfaces without changing the shape of the cross section, and the hydraulic diameters continuously reduce as water saturation increases, directly leading to an increase in the slippage factor. However, for angular pores, the water saturation retains as both films at boundaries and condensations at corners, and the film‐water and corner‐water gradually change their cross‐section shape (from sharp corners to round corners), which further affects the gas slip behavior. Due to the presence of round corners, the ratio of the cross‐sectional area and perimeter, which can also be regarded as the reciprocal of a specific surface area, can even increase at a low water saturation condition. Thus the collisions between gas molecules and pore boundaries weaken, resulting in a slight reduction in the gas slippage factor. This interesting finding in the angular pore case directly explains the contradiction of the published experimental results with the general knowledge (i.e., the gas slip factor always increases as water saturation increases). Thus, the validity of the common assumption regarding actual porous media as capillaries with a circular cross‐section must be considered more carefully. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3529–3541, 2018     

A facile method of preparing highly porous polylactide microfibers

Highly porous polylactide (PLA) microfibers with the diameter of about 14 µm are prepared by melt‐spinning and stretching core–sheath PLA fibers (CSF) and sequent treatment of ethyl acetate. The resultant pores are regular and elliptical. The average values of length of major axis and minor axis of elliptical pores are around 1 and 0.5 μm, respectively. This new and facile method can prepare porous PLA fibers on industrial scale, and nearly overcome all the shortcomings of melt‐spinning and stretching method. In addition, highly porous structure in partially oriented poly(l ‐lactide) yarn (POY) can be also formed by treating POY using ethyl acetate. The obtained pores are irregular. In addition, the formation mechanism of pore structure in CSF is different with the one in POY. The former is the separation of row‐nucleated lamellae induced by stretching while the latter is swelling and subsequent solvent‐induced crystallization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45860.     

Wettability of a microgrid‐structured polymer film with microfabrication utilizing the stick–slip phenomenon

A microgrid structure was formed on the surface of a polyethylene terephthalate (PET) film with an original microfabrication method (termed SS processing) utilizing the stick–slip (SS) phenomenon, and the effect of this surface structure on wettability was evaluated. Microgrid‐structured films could be fabricated by two‐axis SS processing. Moreover, an arbitrary parallelogram microgrid structure could be formed by selecting the direction of the second SS processing with respect to that of the first SS processing. Both water contact angle and water sliding angle of the SS‐processed film were larger than that of the PET film. Hence, the SS‐processed film showed a petal‐like effect. Furthermore, the water sliding angle of the microgrid‐structured film showed anisotropy due to the pinning effect derived from the microgrid structure. As a result, it is revealed that a hydrophobic PET film with a petal‐like effect and anisotropic wettability can be fabricated by SS processing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45140.     

Transformation of self‐assembled structures from spherical aggregates in solution to a network structure on a two‐dimensional surface

Self‐assembled films of brush‐like amphiphilic copolymers with varying hydrophobic contents (fc₁₂, 10–90 mol %) were prepared on glass slides. In addition, the surface tension and contact angles of solutions of these copolymers were also investigated. By combining the data obtained investigating the morphologies of the films, with the micropolarities, dimensions, and morphologies of the copolymer aggregates in solution phase, it was attempted to illustrate how the self‐assembled structures would adapt to a change in their surrounding environment from a three‐dimensional space in the solution phase into a two‐dimensional solid surface. The copolymer chains underwent inter‐ and intramolecular hydrophobic association simultaneously in the solution phase. When fc₁₂ was increased, the stronger hydrophobicity led the side‐chains that were attached to the same backbone to become packed together, and this intramolecular association caused the copolymers to form smaller and more compact spherical aggregates. The solutions of these smaller and more compact spherical aggregates exhibited a lower surface tension and better wetting behavior on glass surfaces. In addition, these solutions ultimately formed thinner and more orderly network‐based porous films on glass surfaces. The observations described in this report revealed that the copolymer assemblies exhibited a morphological transformation from spherical aggregates in solution to a network structure when the copolymer became confined to a solid surface. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41945.     

