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A tubular co-flow reactor to produce macroporous polymer beads by polymerization of medium and high internal phase emulsion (M/HIPE) templates was developed. This reactor allows for improved production rates compared to tubing based microfluidic devices. Water-in-oil (W/O) M/HIPEs, containing methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) monomers in the continuous phase, were injected into a re-circulating carrier phase. The continuous phase of the emulsion droplets was UV polymerized in situ, resulting in polyM/HIPE beads. The emulsion composition was adjusted to produce poly(MMA-co-EGDMA) porous polymer beads with a protective crust and an interconnected internal pore structure. HCl loaded beads were produced by adding the active ingredient into the dispersed emulsion phase, leading to HCl encapsulation in the porous structure of the beads after polymerization. Even after exposure to ambient conditions for 24 h, 60% of the HCl remained in the beads, indicating good encapsulation efficiencies. Thus, it is possible to use such macroporous beads as delivery vehicles.

Micromixers made from emulsion templated macroporous polymers (poly-Pickering-HIPEs) were used to continuously produce polymerizable high internal phase emulsions (HIPE) by injecting a monomer containing continuous phase and aqueous internal phase into micromixers. The interconnected and complex flow path through poly-Pickering-HIPE micromixers resulted in effective mixing by creating local vortices and shear. The emulsion phase volume fraction of the produced HIPE templates can be varied during the process. PolyHIPEs with a porosity gradient ranging from 74% to 89% were produced by altering the phase volume ratio during the emulsification in poly-Pickering-HIPE micromixers. The average pore size of the produced polyHIPEs can be tailored by using poly-Pickering-HIPE micromixers with degrees of interconnectivity ranging from 0.028 to 0.06. The lower the degree of interconnectivity of the micromixer the smaller the droplet size of the produced HIPEs and thus the average pore size of the resulting polyHIPEs.

The abstract is available here: https://uscholar.univie.ac.at/o:1633047

Polyetheretherketone (PEEK) is a high-performance semi-crystalline thermoplastic polymer with outstanding mechanical properties, high thermal stability, resistance to most common solvents, and good biocompatibility. A high temperature thermally induced phase separation technique was used to produce PEEK foams with controlled foam density from PEEK in 4-phenylphenol (4PPH) solutions. Physical and mechanical properties, foam and bulk density, surface area, and pore morphology of foamed PEEK were characterized and the role of PEEK concentration and cooling rate was investigated. Porous PEEK with densities ranging from 110 to 360 kg/m

The abstract is available here: https://uscholar.univie.ac.at/o:1586494

Flexible epoxy foams were successfully prepared by curing medium internal phase emulsions (MIPEs) with a continuous organic phase containing epoxy resin and hardener, surfactant and carbon nanotubes and an aqueous internal phase. Curing the MIPEs at ambient temperature resulted in interconnected polyepoxide foams with average pore size of about 10 μm, while curing the MIPEs (with carbon nanotubes as a thickening agent) at 50 °C resulted in epoxy foams with pore sizes of one magnitude higher. The polyepoxide foams were compressible up to a strain of 70% of their original height and did not fracture. The polyepoxide foams were resilient with energy loss coefficients ranging from 40% to 60%, representing their energy adsorption during cyclic loading.

A series of carbon black filled polyHIPEs was synthesised following a new preparation protocol. 1 wt% carbon black was dispersed in the monomer mixture. In order to enhance the stability of the suspension, in situ polymer grafting of carbon black was performed by initiating the polymerisation prior to emulsifying the formulation. All of the carbon black filled polymer foams synthesised via the new preparation protocol have the characteristics usually observed for polyHIPEs. Carbon black particles are incorporated into the pore walls without affecting the pore structure of the polyHIPEs. The new preparation protocol positively influenced the properties of the resulting polyHIPEs namely the pore interconnectivity is increased and a water permeability of up to 2.3 D is achieved.

We realised spring/spacer elements, which are crucial components of capacitive energy harvesters, by syringe printing of polyurethane diacrylate and ethylhexyl acrylate based high (HIPE) and medium (MIPE) internal phase emulsion templates followed by UV polymerisation. The resulting micropatterned poly(merised)H/MIPEs are very flexible and reversibly compressible to a strain of 50% as cyclic compression test revealed. Dynamic mechanical analysis has shown constant mechanical behaviour of the macroporous polymer springs under a loading/unloading at a frequent of 2 Hz for 10 h, proving the practical durability of the springs. Within a prototype harvester the micropatterned macroporous springs allowed to compartmentalise Hg droplets and provided the required restoring force to operate the device successfully; the capacitive change of the device within one compression-recovery cycle reached 570 pF.

