Stability of surfactant-free high internal phase emulsions and its tailoring morphology of porous polymers based on the emulsions

Stable water-in-oil (w/o) high internal phase emulsions (HIPEs) having an internal phase of up to 95 vol% were prepared. The poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) copolymer particles were used as stabilizer. The HIPEs prepared with addition of copolymer particles to the aqueous phase were stabilized by copolymer particles initially, followed by the mixture of copolymer particles and copolymer as the particles eventually dissolves in the organic phase, and finally by only copolymer. Stable w/o HIPEs having an internal phase of up to 92 vol% were also formed with P(St-MMA-AA) copolymer dissolved in the organic phase as the sole stabilizer. Porous polymers (polyHIPEs) were prepared based on these two types of surfactant-free HIPEs. The morphology of the polyHIPEs, such as the surface roughness of the voids and average void diameter, were tailored by tuning the internal phase volume fraction, NaCl, copolymer, and crosslinker concentrations.     

高内相乳液聚合制备多孔整体聚合物的孔结构调控与表征

以苯乙烯、二乙烯基苯为原料,山梨糖醇酐单油酸酯Span80为乳化剂,过氧化苯甲酰(BPO)为引发剂,氯化钙水溶液为分散相,通过高内相W/O乳液体系制备Poly HIPE。探讨了不同油水比、乳化剂用量和二乙烯基苯含量对聚苯乙烯(PS)/二乙烯基苯DVB型Poly HIPE孔结构、密度和比表面积的影响。结果表明,随着油水比的减小,乳液稳定性增强,Poly HIPE孔径变大,贯通孔数量增多;增加乳化剂用量或单体中二乙烯基苯比例,Poly HIPE的孔径变小,贯通孔数量增多。除此之外,研究还发现油水比的减小使得Poly HIPE的表观密度和比表面积降低,而提高乳化剂用量和二乙烯基苯比例可提高Poly HIPE的表观密度和比表面积。     

Porous interpenetrating network hybrids synthesized within high internal phase emulsions

‘PolyHIPE’ are porous polymers from the polymerization of monomers and crosslinking co-monomers in the continuous phase of high internal phase emulsions (HIPE). Elastomeric polyHIPE have been reinforced through the synthesis of nanocomposites using several different routes including the addition of co-monomers such as vinyltrialkoxysilane, polyhedral oligomeric silsesquioxane (POSS) bearing vinyl groups, or vinyl silsesquioxane (VSQ). This paper describes the synthesis, structure, and properties of hybrid polyHIPE with interpenetrating polymer-inorganic networks synthesized by adding tetraethylorthosilicate (TEOS) to the monomers. The HIPE becomes unstable on addition of 14 mol% TEOS and the resulting polyHIPE contains voids hundreds of micrometers in diameter. On addition of 25 mol% TEOS the large voids become coated with a brittle Si-O shell as the TEOS migrates to the interface between the organic and aqueous phases. In general, the increases in tan δ peak temperature, tan δ peak breadth, and room temperature modulus with increasing TEOS content are similar to those observed with POSS and VSQ. Unlike the polyHIPE containing vinyltrialkoxysilane, POSS, or VSQ, pyrolysis of these hybrid polyHIPE did not yield porous inorganic monoliths.     

Hydrophilic porous polymers based on high internal phase emulsions solely stabilized by poly(urethane urea) nanoparticles

Stable oil-in-water (o/w) Pickering high internal phase emulsions (HIPEs) having an internal phase of up to 95 vol% were prepared with a low-energy emulsification method. A poly(urethane urea) (PUU) aqueous nanodispersion was used as aqueous phase. The PUU nanoparticles of the aqueous nanodispersion acted as a mechanical barrier, and prevented droplet coalescence in the Pickering HIPEs. In addition, open porous hydrophilic polymer foams were obtained by polymerization of the Pickering HIPEs, and the morphology of the foams were tailored by changing the oil:water ratio, PUU nanoparticle and NaCl concentrations. The method used herein provides a simple way to prepare morphology controlled hydrophilic polymer foams using o/w Pickering HIPEs as template.     

Synthesis of open porous emulsion-templated monoliths using cetyltrimethylammonium bromide

In recent years, open porous materials (polyHIPEs) have attracted more and more attention because of their specific properties and applications in biological tissue scaffolds, catalysis supports and ion-exchange resin. However, the surfactants used in this type material were limited to nonionic surfactants or the mix of nonionic surfactant and ionic surfactant. In this work, firstly well-defined polyHIPEs were synthesized by W/O emulsions with ionic surfactant alone (e.g., CTAB). Furthermore, the polyHIPEs with much higher pore volume (14.7 cm³ g⁻¹), uniform pore diameter and cell size were obtained by this method. Both the median pore diameter and average cell size of the polyHIPEs rose with increase of DVB concentration and/or water fraction.     

