Honeycomb-patterned polymer films with tunable pore size and regularity of ordered two- or three-dimensional hexagonal arrays have met with widespread interest in recent years in different areas, for instance as separation and superhydrophobic materials. Herein, 2D honeycomb-patterned films of amphiphilic ferrocenyl-based oligomer with cholesterol as side chains were prepared by the breath-figure method on solid surfaces and their surface-wetting behavior were tested. These films can be simply prepared by spreading a mixture of polymer and organic solvents on a solid surface under moist airflow and at an air/water interface without any extra moist airflow. An ordered 2D hexagonal array of pores with monodisperse size distribution can be obtained over a large area by changing various influencing factors, including humidity, wet volume, concentration, selective solvent, and spreading method, which provides a facile route to regulate the morphology of patterned porous films. The surface-wetting behavior indicates that a higher hydrophobicity of the ferrocenyl-based oligomer honeycomb films can be obtained by modulating the pore size and regularity. It is expected that this could promote the potential application of ordered porous polymer films in hydrophobic materials and biochemistry. 相似文献
In this Article, we addressed a facile method for the fabrication of porous polyimide film with an ordered surface based on the solvent-evaporation-assisted in situ self-assembly of polyamic acid (PAA, precursor of polyimide) and silica microspheres during vacuum-drying of PAA/silica colloid solution. Hydroxyl groups on the surface of silica microspheres have strong hydrogen-bonding with PAA chains, which improve the dispersion of silica microspheres in PAA/DMF solution and further help the self-assembly of PAA/silica colloid solution via solvent evaporation. The approach is simple, neither the preparation of special template nor complex preparation process and precise control over condition is necessary. Furthermore, the method could be employed for mass production of ordered porous polyimide films, and by changing the content and size of silica microspheres, the pore size and porous structure of the porous polyimide films could be tunable. The wettability behavior of the as-prepared porous polyimide films is also studied; the ordered surface topography of the porous polyimide films could change the wettability from hydrophilicity to hydrophobicity. 相似文献
Self-assembly processes and subsequent photo-cross-linking were used to generate cross-linked, ordered microporous structures on the surfaces of well defined four-arm star-shaped poly(D,L-lactide) (PDLLA) thin films. The four-arm star-shaped PDLLAs were synthesized using an ethoxylated pentaerythritol initiator. Solutions of the PDLLAs were cast in a humid environment, and upon solvent evaporation, ordered honeycomb structures (or breath figures) were obtained. Correlations between molar mass, polymer solution viscosity, and pore dimensions were established. The average pore dimension decreased with increasing polymer solution concentration, and a linear relationship was observed between relative humidity and average pore dimensions. Highly ordered microporous structures were also developed on four-arm star-shaped methacrylate-modified PDLLA (PDLLA-UM) thin films. Subsequent photo-cross-linking resulted in more stable PDLLA porous films. The photo-cross-linked films were insoluble, and the honeycomb structures were retained despite solvent exposure. Free-standing, structured PDLLA-UM thin films were obtained upon drying for 24 h. Ordered microporous films based on biocompatible and biodegradable polymers, such as PDLLA, offer potential applications in biosensing and biomedical applications. 相似文献
Organic gels have been synthesized by sol–gel polycondensation of phenol (P) and formaldehyde (F) catalyzed by sodium carbonate
(C). The effect of synthesis parameters such as phenol/catalyst ratio (P/C), solvent exchange liquid and drying method, on
the porous structure of the gels have been investigated. The total and mesopore volumes of the PF gels increased with increasing
P/C ratio in the range of P/C ≤ 8, after this both properties started to decrease with P/C ratio for P/C > 8 and the gel with
P/C = 8 showed the highest total and mesopore volumes of 1.281 and 1.279 cm3 g−1 respectively. The gels prepared by freeze drying possessed significantly higher porosities than the vacuum dried gels. The
pore volume and average pore diameter of the freeze dried gels were significantly higher than those of the vacuum dried gels.