Supported hydrogel membranes were produced by one-pot synthesis by polymerisation of suitable emulsion templates. High internal phase emulsions (HIPEs) with styrene (St), divinylbenzene (DVB) and ethylhexyl acrylate (EHA) in the continuous phase and methacrylic acid (MAA) in the internal phase were polymerised to prepare poly(MAA) hydrogel grafted poly(St- co -DVB- co -EHA) poly(merised)HIPEs. By changing the concentration of the crosslinker, N , N′ -methylenebisacrylamide, in the internal phase of the emulsion template the crosslinking density of the grafted poly(MAA) was tuned. The presence of the hydrogel was indicated by a change in pore morphology, e.g. coverage of the pore throats and the wrinkled pore wall surface, and the increase in the density of the composite polyHIPEs as compared to control polyHIPEs. Moreover, the increase in foam density and reduction of porosity were related to the crosslinking degree of the hydrogel. The water uptake of the composite polyHIPEs exceeded the pore volume of the polyHIPE scaffold supporting the grafted hydrogel. The permeability and rejection of aqueous solutions of polyethylene glycol (PEG) by the hydrogel grafted polyHIPE membranes were strongly pH dependent, the permeability decreased and the rejection of PEG increased with increasing pH due to the increased swelling of the hydrogel. A 91% rejection of 50 kDa PEG for polyHIPE supported hydrogel membranes has been identified, which qualifies such membranes for ultrafiltration applications.

There is increasing focus on the development of bioactive scaffolds for tissue engineering and regenerative medicine that mimic the native nanofibrillar extracellular matrix. Solution blow spinning (SBS) is a rapid, simple technique that produces nanofibers with open fiber networks for enhanced cell infiltration. In this work, highly porous bioactive fibers were produced by combining SBS with thermally induced phase separation. Fibers composed of poly(d,l-lactide) (PLA) and dimethyl carbonate were sprayed directly into a cryogenic environment and subsequently lyophilized, rendering them highly porous. The surface areas of the porous fibers were an order of magnitude higher in comparison with smooth control fibers of the same diameter (43.5 m2·g–1 for porous fibers produced from 15% w/v PLA in dimethyl carbonate) and exhibited elongated surface pores. Macroporous scaffolds were produced by spraying water droplets simultaneously with fiber formation, creating a network of fibers and ice microspheres, which act as in situ macroporosifiers. Subsequent lyophilization resulted in three-dimensional (3D) scaffolds formed of porous nanofibers with interconnected macropores due to the presence of the ice spheres. Nanobioactive glass was incorporated for the production of 3D macroporous, bioactive, therapeutic-ion-releasing scaffolds with potential applications in non-load-bearing bone tissue engineering. The bioactive characteristics of the fibers were assessed in vitro through immersion in simulated body fluid. The release of soluble silica ions was faster for the porous fibers within the first 24 h, with confirmation of hydroxyapatite on the fiber surface within 84 h.

Polymerised high internal phase emulsions (polyHIPEs) have drawn extensive interest in recent years; however, industrial applications do require polyHIPEs to be tough and robust. The mechanical properties of polyHIPEs can be tuned by copolymerisation of polyurethane diacrylate (PUDA) and styrene. The resulting open-porous poly(styrene-co-PUDA)HIPEs were much less brittle and friable when compared to conventional poly(styrene-co-divinylbenzene)HIPEs. Moreover, poly(styrene-co-PUDA)HIPEs have impact strengths up to 10 times higher than poly(styrene-co-divinylbenzene)HIPEs. The styrene/PUDA ratio determines the morphology, thermal and mechanical properties of the poly(styrene-co-PUDA) macroporous polymers. The viscous PUDA promotes the formation of small pores in polyHIPEs. A high PUDA content of the copolymer results in a dual glass transition temperature and low mechanical properties. By using an optimised St/PUDA ratio, we manufactured polyHIPEs with impact strength similar to that of commercial closed-cell polyurethane foam.

Macroporous, low-density polyetheretherketone, polyetherketoneketone, and polyetherimide foams are produced using a high-temperature, thermally induced phase separation method. A high-boiling-point solvent, which is suitable to dissolve at least 20 wt% of these high-performance polymers at temperatures above 250 °C, is identified. The foam morphology is controlled by the cooling procedure. The resulting polymer foams have porosities close to 80% with surface areas up to 140 m2 g-1 and elastic moduli up to 97 MPa.

Macroporous elastomers with fast shape recovery have been produced by polymerisation of emulsion templates. Particle stabilised high internal phase emulsions (HIPEs) containing trimethylolpropane tris(3-mercaptopropionate) (TRIS) and divinylbenzene (DVB) in the continuous phase and a surfactant as additive were prepared. The polymerisation of the HIPEs resulted in elastomeric, open porous poly(TRIS-co-DVB)HIPEs. The average pore size and degree of pore interconnectivity of the polyHIPEs could be controlled by surfactant concentration and energy input during emulsification. The polyHIPEs were compressible up to strains of 70% without failure and characterised by elastic moduli down to 170 kPa. Furthermore, the poly(TRIS-co-DVB)HIPEs exhibited a low hysteresis ratio down to 0.07 during cyclic compression, indicating their rapid recovery and low energy loss during cyclic loading. This renders these materials suitable for applications as springs in energy harvesting devices.

