Variation of the morphology of a carboxylated polymer film by alkali treatment

The variation of the morphology of a carboxylated polymer film cast from tetrahydrofuran solution, in which styrene/methacrylic acid copolymer particles produced by emulsion copolymerization were dissolved, before and after alkali treatment at temperatures higher than the glass-transition temperature was observed with a scanning electron microscope. The treated film had a porous structure. This result provides important evidence for the formation mechanism of the multihollow structure in submicron-sized, carboxylated polymer emulsion particles by the stepwise alkali/acid method and the alkali/cooling method which the authors proposed.     

Macroporous polymer thin film prepared from temporarily stabilized water-in-oil emulsion

We report a simple and convenient method for fabricating ordered porous structure in a polymeric thin film. A temporarily stabilized water-in-oil emulsion, where aqueous droplets were dispersed in the medium of polymer-organic solvent solution, was utilized for the preparation of porous structure. The water-in-oil emulsion was simply prepared by sonicating the mixture of water and polymer-organic solvent solution without any colloid stabilizer. The growth of aqueous droplets was profoundly retarded by dissolving a small amount of sucrose, selectively soluble in the dispersed phase. The prepared emulsion was recovered onto a substrate through dip-coating and subsequently air-dried to get a well-ordered porous polymer film. The polymer content in the polymer solution phase and the compositional ratio of the aqueous phase to the polymer solution phase was optimized to fabricate well-ordered structures.     

Facile method for fabrication of nanocomposite films with an ordered porous surface

This paper presents a novel and facile method for the fabrication of nanocomposite films with ordered porous surface structures. In this approach, a water-borne poly(styrene-co-butyl acrylate-co-acrylic acid)/silica nanocomposite dispersion was synthesized in situ by surfactant-free emulsion polymerization by using 3-allyloxy-2-hydroxy-1-propanesulfonate as a polymerizable surfactant. When this dispersion was dried to form a film at a certain temperature, an ordered porous structure could be directly obtained on the surface of the nanocomposite film. SEM, TEM, and AFM were employed to observe the morphology, and XPS and particle analyzer were used to analyze the surface composition of the ordered porous nanocomposite film and the particle size, respectively.     

Fabrication of Ordered TiO2 Porous Thin Films by Sol-Dipping PS Template Method

Monolayer polystyrene spheres (∼400 nm) array templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS and porous TiO₂ thin films were prepared by using sol-dipping template method to fill TiO₂ sol into the interstices among the close-packed PS templates and then annealing to remove the PS templates. The effects of TiO₂ precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed pore size of the ordered TiO₂ porous thin film depended mainly on PS size and partly on TiO₂ sol concentration. The shrinkage of pore diameter was about 10% for 0.2 M and 20% for 0.4 M TiO₂ sol concentrations. X-ray diffraction (XRD) spectra indicated the porous thin film was anatase structure. The transmittance spectrum showed that optical transmittance of the porous thin film kept above 70% beyond the wavelength of 430 nm. Optical band-gap of the porous TiO₂ thin film (fired at 550^∘;C) was 3.12 eV.     

A polyacrylate prepared using polyurethane surfactants: properties of emulsion and film

The designed polyurethane surfactant (PUS) was used as a macromolecular surfactant for the preparation of polyacrylate emulsion without any other surfactants and stabilizers. The resultant polymer emulsion and film properties were compared with those of the emulsion prepared with sodium dodecyl sulfate (SDS). Long shelf-life of the polymer emulsion can be achieved at proper composition. Polymer particles show core-shell and nano-scale structure with narrow distribution. Thermoanalysis results show phase separation in the polymer film, which leads to gloss decrease with the PUS content increase. Such polymer films show good water resistance and mechanical strength.     

Ordered porous ZnO thin films formed by dip-coating method using PS templates

Monolayer polystyrene spheres (∼400 nm) array templates were assembled orderly on clean glass substrates by dip-coating method from emulsion of polystyrene (PS). Porous ZnO thin films were also prepared by dip-coating method to fill the interstices among the close-packed PS templates with ZnO and annealing to remove the PS templates. Results showed that ZnO sol concentration and dipping time of PS templates in sol had great influences on the morphology of ordered porous ZnO thin films. There was a shrinkage ratio of about 30% from pore to PS. SEM observation showed that the PS array templates had face-centered cubic close-packing. X-ray diffraction (XRD) spectra showed the porous ZnO thin film was wurtzite structure. The optical transmittance decreased with decreasing wavelength of lights, but was kept above 80% beyond the wavelength of 550 nm. Optical band-gap of the porous ZnO thin film annealed at 500°C was 3.22 eV.     

