Exclusion chromatography using porous glass. II. Application to hydrophilic polymers

A chromatograph employing five columns packed with porous glass of pore size 1250 Å to 75 Å provided peak retention volumes (V_R) that were reproducible and essentially independent of sample size and flow rate when aqueous eluents were used. Calibration was carried out with a series of dextran fractions and polystyrene sulfonate samples, both of moderately narrow molecular weight distribution. The universal calibration method, based on hydrodynamic volume, was tested for four different polymer types. All four types produced a common curve within experimental error, which indicates that absolute molecular weight distributions may be derived from aqueous exclusion chromatography data for at least these polymer types. Additional study using a higher salt concentration produced hydrodynamic-volume plots that superposed with those above. The use of the same set of porous glass columns with polystyrene standards in three different organic solvents produced calibration curves that agreed well with the aqueous curves after corrections were made for differences in available pore volumes.     

废弃物衍生分级多孔炭的制备及吸附应用进展

分级多孔炭因其高比表面积、大孔容及分级孔结构,目前广泛应用于超级电容器、锂离子电池、催化及吸附等领域。废弃物在热解气化过程中残留的碳基材料则是制备分级多孔炭很好的前体。本文根据废弃物来源及自身特性间的差异,对生物质和非生物质废弃物作为原料制备的分级多孔炭的特性及应用进行了综述及总结。并对不同制备方法的优劣及适用对象进行了比较。对分级多孔炭在挥发性有机物（VOCs）吸附、CO₂吸附捕集、染料吸附、抗生素以及酚类物质的吸附过程进行分析,总结出废弃物基多孔炭在孔径结构及表面杂原子掺杂情况下的优势能够增强这几类物质的吸附效果。结合已有文献,对废弃物基分级多孔炭的制备、孔径设计及表面官能团设计提出展望。     

Sorption of poly(vinyl acetate) on cellulose. II. The role of the porous structure

The adsorption of poly(vinyl acetate) from benzene solution onto cellulosic materials having various porous structures was measured in an attempt to investigate the role of the pore size distribution in the sorption process. The variety of cellulose porous structures was obtained by combinations of different swelling agents—water, ethylenediamine, sodium hydroxide solution—with different subsequent drying treatments. The pore structure analysis was based on benzene desorption isotherms. The porosity of cellulose is responsible for selective adsorption of the smaller macromolecules from an unfractionated polymer solution. The amount of sorbed polymer increases when the polymer solution contains a greater fraction of lower molecular weight polymer. Only the pores above a certain size are accessible to the polymer. The amount of polymer sorbed is proportional to the area of such pores but is otherwise independent of the effects produced by swelling pretreatments.     

Effect of Casting Solution on Morphology and Performance of PVDF Microfiltration Membranes

The effects of preparation‐influencing parameters such as polymer concentration, thickness of casting solution, and type of solvent on morphology and performance of poly(vinylidene difluoride) (PVDF) microfiltration membranes for the treatment of emulsified oily wastewater were investigated. Flat‐sheet membranes were prepared from a casting solution of polymer and additive in various solvents by immersing the prepared films in nonsolvent‐containing mixtures of water and 2‐propanol. The membranes were characterized using scanning electron microscopy. Increasing the polymer concentration and membrane thickness significantly affected the pore size, leading to permeate flux decrease. An attempt was made to correlate the effect of the solvent on membrane morphology and performance employing solubility parameters between solvent and nonsolvent).     

Hierarchical porous MgBO2(OH) microspheres:Hydrothermal synthesis,thermal decomposition,and application as adsorbents for Congo red removal

A facile eco-friendly hydrothermal route(180 °C, 12.0 h) has been developed for the first time to the uniform hierarchical porous MgBO_2(OH) microspheres without the aid of any organic additive, surfactant or template, by using the abundant MgCl_2·6 H_2 O, H_3BO_3 and NaOH as the raw materials. The as-obtained porous microspheres exhibit a specific surface area of 94.752 mg·g~(-1), pore volume of 0.814 cm3·g~(-1), and ca. 84.0% of which have a diameter of 2.25–3.40 μm. The thermal decomposition of the porous MgBO_2(OH) microspheres(650 °C,2.5 °C·min~(-1)) leads to the porous Mg_2B_2O_5 microspheres with well-retained morphology. When utilized as the adsorbents for the removal of CR from mimic waste water, the present porous MgBO_2(OH) microspheres exhibit satisfactory adsorption capacity, with the maximum adsorption capacity q~(-1) mof 309.1 mg·g, much higher than that derived from most of the referenced adsorbents. This opens a new window for the facile green hydrothermal synthesis of the hierarchical porous MgBO_2(OH) microspheres, and extends the potential application of the 3 D hierarchical porous metal borates as high-efficiency adsorbents for organic dyes removal.     