International audience; Emulsions, foams, and foamed emulsions have been used successfully as templates for the synthesis of macroporous polymers. Based on this knowledge this Minireview presents strategies to use, optimise, and upscale these templating methods to synthesise tailor‐made porous polymers. The uniqueness of such polymers lies in the ability to tailor their structures and, therefore, their properties. However, systematic studies on structure–property relations are lacking mainly because the templating scientific community is “split into two”: the polydisperse and monodisperse camps. Thus, it is time to build a bridge between the camps, that is, to synthesise porous polymers with very different structures from the same precursors to determine the relationship between the structure and the properties.

Herein we present a systematic study of the antagonistic interaction between magnetite nanoparticles (Fe3O4) and nonionic hydrophobic surfactant in Pickering highly concentrated emulsions. Interfacial tension measurements, phase behavior, and emulsion stability studies, combined with electron microscopy observations in polymerized systems and magnetometry, are used to support the discussion. First, stable W/O highly concentrated emulsions were obtained using partially hydrophobized magnetite nanoparticles. These emulsions experienced phase separation when surfactant is added at concentrations as low as 0.05 wt %. Such phase separation arises from the preferential affinity of the surfactant for the nanoparticle surfaces, which remarkably enhances their hydrophobicity, leading to a gradual desorption of nanoparticles from the interface. W/O emulsions were obtained at higher surfactant concentrations, but in this case, these emulsions were mainly stabilized by surfactant molecules. Therefore, stable emulsions could be prepared in two separate ranges of surfactant concentrations. After polymerization, low-density macroporous polymers were obtained, and the adsorption and aggregation of nanoparticles was analyzed by transmission electron microscopy. The progressive displacement of the nanoparticles was revealed: from the oil-water interface, in which aggregated nanoparticles were adsorbed, forming dense layers, to the continuous phase of the emulsions, where small nanoparticle aggregates were randomly dispersed. Interestingly, the results also show that the blocking temperature of the iron oxide superparamagnetic nanoparticles embedded in the macroporous polymers could be modulated by appropriate control of the concentrations of both surfactant and nanoparticles.

Emulsion templated macroporous polymers, called poly(merised) high internal phase emulsions (polyHIPEs), are considered for a wide variety of applications ranging from supports for chemical reactions to bone grafts; however this review focuses only on applications of polyHIPEs in the field of fluid separations. PolyHIPEs are produced by polymerisation or solidification of the continuous phase of a HIPE and removal of the internal emulsion phase. They possess an interconnected pore structure giving them a significant permeability. This review provides a brief overview of what polyHIPEs are and then examines their potential for fluid separation applications. So far polyHIPEs are used as filters, membranes, ion exchange columns for protein purification, chromatography, chemical scavenging, absorption and for breaking emulsions.

Emulsion templates containing monomers in both emulsion phases were used to manufacture polystyrene-co-divinylbenzene based polymerized high internal phase emulsions (polyHIPEs) which have been reinforced by poly(methacrylic acid) (polyMAA) and poly(dimethyl aminoethyl methacrylate) (polyDMAEMA). The morphology of the hydrogel-filled polyHIPEs is affected by the hydrogels synthesized in the aqueous emulsion phase. The pore structure of polyMAA-filled polyHIPEs is highly interconnected indicating the formation of a methacrylic acid-co-styrene copolymer at the oil/water interface of the emulsion templates during synthesis. However, polyDMAEMA-filled polyHIPEs are predominately closed celled and the pore walls are covered by grafted hydrogel. The ability of the hydrogel-filled polyHIPEs to absorb water decreased with increasing crosslinking density of the hydrogels. The dry hydrogel reinforced the polyHIPE scaffolds possessed higher elastic moduli and crush strengths than the control polyHIPEs. The reinforcing ability of the dry hydrogels was further enhanced by increasing their degree of crosslinking. However, the reinforcement could be “switched off” simply by hydrating the hydrogels. The switchable mechanical properties of the hydrogel-filled polyHIPEs could potentially be utilized in smart humidity sensor technology.

Emulsion templating is an effective route to prepare low-density, interconnected macroporous polymers known as poly(merised)High and Medium Internal Phase (Ratio) Emulsions. Here, we provide evidence that the interconnectivity of polyMIPEs is strongly dependent on the initiator used for the polymerisation of the continuous phase of the template. The characteristic interconnected pore structure can be observed if an oil soluble initiator, we used α,α′-azoisobutyronitrile, is used irrespectively of the surfactant employed to stabilise the emulsion templates. However, polymerisation of the continuous emulsion phase initiated by water-soluble initiators such as redox initiators or potassium peroxodisulfate results in low pore interconnectivity or even closed celled polyMIPEs.