T-butanol emerged as the preferred solvent for the removal of water from the PF hydrogel prior to drying, as significantly
higher pore volumes and specific surface areas were obtained in the corresponding dried gels. The results showed that freeze
drying with t-butanol and lower P/C ratios were favourable conditions for the synthesis of highly mesoporous phenol–formaldehyde
gels. 相似文献
In our previous work, the CdS nanoparticles/cellulose films exhibited significantly high photocatalytic H2 production efficiency under visible light irradiation than the ordinary CdS photocatalyst. In present paper, the CdS nanoparticles
were synthesized in situ in pores of the regenerated cellulose substrate and the porous structure of cellulose, formation
of the CdS nanoparticles and interactions between CdS and cellulose matrix in the composite films were investigated deeply.
The experimental results indicated that the micro-nano-porous structure of the cellulose matrix could be used easily to create
inorganic nanoparticles, which supplied not only cavities for the formation of nanoparticles, but also a shell (semi-stiff
cellulose molecules support the pore wall) to protect their nano-structure. When the cellulose films with porous structure
at wet state were immersed into inorganic ions solution, the ions interacted immediately with the –OH groups of cellulose,
and then transformed into inorganic composite via another treatment, finally inorganic nanoparticles formed during the dry.
The pore size of the cellulose matrix decreased from 180 nm (at wet state) to about 18 nm (at dry state), leading to the formation
of nanoparticles. The results revealed that the CdS nanoparticles with a mean particle diameter about 6 nm were dispersed
well, and were immobilized tightly in the cellulose matrix, resulting in a portable photocatalyst with high efficiency for
photocatalytic for H2 evolution. This is simple and “green” pathway to prepare the organic–inorganic hybrid materials. 相似文献
Monodisperse porous polymer particles in the size range of 10 μm in diameter were prepared via seeded emulsion polymerization. Linear polymer (polystyrene seed) or a mixture of linear polymer and solvent or nonsolvent were used as inert diluents. The pore diameters of these porous polymer particles were on the order of 1000 Å with pore volumes up to 0.9 mL/g and specific surface areas up to 200 m2/g. The physical features of the porous polymer particles depended on the diluent type and the crosslinker content, as well as the molecular weight of polymer seed particles. By varying the molecular weight of the linear polymer, monodisperse porous polymer particles with different pore size distribution could be synthesized. Polymer seed with a low degree of crosslinking instead of linear polymer could also be used to prepare monodisperse porous polymer particles with smaller pore volume and pore size. 相似文献
In this study, porous poly(L-lactic acid) (PLLA) films are prepared via a facile and low-cost approach using poly(ethylene glycol) (PEG) and solution casting. In contrast to most studies, the PEG/PLLA samples are further processed under different crystallization conditions (i.e., different PLLA crystallization temperatures) before PEG removal. As the PEG is extracted via solvent at higher PLLA crystallization temperatures, the resultant PLLA samples have larger pores. Interconnected fibrillar-shaped pores are found in all systems, and the fibrillar-porous structure width is ~150 nm–1.2 μm, as observed via scanning electron microscopy. These pore sizes can be tuned by adjusting the blend composition and crystallization temperature. In addition, PEG/PLLA blends are subjected to hydrolytic degradation analysis according to their crystallization conditions. Higher PLLA crystallization temperature yields higher PLLA crystallinity and larger pores, as well as reduced surface interaction with water. Therefore, the PLLA degradation rate is decreased. The developed PLLA films have potential applications in drug delivery and tissue engineering. 相似文献
Monodisperse porous styrene-divinylbenzene copolymer particles were prepared via seeded emulsion polymerization using a mixture of linear polymer (polystyrene seed) and non-solvent as inert diluent. Experimental evidence was presented to describe the mechanism of formation of porous polymer particles during the copolymerization and solvent extraction stages, in which porosity was a consequence of phase separation in the presence of diluents. Pore structure formation was investigated by changes in copolymerization kinetics, gel content, crosslinking density, particle morphology, surface area, pore volume, and pore size distribution. The process of copolymerization was presented, based on the concepts of production, agglomeration, and fixation of the interior gel microspheres of polymer particles. A portion of linear polymer used as diluent was found to participate in the network structure while the porous matrix was built-up. The influence of the removal of the linear polymer from the matrix pores during the solvent extraction process on the porous structure was also discussed. 相似文献