Monitoring entering and spreading of emulsion droplets at an expanding air/water interface: a novel technique

The entering and spreading of emulsion droplets at quiescent and expanding air/water interfaces was studied using a new apparatus consisting of a modified Langmuir trough in which the air/water interface can be continuously expanded by means of rollers in the place of traditional barriers. When sodium caseinate and whey protein isolate-stabilized emulsion droplets were injected under the surface of sodium caseinate and whey protein isolate solutions, respectively, it appeared that the droplets entered the air/water interface only if the air/water surface pressure did not exceed a threshold value of approximately 15 mN/m. This condition was satisfied either under quiescent conditions for low protein concentrations or by continuous expansion of the interface at higher protein concentrations. According to equilibrium thermodynamics, entering of the droplets and the formation of lenses should occur for all the systems investigated, but this was not observed. At surface pressures higher than approximately 15 mN/m, immersed emulsion droplets were metastable. This is probably due to a kinetic barrier caused by the formation of a thin water film bounded by protein adsorption layers between the emulsion droplet and the air/water interface.     

医用钛表面组织结构和形貌特征与表面生物活性的研究

通过物理、化学或者电化学表面改性的方法改变钛表面氧化钛膜的结构、化学成份等可赋予钛金属及其合金生物活性,从而在体内实现材料与硬组织间的生物活性结合。本文探讨钛表面氧化钛膜的结构、化学成份、表面形貌和微观结构对其生物活性的影响。     

丙烯酸丁酯-醋酸乙烯酯共聚物胶乳粒子的结构和性能

电镜观察表明,丙烯酸丁酯-醋酸乙烯酯共聚物胶乳粒子均为核-壳结构,若配料比不同,含量大者为核,而加料方式不同,则先加者先聚合成核.微观结构不同,可明显地影响胶膜的力学性能、T_g和耐水性.根据胶乳粒子微观结构的观察结果,认为当醋酸乙烯酯>50mol%时,共聚的引发和成核是在水相中进行的.     

不同溶剂制备的聚乳酸多孔微球的形成机理

利用改进的双乳液溶剂挥发法制备了多孔聚乳酸( PLA)微球.通过采用具有不同沸点和水溶性的有机溶剂制备得到不同多孔结构的PLA微球.结果发现以二氯甲烷、氯仿和甲苯为溶剂制备的微球具有相似的均匀多孔结构,而以乙酸乙酯制备的微球却具有中空结构和多孔的壳层.通过进一步的实验研究了溶剂种类对于微球多孔结构的影响.结果表明溶剂的...     

Research on the implementing conditions of inverse emulsion-breath figure method

The relationships between three steps of the inverse emulsion-breath figure (Ie-BF) method, including emulsion preparation, film casting and hydrophilic component loading, are explored by adjusting the experimental factors of the three implementing processes. For emulsion preparation step, the influence of the ultrasonification, the concentration of emulsifier and the addition of polymer on the size of the emulsion droplets are investigated. For film casting step, the influence of environmental humidity and several factors concerning the emulsion preparation on the porous structure of the resultant films are studied. It has been proved that high humidity is a necessity for obtaining surface pores, and multi-layered pores with disordered distribution can be formed in the bulk layer of the film when high water/oil ratio is used in making the emulsion. Bovine serum albumin is loaded into the emulsion water droplets, and by implementing the Ie-BF method under the condition of water/oil ratio being as low as 0.02 vol%, selective protein enrichment within the interior of the top-layer pores is still realized. It reflects the characteristics of “high efficiency, targeted assembly” in the step of hydrophilic component loading.     

Monodisperse porous polymer particles: Formation of the porous structure

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.     

Emulsion polymerization of divinyl monomers stabilized by sodium dodecyl sulfate and bis(2‐ethylhexyl)sulfosuccinate sodium salt

The emulsion polymerization of divinyl monomers is investigated. Emulsions were obtained in the presence of sodium dodecyl sulfate and bis(2‐ethylhexyl)sulfosuccinate sodium salt as surfactants. The influence of monomer type and kind of surfactant on the particle size distribution is studied. The porous structure of the broken emulsions is also determined. The results indicate that the diameter of nanospheres obtained from two divinyl monomers are significantly larger than those obtained from polystyrene. Aggregation of the particles and the pore‐forming diluent added to the emulsion are responsible for the existence of pores. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3967–3973, 2002     

Film forming characteristics of oil-in-water emulsion with super-low oil concentration

The oil-in-water emulsion has been widely used as lubricant in metal working such as metal rolling and cutting. The film formation ability of emulsion was considered as an important evaluation factor. Thus the film formation mechanism and characteristics of emulsion have been widely investigated. However, the mechanism is still dubious and film forming characteristics were seldom discussed under an oil volume percentage of 0.05%. In this paper, a lubricating film testing apparatus is used to investigate the film forming characteristics of oil-in-water emulsion between the surface of a steel ball and that of a glass disc coated with chromium. By carrying out experiments under extremely low oil volume percentages (0.005–2.5%), some new phenomena are found in our program. The film formation mechanism of oil-in-water emulsion is discussed based on the different film forming performances of emulsion with different oil volume percentages. New viewpoints on the film formation of emulsion are put forward in this paper.     

