Recently, a series of new monomers and polymerization mechanisms has been applied to the templating of high internal phase emulsions (HIPEs) providing a route to hierarchically porous materials with ...a range of functionalities and applications. The high degree of control over the pore size is another attractive feature of these materials. Usually, the continuous phase contains monomers, the droplet phase is used to template the large, primary pores, which are interconnected by secondary pores. The addition of nonpolymerizable components to the continuous phase can result in phase separation during polymerization and tertiary pores. Applications include polymer supports for catalysis and synthesis, separation and filtration, cell culture media, enzyme supports, and structural and isolation applications.
High internal phase emulsion (HIPE) templating provides a route to hierarchically porous materials with a range of functionalities and applications. Usually, the continuous phase contains monomers and the droplet phase is used to template the primary pores, which are interconnected by secondary pores.
•Highly porous functional polymer supports applied for sorption of heavy metal ions from aqueous solutions.•Interconnected porous structure of polymer allows for more efficient contact of reactive ...sites with analytes.•Dynamics of metal removal facilitated by flow mode of experiment.•Chemisorption rather than physisorption prevailing mechanism of removal.
Removal of silver, lead and cadmium ions from both model solutions and real contaminated water was achieved, in a flow through manner, by using highly porous functionalized poly(glycidyl methacrylate) materials, prepared by the polymerisation of high internal phase emulsions (polyHIPE), with significant sorption differences between metals allowing for selective removal. PolyHIPEs, initially prepared from glycidyl methacrylate as a functional monomer, were functionalized with pentaerythritol tetrakis(3-mercaptopropionate), 1,9-nonanedithiol and 2-aminobenzenethiol via the epoxy ring opening on the polymer supports and applied in a flow-through manner via encasements into dedicated disk holders. Capacity of 21.7mg Ag per gram of polymer was found for 1,9-nonanedithiol functionalized polymers, while the capacity was decreasing with the decreasing ionic radius of the metal; the dynamics of sorption also depended on metal ion size and furthermore on the thiol used for the polymer functionalization.
A facile method for the preparation of hierarchically porous spherical particles using high internal phase water-in-oil-in-water (w/o/w) double emulsions via the photopolymerization of the ...water-in-oil high internal phase emulsion (w/o HIPE) was developed. Visible-light photopolymerization was used for the synthesis of microspherical particles. The HIP emulsion had an internal phase volume of 80% and an oil phase containing either thiol pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) or trimethylolpropane tris(3-mercaptopropionate) (TMPTMP) and acrylate trimethylolpropane triacrylate (TMPTA). This enabled the preparation of microspheres with an open porous morphology, on both the surface and within the microsphere, with high yields in a batch manner. The effect of the thiol-to-acrylate ratio on the microsphere diameter, pore and window diameter, and degradation was investigated. It is shown that thiol has a minor effect on the microsphere and pore diameter, while the acrylate ratio affects the degradation speed, which decreases with increasing acrylate content. The possibility of free thiol group functionalization was demonstrated by a reaction with allylamine, while the microsphere adsorption capabilities were tested by the adsorption of methylene blue.
High internal phase emulsions (HIPEs), with densely packed droplets of internal phase and monomers dispersed in the continuous phase, are now an established medium for porous polymer preparation ...(polyHIPEs). The ability to influence the pore size and interconnectivity, together with the process scalability and a wide spectrum of possible chemistries are important advantages of polyHIPEs. In this review, the focus on the biomedical applications of polyHIPEs is emphasised, in particular the applications of polyHIPEs as scaffolds/supports for biological cell growth, proliferation and tissue (re)generation. An overview of the polyHIPE preparation methodology is given and possibilities of morphology tuning are outlined. In the continuation, polyHIPEs with different chemistries and their interaction with biological systems are described. A further focus is given to combined techniques and advanced applications.
For the isolation of selected phenolic compounds from dried chokeberries, natural deep eutectic solvents (NADESs) were investigated as a green alternative to conventionally used extraction solvents. ...Four types of NADESs were synthesised, with choline chloride as the hydrogen bond acceptor in combination with different hydrogen bond donors (sugars, organic acid and urea). Ultrasound-assisted extraction was used to improve the extractability of the phenolic compounds and the results were compared to those obtained with 80% methanol as the extraction media. The highest values of total phenols and total flavonoids were found in the extract obtained with choline chloride-fructose NADES (36.15 ± 3.39 mg gallic acid g
dry weight (DW) and 4.71 ± 0.33 mg rutin g
DW, respectively). The extraction recoveries for the individual phenolic compounds depended strongly on the phenolic compound's structure, with relative mean values between 70% and 97%.
Combining high internal phase emulsion templating with thiol‐ene click chemistry produces porous polymers with high yields and degradable ester linkages. This study compares the influence of the ...monomer functionalities (tri versus tetra), internal phase volume, and initiation type (photo versus thermal) on the morphological and mechanical properties of poly(high internal phase emulsions) (polyHIPEs). For the synthesis of the polyHIPEs pentaerythritol tetrakis(3‐mercaptopropionate) (PETMP, tetrafunctional), trimethylolpropane tris(3‐mercaptopropionate) (TMPTMP, trifunctional), pentaerythritol tetraacrylate (PETA, tetrafunctional), and trimethylolpropane triacrylate (TMPTA, trifunctional) are used. The main factors influencing the properties of the polyHIPEs are the monomer structures and the internal phase volume, while the initiation type influences the morphology of the trifunctional system (pore size and morphology type) resulting in an interconnected cellular morphology in all cases except in the case of the photopolymerization of the emulsion with 85 vol% of the internal phase. The average pore diameter of the trifunctional system ranges from 8.0 to 27.8 µm, while for the tetrafunctional system it ranges from 8.1 to 12.3 µm. The compression moduli of the trifunctional system range from 0.093 to 0.240 MPa and for the tetrafunctional system they range from 1.906 to 7.670 MPa. The compression moduli decrease with increasing internal phase volume (porosity).
