Advances in Tailoring Resorcinol‐Formaldehyde Organic and Carbon Gels

Elkhatat, Ahmed M.; Al‐Muhtaseb, Shaheen A.

doi:10.1002/adma.201100283

Cited by 418 publications

(324 citation statements)

References 98 publications

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“…Among different options, polymeric organic and carbon gels are postulated as interesting materials in many diverse fields due to their relatively low-cost and unique physical, chemical, and electrochemical properties that may be tuned during the synthesis and processing [2][3][4][5]. Industrial applications in sectors such as adsorbents for gas separation [6], catalyst supports [7,8], energy storage devices [9][10][11], capacitive deionization [12][13] and so forth have been largely studied since the first work of Pekala and coworkers [14].…”

Section: Introductionmentioning

confidence: 99%

“…In these two decades numerous articles have appeared in the literature describing various synthesis and processing conditions and their effects on the final structure (morphology, texture, composition) and performance [2][3][4][5]15]. To date most of the synthesis are based upon the catalyzed polycondensation of resorcinol (R)-formaldehyde (F) mixtures in water, although some alternative harmless and naturally available precursors have also been described [16,17].…”

Section: Introductionmentioning

confidence: 99%

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Fast synthesis of micro/mesoporous xerogels: Textural and energetic assessment

Isaacs-Páez

Haro

Juárez-Pérez

et al. 2015

Microporous and Mesoporous Materials

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The sol-gel polymerization of resorcinol/formaldehyde mixtures to obtain porous gels is typically a long process performed throughout several days. In this work, we have explored an experimental approach to reduce the time necessary to obtain porous gels based on mild polymerization conditions and direct drying. We have analyzed the effects of the temperature and time of the gelation/aging step on the porosity of the gels, as well as the impact on the overall energetic cost of the process. Data have shown that well-developed micro-mesoporous architectures can be obtained within less than a day. The temperature of the gelation/aging step mainly affects the mesopore network, whereas the microporosity is determined by the composition of the precursor's mixture. The exclusion of the solvent exchange step yields soft mechanically fragile porous gels with structural limitations upon carbonization at high temperature in inert atmosphere, due to the surface tensions applied to the backbone during the evolution of volatiles. The mesopore structure lost during carbonization is not recovered upon activation in CO 2 atmosphere, but it is preserved upon chemical activation in K 2 CO 3 and the resulting gel exhibits a bimodal micro-mesoporous distribution. Furthermore, the energy savings of this route are similar to those obtained using microwave-heating in terms of grams of xerogel per kilowatt hour of energy consumed for similar textural properties. The correlation between the energy power consumed and the textural parameters is a useful tool to optimize the synthesis.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fast synthesis of micro/mesoporous xerogels: Textural and energetic assessment

Isaacs-Páez

Haro

Juárez-Pérez

et al. 2015

Microporous and Mesoporous Materials

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“…There are, at least, four different types of materials named "cryogels": (i) gelatinous precipitate forming during cryoprecipitationblood plasma treatment upon cooling to ca. 4°C [57]; (ii) frozen polymeric or other hydrogels used 14 as antipyretic materials or materials for thermal energy storage [58]; (iii) polymeric and inorganic cryogels produced using sol-gel technology with subsequent freeze-drying including individual and mixed inorganic oxides, polymers, hybrids, composites, and carbon cryogels (the latter is prepared by carbonisation of polymeric cryogels) [59][60][61][62][63][64][65][66][67] There are many cryogels prepared from synthetic polymers such as poly(vinyl alcohol), PVA, which was one of the first polymers used in cryogel preparation [2][3][4]36,38,74,78,82]. PVA alone or in combination with other polymers or proteins is very popular material for the cryogel preparation because its structure containing the (-CH 2 -C(OH)H-) n chain allows various degrees of cross-linking with the participation of the active COH groups, different cross-linkers and co-polymers.…”

