Simple Solvent Evaporation Method Research Articles

Hierarchical structures based on self-assembled diblock copolymers within honeycomb micro-structured porous films

This article details the preparation of hierarchically ordered microporous films using the so-called breath figure approach combined with the self-assembly of well-defined poly(n-butyl acrylate)-block-polystyrene or poly(tert-butyl acrylate)-block-polystyrene copolymers synthesized by nitroxide-mediated polymerization. The first level of organization was the hexagonal pattern of pores at the micrometre length scale leading to iridescence properties and surface hydrophobicity of the honeycomb structured films. Optical microscopy with the corresponding 2-Dimensional Fast Fourier Transform highlighted the ordering of the pores over a large scale (∼1 cm2). The second level of structuring was provided by the diblock copolymers chosen for their ability to self-assemble into ordered nanophases. The nanoscale morphology of both the honeycomb films and the corresponding thermally annealed continuous films was systematically investigated by atomic force microscopy (AFM) and small angle neutron scattering (SANS). The film characterization revealed a nanostructuration of the acrylate-based coil–coil diblock copolymer within the walls of the highly ordered microporous films obtained via a simple solvent evaporation method under humid atmosphere. The four synthesized diblock copolymers exhibited different macromolecular features with respect to the Flory–Huggins interaction parameter, the glass transition temperature of each block and the weight fraction of each monomer that influenced the quality of either the micropores structuration or the nanophase segregation.

Hierarchical structures in AB/AC type diblock-copolymer blend particles

This paper describes the first preparation of diblock-copolymer blend particles with hierarchical inner structures. AB/AC type diblock-copolymer blend particles were successfully prepared by a simple solvent evaporation method. The inner phase separation structures can be controlled by changing the molecular weight combinations of common polymer segments. Furthermore, the one-to-one blend of two diblock-copolymers formed Janus particles with two different domains of microphase separation. Pd ions were successfully introduced into the particles with the onion-like structure. These organic-inorganic composite particles can be used as a novel class of nanomaterials applicable to photonics and electronics.

Photoluminescent Honeycomb Films Templated by Microwater Droplets

The europium polyoxometalate anion, [EuW(10)O(36)](9-), can be transferred from an aqueous phase into a chloroform phase through encapsulation by dioctadecyldimethylammonium (DODMA(+)). The formed (DODMA)(9)[EuW(10)O(36)] complexes can self-assemble into ordered, uniform porous honeycomb films by using a simple solvent-evaporation method at the air/water interface without any extra moist airflow. TEM, SEM, and AFM observations show porous morphologies with pores having a diameter of about 2 microm and a wall depth of about 0.8 microm. The microlamellar structure and crystalline nanoaggregates of (DODMA)(9)[EuW(10)O(36)] complexes in films are characterized by XRD measurements and high-resolution TEM observations. During self-assembly into porous honeycomb films, it is speculated that the cooled microwater droplets that are induced by the quick evaporation of chloroform act as the templates for pores and that (DODMA)(9)[EuW(10)O(36)] complexes are deposited around pores. Because of the intrinsic fluorescence of [EuW(10)O(36)], the photoluminescent porous honeycomb films of (DODMA)(9)[EuW(10)O(36)] complexes can emit fluorescence when they are excited by UV light. It is expected that this will meet more requirements of new materials for fluorescence, separation membranes, microstructured electrode surfaces, containers, and reactors.

Polymeric Nano-half-shells Prepared by Simple Solvent Evaporation Method

Polymeric Nano-half-shells Prepared by Simple Solvent Evaporation Method

Formation mechanism and morphology modulation of honeycomb hybrid films made of polyoxometalates/surfactants at the air/water interface

Highly ordered honeycomb hybrid films of nanometer-scale polyoxometalates and surfactants were fabricated by a simple solvent-evaporation method at the air/water interface. A good template by micrometer water droplets which are condensed from water vapor because of the quick evaporation of organic solvents plays an important role in the self-patterning of honeycomb films. The morphologies of the thin films can be modulated by the solvent volatility which can not only influence the pore size of the film but also determine whether or not a regular porous structure can be achieved at all. The faster the volatility of organic solvents, the smaller the pores of films. Higher hydrophobicity and larger surface coverage which are induced by the surface encapsulation of a polyoxometalate by cationic surfactants with longer double carbon chains are beneficial to the organization of porous structures. It is also found that the morphologies of the thin films can be changed when the thin films are dropped at different supporting solution interfaces. It is well demonstrated that the morphologies of the fabricated hybrid films are modulated by appropriate controls.