Trifunctional and tetrafunctional monomers are used for the preparation of super porous networks via high internal phase emulsions and thiol‐ene click chemistry. Interconnected cellular morphology of monolithic polymers is obtained while there is a substantial influence of the monomer structure, initiation type, and porosity on the mechanical and morphological properties.
The influence of a polymerisation mechanism (reversible addition-fragmentation chain transfer; RAFT vs. free radical polymerisation; FRP) on the porous structure of highly porous ...poly(styrene-co-divinylbenzene) polymers was investigated. The highly porous polymers were synthesised via high internal phase emulsion templating (polymerizing the continuous phase of a high internal phase emulsion), utilising either FRP or RAFT processes. Furthermore, residual vinyl groups in the polymer chains were used for the subsequent crosslinking (hypercrosslinking) applying di-tert-butyl peroxide as the source of radicals. A significant difference in the specific surface area of polymers prepared by FRP (between 20 and 35 m
/g) and samples prepared by RAFT polymerisation (between 60 and 150 m
/g) was found. Based on the results from gas adsorption and solid state NMR, it could be concluded that the RAFT polymerisation affects the homogeneous distribution of the crosslinks in the highly crosslinked styrene-co-divinylbenzene polymer network. During the initial crosslinking, RAFT polymerisation leads to the increase in mesopores with diameters between 2 and 20 nm, resulting in good accessibility of polymer chains during the hypercrosslinking reaction, which is reflected in increased microporosity. The fraction of micropores created during the hypercrosslinking of polymers prepared via RAFT is around 10% of the total pore volume, which is up to 10 times more than for polymers prepared by FRP. Specific surface area, mesopore surface area, and total pore volume after hypercrosslinking reach almost the same values, regardless of the initial crosslinking. The degree of hypercrosslinking was confirmed by determination of the remaining double bonds by solid-state NMR analysis.
1,6-hexanediol diacrylate (HDDA) or divinyl adipate (DVA) and pentaerythritol tetrakis(3-mercaptopropionate) (TT) were polymerised via a thiol-ene radical initiated photopolymerisation using ...emulsions with a high volume fraction of internal droplet phase and monomers in the continuous phase as precursors. The porous structure derived from the high internal phase emulsions (HIPEs) followed the precursor emulsion setup resulting in an open porous cellularly structured polymer. Changing the emulsion composition and polymerisation conditions influenced the resulting morphological structure significantly. The investigated factors influencing the polymer monolith morphology were the emulsion phase ratio and surfactant concentration, leading to either interconnected cellular type morphology, bicontinuous porous morphology or a hollow sphere inverted structure of the polymerised monoliths. The samples with interconnected cellular morphology had pore diameters between 4 µm and 10 µm with approx. 1 µm sized interconnecting channels while samples with bicontinuous morphology featured approx. 5 µm wide pores between the polymer domains. The appropriate choice of emulsion composition enabled the preparation of highly porous poly(thiol-enes) with either polyHIPE or bicontinuous morphology. The porosities of the prepared samples followed the emulsion droplet phase share and could reach up to 88%.
Porosity in polymers and polymeric materials adds to their functionality due to achieving the desired tailored characteristics porosity offers, such as improved mass transfer through the material, ...improved accessibility of reactive sites, reduced overall mass, tunable separation properties, etc. Therefore, applications in many fields, e.g. catalysis, separation, solid phase synthesis, adsorption, sensing, biomedical devices etc., drive the development of polymers with controlled morphology in terms of pore size, shape, interconnectivity and pore size distribution. Of particular interest are polymers with distinct bimodal or hierarchical pore distribution as this enables uses in applications where pore sizes on multiple levels are needed. Emulsion templating can be used for the preparation of polymers with included interconnected spherical pores on the micrometre level while post polymerisation crosslinking adds micro porosity. Combined use of both techniques yields multi-level and hierarchically porous materials with great application potential.
With the aim to study the influence of monomer ratio in poly(high internal phase emulsions) (polyHIPEs) on the polymer network architecture and morphology of poly(vinylbenzyl ...chloride-co-divinylbenzene-co-styrene) after hypercrosslinking via the internal Friedel–Crafts process, polyHIPEs with 80% overall porosity were prepared at three different initial crosslinking degrees, namely 2, 5, and 10 mol.%. All had typical interconnected cellular morphology, which was not affected by the hypercrosslinking process. Nitrogen adsorption and desorption experiments with BET and t-plot modelling were used for the evaluation of the newly introduced nanoporosity and in combination with elemental analysis for the evaluation of the extent of the hypercrosslinking. It was found that, for all three initial crosslinking degrees, the minimum amount of functional monomer, 4-vinylbenzyl chloride, was approximately 30 mol.%. Hypercrosslinking of polymers with lower concentrations of functional monomer did not result in induction of nanoporosity while the initial crosslinking degree had a much lower impact on the formation of nanoporosity.
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