Ordered porous films of polymers with uniform pore size and ordered porous structure are extensively applied in many fields such as separation, biology, photoelectric devices, templates, and other fields, which is the current research frontier in the field of porous films. Among different methods of preparing ordered porous films, the method of breath figure (BF) has attracted much attention due to its simplicity and adjustability. Many factors have been proved to influence the structure of the porous films by the BF method and the used polymer is the most important one. Recently, under the background of energy crisis and environmental pollution, polymers from biomass have received a lot of attention because of their advantages of low carbon, green, good biocompatibility, and easy modification. Up to now, a large number of porous films of biomass-based polymers including cellulose, polylactic acid, and urushiol-based polymers have been prepared by the BF method. Therefore, this article is to make a detailed review of the physicochemical modification of biomass-based polymers, the preparation of ordered porous films via BF and their applications. The method of BF is firstly introduced. The research progress of porous films of biomass-based polymers including cellulose, polylactic acid, and urushiol-based polymers prepared by the BF method is then reviewed. Finally, this review highlights the use of honeycomb films as cell culture substrates, drug delivery, wound dressings, optoelectronic devices and mimicking woody cell walls. The prospects for the development of porous films of biomass-based polymers are proposed. Future research could focus on the preparation of ordered, functional, and biocompatible porous films with smaller pore sizes for more applications in different fields, such as separation, tissue engineering, and controlled release of drugs.
Graphic abstract
Ordered porous films of biomass-based polymers via physical and chemical modification would be prepared by the breath figure method for different applications.
The morphology of polymers prepared through the photoinduced polymerization of oligo(carbonate dimethacrylate) in the presence
of different nonpolymerizable additives (methanol, dinonyl phthalate, hexane, toluene, benzene, and carbon tetrachloride)
is studied via the method of atomic force microscopy. Depending on the nature and concentration of an additive, the photoinduced
polymerization of the above composite systems is shown to be accompanied by microphase separation and formation of a porous
polymeric material. In the case of methanol, homogeneous porous structures with characteristic pore sizes of several hundred
nanometers are formed. In the case of dinonyl phthalate, the characteristic pore sizes lie below 100 nm. The synthesized porous
polymers can sorb both polar and nonpolar solvents. The photoinduced polymerization of an oligomer in the medium of toluene,
benzene, or carbon tetrachloride leads to the formation of polymer nanoparticles whose dimensions are controlled by the nature
of a solvent. 相似文献
Spin-coated films of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) and carboxymethylcellulose
acetate butyrate (CMCAB) have been characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements.
The films were spin-coated onto silicon wafers, a polar surface. Mean thickness values were determined by means of ellipsometry
and AFM as a function of polymer concentration in solutions prepared either in acetone or in ethyl acetate (EA), both are
good solvents for the cellulose esters. The results were discussed in the light of solvent evaporation rate and interaction
energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology,
surface roughness and surface wettability were also investigated.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Macroporous gels (MGs) with a broad variety of morphologies are prepared using the cryotropic gelation technique, i. e. gelation at subzero temperatures. These highly elastic hydrophilic materials can be produced from practically any gel-forming system with a broad range of porosity extending from elastic and porous gels with pore sizes up to 1.0 microm to elastic and sponge-like gels with pore sizes up to 100 microm. The versatility of the cryogelation technique is demonstrated by use of different chemical reactions (hydrogen bond formation, chemical cross-linking of polymers, free radical polymerization) mainly in an aqueous medium. Appropriate control over solvent crystallization (formation of solvent crystals) and rate of chemical reaction during the cryogelation allows the reproducible preparation of cryogels with tailored properties. Different approaches, such as chemical modification of reactive groups, grafting of the pore surface with an appropriate polymer, or direct copolymerization with functional monomers are used for control of the surface chemistry of MGs. Typically, MGs with pore sizes up to 1.0 microm are produced in the shape of beads and MGs with pore size up to 100 microm are prepared as monoliths, discs, and sheets. The difference in porous structure of MGs defines the main applications of these porous materials. Elastic beaded MGs are mostly used as carriers for cell and enzyme immobilization or for capture of low-molecular weight targets from particulate-containing fluids in expanded-bed mode. However, the elastic and sponge-like MG monoliths with interconnected pores measuring hundreds of mum have been successfully used as monolithic columns for chromatography of particulate-containing fluids (crude cell homogenates, viruses, whole cells, wastewater effluents) and as three-dimensional scaffolds for mammalian cell culture applications. 相似文献