Factors controlling surface morphology of porous polystyrene membranes prepared by thermally induced phase separation

A special device for preparing porous polymer membranes through a thermally induced phase separation (TIPS) process was designed and machined; it included a solution container, a membrane‐forming platform, a coldplate, a temperature‐decreasing system and a temperature‐supervising system. Polystyrene was selected as the model polymer from which to prepare porous membranes using the device due to its better understood TIPS and good biocompatibility with cells. The major factors controlling surface morphology and cell size, ie volume fraction of polystyrene (ϕ₂), quench rate and solvent‐removing methods, were studied. Fixing the coldplate temperature, when ϕ₂ is as low as 0.045, provokes the formation of round pores on both the bottom and top surfaces of the membrane; when ϕ₂ = 0.16 no pores are formed on either surface; when ϕ₂ = 0.087 pores form on the top surface, but not on the bottom surface. When ϕ₂ = 0.087 the cell size is very small or no pores are formed on the bottom surface, whereas the top surface shows a regular decrease of the pore sizes and an increase of the pore number and pore area, along with a decrease of the coldplate temperature. The side near the coldplate is dense, and the dense layer aligns along the coldplate, while the side away from the coldplate is like a porous foam, the shape of which is isotropic and the surfaces are interconnected with each other three dimensionally. On the top surface of a membrane obtained by ethanol extraction, the cell size is enlarged and the cell number reduced, but the surface morphology and the whole area remained almost the same when compared to samples obtained by freeze drying in the same membrane‐forming conditions. The isotropic, uniformly distributed and round pores suggest that the mechanism of phase separation is a spinodal liquid–liquid decomposition under our research conditions. © 2000 Society of Chemical Industry     

Surface,Biocompatible and Hemocompatible Properties of Meta‐Amorphous Titanium Oxide Film

This study involved modification of the surface of Ti by micro‐arc oxidation (MAO). A rough and porous oxide film with good wettability was formed on the Ti surface. This MAO‐treated film exhibited a meta‐amorphous structure comprising crystalline anatase and rutile TiO₂ as well as amorphous phases. In addition, the incorporation of Ca and P in the MAO‐treated film was induced by micro‐arc discharge. The biological responses of the MAO‐treated surfaces were evaluated by observing the adhesion of MG63 osteoblast‐like cells and platelets. The MAO‐treated Ti had a considerably better biocompatibility and blood compatibility than untreated Ti.     

Flexible patch‐type hydrochromic polydiacetylene sensor for human sweat pore mapping

Owing to their stimulus‐responsive colorimetric property, polydiacetylenes (PDAs) have been extensively investigated in the context of sensor applications. Incorporation of PDAs in matrix polymers can be utilized to add additional advantageous features into these sensors, like processability, mechanical flexibility, and mass production capability. In the current investigation, a new type of hydrochromic PDA sensor, which consists of a polydiacetylene‐polyethylene oxide (PDA‐PEO) composite film, was developed. The results of the study demonstrate that the hydrochromic film, which displays a blue‐to‐red color transition upon hydration, can be used to map human sweat secreting pores. The hygroscopic PEO component of the system enables local sweat to penetrate into the sensor film. The highly π‐conjugated, imidazolium group containing PDA in the system functions as the hydrochromic material, which undergoes a blue‐to‐red transition and a corresponding fluorescence turn‐on in response to contact with a nanoliter of sweat. In response to deposition of a fingerprint, water arising from individual sweat secreting pores promotes a change that leads to formation of a discrete fluorescence microdot pattern. The most important feature of the new sensor film is mechanical flexibility that gives it with the ability to be utilized to map sweat pores located on highly curved skin surfaces, such as those found on palms, soles, backs, and faces. Accordingly, this attribute offers critical advantages in cosmetics and biomedical applications because it enables recognition of active and inactive sweat pores on curved skin surfaces where rigid or paper‐type sweat pore sensors are ineffective. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44419.     

