Dingcai Wu,*,† Fei Xu,† Bin Sun,† Ruowen Fu,† Hongkun He,‡ and Krzysztof Matyjaszewski*,‡ †Materials Science Institute, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China ‡Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States

Design and Preparation of Porous Polymers

Emulsions stabilized with solid nanoparticles: Pickering emulsions

Owing to their immense potential in energy conversion and storage, catalysis, photocatalysis, adsorption, separation and life science applications, significant interest has been devoted to the design and synthesis of hierarchically porous materials. The hierarchy of materials on porosity, structural, morphological, and component levels is key for high performance in all kinds of applications. Synthesis and applications of hierarchically structured porous materials have become a rapidly evolving field of current interest. A large series of synthesis methods have been developed. This review addresses recent advances made in studies of this topic. After identifying the advantages and problems of natural hierarchically porous materials, synthetic hierarchically porous materials are presented. The synthesis strategies used to prepare hierarchically porous materials are first introduced and the features of synthesis and the resulting structures are presented using a series of examples. These involve templating methods (surfactant templating, nanocasting, macroporous polymer templating, colloidal crystal templating and bioinspired process, i.e. biotemplating), conventional techniques (supercritical fluids, emulsion, freeze-drying, breath figures, selective leaching, phase separation, zeolitization process, and replication) and basic methods (sol–gel controlling and post-treatment), as well as self-formation phenomenon of porous hierarchy. A series of detailed examples are given to show methods for the synthesis of hierarchically porous structures with various chemical compositions (dual porosities: micro–micropores, micro–mesopores, micro–macropores, meso–mesopores, meso–macropores, multiple porosities: micro–meso–macropores and meso–meso–macropores). We hope that this review will be helpful for those entering the field and also for those in the field who want quick access to helpful reference information about the synthesis of new hierarchically porous materials and methods to control their structure and morphology.

/pdf/hierarchically-porous-materials-synthesis-strategies-and-568soqnq77.pdf

Hierarchically porous materials: synthesis strategies and structure design

PolyHIPEs: Recent advances in emulsion-templated porous polymers

Porous materials are currently of great scientific as well as technological interest. A strategy that is increasingly employed to prepare highly porous and well defined macroporous polymers is emulsion templating, whereby the droplets of a high internal phase emulsion are used to create pores in a solid material by curing or polymerization of the emulsion continuous phase. This Feature Article covers recent work in this area, focusing on: the preparation of such materials from new precursors and via novel approaches; the chemical modification of existing materials; and the application of the resulting porous structures in diverse areas of science and technology.

Functional Porous Polymers by Emulsion Templating: Recent Advances

High internal phase emulsion templates solely stabilised by functionalised titania nanoparticles

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)

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pola.22878

Mariely Salgueiro

Papers

High internal phase emulsion templates solely stabilised by functionalised titania nanoparticles

Nanocomposite foams obtained by polymerization of high internal phase emulsions