High internal phase emulsion templating as a route to well-defined porous polymers

The use of high internal phase emulsions (HIPEs) as templates to create highly porous materials (PolyHIPEs) is described. Polymerisation occurs around emulsion droplets, which create voids in the final material. The void fraction is very high and can reach levels of 0.99. Varying the emulsion composition can control features of the morphology of the resulting porous materials, such as the void diameter and degree of interconnection. Other parameters can also be varied, for example surface area can be increased from 3 to around 700 m² g⁻¹. Rubbery materials can be produced from hydrophobic elsatomers and PolyHIPEs with high thermo-oxidative stability are prepared from high performance materials such as poly(ether sulfone). The highly porous materials so produced are finding applications in areas such as solid supported organic chemistry, sensors, cell culturing and tissue engineering.     

Macroporous materials from water-in-oil high internal phase emulsion stabilized solely by water-dispersible copolymer particles

Water-in-oil (W/O) high internal phase emulsions (HIPEs) were prepared by utilizing water-dispersible copolymer particle stabilizer, whose concentration in the internal phase could reach as high as 12.0 wt% (equivalent to 52 wt% relative to the continuous phase). Accordingly, the macroporous materials with high content of skeleton substance would be obtained by the dissolving of these copolymer particles into the continuous phase and without any chemical reaction. And the morphology, the density and the mechanical property of the macroporous materials could be easily tailored through varying the standing time after emulsification, particle concentration in the aqueous phase and the internal phase volume ratio.     

Synthesis of emulsion-templated porous polyacrylonitrile and its pyrolysis to porous carbon monoliths

PolyHIPEs are emulsion-templated polymers synthesized within high internal phase emulsions (HIPEs). The miscibility of acrylonitrile (AN) with water has made it difficult to synthesize PAN-based polyHIPEs. This paper describes the successful synthesis of PAN-based polyHIPEs by crosslinking through copolymerization with divinylbenzene (DVB), by stabilization with a polyglycerol polyricinoleate surfactant, and by initiation with both oil- and water-soluble initiators. The PAN-based polyHIPEs had porosities of over 86% and porous structures that were different from those of typical polyHIPEs. This paper also describes the production of porous carbon monoliths through the pyrolysis of these PAN-based polyHIPEs. Pyrolysis did not produce significant changes in the porous structures, which were quite similar to those of the original polyHIPEs. The porosities were around 95% and the carbon monoliths were largely macroporous and mesoporous, with some microporosity. These results indicate that PAN-based polyHIPE templates can be used for the a priori design of porous carbon monoliths.     

Polymerization and carbonization of high internal phase emulsions

High internal phase emulsions (HIPEs) of styrene and divinylbenzene (DVB), with 0–40 % vinylbenzyl chloride (VBC) in the oil phase, were polymerized to give porous polymers (pore volumes 84–92 %), which were sulfonated and carbonized at temperatures up to 700 °C to obtain macroporous carbon monoliths. On carbonization, overall sample dimensions decreased, whilst percentage pore volume, compressive strength and compressive modulus increased. Scanning electron microscopy (SEM) showed typical HIPE‐derived structures of cages (several µm across), interconnected by smaller windows, for polymer and carbon samples. Distributions of cage and window size were evaluated from electron micrographs. Average cage and window sizes decreased on carbonization approximately in proportion to the reduction in overall sample dimensions, and also decreased with increasing VBC content in the HIPE. Mercury intrusion porosimetry gave distributions of pore size in reasonable agreement with area‐distributions of window size determined from SEM images. Copyright © 2004 Society of Chemical Industry     

Effect of oil type on stability of high internal phase water-in-oil emulsions with super-cooled internal phase

This study considered the stability and rheology of a type of high internal phase water-in-oil emulsions (W/O) emulsion. The aqueous phase of the emulsions is a super-cooled inorganic salt solution. The oil phase is a mixture of industrial grade oils and stabilizer. Instability of these systems manifests as crystallization of the metastable dispersed droplets with time. This work focused on the effects of oil polarity and oil viscosity on the stability of these emulsions. Ten types of industrial oils, covering the viscosity range 1.4–53.2?cP, and with varying polarity, were used in combination with polymeric poly(isobutylene) succinic anhydride (PIBSA) and sorbitan monooleate (SMO)-based surfactants. The effect of oil relative polarity on rheological parameters of the emulsion was evident mainly in the emulsions stabilized using polymeric surfactant, whereas the oil viscosity did not show any significant effect. The optimum stability of the emulsions stabilized with SMO was achieved using high polar oils with a viscosity of 3?±?0.5?cP. However, when using the PIBSA surfactant, the best emulsion stability was achieved with low polar, high viscosity oils.     

