Ideally selective diisocyanate building blocks: New perspectives for dendrimers and coating binders

Using zirconium (IV) salts as catalyst, the reaction of a diisocyanate carrying one tertiary and one primary isocyanate group (IMCI, DIMP) with alcohols can be conducted with complete regioselectivity. This unique selectivity enables the use of a diisocyanate building block in unprecedented ways. Incomplete regioselectivity of diisocyanates, as commonly encountered in currently commercial ones like IPDI and TDI, inevitably leads to polydisperse products in reaction with polyols. The ultimate monodisperse polymer architecture, dendrimers, can now be made in a facile, straightforward manner using IMCI as the ideal diisocyanate building block. Coating applications of this unique building block are not restricted to these perfect branching polymers, but also include isocyanate-functional coating resins. Without any increase in polydispersity, a hydroxyl-functional polyester can be end-capped with the IMCI diisocyanate and subsequently serve as a crosslinker in powder coatings.     

Nanoparticles: scaffolds and building blocks

Nanoparticles provide key tools for bridging the gap between "bottom-up" synthetic methods and "top-down" fabrication. In this Account we describe some of the unique structural aspects of nanoparticles and the use of these attributes to the creation of devices with tunable specificity and environmental response. We also explore the use of nanoparticles as "building blocks" for the creation of nanocomposite materials that feature structural control from the molecular to the micron scale.     

异氰酸酯型树枝状大分子的合成及应用

树枝状大分子在化学、生物医学、环境保护等领域应用广泛,是近年来发展迅速的一类新型材料。介绍了树枝状大分子的研究进展、结构性能、合成方法及其应用,论述了以异氰酸酯化合物为新型单体的树枝状大分子的合成。     

Oleochemical products as building blocks for polymers

The use of oleochemical derivatives is dominated by applications in the field of surfactants and emulsifiers. There also is a remarkable amount of highly specialised uses, for example in lubricants and as additives to modify the characteristics of polymers. Besides this, some products have been developed on the basis of oleochemical building blocks in the polymer backbone. Starting with oleic acid, the difunctional azelaic acid (C-9) is produced by ozonolysis for application in high-value polyesters and polyamides. Pyrolysis of castor oil or ricinoleic acid is the commercial route to sebacic acid (C-10). Castor oil itself is used as a polyol for the production of polyurethanes. Similar polyols with modified viscosity and application characteristics are made by epoxidation and ring-opening reactions of unsaturated fatty acid derivatives. Dimer acid (C-36) is obtained by a double bond reaction of C₁₈ unsaturated fatty acids. By using hydrogenation technology, which is wellknown in the oleochemical industry to produce fatty alcohols, dimerdiols can be prepared from dimer acid. This dimerdiol is of great interest in polyurethane application fields in general, because it is a liquid, hydrophobic, long-chain raw material with two primary hydroxyl groups. By condensation of dimerdiol to building blocks with a molecular weight around 2,000 it is possible to prepare soft segments, that allow the production of thermoplastic polyurethanes (TPU) with modified application characteristics. Two different soft segments based on dimerdiol, ethers, and carbonates are discussed. The advantages for TPUs prepared from these building blocks are hydrolytic and oxidative stability and resistance to saponification and polar solvents.     

有机合成化学中新的构件--Japanese试剂

介绍了Ｊａｐａｎｅｓｅ试剂的制备、结构和化学反应。并就Ｊａｐａｎｅｓｅ试剂在有机合成中的应用加以概述。     

Synthesis of large building blocks for dendritic polyethers

Summary Building blocks containing multi-aryl ethers linkage in larger size for rapid building larger dendrimers were prepared with 3,5-di(4-hydroxyphenoxy)benzyl alcohol (1) as branch monomer and 1,3,5-tri(4-hydroxyphenoxy)benzene (2) as core molecule. Two generation of dendritic polyethers (12 and 15) were obtained by Fréchet convergent approach with 3,5-diphenoxybenzyl bromide (3) as starting molecule. They were characterized firstly by ¹H-NMR, ¹³C-NMR, and MS.     