Rapid formation of flexible silk fibroin gel‐like films

Flexible silk fibroin gel‐like films with microporous morphology were prepared from B. mori silk fibroin fibers directly solubilized in formic acid/CaCl₂ solvent. These films were characterized by several analysis techniques to determine the structure and properties of films. The pore size of gel‐like films can be adjusted through SF concentration and Ca ions concentration. The controllable pore size in gel‐like films was grew from 3–5 μm to 100 μm under the increase of fibroin concentration from 1.0 wt % to 8.0 wt %. At the same time, the water content of silk fibroin gel‐like film decreased from 83.5 ± 3.4% to 68.2 ± 2.6%. With increasing Ca ions contents from 2.0 wt % to 10.0 wt % in dissolution process, the pore size and water content of silk fibroin gel‐like films grew larger, especially its water content values reached 86.2 ± 4.0% at 10.0 wt % Ca ions concentration. At wet condition, the gel‐like film with β‐sheet structure showed higher breaking stress (4.26 ± 0.31 MPa) and elongation (45.45 ± 15.79%) at 8.0 wt % concentration. With the preparation method, the membrane is hydrophilic and the pore size is adjustable, which contributes to high toughness and favorable cell growth environment, suggesting that these silk fibroin gel‐like films can be a potential candidate scaffold for biomedical applications, such as wound dressing, facial mask, contact lenses, etc. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41842.     

Controllable fabrication and catalytic performance of nanosheet HZSM‐5 films by vertical secondary growth

Nanosheet HZSM‐5 film vertically grown on the substrate with the tailorable macro‐ and meso‐pores between the layers of nanosheets is hydrothermally synthesized by seed‐assisted secondary growth method. The as‐prepared nanosheet HZSM‐5 film exhibits reaction rate enhancement up to 312% in catalytic cracking of n‐dodecane as well as twice light olefins selectivity, ascribed to the better mass transfer of reactants in the hierarchical porous structure and the ultra‐thin b‐axis pores of nanosheets. © 2018 American Institute of Chemical Engineers AIChE J, 64: 1923–1927, 2018     

Fabrication of porous thick films using room-temperature aerosol deposition

A novel technique for the rapid room-temperature deposition of porous ceramic, glass, or metal thick films using the aerosol deposition (AD) method is presented. The process is based on the co-deposition of the desired film material and a second water-soluble constituent, resulting in a ceramic-ceramic composite. Following the subsequent removal of water-soluble end member, a network of pores is retained. To demonstrate the process, porous BaTiO₃ thick films were fabricated through co-deposition with NaCl. Microstructural images show the clear development of a porous structure, which was found to enhance the dielectric properties over dense thick films, possibly related to the lower extent of internal residual stress. This simple but highly effective porous structure fabrication can be applied to any film and substrate material stable in water and is promising for the application of AD-processed films in gas sensors, solid oxide fuel cells, and humidity sensors.     

Pre‐Vulcanization of Large and Small Natural Rubber Latex Particles: Film‐Forming Behavior and Mechanical Properties

The pre‐vulcanized large rubber particle (LRP) and small rubber particle (SRP) latices are independently prepared to investigate their film‐forming process and mechanical properties after being cast into films. The surface morphologies and roughness of both LRP and SRP films are found to be dependent on crosslink densities. The networks inside each rubber particle (RP) restrict particle deformation resulting in residual contour of RP within the film surface. For highly crosslinked RP, the collapse of the top surface of the RPs in the LRP films appears to create many “crater‐like” structures within the film surfaces, while they present only protruding particles within the SRP and blend films. This seems to indicate that LRPs are easier to coalesce and form film than SRPs. Additionally, dynamic and mechanical properties and strain‐induced crystallization (SIC) behaviors of the latex films, are effectively enhanced after pre‐vulcanization. The pre‐vulcanized LRP films perform better tensile properties and SIC than the SRP can.     

Hierarchical porous ceramics with multiple open pores from boehmite gel emulsions

Ceramic foam materials with highly porous microstructure are playing vital role in increasing areas, especially for those with requirements for open channels and superior specific surface area. In this work, a simple and versatile approach to prepare ceramic foams with open pores has been proposed, that is gelation of boehmite nanoparticle-assembled emulsions. Notably, hierarchical porous microstructure with open channels and uniform pore structure has been built. High specific surface area up to389.4 m²/g is attainable, making it excellent adsorption material when combining the merit of hierarchical pore structure. Furthermore, lattice-shaped ceramics are prepared via direct ink writing gelled emulsion, displaying the potential of forming lightweight material with complex shape and designable macrostructure. The three-dimensional (3D) printed foams exhibit multiple open pores, which cover length scale from mm scale, to μm scale and nm scale, making them promising materials in several fields like adsorption and gas filtrations, etc.