Polymerized high internal‐phase emulsions: Properties and interaction with water

The synthesis and characterization of novel polymerized high internal‐phase emulsions (polyHIPE) materials are described. Homogeneous, highly porous, low‐density, open‐cell crosslinked copolymers were prepared by polymerizing the continuous phase of HIPE containing styrene and varying amounts of 2‐ethylhexyl methacrylate. The glass transition temperatures (T_gs) of the homopolymers were similar to the literature values, but the copolymer T_gs were lower than expected. These results indicate that the copolymer composition is richer in 2‐ethylhexyl methacrylate than the feed composition. The homopolymer moduli, calculated from the foam moduli, were similar to the literature values. The influence of composition and surface treatment on the water absorbed by the foams was investigated. For example, washing a polyHIPE based on poly(ethylhexyl acrylate) in water at 70°C increased water absorption because of the removal of the residual salt. Adding a fluorinated comonomer to the HIPE reduced hydrophilicity and, thus, water absorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2018–2027, 2002; DOI 10.1002/app.10555     

高内相乳液法制备聚丙烯酰胺多孔水凝胶及应用

以亲水性二氧化硅纳米粒子（N20）和乳化剂Tween80为复合稳定剂,环己烷为油相制备高内相乳液,再以此乳液为模板制备聚丙酰胺（PAM）多孔水凝胶。乳液光学显微镜照片及PAM多孔水凝胶SEM照片表明N20用量及Tween80用量对材料孔径形貌及直径有直接影响;压汞仪数据表明当N20用量为3%、Tween80用量为9%时,多孔水凝胶平均孔径为38.06nm,孔隙率为77.54%,20h饱和吸水率可达402g/g;吸附实验表明PAM多孔水凝胶对Mn(Ⅱ)具有良好的吸附性能,吸附过程符合准二级动力学方程,属于化学吸附,当溶液pH为4时,120min可达吸附饱和,吸附量为474.64mg/g。     

Preparation of a monolithic and macroporous superabsorbent polymer via a high internal phase Pickering emulsion template

A superabsorbent polymer (SAP) possesses an ability to absorb an aqueous solution up to several hundred times its own weight. To utilize a SAP effectively, a high absorption rate is also essential in addition to a high absorption capability. Herein, using a template based on a high internal phase Pickering emulsion (HIPPE) stabilized by aluminum oxide (Al₂O₃) nanoparticles, we synthesize a SAP with a high absorption rate by forming macropores. In particular, by adjusting three different parameters, the concentration of the crosslinker, the internal volume fraction of the emulsion, and the particle concentration, we successfully formed a HIPPE-templated SAP with a high absorption rate for a saline solution, which was 51.6 g g⁻¹ of the absorbency within 10 s. We confirm that the swelling kinetics is mainly determined by the interconnectivity between the internal macro-pores. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48133.     

两亲嵌段共聚物基高内相乳液模板的制备与应用研究进展

多孔聚合物材料具有孔隙率高、加工性能好、质量轻的特点,在化学工程、生物医学工程及环境工程等领域具有广阔的应用前景。高内相乳液模板法为多孔聚合物材料提供了一种简单高效的制备途径,且以此方法制备的多孔材料形状及结构可控,因而引起了人们的广泛关注。本文聚焦于两亲嵌段共聚物稳定的高内相乳液及其所制备多孔聚合物的最新研究进展。同时,介绍了该类型多孔聚合物材料在吸附分离、生物医学、能量存储及催化材料等领域的应用。最后,对该领域的未来发展进行了展望。     

阳离子型聚氨酯乳液的合成与性能初探

对阳离子水性聚氨酯乳液及其膜性能进行了初步的研究。用N -2 10 ,甲苯二异氰酸酯 (TDI) ,N -甲基二乙醇胺(MDEA)为原料 ,以及丙酮作为溶剂来制备阳离子型水分散聚氨酯。讨论了MDEA的用量和NCO/OH比值对乳液及其膜性能的影响。并进行了红外光谱分析。     

内相粒径对现场混装乳化炸药基质抗振动性能的影响

通过改变乳化分散机转速制备不同内相粒径的现场混装乳化炸药基质试样,使用调速振荡器模拟不同粒径基质试样在运输中受振动过程,测试受振动前后基质试样的内相粒径、微观结构、硝酸铵析出量和黏度变化,评估内相粒径对现场混装乳化炸药基质抗振动性能的影响。实验结果表明,随着内相液滴粒径增大,乳化炸药基质的抗振动性能减弱,内相粒径大于5.00 μm的基质更易受振动作用破乳析晶。内相粒径为9.47 μm的1^#基质多分散指数(PDI)为2.78,在1个振动周期后明显破乳失稳,3个振动周期后的析晶量增大143%、黏度增大1.4倍,破乳严重且黏度过大不利于泵送;内相粒径为3.97 μm的5^#基质PDI为1.88,3个振动周期后析晶量增大52%、黏度增大1.07倍,仍保持乳化炸药基质形态,有较好的稳定性。内相粒径过大的乳化炸药受振动后内部液滴易析晶导致性能降低,实际生产中应控制炸药基质制备时的内相粒径小于5.00 μm。     