2-Aminothiophenol as building blocks for novel heterocycles

Herein, the chemistry of 2-aminothiophenol has been utilized in the synthesis of several interesting products such as oxidation and reaction with π-deficient compounds. On oxidizing 2-aminothiophenol by sodium hypochlorite furnishes 2-[(2-aminophenyl)-dithio]aniline. Treatment of the obtained product with acetyl chloride affords N-(2-[2-(acetylamino)-phenyl-disulphanyl)-phenyl]acetamide. Reaction of the former acetamide with POCl₃ yields 2-methyl-1,3-benzothiazole. Moreover, (3,4,8,9)-dibenzo-2,7-dithia-5,10-diaza4 Field, L. and Lawson, J. E. 1958. J. Am. Chem. Soc., 80: 838[Crossref], [Web of Science ®] , [Google Scholar] 4 Field, L. and Lawson, J. E. 1958. J. Am. Chem. Soc., 80: 838[Crossref], [Web of Science ®] , [Google Scholar] 4 Field, L. and Lawson, J. E. 1958. J. Am. Chem. Soc., 80: 838[Crossref], [Web of Science ®] , [Google Scholar]propellane is formed on reacting the target 2-aminothiophenol with cyclohexane-1,2-dione, whereas its reactions with electron π-acceptors such as 2,3-dichloro-1,4-naphthoquinone (DCHNQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetra-cyanoethylene (TCNE), and 1-(dicyanomethylen)acenaphthen-2-one yield various heterocycles.     

Hierarchical structures via self-assembling protein-polymer hybrid building blocks

In this study we demonstrate that different hierarchically self-assembled materials can be formed by recently developed ferritin-polymer hybrid conjugates. Via interfacial self-assembly in combination with small-pore extrusion followed by inter-particle UV cross-linking, different states of capsule structures were obtained ranging from single capsules to capsules entrapped in fibers and high density capsule assemblies. The release of the capsule contents is regulated using different solvent combinations and visualized by entrapment of a lipophilic molecular dye. The structures and release properties were investigated using (fluorescence) microscopy and UV–Vis spectroscopy.     

The alkyl glycidyl ether as synthetic building blocks

Alkyl glycidyl ether is one of the most useful key materials for industrial applications because the addition reaction of various kinds of nucleophilic reagents to the reactive epoxy bond of the glycidyl ethers has led to glyceryl ether derivatives. Glyceryl ether exhibits many interesting physical and pharmacological properties. The alkyl glycidyl ether can presently be produced at an industrial scale under the phase-transfer catalytic Williamson ether synthesis. We have reviwwed some addition reactions of the alkyl glycidyl ether and possibilities for use as the building blocks for the syntheses of surfactants, pharmaceuticals, etc. that contain glyceryl ether skeletons. Typical examples of alkyl glyceryl ether derivatives include: amino ether as cosmetic material, and isodiglycerin mono- and dialkyl ethers and triglycerin monoalkyl ether as a cosmetic or a pharmacologically useful material, respectively. Another interesting reaction is the rearrangement of the epoxy bond of the alkyl glycidyl ether, which gives alkoxy ketone in a one-pot synthesis.     

Photochromic molecules as building blocks for molecular electronics

Energy and electron transfer processes can be easily induced by a photonic excitation of a donor metal complex ([Ru(bpy)3]2), which is connected via a wire-type molecular fragment to an acceptor metal complex ([Os(bpy)3]2+). The rate constant for the transfer process can be determined by emission measurements of the two connected metal complexes. The system can be modified by incorporation of a switching unit or an interrupter into the wire, influencing the transfer process. Such a molecular device corresponds to an interrupter, mimic the same function applied in molecular electronics. We have used organic switches, which show photochromic properties. By irradiation with light of different wavelengths, the switch changes its functionality by a photochemical reaction from an OFF- to an ON-state and vice versa. The ON- respectively OFF-state is manifested by a color change but also in different conductivity properties for energy and electron transfer processes. Therefore, the mentioned molecular device can work as a simple interrupter, controlling the rate of the transfer processes.     

Utilization of coal combustion byproducts in building blocks

Some mechanical and durability properties of composite material produced with by-products of Orhaneli power plant (flue gas desulfurization sludge, fly ash and bottom ash), cement and hydrated lime were investigated. To improve the mechanical properties (compressive and flexural strength) of this material, steam curing was applied and the effect of chemical admixture (high water reducing agent) was investigated. Some physical properties and water resistance of the mixtures were also determined. Furthermore, microstructure of the specimens was investigated using scanning electron microscopy. Finally, to produce construction elements, prototypes of building blocks were manufactured by using some of these mixtures. All kind of power plant wastes (flue gas desulfurization sludge, fly ash, bottom ash) can be utilized with these mixtures, which consist of 90% of coal combustion byproducts. It seems to be a promising material for composite construction elements such as building blocks.     

Dendrimer-encapsulated gold nanoparticles as building blocks for multilayer microshells

We report the effect of gold nanoparticles encapsulated into the shell-forming PAMAM dendrimers on the assembly and properties of multilayer microshells. We demonstrate that the PAMAM-encapsulated gold nanoparticles change dramatically the optical spectroscopic properties of microcapsule dispersions, without significantly affecting the stiffness of microcapsules. Our results indicate that the use of dendrimer-protected nanoparticles as building blocks opens numerous possibilities to vary the composition and diverse properties of microshells without changing their stiffness.     