Summary Gravel packs are conventionally used as a permeable solid layer in the annulus between a production screen and the walls of the wellbore in weakly consolidated subterranean formations. Gravel packing is a well-known technique for sand control, whereby unconsolidated fines produced from the soft formation are filtered away from the production fluids. However, gravel packs can be problematic. The bridging of sand particles within the gravel pack can create voids that can result in mechanical failures or significantly reduce the effectiveness of gravel packs to restrain fines from flowing along with the hydrocarbons produced. As an alternative, we present a pioneering method to prepare void-free and mechanically sound permeable barriers in subterranean formations as an alternative to gravel packing. The method of preparation involves the curing of Pickering water-in-oil medium-internal-phase emulsions (MIPEs) or high-internal-phase emulsions (HIPEs) containing monomers in the annular space between a rock formation and pipe. The emulsions were prepared simply by adding low amounts of nonionic surfactant and dispersant to premade Pickering emulsions that were stabilized by oleic-acid (OA) -modified silica particles. The resulting macroporous solid materials, known as “poly(merised)Pickering-M/HIPEs,” have a gas permeability of up to 2.6 darcys and are highly interconnected and permeable to hydrocarbons. This paper shows that it is possible to tailor the gas permeability and mechanical performance of the permeable barrier by altering the emulsion internal-phase volume, the volume of surfactant added to the premade Pickering emulsion, and the composition and constituents of the continuous monomer phase; styrene, divinylbenzene (DVB), and poly(ethylene glycol) dimethacrylate were used in the monomer phase.

Inspired by natural porous materials, such as wood, bamboo and spongy bone consisting of individual structural units that are hierarchically arranged to optimise mechanical properties such as strength and toughness, synthetic macroporous polymers with enhanced physical properties were created by emulsion templating. Hierarchical poly(merised) high internal phase emulsions (HIPE) were created from HIPEs stabilised simultaneously by particles and a surfactant. In these HIPEs, surfactant stabilised and particle stabilised water droplets coexist, which upon polymerisation of the minority oil phase gives rise to macroporous polymers with a hierarchical pore structure. An improvement of the mechanical properties of our hierarchically structured macroporous polymers at equal porosity was observed, due to a more efficient packing of pores in a configuration that improves mechanical strength despite the presence of interconnecting pore throats. Moreover, the permeability of the hierarchically structured polyHIPEs are exceeding those measured for conventional polyHIPEs made from surfactant only stabilised HIPEs.

We polymerised the continuous styrene/divinylbenzene monomer phase of high internal phase emulsions (HIPEs) containing 70 vol.% cement slurry as internal phase to synthesise polymer cement hybrid materials. These novel cement containing poly(merised)HIPEs have an interconnected bi-phasic structure consisting of an interpenetrating network of set cement and polymer. Incorporating 14 wt.% of polymer into the cement resulted in an increased compressive strain to failure as compared to pure set cement but both elastic modulus and crush strength decreased. These novel polymer cement hybrid materials have a better chemical resistance against acetic acid then pure cement and showed also no shrinkage when exposed to xylene and dodecane.

Emulsion templating using high internal phase emulsions is an effective route to prepare low density and high porosity macroporous polymers known as polymerized high internal phase emulsions (polyHIPEs). Conventional polyHIPEs, synthesized from surfactant stabilized w/o emulsions have low permeabilities and poor mechanical properties. We present interconnected open macroporous low density nanocomposites produced by polymerizing the continuous phase of emulsion templates, which contained styrene, polyethyleneglycoldimethacrylate, and silylated silica particles. Polyethyleneglycoldimethacrylate and the silylated silica particles acted as crosslinker. The functionalized silica particles were incorporated into the polymer, which resulted in a significant improvement of the mechanical properties of the polyHIPEs without affecting the interconnected and permeable pore structures. The polyHIPEs contained up to 60 wt % silylated silica particles. Young's modulus of the reinforced macroporous polymers increased up to 600% compared with nonreinforced macroporous polymers. The mechanical performance was further increased by increasing the foam density of the macroporous nanocomposites from around 200 to 370 g/cm3 by raising the organic phase volume of the emulsion templates from 20 to 40 vol %. The macroporous polymers synthesized from less concentrated emulsions also possessed interconnected open porous although less permeable structures. The polyHIPE nanocomposites have a permeability of about 200 mD, whereas the polyMIPE nanocomposites still have permeabilities of around 50 mD. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1979–1989, 2010