Polymeric Nano-half-shells prepared by Simple Solvent Evaporation Method

F127 (poloxamer) to the organic phase. Generally, half-shells are not thought to be produced sponta-neously, because of their high surface tension. Thus, polox-amer seems to play a key role in generating the thermodynami-cally unfavorable structure of nano-half-shells. PLGA nanoparticles were prepared with an organic phase of methylene chloride containing various amounts of polox-amer (0, 0.5, 1.0, 1.5, 2.0 and 2.5%; w/v) respectively with 5% (w/v) PLGA (50:50, Mw 28,032) to verify whether poloxamer could affect the nanostructures. The oil-in-water emulsion was produced by using an ultrasonic processor to emulsify 4 mL of methylene chloride solution into 40 mL of 1% (w/v) poly(vi-nylalcohol) (Mw 30,000~ 70,000) aqueous solution and then stirred for 12-18 hours at room temperature to evaporate meth-ylene chloride. After evaporation, the solidified PLGA nano-particles were washed twice with distilled water by cen-trifugation at 20,000 rpm for 10 minutes, and lyophilized.

Fabrication micro-tube of substituted Zn–phthalocyanine in large scale by simple solvent evaporation method and its surface photovoltaic properties

Micro-tubular structure of tetra(2-isopropyl-5-methylphenoxy) substituted Zn–phthalocyanine (T2) has been obtained in large scale by simple solvent evaporation method. FE-SEM micrographs indicate that most of the micro-tubes are in hollow rectangular shape. XRD measurement demonstrated that the walls of the micro-tubes are arranged in highly ordered nanoscopic structure. Both the XRD measurement and the UV–vis absorption spectrum of the micro-tubes indicated an H-aggregate of the substituted Zn–phthalocyanine molecules (2) in the micro-tubes. Formation mechanism of micro-tube has been proposed. Field-induced surface photovoltage spectrum (EFISPS) inferred that (T2) has p-type character.

A Porous ITO Nanoparticles Modified Electrode for the Redox Liquid Immobilization

AbstractTin‐doped indium oxide (ITO) nanoparticles (ca. 20 nm in diameter) were deposited onto electrode surfaces employing a simple immersion, withdrawal and solvent evaporation method. The resulting ITO films are irregularly packed and highly porous and they promote electron transport. When water insoluble redox liquids are immobilized within the porous film efficient electrochemical reactions occur at the solid‐liquid and at liquid‐liquid interfaces. Scanning electron microscopy reveals a macroscopically uniform surface of the deposit. The thickness of the film estimated by atomic force microscopy is proportional to the number of deposited layers with a thickness increase per single immersion and withdrawal step equal to approximately 60 nm. However, the films are deposited non‐uniformly and the thickness only provides an average parameter. The results of voltammetric experiments performed in aqueous electrolyte solution indicate good adhesion and wetting of the deposit. The surface electroactivity towards the electrooxidation of ferrocenedimethanol provides highly reversible responses without any blocking effects. The ITO nanoparticle modified electrode surface was impregnated with nanomole amounts of a hydrophobic redox liquid, tert‐butylferrocene, and then immersed in the aqueous electrolyte solutions. The value of the voltammetric peak current and the efficiency of the multi‐phase electrode process improved proportional to the number of immersion and withdrawal steps from ITO nanoparticles suspension. This improvement is also observed after further electrode modification with a hydrophobic thin film via sol‐gel processing of methyltrimethoxysilane. In this case the porous film at the electrode surface can be surface modified to provide affinity to certain liquids or analytes.