Partially ordered porous structures on layer-by-layer polyaniline/poly(vinyl sulfate sodium) ultrathin films: Easy fabrication of robust submicroscopic patterning

The use of polyaniline (PANI) as a conductive material has steadily increased in recent years due to its interesting physicochemical properties, low manufacturing cost, and easy processing. This conductive material, associated with the diffraction properties of organized nanostructures in thin films, has excellent application potential in microelectronics and photonic devices. Initially, this work presents improvement routes for the breath figure method (a nanopatterning technique) in polystyrene (PS) films through the control of film deposition parameters and the presence of water in the polymer solution. Such improvements are then extended to the production of PANI nanostructures, in the form of pores, from patterned porous PS films. Consequently, PANI films with a partially ordered pore structure (mean pore diameter of ~100 nm) are produced in a facile and easily scalable method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48597.     

坡缕石/聚乙二醇/丙烯酸水凝胶的表征及其对阳离子染料的吸附性能

采用红外光谱、X射线衍射和扫描电镜对辉光放电电解等离子体引发制备的坡缕石/聚乙二醇/丙烯酸(PGS/PEG/AA)水凝胶的结构和形貌进行了表征.研究了其对阳离子型染料亚甲基蓝、结晶紫、孔雀石绿和罗丹明B的吸附行为,考察了pH值、吸附时间对吸附性能的影响,同时探讨了可能的吸附机理.结果表明,PGS、PEG和AA发生接枝共聚形成水凝胶,组分间相容性好,表面呈现褶皱和深浅不均匀的孔洞;吸附的最佳pH值为6.2左右,吸附时间为3h,吸附动力学符合准二级模型,阳离子染料在PGS/PEG/AA上的吸附是由离子交换、氢键、范德华力等共同作用的物理化学过程.     

Preparation of crosslinked membranes with controlled pore size distribution

A technique has been developed to prepare crosslinked, porous/asymmetric membranes from poly(styrene-co-divinylbenzene). Mixtures of styrene monomer, divinylbenzene, benzoin (a photo-initiator), and some dead polystyrene are dissolved in a cosolvent and cast on a flat, transparent substrate. The coating is then irradiated with a UV lamp and subsequently phase separated by exposure to a nonsolvent bath. Pores are generated by phase separation induced by nonsolvent ingression. Crosslinking is achieved via the photo-initiated incorporation of divinylbenzene with styrene, while the membrane morphology evolves. A mechanism for the formation of crosslinked membranes prepared by this technique has been proposed. Experimental results systematically examine the effects of crosslinking and nonsolvent/solvent combinations on pore size and overall membrane structure. Temperature and solvent treatments on the finished membrane structure are also studied.     

Application of genetic algorithm in calculation of the phase behavior of binary and ternary polymer solutions

A genetic algorithm as an optimization procedure has been developed to predict the phase behavior of polymer solutions. The phase equilibrium diagrams of binary and ternary polymer solutions have been determined using the appropriate form of Flory–Huggins free-energy function for polymer solutions. A concentration and temperature dependent form of the interaction parameter has been used to reflect the effect of temperature and polymer properties in the free-energy form. The proposed genetic algorithm is applied to compare the phase behavior results of some typical polymer solutions with the results of the classical determination methods and then applied to some conventional ternary polymer solutions as polymer–solvent–nonsolvent systems. The proposed algorithm use a set of individual states as the initial chromosomes and uses the general rules as crossover, mutation, and with use of a fractional objective function determines the binodal points or the phase diagram boundaries of polymer solutions. The properties of an industrially relevant polymer solution, a polystyrene–cyclohexane solution, have been used to emphasize on the industrial application of the proposed algorithm. The algorithm has been used to predict the phase behavior of the two polymer–solvent–nonsolvent systems as polystyrene-butanone-methanol and polystyrene-butanone-propanol at three different temperatures and results show good agreement with the experimental observations. The algorithm also has the capability to predict both the concentration-independent and concentration-dependent interaction parameters among the different components. The genetic algorithm is an easy-to-use, state-of-art, and very fast optimization tool, and has very strong capability to solve nonlinear systems in chemical and polymer engineering topics.     