Highly open porous polymer foams obtained via the polymerization of the continuous monomer phase of concentrated emulsions are very attractive materials for a wide range of applications due to their low density and interconnected pore structure. Emulsion templating has emerged as an effective route to prepare well-defined porous polymer foams having a morphology defined by the structure of the emulsion template at the gel-point of the polymerization; the most intensely studied emulsion templates are high internal phase emulsions (HIPEs). HIPEs have been defined as highly concentrated emulsions in which the internal phase occupies more than 74% of the emulsion volume. Although there are a number of publications relating to oil in water (o/w) emulsion templates, most commonly, polyHIPEs are synthesized by polymerizing the continuous monomer phase of water in oil (w/o) systems. The aqueous phase of w/o HIPEs commonly contains low concentrations of an electrolyte, such as CaCl2 2H2O, to suppress Ostwald ripening. The organic, continuous phase consists of monomers and crosslinkers as well as either a nonionic surfactant, such as Span 80, or a particulate emulsifier, such as titania, to stabilize the droplets in a HIPE against coalescence. Depending on the type of the initiator used, it is either dissolved in the aqueous phase (potassium persulphate) or in the organic phase [a,a0-azoisobutyronitrile (AIBN)]. Importantly, the HIPE templating route not only provides control over morphology and properties of the resulting polymer foams but a simple means to generate any given shape by molding the emulsion before polymerization. A variety of potential applications for polyHIPEs have been explored by academics, including filter modules, ion exchange resins, monolithic microbioreactors with immobilized bacteria or for the separation of protein mixtures, matrices for cell culture and scaffolds for tissue engineering. However, industrial applications of these materials, not only in harsh environments, have been limited particularly by the relatively poor mechanical performance of polyHIPEs. There are a number of routes to modifying the mechanical properties of polyHIPEs, although all have limitations. The choice of the monomers and crosslinker has a strong effect on the mechanical behavior; for example, the common polyHIPEs based on styrene and divinylbenzene (DVB) are brittle and chalky whereas replacing some of the styrene by 2-ethylhexylacrylate leads to elastomeric polyHIPEs. The use of a stress reducing crosslinker, such as polyethylene glycol dimethacrylate, instead of DVB, results in Correspondence to: A. Bismarck (E-mail: a.bismarck@ imperial.ac.uk)

We report on the successful use of particle-stabilized Medium Internal Phase Emulsion (MIPE) templates for the synthesis of porous polymer foams. In this case, carbon nanotubes (CNTs) were used to stabilize the minority phase as the continuous phase, through adsorption at the interface. The addition of the CNTs not only provides processing advantages (no need for traditional non-ionic molecular surfactants) but also enhances the mechanical and electrical properties of the final polyFoams. This approach allows the manufacture of both closed- and open-celled porous polymer foams in a one-pot process with porosities up to 66%.

It is our aim to produce macroporous polymers in complex shapes by printing as printing techniques are versatile, give excellent control over the design of the pattern and allow for rapid prototyping. However, inks are required, which can ultimately be cured into macroporous polymers. We, therefore, utilised high and medium internal phase emulsions with a polymerisable continuous phase and an internal droplet phase, which serves as template, as inks in the printing process. Subsequent polymerisation leads to the macroporous polymers. Emulsion templates containing styrene-butadiene-styrene rubber, thiol crosslinker and benzene or toluene as diluting solvent in the continuous phase were syringe printed into cage patterns. Thereby, the wall thickness was controlled by the outer diameter of the needles used, which was varied between 300µm to 750µm. By doing so we were able to print individual cages with sizes between 0.6×0.6mm2 and 2×2mm2 processing well defined and distinct walls. Subsequent UV polymerisation and drying gives rise to a macroporous polymer network within the walls.

We present new evidence that the formation of pore throats (windows) or pore interconnects in polymerised High Internal Phase Emulsions (polyHIPEs) is most likely due to a mechanical action exerted during the post-synthesis processing of the porous polymer monolith. We would like to invite researchers interested in this field to reopen the discussion on the mechanism which lead to the formation of pore throats during the polymerisation of concentrated emulsion templates.

The aim of this work was to synthesise highly open porous low-density polymer foams with superior mechanical properties by the polymerisation of the organic phase of concentrated emulsions. The continuous organic phase of the concentrated emulsion template occupying up to 40 vol% was polymerised leading to polymer foams with much improved mechanical properties. The Young's modulus as well as the crush strength of the foams was further increased dramatically by reinforcing the polymer phase with nanosized silica particles. To ensure that the silica particles were covalently incorporated into the polymer network, methacryloxypropyltrimethoxysilane (MPS) was added to the formulation, which reacts with the silica via hydrolysis reactions. The Young's modulus of silica reinforced foams increased by 280% and the crush strength by 218% in comparison to foams without reinforcement.

The surface properties of original high strength and preoxidized high modulus carbon fibers were altered by electrocopolymerizing acryl amide and carbazole and therefore depositing a copolymer coating onto the fibers. Scanning electron microscopy and zeta-potential measurements confirmed the presence of a rough but dense and continuous electrocoating with a basic surface character. Therefore, ‘good’ adhesion behavior between the electrocoated carbon fibers and an epoxy resin matrix should be expected. The interfacial adhesion was measured using the single fiber pull-out and single fiber indentation test. It was shown that only ‘intermediate’ adhesion was present between the carbon fibers and the electrocoating, but superior adhesion between the coating and epoxy resin exists. The single fiber model composites always failed at the fiber/electrocoating interface. However, as shown by using the indentation test, the interfacial adhesion between fibers and electrocoating can be significantly improved if preoxidized fibers are used as substrate for electropolymerization. A very high tensile strength for the electrocoating can be expected as derived from the single fiber pull-out tests.

