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

Membrane-based techniques for the separation and purification of proteins: an overview.

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

The design of hydrogen storage materials is one of the principal challenges that must be met before the development of a hydrogen economy. While hydrogen has a large specific energy, its volumetric energy density is so low as to require development of materials that can store and release it when needed. While much of the research on hydrogen storage focuses on metal hydrides, these materials are currently limited by slow kinetics and energy inefficiency. Nanostructured materials with high surface areas are actively being developed as another option. These materials avoid some of the kinetic and thermodynamic drawbacks of metal hydrides and other reactive methods of storing hydrogen. In this work, progress towards hydrogen storage with nanoporous materials in general and porous organic polymers in particular is critically reviewed. Mechanisms of formation for crosslinked polymers, hypercrosslinked polymers, polymers of intrinsic microporosity, and covalent organic frameworks are discussed. Strategies for controlling hydrogen storage capacity and adsorption enthalpy via manipulation of surface area, pore size, and pore volume are discussed in detail.

Nanoporous Polymers for Hydrogen Storage

Structurally well-defined macromolecules are ubiquitous in nature, with enzymes as prime examples. They are admired not only for the beauty of their structures but also for their ability to catalyze a variety of chemical transformations under mild conditions. For example, nitrogenase catalyzes nitrogen fixation under physiological conditions,1,2 whereas the same reaction in a chemical reactor by the Haber-Bosch process requires ultrahigh pressures and temperatures. The key to the functions of enzymes is the monodispersity and completely controlled amino acid (monomer) sequences of the polymer chain in the biomacromolecule, leading to highly ordered three-dimensional structures. This control combined with the existence of polar functional groups on the amino acid residues precisely located near the active center orchestrates the activity of enzymes. By extrapolating from the structural and functional features of enzymes, one should be able to create new polymers with new properties and/or functions based on precise control of macromolecular structures, namely, molecular weight, molecular weight distribution (MWD), monomer sequence, topology, functional groups, and stereochemistry (tacticity). Controlling all of these factors is a formidable challenge, but significant advances have been made toward this goal since the advent of controlled/living radical polymerization (LRP). Living anionic,3,4 cationic,5 and coordination polymerization6-8 have already been used to control molecular weights and MWDs of the resulting polymers and monomer sequences through block copolymer synthesis. However, these * To whom correspondence should be addressed. E-mail: yamago@ scl.kyoto-u.ac.jp. Shigeru Yamago received his B.S. and Ph.D in chemistry from Tokyo Institute of Technology in 1986 and 1991, respectively, under the supervision of Professor Eiichi Nakamura. During that time, he joined Professor Peter Vollhardt’s group at U.C. Berkeley as a summer student (1988). He became an assistant professor at Tokyo Institute of Technology in 1991 in the group of Professor Eiichi Nakamura and then moved to Kyoto University in 1995 in the group of Professor Jun-ichi Yoshida. He was a Visiting Scientist in Dr. Chryssostomos Chatgilialoglu’s group at Consiglio Nazionale delle Ricerche in Bologna (2000). In 2003, he was appointed Professor of Osaka City University. He had been a Research Fellow of PRESTO program in the Japan Science and Technology Agency from 2002 to 2006. In 2006, he joined Institute for Chemical Research at Kyoto University where he holds Professorship. He received the Incentive Award in Synthetic Organic Chemistry from the Society of Synthetic Organic Chemistry, Japan, in 2001. His research interests include synthetic organic and polymer chemistry, radical chemistry, and element chemistry. Chem. Rev. 2009, 109, 5051–5068 5051

Precision Polymer Synthesis by Degenerative Transfer Controlled/Living Radical Polymerization Using Organotellurium, Organostibine, and Organobismuthine Chain-Transfer Agents

Preparation and characterisation of poly(high internal phase emulsion) methacrylate monoliths and their application as separation media

4-Hydroxymethyl phenyl (Wang linker) moieties and tris(hydroxymethyl)aminomethane were immobilised onto vinylbenzyl chloride/divinylbenzene porous polymer matrixes via displacement of the chlorine in chloromethyl groups. Both monolithic forms and ground particles of polymerised high internal phase emulsions (PolyHIPE, 90% pore volume) of 4-vinylbenzyl chloride/divinylbenzene (molar ratio of 60/40, 75/25 and 78/22) and also chloromethylated polystyrene beads gave high conversions thus yielding functionalised polymers with a remarkably high loading of OH groups per gram of polymer support (highest obtained loading 8.1 mmol of OH groups per gram of polymer). The reactivity of these novel polymer supports was demonstrated by the immobilisation of 4-iodobenzoic acid, which is frequently used in the preparation of biaryl compounds by Suzuki coupling reactions. Additionally, the emulsion-derived polymers were used to scavenge acetyl chloride and a dependence of scavenging ability on the porosity was found (being higher with higher porosity).

Hydroxy-derivatised emulsion templated porous polymers (PolyHIPEs): Versatile supports for solid and solution phase organic synthesis

A series of monolithic crosslinked polymers with 2,4,6-trichlorophenyl acrylate as a reactive component was prepared by free radical polymerization of the internal phases of high internal phase emulsions (HIPEs). The volume ratio of water to oil phase (void volume; 60–90%), crosslinker type (divinylbenzene or ethylenglycol dimethacrylate) and quantity (30–50 mol %) and type of porogenic solvent (chlorobenzene, toluene, chloroform, dichloroethane) were altered to study these effects on the structure and reactivity of the monolithic polymers. The polymer supports were characterized by scanning electron microscopy (SEM), FTIR spectroscopy, elemental analysis and mercury intrusion porosimetry. SEM images revealed an open cellular structure with voids between 1 and 12 μm and window sizes between 0.3 and 3 μm. The porogen had an influence on the surface area, being larger with added porogen and the influence being highest with toluene. Adding toluene also influenced the void size, increasing the average diameter from ∼2 μm (no porogen) to ∼12 μm (added toluene). Monolithic supports were functionalized by reaction of the ester moieties with tris(2-aminoethyl)amine derivative and by hydrolysis of the ester groups to carboxylic acids. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4043–4053, 2007

Nermina Leber

Papers

Preparation and characterisation of poly(high internal phase emulsion) methacrylate monoliths and their application as separation media

Hydroxy-derivatised emulsion templated porous polymers (PolyHIPEs): Versatile supports for solid and solution phase organic synthesis

2,4,6‐trichlorophenyl acrylate emulsion‐templated porous polymers (PolyHIPEs). Morphology and reactivity studies