EFFECTS OF SOLUTE ADSORPTION ON HINDERED DIFFUSION UPTAKE RATES IN FINITE BATH EXPERIMENTS

This work investigates the effects of solute adsorption on hindered diffusion behavior in porous catalysts. A mathematical model describing the adsorptive diffusion process is developed. The model, termed the shrinking pore model, incorporates the local reduction in catalyst pore diameter due to the adsorption of solute molecules on the pore walls. The influence of the adsorbed solute layer is found to depend on two additional parameters, reflecting the relative degree of adsorption and molecule/pore size ratio. Hindered diffusion experiments are performed for diffusion controlled adsorptive uptakes of two solute molecules, quinoline and polystyrene, from cyclohexane on a porous catalyst. Comparison of the experimental data and model simulation results shows that for the larger polystyrene solute the shrinking pore model better represents the uptake behavior than the conventional model which assumes constant catalyst properties, e.g. pore diameter, during the uptake process. Experimental measurements were found to be in good agreement with model simulations after accounting for additional hindered diffusional effects due to an adsorbed solute layer on the pore walls. The additional hindrance due to the adsorbed solute was found to be very significant for the uptake of the larger polystyrene solute, whereas it was not significant for the smaller quinoline solute.     

Monodisperse‐porous poly(styrene‐co‐divinylbenzene) beads providing high column efficiency in reversed phase HPLC

A multistage polymerization protocol, the so‐called “modified seeded polymerization,” was developed for the production of monodisperse‐porous poly(styrene‐co‐divinylbenzene) providing high column efficiency as a packing material in reversed phase high performance liquid chromatography (RPLC). In the first stage of the multistage production, uniform polystyrene seed particles, produced by dispersion polymerization, were swollen by an organic agent (i.e., the diluent) and then by a monomer mixture containing styrene and divinylbenzene. The final porous particles were obtained in the monodisperse form by the polymerization of monomer mixture in the seed particles. By the use of a small size seed latex with low molecular weight and by the selection of the appropriate diluent, relatively small monodisperse‐porous particles with suitable pore structure could be achieved. In the reversed phase separation of alkylbenzenes, under isocratic conditions, theoretical plate numbers up to 40,000 plates/m were achieved by using 5.2 μm porous particles, obtained by a toluene‐dibutyl phthalate mixture as the diluent. No significant decrease in the resolution power was observed by the fourfold increase in the mobile phase flow rate. The column efficiency and the resolution observed with 5.2 μm monodisperse‐porous particles were significantly higher with respect to the currently available polymer based packing materials used in the reversed phase HPLC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1430–1438, 2005     

Tailoring of a γ-Alumina Membrane with a Bimodal Pore Size Distribution for Improved Permeability

Porous γ-alumina with a bimodal pore size distribution has been developed by adding nanosized polystyrene beads to boehmite sol as templating units. The primary pore diameter is in the range of 4–6 nm and the secondary pore diameter is ca. 50 nm with minor pore shrinkage. The unsupported γ-alumina with different porous structures are characterized using thermogravimetric analysis, Fourier transform infrared spectra, X-ray diffraction, N₂ adsorption/desorption, and transmission electron microscopy. γ-alumina with a bimodal porous structure shows reduced transport resistance compared with γ-alumina with a unimodal porous structure in the dye adsorption test. Although the thickness of γ-alumina thin layer increases when more secondary pores are generated, a γ-alumina membrane with a bimodal pore size distribution shows diminution of transport resistance in the water permeability study also.     

PEEKWC ultrafiltration hollow‐fiber membranes: Preparation,morphology, and transport properties

A series of hollow‐fiber membranes was produced by the dry–wet spinning method from PEEKWC, a modified poly(ether ether ketone) with good mechanical, thermal, and chemical resistance. The fibers were prepared under different spinning conditions, varying the following spinning parameters: polymer concentration in the spinning solution, height of the air gap, and bore fluid composition. The effect of these parameters on the water permeability, the rejection of macromolecules (using dextrane with an average molecular weight of 68,800 g/mol), and the morphology of the membranes was studied. The results were also correlated to the viscosity of the spinning solution and to the ternary polymer/solvent/nonsolvent phase diagram. The morphology of the cross section and internal and external surfaces of the hollow fibers were analyzed using scanning electron microscopy (SEM). All membranes were shown to have a fingerlike void structure and a skin layer, depending on the spinning conditions, varying from (apparently) dense to porous. Pore size measurements by the bubble‐point method showed maximum pore sizes ranging from 0.3 to 2 μm. Permeability varied from 300 to 1000 L/(h^?1 m^?2 bar) and rejection to the dextrane from 10 to 78%. The viscosity of polymer solutions was in the range of 0.2 to 3.5 Pa s. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 841–853, 2004     

Controllable morphology and wettability of polymer microspheres prepared by nonsolvent assisted electrospraying