内相粒径对现场混装乳化炸药基质抗振动性能的影响

通过改变乳化分散机转速制备不同内相粒径的现场混装乳化炸药基质试样,使用调速振荡器模拟不同粒径基质试样在运输中受振动过程,测试受振动前后基质试样的内相粒径、微观结构、硝酸铵析出量和黏度变化,评估内相粒径对现场混装乳化炸药基质抗振动性能的影响。实验结果表明,随着内相液滴粒径增大,乳化炸药基质的抗振动性能减弱,内相粒径大于5.00 μm的基质更易受振动作用破乳析晶。内相粒径为9.47 μm的1^#基质多分散指数(PDI)为2.78,在1个振动周期后明显破乳失稳,3个振动周期后的析晶量增大143%、黏度增大1.4倍,破乳严重且黏度过大不利于泵送;内相粒径为3.97 μm的5^#基质PDI为1.88,3个振动周期后析晶量增大52%、黏度增大1.07倍,仍保持乳化炸药基质形态,有较好的稳定性。内相粒径过大的乳化炸药受振动后内部液滴易析晶导致性能降低,实际生产中应控制炸药基质制备时的内相粒径小于5.00 μm。     

改性蒙脱土的制备及其协同海藻酸衍生物稳定Pickering乳液的研究

以十六烷基三甲基溴化铵(CTAB)作为疏水改性剂,利用湿法球磨对蒙脱土(MMT)进行改性,制备了插层型的改性蒙脱土(CMMT)。采用SEM、zeta电位分析仪、FT-IR、XRD、TEM和TGA对CMMT进行表征。进而,以两亲性海藻酸衍生物(Ugi-Alg)协同CMMT来稳定Pickering乳液,探究改性剂添加量不同时制备的CMMT对Pickering乳液稳定性的影响。实验结果显示,CTAB在湿法球磨的机械作用下插入了MMT微粒片层中。Ugi-Alg吸附于CMMT微粒表面,使CMMT微粒在油/水界面的聚集能力增强。当CTAB的添加量为1.0倍CEC时,CMMT微粒的带电量最低,乳液稳定性最高。     

Synthesis and in situ functionalization of microfiltration membranes via high internal phase emulsion templating

The continuous phase of high internal phase emulsions (HIPEs) can be polymerized to produce highly porous materials, known as polyHIPEs. The aim of this work was to synthesize polyHIPE microfiltration membranes having a hydrophobic bulk and a hydrophilic surface to enhance their performance. Therefore, in situ functionalization was performed through interfacial copolymerization of a hydrophobic monomer (butyl acrylate) in the continuous phase with a hydrophilic monomer (sodium acrylate) in the disperse phase. The functionalization of polyHIPEs was studied by using conductometric titration and Fourier transform IR spectroscopy. We show that the surface charge density of poly(butyl acrylate)‐based polyHIPEs can be controlled by varying the concentration of sodium acrylate in the disperse phase. PolyHIPE microfiltration membranes have higher intrinsic permeability (around 1.31 × 10^?8 m²) in comparison to conventional microfiltration membranes. The interfacial copolymerization of sodium acrylate increases the permeability of microfiltration membranes. In addition, the rejection of polyHIPE microfiltration membranes was studied for the separation of microalgae. © 2019 Society of Chemical Industry     

Investigation of porous polydimethylsiloxane structures with tunable properties induced by the phase separation technique

This article reports the fabrication and characterization of porous polydimethylsiloxane (PDMS) structures developed by the solvent evaporation-induced phase separation technique. Ternary systems containing water/tetrahydrofuran (THF)/PDMS with various concentrations are produced to form a stable solution. The porous PDMS structures are formed by removing the solvent (THF) and nonsolvent (water) phases during the stepping heat treatment procedure. The analytical ternary phase diagram is constructed based on the thermodynamic equilibrium state in the polymer solution to explain the stable/unstable formulations and the possible composition change path. The results show that the isolated pores with the adjustable pore size ranging from 330 to 1900 μm are obtained by tuning the water to the THF ratio. The mechanical properties of the porous PDMS structures are determined by conducting the tensile tests on the prepared dog bone-shaped specimens. A wide range of elastic modulus ranging between 0.49 and 1.05 MPa was achieved without affecting the density of the porous sample by adjusting the solvent and non-solvent content in the solution. It is shown that the flexibility of the porous structures can be improved by reducing the ratio of water to THF and decreasing the PDMS content. The porosity measurements reveal that the PDMS concentration is the major phase controlling the porosity of the structure, while the effect of water/THF is negligible.