Synthesis of components for supramolecules incorporating cycloheptatriene building blocks

Molecular threads I – III incorporating 1,3,5-cycloheptatriene units have been synthesized by three methods. Bridges were designed as ether ( 9 , 14 , 18 and 22 ), ester ( 4 and 14 ) and amino functions ( 25 ), respectively, The attachment of a second aryl residue at the seven-membered ring by nucleophilic attack of activated aromatic compounds such as anilines on tropylium salts resulted in the formation of two regioisomers ( 26 and 27 ). The macrocycles 28 were formed under high dilution conditions in good yields.     

Intragranular nanocomposite powders as building blocks for ceramic nanocomposites

A powder-based bottom-up processing scheme is introduced for the production of ceramic nanocomposites. Internal displacement reactions between solid solution powders and metallic reactants proceeding via gaseous intermediates are utilized to generate nanostructured building blocks for the synthesis of ceramic nanocomposites. Subsequent rapid sintering results in ceramic nanocomposites, whose microstructures are inherited from the building blocks. This processing scheme is demonstrated for the production of titanium carbide nanocomposites featuring up to 28 wt.% intragranular tungsten inclusions derived from titanium-tungsten mixed carbide powders. Heat treatment of mixed carbide powders in evacuated ampoules containing titanium sponge and iodine at 1000°C for 24 h resulted in nanocomposite powders featuring tungsten precipitates within titanium carbide grains that were subsequently consolidated via spark plasma sintering at 1300°C for 10 min to produce titanium carbide/metallic tungsten nanocomposites. Transformation of mixed titanium–tungsten carbide powders to titanium carbide/metallic tungsten nanocomposite powders was analyzed via X-ray diffraction. Electron microscopy observations of microstructures pre- and post- sintering showed that the intragranular character of nanocomposite powders can be retained in sintered ceramic nanocomposites. The building block approach demonstrated in this work represents an improved method to make ceramic nanocomposites with majority intragranular character.     

End-functionalized polymers: Versatile building blocks for soft materials

We present a concise review of telechelic polymers of various architectures, focusing on the structure, solute solvent interactions, aggregation processes, equilibrium and dynamical properties and applications. Telechelics are macromolecules with functionalized, mutually attractive end-groups, which assume a variety of conformations that depend on solvent quality, salinity and pH of the solvent, as well as on the particular macromolecular architecture. In concentrated solutions, telechelic polymers offer unique possibilities to create novel materials with distinct rheological properties. Depending on chemistry and architecture, they can create percolating clusters and transient gels or they can show macroscopic phase separation into a dilute and a structured dense phase. The possibility to externally steer the morphology of these structures and the concomitant physical properties of the materials renders telechelic polymers into important and versatile building blocks for modern materials science.     

Crosslinkable PEO-PPO-PEO triblocks as building blocks of thermo-responsive nanoshells

A series of thermo-responsive nanoshells were generated by shell-crosslinking poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) dimethacrylate triblocks. The nanoshells produced displayed a remarkable and reversible change in size, within a narrow temperature interval. The effect of the concentration of the PEO-PPO-PEO dimethacrylate was studied within the 0.2-4.0 wt% range. Increasing the reaction temperature favored the formation of tubular nanoshells, due to the transformation of the PEO-PPO-PEO micelles from a spherical geometry to rod-like shape at a higher temperature. Blending PEO-PPO-PEO triblocks into the PEO-PPO-PEO dimethacrylate micelles, decreased the crosslink density of the nanoconstructs formed, and resulted in nanoshells attaining larger volumetric differentials. The addition of water soluble organic solvents to the aqueous medium resulted in the increase of the size of the nanoshells and shifted their transition to higher temperatures, whereas increasing the ionic strength of the solution caused the nanoshells to shrink.     

Cationic polyelectrolytes from natural building blocks of chitosan and inulin

Novel chitosan-N-inulin graft copolymers with different degree of substitution (DS) of chitosan were synthesized via water-soluble 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide mediated reaction. Chemical structure and composition of the chitosan derivatives was confirmed by chemical analysis, FT-IR, XPS, ¹H and ¹³C NMR spectroscopy, and potentiometry. Chitosan–inulin copolymers were high-molecular-weight hydrophilic products soluble in water in a wide pH range forming extraordinary viscous solutions. Intrinsic viscosity of N-modified chitosans was sharply suppressed by added electrolyte and had tendency to decrease at higher DS of chitosan. pK_α values of the chitosan–inulin copolymers determined from potentiometric titration data using Henderson–Hasselbalch equation were in the range 6–7 slightly increasing at higher DS. Novel water-soluble chitosan copolymers retained cationic properties of chitosan and could be used as surface conditioners.