Section: Types Of Cryogel Based Composite and Hybrid Materialsmentioning

confidence: 99%

Cryogels: Morphological, structural and adsorption characterisation

Gun'ko

Savina

Mikhalovsky

2013

Advances in Colloid and Interface Science

282

205

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*Graphical Abstract (for review)Cryotripic gelation technique allows the synthesis of solid and soft macroporous gels Textural characterisation of cryogel in native superhydrated state with noninvasive methods Adsorption and diffusion characteristics of macroporous cryogels with respect to macromolecules and cells Theoretical modelling of adsorption from aqueous media *Highlights (for review) Please find the revised manuscript entitled "Cryogels: morphological, structural and adsorption characterisation" by Vladimir M. Gun'ko, Irina N. Savina, Sergey V. Mikhalovsky to re-consider for publication in the "Advances in Colloid and Interface Science"The paper was completely edited and changed according to reviewers comments.Sincerely yours, Prof. V. M. Gun'koCover Letter ABSTRACTExperimental results on polymer, protein, and composite cryogels and data treatment methods used for morphological, textural, structural, adsorption and diffusion characterisation of the materials are analysed and compared. Treatment of microscopic images with specific software gives quantitative structural information on both native cryogels and freeze-dried materials that is useful to analyse the drying effects on their structure. A combination of cryoporometry, relaxometry, thermoporometry, small angle X-ray scattering (SAXS), equilibrium and kinetic adsorption of low and high-molecular weight compounds, diffusion breakthrough of macromolecules within macroporous cryogel membranes, studying interactions of cells with cryogels provides a consistent and comprehensive picture of textural, structural and adsorption properties of a variety of cryogels. This analysis allows us to establish certain regularities in the cryogel properties related to narrow (diameter 0.4 < d < 2 nm), middle (2 < d < 50 nm) and broad (50 < d < 100 nm) nanopores, micropores (100 nm < d < 100 m) and macropores (d > 100 m) with boundary sizes within modified life science pore classification. Particular attention is paid to water bound in cryogels in native superhydrated or freeze-dried states. At least, five states of water -free unbound, weakly bound (changes in the Gibbs free energy G < 0.5-0.8 kJ/mol) and strongly bound (G > 0.8 kJ/mol), and weakly associated (chemical shift of the proton resonance  H = 1-2 ppm) and strongly associated ( H = 3-6 ppm) waters can be distinguished in hydrated cryogels using 1 H NMR, DSC, TSDC, TG and other methods. Different software for image treatment or developed to analyse the data obtained with the adsorption, diffusion, SAXS, cryoporometry and thermoporometry methods and based on regularisation algorithms is analysed and used for the quantitative morphological, structural and adsorption characterisation of individual and composite cryogels, including polymers filled with solid nano-or microparticles.

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“…Carbon gel is a porous carbon material that can be synthesized by aqueous polycondensation of phenolic substances with formaldehyde and subsequent drying and pyrolysis in an inert atmosphere (Al-Muhtaseb and Ritter, 2003;El-Khatat and Al-Muhtaseb, 2011). Yamamoto et al (2008) fabricated carbon cryogel microspheres using direct SPG ME (Figure 21).…”

Section: Integration Of Membrane Emulsification and Sol-gel Polycondementioning

confidence: 99%

Structured microparticles with tailored properties produced by membrane emulsification

Vladisavljević

2015

Advances in Colloid and Interface Science

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This paper provides an overview of membrane emulsification routes for fabrication of structured microparticles with tailored properties for specific applications. Direct (bottom-up) and premix (top-down) membrane emulsification processes are discussed including operational, formulation and membrane factors that control the droplet size and droplet generation regimes. A special emphasis was put on different methods of controlled shear generation on membrane surface, such as cross flow on the membrane surface, swirl flow, forward and backward flow pulsations in the continuous phase and membrane oscillations and rotations. Droplets produced by membrane emulsification can be used for synthesis of particles with versatile morphology (solid and hollow, matrix and core/shell, spherical and non-spherical, porous and coherent, composite and homogeneous), which can be surface functionalised and coated or loaded with macromolecules, nanoparticles, quantum dots, drugs, phase change materials and high molecular weight gases to achieve controlled/targeted drug release and impart special optical, chemical, electrical, acoustic, thermal and magnetic properties. The template emulsions including metal-in-oil, solid-in-oil-in-water, oil-in-oil, multilayer, and Pickering emulsions can be produced with high encapsulation efficiency of encapsulated materials and narrow size distribution and transformed into structured particles using a variety of different processes, such as polymerisation (suspension, mini-emulsion, interfacial and in-situ), ionic gelation, chemical crosslinking, melt solidification, internal phase separation, layer-by-layer electrostatic deposition, particle self-assembly, complex coacervation, spray drying, sol-gel processing, and molecular imprinting. Particles fabricated from droplets produced by membrane emulsification include nanoclusters, colloidosomes, carbon aerogel particles, nanoshells, polymeric (molecularly imprinted, hypercrosslinked, Janus and core/shell) particles, solder metal powders and inorganic particles. Membrane 2 emulsification devices operate under constant temperature due to low shear rates on the membrane surface, which range from (1−10) × 10 3 s −1 in a direct process to (1−10) × 10 4 s −1 in a premix process.Keywords: Membrane Emulsification; Polymeric microsphere; Microgel; Janus Particle; Core/Shell Particle, Colloidosome. Membrane emulsificationMembrane emulsification (ME) involves preparation of emulsions by pressing a pure dispersed phase or pre-emulsified mixture of the dispersed and continuous phase through a microporous membrane under controlled injection rate and shear conditions. In direct membrane emulsification (DME), one liquid (a dispersed phase) is injected through a microporous membrane into another immiscible liquid (the continuous phase) (Nakashima et al., 1991;, which leads to the formation of droplets at the membrane/continuous phase interface ( Figure 1a). In premix membrane emulsification (PME) (Figure 1b), a pre-emulsion is pressed through the membrane (...

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Advances in Tailoring Resorcinol‐Formaldehyde Organic and Carbon Gels

Cited by 418 publications

References 98 publications

Fast synthesis of micro/mesoporous xerogels: Textural and energetic assessment

Fast synthesis of micro/mesoporous xerogels: Textural and energetic assessment

Cryogels: Morphological, structural and adsorption characterisation

Structured microparticles with tailored properties produced by membrane emulsification

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