Reduced graphene oxide (rGO) is known to be electrically conductive and adsorb at oil–water interfaces. It has also been shown to mechanically reinforce bulk materials. This work combines these favourable characteristics of two-dimensional rGO to develop 3D macroporous polymer nanocomposites via emulsion templating. rGO proved to be an efficient emulsifier as only 0.2 mg/ml (with respect to the oil phase) of rGO was required to stabilise water-in-oil high internal phase emulsions (HIPE) of up to 80 vol.% internal phase. After polymerisation of the continuous minority monomer (styrene and divinylbenzene) phase, macroporous polymer nanocomposites with tuneable microstructures were obtained. The storage modulus of rGO-poly(styrene-co-divinylbenzene) HIPEs increased by almost an order of magnitude when the rGO concentration used to stabilise the HIPE template increased from 0.4 to 5.0 mg/ml. The adsorption and organisation of rGO at the o/w interface in HIPEs prior to polymerisation and partial aggregation in the polymer cell walls after polymerisation resulted in conductive nanocomposites with a rGO content of as low as 0.006 vol.% (with respect to bulk polymer volume or 0.8 mg/ml with respect to the monomer volume used in the emulsion template) compared to 0.1 vol.% for dense nanocomposites previously reported. This provided evidence for the efficient arrangement of rGO within the macroporous polymer nanocomposite, creating an electrically conductive network.

A series of copolymers were synthesized by chemically oxidative polymerization of pyrrole (PY) and m -toluidine (MT) in hydrochloride aqueous medium at ambient temperature. The yield, intrinsic viscosity, and solubility of the copolymers were studied by changing PY/MT molar ratio from 0/100 to 88/12. The as-prepared PY/MT copolymer bases were characterized by FT–IR, UV–VIS, 1 H NMR, DSC, and wide-angle X-ray diffraction. The results suggested that the oxidative polymerization from pyrrole and m -toluidine is exothermic and the resulting copolymers are more easily soluble in most of the organic solvents than polypyrrole. The polymer obtained is a real copolymer containing pyrrole and m -toluidine units, but the PY content calculated on the basis of the proton NMR spectra is lower than feed PY content.

The electrocopolymerization of carbazole and acrylamide on highly oriented pyrolytic graphite (HOPG) from ACN solutions via cyclovoltammetry (CV) was studied in order to evaluate the possibility to deposit uniform and thin but pinhole-free and still reactive coatings onto graphite-like substrates. The morphology of the coatings was investigated using atomic force microscopy and the coating thicknesses and optical parameters were measured using ellipsometry. It was found that under the chosen conditions thin (coating thickness hf>180 nm) and relatively smooth (root mean square surface roughness RMS 50 nm) no pinholes could be detected. It was found that the thickness of the deposited coatings increases almost linearly with increasing number of CV-cycles while keeping all other experimental parameters (scan rate and comonomer concentration ratio) constant. No influence of the comonomer concentration ratio on the film thickness and coating appearance could be observed, however, at quite low initial concentrations. However, the CV-scanning rate has quite a significant influence on the thickness of the deposited coatings. Higher scan rates (100 mV/s) result in thin (hf≈22 nm) coatings whereas at lower scan rates (

A series of copolymers were synthesized by chemically oxidative polymerization of pyrrole (PY) and o -anisidine (AS) in acidic aqueous medium. The yield, intrinsic viscosity, and solubility of the copolymers were studied by changing the monomer molar ratio, initial polymerization temperature, oxidant, ratio of monomer over oxidant, acidic medium, and adding dodecylbenzene sulfonate. As prepared PY/AS copolymer powder, was characterized by FT-IR, UV–Vis, 1 H NMR, DSC, and TG techniques. The results showed that the oxidative polymerization from PY and o -anisidine is exothermic and the resulting copolymers exhibit an enhanced solubility in most of the organic solvents as compared with polypyrrole. The polymer obtained by the oxidative polymerization is a real copolymer containing pyrrole and o -anisidine units. The PY molar content calculated based on the 1 H NMR spectra is slightly lower than feed PY content when feed PY content is lower than 30 mol%. The thermostability of the PY/AS copolymer increases with increasing PY unit content.

High Internal Phase Emulsions (HIPEs) are important for a wide range of applications in the food, cosmetic, pharmaceutical and petroleum industries. If the continuous phase is polymerizable, HIPEs can be used as templates for the synthesis of highly porous polymers with potential applications as low weight structures or scaffolds in tissue engineering. HIPEs are characterized by a minimum internal phase volume ratio of 0.74 but Lissant first defined this minimum as 0.7. HIPEs consisting of a continuous organic phase and an internal aqueous phase (w/o emulsion), are commonly stabilized by large amounts of surfactants. Particle-stabilized emulsions also known as Pickering-emulsions have recently attracted much interest. Unlike surfactants, particles irreversibly adsorb at the interface of emulsions due to their high energy of attachment which makes them good emulsifiers. The ability of particles to adsorb at the interface between the two phases is primarily dependent on the wettability of the particles. Hydrophilic particles such as metal oxides tend to stabilize o/w emulsion while hydrophobic particles such as carbon tend to stabilize w/o emulsions. Nevertheless, it is possible to modify the wettability of particles by adsorbing surfactant molecules onto the particle surfaces or by silanation. All reports on particle-stabilized emulsions deal with emulsions having internal phase levels elow 70 vol.-%. Kralchevsky et al. developed a thermodynamic model, which predicts that

WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW The radical polymerization of methylmethacrylate (1) intheabsence andpresence of potential transfercompoundssuch as 2-(4-methoxyphenylazo)anthraquinone (4) and2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)-phenol (5) is described. Neither the phenylazoanthraqui-none nor the phenylbenzotriazol group affect the radicalpolymerization of MMA concerning the polymer proper-ties of the respectively obtained PMMA (P1). Thesynthesis of the copolymer P2 by radical copolymeriza-tion of 3 mol% 2-[4-(6-methacryloyloxyhex-1,6-diy-loxy)-phenylazo]anthraquinone (2) and 97 mol% 2-[3-(2H-benzotriazol-2yl)-4-hydroxyphenyl]ethylmethacry-late (3) is described. The composition of the randomlikecopolymerP2correspondstothemonomerfeed.Sincethemolar mass of P2 is high (M

Magnetic macroporous polymers have been successfully prepared using Pickering high internal phase ratio emulsions (HIPEs) as templates. To stabilize the HIPEs, two types of oleic acid-modified iron oxide nanoparticles (NPs) were used as emulsifiers. The results revealed that partially hydrophobic NPs could stabilize W/O HIPEs with an internal phase above 90%. Depending upon the oleic acid content, the nanoparticles showed either an arrangement at the oil-water interface or a partial dispersion into the oil phase. Such different abilities to migrate to the interface had significant effects on the maximum internal phase fraction achievable and the droplet size distribution of the emulsions. Highly macroporous composite polymers were obtained by polymerization in the external phase of these emulsions. The density, porosity, pore morphology and magnetic properties were characterized as a function of the oleic acid content, concentration of NPs, and internal phase volume of the initial HIPEs. SEM imaging indicated that a close-cell structure was obtained. Furthermore, the composite materials showed superparamagnetic behavior and a relatively high magnetic moment.

Inspired by natural porous materials, such as wood, bamboo and spongy bone consisting of individual structural units that are hierarchically arranged to optimise mechanical properties such as strength and toughness, synthetic macroporous polymers with enhanced physical properties were created by emulsion templating. Hierarchical poly(merised) high internal phase emulsions (HIPE) were created from HIPEs stabilised simultaneously by particles and a surfactant. In these HIPEs, surfactant stabilised and particle stabilised water droplets coexist, which upon polymerisation of the minority oil phase gives rise to macroporous polymers with a hierarchical pore structure. An improvement of the mechanical properties of our hierarchically structured macroporous polymers at equal porosity was observed, due to a more efficient packing of pores in a configuration that improves mechanical strength despite the presence of interconnecting pore throats. Moreover, the permeability of the hierarchically structured polyHIPEs are exceeding those measured for conventional polyHIPEs made from surfactant only stabilised HIPEs.

Gravel packs, most commonly occurring as sand slurries, are conventionally employed as a permeable solid layer in the annulus between a production screen and walls of the wellbore in weakly consolidated subterranean formations (Powell et al. 2006). Gravel packing is a well-known technique for sand control, whereby unconsolidated fines produced from the soft formation are filtered away from the production fluids (Penberthy and Shaughnessy 1992; Saucier 1974; Powell et al. 2006; Tiffin et al. 1998). Unconsolidated fines are highly challenging, as they are expensive to dispose of and can cause erosion of surface equipment, casing failure, clogging of production pipes, and production loss (Penberthy and Shaughnessy 1992; Sparlin and Hagen 1985). However, gravel packs can be problematic. Bridging of sand particles within the gravel pack can create voids, which can result in mechanical failures or significantly reduce the effectiveness of gravel packs to restrain fines from flowing along with the hydrocarbons produced (Suman 1974; Tiffin et al. 1998; Powell et al. 2006). As an alternative, this paper presents a pioneering method to prepare void-free and mechanically sound permeable barriers in subterranean formations as an alternative to gravel packing. The method of preparation involves the curing of Pickering water-in-oil medium- or high-internal-phase emulsions containing monomers in the annular space between a rock formation and pipe. The emulsions were prepared by simply adding low amounts of nonionic surfactant and dispersant to premade Pickering emulsions, which were stabilized by oleic-acid (OA) modified silica particles (Ikem et al. 2008). The resulting solid materials, known as "poly-Pickering-M/HIPE,"have a gas permeability of up to 2.6 darcies and are highly interconnected and permeable to hydrocarbons (Ikem et al. 2010b). This paper shows that it is possible to tailor the gas permeability and mechanical performance of the permeable barrier by altering the emulsion internal-phase volume, the volume of Hypermer 2296 added to the premade Pickering emulsion, and the composition and constituents of the continuous monomer phase; styrene, divinylbenzene (DVB), and poly(ethylene glycol) dimethacrylate (PEGDMA) were used in the monomer phase.