Polymethylmethacrylate (PMMA) microspheres with various morphologies are fabricated by nonsolvent assisted electrospraying. The morphology evolution is determined by nonsolvent properties including the solubility parameter, surface tension and viscosity, and nonsolvent induced phase separation is the main reason for the formation of the porous and/or hollow structures. It is found that nonsolvent possessing a high surface tension is beneficial to the formation of a hollow structure, while the large phase separation tendency between nonsolvent and the polymer can promote pore generation on the sphere surface. The nanosized pores, especially hierarchical pores, can enhance the hydrophobicity of the substrate surface coated with these microspheres. On the other hand, nonsolvent with a large viscosity could prevent the growth of the phase separated nuclei, leading to the presence of relatively small and discontinuous pores on the microsphere surface, which can finally cause the decrease of the contact angles. The surface pores of the electrosprayed microspheres are even eliminated if polymer additive, i.e., PVP, is incorporated into the polymer-solvent-nonsolvent solution. The addition of PVP renders the microsphere coated surface hydrophilic, which can be completely wetted by water droplets.     

PolyHIPE: IPNs, hybrids, nanoscale porosity, silica monoliths and ICP-based sensors

Typical polyHIPE (porous polymers from high internal phase emulsions) have a cellular structure with volume fractions from 0.2 to 0.04, cell diameters from 15 to 25 μm and intercellular pore diameters from 0.5 to 10 μm. Unique interpenetrating polymer networks synthesized within the polyHIPE exhibited enhanced mechanical properties and an extended temperature range for damping. Hybrid polyHIPE that combine an inorganic polysilsesquioxane network with an organic polystyrene network exhibited superior high temperature mechanical properties and enhanced thermal stability. A nanoscale porosity in the cell walls, produced through the addition of a porogen to the HIPE, reduced the density and significantly enhanced the specific surface area. Porous silica monoliths with silica volume fractions of as low as 0.02 were produced through the pyrolysis of hybrid polyHIPE. PolyHIPE coated with an intrinsically conducting polymer exhibited reversible and repeatable changes in conductivity on exposure to acetone vapor, demonstrating their potential as sensor materials.     

Water-assisted formation of honeycomb structured porous films

Honeycomb structured porous materials were formed using four different casting variations of the water droplet templating method. The film quality of the materials generated from these casting techniques (airflow, cold stage, casting on water, and emulsion methods) was investigated by altering the polymer architecture and composition. Linear, star, and comb polystyrene as well as an amphiphilic diblock copolymer comprised of polystyrene-block-poly(dimethylacrylamide) (PS-b-PDMA) were previously synthesized and cast into films via these techniques. While irregular pore distributions were observed for linear polystyrene films generated by every technique screened, increasing the architectural complexity of the polymer yielded more regular films for a broad range of casting conditions for each of the techniques. With the exception of linear polystyrene, the airflow casting technique was shown to be the only technique capable of generating regular porous films for all of the polymeric materials.     

Turbidimetric determinations of theta compositions

The turbidimetric titration method of determining theta conditions developed by Elias and modified by Cornet and van Ballegooijen has been extended and generalized for different types of polymer–solvent–nonsolvent systems. The modified procedures for the determination of theta compositions have been verified with the following systems: polystyrene–cyclohexane–n-hexane, polystyrene–cyclohexane–n-butanol, and polystyrene–toluene–nonsolvent.     

相转化法聚合物/溶剂/非溶剂铸膜体系的热力学计算

计算了相转化法铸膜体系中常见的典型三元相图,分析了聚合物与溶剂之间、聚合物与非溶剂之间、溶剂与非溶剂之间的相互作用参数对聚合物/溶剂/非溶剂铸膜液体系相图的影响,以及体系温度和聚合物摩尔体积对聚合物/溶剂/非溶剂铸膜液体系相图的影响。根据溶剂-非溶剂汽液平衡数据和溶解度参数得到了溶剂-非溶剂、溶剂与聚合物以及非溶剂与聚合物之间的Flory-Huggins相互作用参数,从而获得了几种常见铸膜液体系的相图。同时,利用聚合物/溶剂/非溶剂铸膜液体系的相图数据对热力学模型的参数进行了优化,取得了与实验结果较一致的计算结果。     

Polymer template fabrication of porous hydroxyapatite scaffolds with interconnected spherical pores

Porous hydroxyapatite (HA) scaffolds with interconnected spherical pores were fabricated by slip casting using a polymer template. Templates were produced using polymer beads, NaCl, and adhesive (N100). Effects of the preparation process on the pore structures and mechanical properties of the porous HA scaffolds were investigated. Pore interconnectivity was improved by adding NaCl particles with appropriate diameters to the polymer template. The size of the adhesive area could be controlled by adjusting the concentration of N100. The pore size could be controlled between 200 ± 42 and 400 ± 81 μm, and the porosity between 50.2 and 73.1%, by changing the size of the polymer beads and the volume of the NaCl particles. The compressive strength decreased as the porosity or pore size increased.