包埋于PLGA膜中的BSA海藻酸钙微球的制备及其释放行为

在组织工程中，为了促进和调节细胞在细胞支架上的增殖和分化，一些特殊的生物活性分子(生长因子(Growth Factor，简称GF))，必须引入支架．这些生长因子是一类具有诱导和刺激细胞增殖、维持细胞存活等生物效应的多肽蛋白类物质，因此，在组织工程研究中，生长因子是三个重要因素之一，     

Synthesis of porous poly(styrene-co-acrylic acid) microspheres through one-step soap-free emulsion polymerization: whys and wherefores

Synthesis of porous poly(styrene-co-acrylic acid) (PS-co-PAA) microspheres through one-step soap-free emulsion polymerization is reported. Various porous PS-co-PAA microspheres with the particle size ranging from 150 to 240 nm and with the pore size ranging from 4 to 25 nm are fabricated. The porous structure of the microspheres is confirmed by the transmission electron microscopy measurement and Brunauer-Emmett-Teller (BET) analysis. The reason for synthesis of the porous PS-co-PAA microspheres is discussed, and the phase separation between the encapsulated hydrophilic poly(acrylic acid) segment and the hydrophobic polystyrene domain within the PS-co-PAA microspheres is ascribed to the pore formation. The present synthesis of the porous PS-co-PAA microspheres is anticipated to be a new and convenient way to fabricate porous polymeric particles.     

氟含量对含氟丙烯酸酯共混乳胶膜梯度结构和表面性能的影响

首先将制备出的平均粒径较小的含氟丙烯酸酯均聚物乳液与平均粒径较大的纯丙烯酸酯共聚物乳液按不同的比例( 1/9,2/8,3/7,4/6,5/5)共混,接着将各共混乳液在室温下(20℃)玻璃基材上干燥后,于110℃/210℃下热处理一段时间.运用接触角法,XPS、AFM、SEM-EDX等详细研究了共混乳胶膜中含氟组分含量对...     

A novel technique for improving interferometric determination of emulsion film thickness by digital filtration

Determination of the thickness of emulsion films by using the film interferometric images is usually less accurate than that of foam films, due to the close values of the refractive indices of the liquid film and adjacent liquid phases (hence, low contrast and high level of noise at high magnification). A new technique was developed to improve the thickness determination by obtaining the interferometric images without directly filtering the illuminating light, as is usually done in the classical Scheludko interferometric technique. The new method then uses digital filtration during the off-line image post-processing to obtain monochromatic interferometric images required for the thickness determination. The technique was tested with foam films stabilised by sodium dodecyl sulfate and successfully applied to determine thickness of toluene-water-toluene emulsion films using the green and red digital filters. Results for emulsion film thickness determined by either the green or red digital filtration are comparable, thus validating the new technique developed here for emulsion films.     

Gold nanoparticle-embedded porous graphene thin films fabricated via layer-by-layer self-assembly and subsequent thermal annealing for electrochemical sensing

A uniform three-dimensional (3D) gold nanoparticle (AuNP)-embedded porous graphene (AuEPG) thin film has been fabricated by electrostatic layer-by-layer assembly of AuNPs and graphene nanosheets functionalized with bovine serum albumin and subsequent thermal annealing in air at 340 °C for 2 h. Scanning electron microscopy (SEM) investigations for the AuEPG film indicate that an AuNP was embedded in every pore of the porous graphene film, something that was difficult to achieve with previously reported methods. The mechanism of formation of the AuEPG film was initially explored. Application of the AuEPG film in electrochemical sensing was further demonstrated by use of H(2)O(2) as a model analyte. The AuEPG film-modified electrode showed improved electrochemical performance in H(2)O(2) detection compared with nonporous graphene-AuNP composite film-modified electrodes, which is mainly attributed to the porous structure of the AuEPG film. This work opens up a new and facile way for direct preparation of metal or metal oxide nanoparticle-embedded porous graphene composite films, which will enable exciting opportunities in highly sensitive electrochemical sensors and other advanced applications based on graphene-metal composites.     

Effect of calcination temperature on the microstructure of porous TiO<Subscript>2</Subscript> film

To obtain porous TiO₂ film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO₂ film was fabricated by the dip-coating technique on glass substrates using this solution. The TiO₂ film was calcined at 500 °C. The maximum thickness of the film from one-run dip-coating was ca. 740 nm. The film was composed of nanosized particle and pores. The porosity of the TiO₂ film was increased by addition of trehalose dihydrate to the sol. The porous TiO₂ films were calcined at different temperatures. The effects of calcination temperature on the microstructure of the porous TiO₂ film were investigated. The porous film prepared from sol containing trehalose still kept the porous structure after calcination at 950 °C. The phase transition temperature of the film from anatase to rutile was shifted from 650 to 700 °C by addition of trehalose to the sol.