High temperature activation of carbon nanotubes (CNTs) provides a new and highly versatile functionalisation strategy. The reaction allows the attachment of a wide variety of functional species onto the nanotube surface at grafting ratios between 1–8 wt%, whilst maintaining the intrinsic properties of the untreated materials. The underlying, radical-based, reaction mechanism has been established by quenching experiments and EPR studies. The distribution of the functionalised sites has been investigated at the microscopic scale using tagging reactions. The grafted products have been characterized by electron microscopy, thermal analysis (TGA), Raman spectroscopy, and inverse gas chromatography (IGC). The change in the CNT surface properties after grafting has been quantified in terms of dispersive and specific surface energies, and altered dispersibilities in a broad range of solvents. It is possible to carry out the reaction using gas phase reagents, providing a clean, efficient, and scalable methodology, relevant to a diverse range of applications.

Particle-stabilized high internal phase emulsions have been used to synthesize tough and very high porosity macroporus polymers with a closed-cell pore structure. In this study, we show that Pickering water-in-oil emulsion templates with up to an 85 vol % internal phase can be stabilized by only 1 wt % of titania particles with their surfaces suitably modified by the adsorption of 3.5 +/- 0.5 wt % oleic acid. The pore structure and mechanical properties of the resulting macroporous polymers were tailored by altering the internal phase volume ratio of the emulsion template and the titania particle concentration used to stabilize the emulsion templates. The pore size and pore size distributions increase with increasing internal phase volume of the emulsion template as well as decreasing titania particle concentration used to stabilize the emulsion template. The mechanical properties, namely, Young's modulus and the crush strength of the macroporous polymers, increased with decreasing porosity and increasing foam density. The toughest macroporous polymer had the lowest porosity but also the smallest pore size and narrowest pore size distribution.

Porous polymer foams (poly-Pickering-HIPEs) have been synthesised from stable high internal phase emulsion templates solely stabilised by low concentrations of functionalised titania nanoparticles.

Highly interconnected macroporous polymers can be produced by the polymerization of high internal phase emulsions (HIPEs) with a dispersed phase exceeding 74 vol%. Until recently, it was thought that poly(merized)HIPEs with a maximum reported gas permeability of 0.46 D could only be produced by the polymerization of surfactant stabilized HIPE templates. However, highly permeable macroporous polymers with a gas permeability of up to 2.6 D were successfully prepared by adding small amounts of a non-ionic surfactant to pre-made Pickering emulsion templates; poor mechanical properties (crush strengths of ≤2.2 MPa) however limit the applicability of these materials. The mechanical properties were improved by altering the composition of the emulsion template. This involved using the flexible crosslinker polyethylene glycol dimethacrylate (PEGDMA), alongside other organic additives like divinylbenzene (DVB) and squalene in the organic phase. We also increased the material density by using medium internal phase emulsion (MIPE) templates and increased the surfactant concentration added to the pre-made Pickering-MIPEs. The resulting materials were characterized in terms of pore structure, gas permeability and mechanical performance. SEM images revealed pores of up to 1700 μm in diameter and interconnecting pore throats of up to 100 μm in diameter. The highest gas permeability and crush strength achieved were 0.92 ± 0.09 D and 5.6 ± 0.1 MPa, respectively, for a macroporous polymer synthesized from a Pickering-MIPE containing 50 : 40 : 10 (by volume) styrene, PEGDMA and DVB respectively, in the organic phase, to which 10 vol% Hypermer 2296 was added.

Interconnected macroporous polymers can be made by polymerisation of emulsion templates consisting of an aqueous phase and a monomer phase (typically styrene and divinylbenzene) in which the aqueous (internal) phase is in the form of drops and the monomer phase is the continuous phase between the drops. Until recently it was thought that interconnected macroporous polymers could only be produced from the polymerisation of high internal phase emulsion (HIPE) templates with an internal phase level exceeding 74 vol%. Improvement of the poor mechanical performance, characteristic of such macroporous polymers, was achieved simply by increasing the material density of the macroporous polymer. However, this required a reduction in the internal phase volume of the emulsion template. Polymerisation of the continuous organic phase of emulsion templates with an internal phase volume ranging from 84 vol% to 70 vol% resulted in the production of poly(merised)HIPEs, polymerisation of medium internal phase emulsions with internal phase volume ranging from 70 vol% to 30 vol% in polyMIPEs and polymerisation of a low internal phase emulsion with an internal phase volume of 25 vol% in a polyLIPE. The resulting macroporous polymers were characterised in terms of mechanical and structural properties as well as gas and mercury permeability. Compression tests show that mechanical properties improved as the material density was increased. Gas and mercury permeability measurements show that as the internal phase volume of the emulsion template is reduced, the permeability of the resultant macroporous polymer is also reduced. However, surprisingly even macroporous polymers produced from low internal phase emulsion templates (25 vol%) were permeable with a gas permeability of 2.6 × 10−14m2 indicating that polyLIPEs are still interconnected macroporous polymers. Reconstruction modelling of the transport properties of porous materials shows that the permeability of a porous material with similar structures to that of the macroporous polymers increases exponentially with the porosity.

Fully renewable macroporous thermosetting and UV-cured cellulose nanocomposites have been synthesized from medium and high internal phase water-in-acrylated soybean oil emulsions stabilized solely by hydrophobized bacterial cellulose nano-fibrils.