Asymmetric Hydroformylation Using a Rhodium Catalyst Encapsulated in a Chiral Capsule

Supramolecular capsules can be used to change the activity and selectivity of a catalyst through the influence of the second coordination sphere, reminiscent of how enzymes control the selectivity of their processes. In enzymes, this approach is used to also control the enantioselectivity of reactions in which the active catalytic site is often not chiral but the second coordination sphere is. We are interested in the possibility to generate a chiral second coordination sphere around an otherwise achiral transition metal complex for asymmetric catalysis. In this paper we show that the ligand template approach can be used to generate a chiral second coordination sphere around a rhodium complex, which is used in asymmetric hydroformylation.     

PLMA‐b‐POEGMA amphiphilic block copolymers: Synthesis and self‐assembly in aqueous media

The synthesis and self‐assembly properties in aqueous solutions of novel amphiphilic block copolymers composed of one hydrophobic poly (lauryl methacrylate), (PLMA) block and one hydrophilic poly (oligo ethylene glycol methacrylate) (POEGMA) block are reported. The block copolymers were prepared by RAFT polymerization and were molecularly characterized by size exclusion chromatography, NMR and FT‐IR spectroscopy, and DSC. The PLMA‐b‐POEGMA amphiphilic block copolymers self‐assemble in nanosized complex nanostructures resembling compound micelles when inserted in aqueous media, as supported by light scattering and TEM measurements. The encapsulation and release of the model, hydrophobic, nonsteroidal anti‐inflammatory drug indomethacin in the polymeric micelles is also investigated. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 155–163     

Techniques of aligning carbon nanotubes

This paper reviews major techniques of aligning carbon nanotubes, either during the growth or by the post-growth processing. A number of post-processing alignment techniques are discussed, which employ mechanical stretching, fracture, compression, friction, filtration, fiber drawing, gas flow, liquid crystals, Langmuir-Blodgett technique, acoustic, magnetic and electric fields. The suitability of those techniques to industrial applications is analyzed.      

Polycationic‐Shelled Capsular and Tubular Nanostructures and Their Anionic–Guest Binding Properties

For the development of novel nanospace with unique electrostatic character, we prepared new capsular and tubular nanostructures by the quantitative assembly of metal ions and bent bisacridinium ligands. The capsule and tube have closed spherical and open cylindrical cavities, respectively, with diameters of around 1 nm surrounded by cationic polyaromatic panels. Thanks to the facile synthetic protocol (three steps), another polycationic capsule with an elliptical nanocavity was also prepared by using an elongated ligand. In spite of the absence of pendant hydrophilic groups, the spherical polyaromatic capsule shows sufficient water solubility due to the polycationic shell. Moreover, the highly cationic cavity (12+) can selectively encapsulate anionic organic compounds in water.     

Nonionic Dendritic and Carbohydrate Based Amphiphiles: Self‐Assembly and Transport Behavior

Herein, a new series of non‐ionic dendritic and carbohydrate based amphiphiles is synthesized employing biocompatible starting materials and studied for supramolecular aggregate formation in aqueous solution. The dendritic amphiphiles 12 and 13 possessing poly(glycerol) [G2.0] as hydrophilic unit and C‐10 and C‐18 hydrophobic alkyl chains, respectively, exhibit low critical aggregation concentration (CAC) in the order of 10⁻⁵m and hydrodynamic diameters in the 8–10 nm range and supplemented by cryogenic transmission electron microscopy. Ultraviolet‐visible (UV‐Vis) and fluorescence spectroscopy suggests the effective solubilization of hydrophobic guests by the self‐assembled architectures, with the nanotransporters 12 and 13 possessing the highest encapsulation efficiency of 80.74 and 98.03% for curcumin. Efficient uptake of encapsulated curcumin in adenocarcinomic human alveolar basal epithelial (A549) cells is observed by confocal laser scanning microscopy. Amphiphiles 12 and 13 are non‐cytotoxic at the concentrations studied, however, curcumin encapsulated samples efficiently reduce the viability of A549 cells in vitro. Experimental studies indicate the ability of amphiphile 13 to encapsulate 1‐anilinonaphthalene‐8‐sulfonic acid (ANS) and curcumin with binding constant of 1.16 × 105⁵m ⁻¹ and 1.43 × 10⁶m ⁻¹, respectively. Overall, our findings demonstrate the potential of these dendritic amphiphiles for the development of prospective nanocarriers for the solubilization of hydrophobic drugs.     

Grafting of PMMA brushes on titania nanoparticulate surface via surface-initiated conventional radical and “controlled” radical polymerization (ATRP)

Stable dispersion of titania nanoparticles in organic solvents are obtained by grafting poly(methyl methacrylate) layer on to the surface. Titania nanoparticles are synthesized through the hydrolysis of titanium (IV) isopropoxide. The average size of the titania particles is found to be 15 ± 2 nm. The polymer layer was introduced onto the surface by immobilizing the initiating moiety. Azo initiator moiety required for surface-initiated conventional free radical polymerization and a tertiary bromide initiator moiety required for ATRP are attached covalently to the titania nanoparticulate surface through the surface hydroxyl groups. The “encapsulation” of PMMA layer results in the steric stabilization of the titania nanoparticles. Another important finding is that it is possible to grow polymer layer in a controlled fashion.     

A Microgel Construction Kit for Bioorthogonal Encapsulation and pH‐Controlled Release of Living Cells

pH‐Cleavable cell‐laden microgels with excellent long‐term viabilities were fabricated by combining bioorthogonal strain‐promoted azide–alkyne cycloaddition (SPAAC) and droplet‐based microfluidics. Poly(ethylene glycol)dicyclooctyne and dendritic poly(glycerol azide) served as bioinert hydrogel precursors. Azide conjugation was performed using different substituted acid‐labile benzacetal linkers that allowed precise control of the microgel degradation kinetics in the interesting pH range between 4.5 and 7.4. By this means, a pH‐controlled release of the encapsulated cells was achieved upon demand with no effect on cell viability and spreading. As a result, the microgel particles can be used for temporary cell encapsulation, allowing the cells to be studied and manipulated during the encapsulation and then be isolated and harvested by decomposition of the microgel scaffolds.