This paper presents the characterization of TiO2 nanostructures obtained by low-voltage anodization using alternate current electrochemical microscopy (AC-SECM) and photoelectrochemical
(PEC) measurements. TiO2 nanostructures were obtained from the exposure of titanium foils to several aqueous acidic solutions of hydrofluoric acid + phosphoric
acid at potentials of 1 to 3 V. Scanning electron microscopy, X ray diffraction, and atomic force microscopy studies evidence
the formation of a thin porous amorphous layer (<600 nm) with pore size in the range of 200–1,000 nm. By AC-SECM studies at
different bias, we were able to confirm the unambiguous semiconducting properties of as-obtained porous titania films, as
well as differences in surface roughness and conductivity in specimens obtained at both potentials. The difference in conductivity
persists in air annealed samples, as demonstrated by electrochemical impedance spectroscopy and PEC measurements. Specimens
obtained at 3 V show lower photocurrent and dark current than those obtained at 1 V, regardless of their larger conductivity,
and we proposed it is due to differences on the oxide layer formed at the pore bottom. 相似文献
Aqueous 5 wt% LiOH/12 wt% urea solution pre-cooled to −12 °C has a more powerful ability to dissolve cellulose compared to
that of NaOH/urea and NaOH/thiourea solution system. The influences of the cellulose concentration and coagulation temperature
on the structure, pore size and mechanical properties of the cellulose films prepared from LiOH/urea system were investigated.
The cellulose films exhibited good mechanical properties either at wet or dry state and their pore size and water permeability
at wet state can be controlled by changing the cellulose concentration or coagulation temperature. With a decrease of the
coagulation temperature, the mechanical properties and optical transmittance of the cellulose films enhanced, as a result
of the formation of relative smaller pore size and denser structures. This work provided a promising way to prepare cellulose
films with different pore sizes at wet state and good physical properties at dry state. 相似文献
By utilizing surfactant aggregates as supramolecular templates, mesoporous and mesostructured silicas with highly ordered structures became available. The resulting mesoporous silicas are promising candidates to host various photo- and electro-active species along with catalytically active species, due to their large and controllable pore sizes, highly ordered pore arrangements with low dimensional geometries, and reactive surfaces. We have developed the rapid solvent evaporation method, which is a modified sol-gel process, for synthesizing the mesostructured silica-surfactant films as well as the mesoporous silica films. Supported thin films, self-standing films and bubbles of mesoporous silicas have been synthesized by the rapid solvent evaporation method. The microstructures of the films have also been successfully controlled by changing the synthetic conditions. Taking advantage of the ease of synthetic operation and the transparency and homogeneity of the resulting materials, we have been interested in the introduction of functional units into the mesostructured materials. This paper reports the synthesis of transparent films of titanium- and aluminum-containing nanoporous silicas to modify the surface properties (such as adsorptive and catalytic) of nanoporous silicas. The incorporation of Al led to the formation of cation exchange or acidic sites on the mesopore surface, as revealed by the cationic dye adsorption experiments. The photocatalytic reactions of the Ti-containing nanoporous silica films were also examined. 相似文献
Catalysis, chemical separations, and energy conversion devices often depend on well-defined mesoporous materials as supports or active component elements. Herein, we show that ordered assembled organic surfactant films can directly template porous inorganic solids with surface area exceeding 1000 m(2)/g by infusing the polymers with reactive inorganic vapors, followed by anneal. The specific surface area, pore size, chemical composition, and overall shape of the product material are tuned by choice of the polymer and precursor materials as well as the influsion and postinfusion treatment conditions. X-ray diffraction, infrared spectroscopy, and electron microscopy show that vapor infusion changes both the physical and chemical structure of the starting ordered polymer films, consistent with quantified trends in specific surface area and pore size distribution measured by nitrogen adsorption after film annealing. This method yields porous TiO(2) films, for example, that function as an anode layer in a dye-sensitized solar cell. 相似文献