There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Covalent organic frameworks (COFs) represent an exciting new type of porous organic materials, which are ingeniously constructed with organic building units via strong covalent bonds. The well-defined crystalline porous structures together with tailored functionalities have offered the COF materials superior potential in diverse applications, such as gas storage, adsorption, optoelectricity, and catalysis. Since the seminal work of Yaghi and co-workers in 2005, the rapid development in this research area has attracted intensive interest from researchers with diverse expertise. This critical review describes the state-of-the-art development in the design, synthesis, characterisation, and application of the crystalline porous COF materials. Our own opinions on further development of the COF materials are also presented for discussion (155 references).

Covalent organic frameworks (COFs): from design to applications

Porous, Covalent Triazine-Based Frameworks Prepared by Ionothermal Synthesis

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

The paper evaluates accumulated information about the apparent inner surface area ( S app ), pore volume ( W o ), pore size (diameter, D ), and pore size distribution (PSD) of the single-phase hypercrosslinked polystyrene networks prepared by an intensive post-crosslinking of either dissolved linear polystyrene or swollen gel-type styrene–divinylbenzene copolymers. Critical analysis of data obtained by conventional physical methods used for the characterization of porous solids (low temperature adsorption of nitrogen or argon, mercury intrusion porosimetry, inversed size exclusion chromatography, electronic microscopy, positronium annihilation) reveals the most trustworthy porosity parameters of the above hypercrosslinked polystyrene resins as S app  ⩾ 1000 m 2 /g, W o in the range of 0.3–0.5 cm 3 /g, D in dry networks from 4–5 to 30 A and only slightly increasing in swollen samples. The hypercrosslinked networks thus present first basically microporous polymeric material that exhibits narrow PSD resulting from a statistically uniform distribution of crosslinks.

Porous structure of hypercrosslinked polystyrene: State-of-the-art mini-review

Hypercrosslinked polystyrene networks have been recognised since the 1970s. They were prepared by extensive crosslinking of linear polystyrene chains in a strongly solvating media. Generally, the basic principle of obtaining hypercrosslinked polymers consists in the formation of a rigid highly solvated three-dimensional network. Owing to the high rigidity and reduced degree of chain entanglement, such “expanded” networks are characterized by loose chain packing, i.e., high free volume, and the unique ability to swell in both good solvents and non-solvents. In addition to the above polymer-analogues transformation of polystyrene, the article expands the synthesis techniques to polymerization and polycondensation procedures and also involves other types of polymers and monomers. Typical examples of preparing hypercrosslinked networks include the crosslinking of linear chains of polysulfone and polyarylates, copolymerization of styrene with a large amount of divinylbenzene, self-condensation of p -xylylene dichloride. All resulting materials differ substantially from classical polymers of the same chemical nature and comprise a new class of hypercrosslinked polymeric materials. Some polymers described in the literature were shown to also belong to the hypercrosslinked family.

Hypercrosslinked polymers: basic principle of preparing the new class of polymeric materials

Ligand chromatography as a novel method for the investigation of mixed complexes: stereoselective effects in α-amino acid copper(II) complexes

The nature of chiral recognition: Is it a three‐point interaction?

A novel chiral phase system is presented for the resolution of unmodified α-amino acid racemates which is composed of a reverse phase packing coated with N-alkyl-L-hydroxyproline (where alkyl is n-C7H15-, n-C10H21- and n-C16H33-) and a hydro-organic eluent containing copper(II)acetate. The factors controlling retention and enantioselectivity such as concentration of Cu(II)ion and pH of the eluent, addition of NH4Ac to the eluent, type and content of organic solvent of hydro-organic eluent and column temperature were examined. The extremely high enantioselectivity observed (α up to 16) is assumed to be caused by a three site sorbate-sorbent interaction involving bidentate coordination of two amino acids to a Cu(II)ion and hydrophobic attractions between hydrocarbon side chains of amino acids and the n-octadecyl groups of the support. The efficiency and selectivity of the system permits resolution of up to 7 racemic amino acids into enantiomers within 35 minutes on a conventional HPLC apparatus.

Vadim A. Davankov

Papers

Porous structure of hypercrosslinked polystyrene: State-of-the-art mini-review

Hypercrosslinked polymers: basic principle of preparing the new class of polymeric materials

Ligand chromatography as a novel method for the investigation of mixed complexes: stereoselective effects in α-amino acid copper(II) complexes

The nature of chiral recognition: Is it a three‐point interaction?

Separation of unmodified α-amino acid enantiomers by reverse phase HPLC