Ladder polymers -- molecules made of adjacent rings sharing two or more atoms -- are challenging to synthesize, because they require highly selective, quantitative reactions to avoid the formation of branching structures or of interruptions in the ring sequence in the polymer chain.
Moreover, most existing strategies for the synthesis of ladder polymers suffer from severe limitations in terms of selectivity and quantitativity. Another important type of molecules are molecules with a helical structure (such as DNA and proteins), which play an important role in molecular recognition and catalysis.
A construction of macro-scale architectures with a helical ladder shape is not even a challenge, but it's a different story when it comes to a molecular scale. Here, the efficient synthesis of one-handed helical ladder polymers is established through a trifluoroacetic acid (TFA)-assisted intramolecular cyclization of chiral triptycenes.
Credit: Kanazawa University
Usage Restrictions: The image may only be used with appropriate caption and credit.
Thus, the fabrication of molecules that possess both a ladder and a helical structure could open up new applications of polymeric materials.
Tomoyuki Ikai, Timothy M. Swager and colleagues from an international collaboration started from triptycene, an aromatic hydrocarbon that is an achiral molecule, but from which chiral derivatives can be obtained by introducing substituents in the benzene rings in an asymmetric manner.
Optically active triptycenes have practical uses as chiral materials, for example for chiral separation and circularly polarized luminescent materials.
The researchers then used the chiral triptycenes as a framework to efficiently form single-handed helical ladder polymers using electrophilic aromatic substitution. Steric repulsion in the system resulted in the formation of one-handed twisted ladder units.
The reactions were quantitative and regioselective (that is, there is a preferred direction of chemical bonding), which enabled the synthesis of optically active ladder polymers with well-defined helical geometry. No byproducts were detected.
Several techniques, including spectroscopy and microscopy techniques, were used to characterize the reaction products during synthesis, and molecular dynamics simulations were employed to understand the structure of the resulting molecules, confirming the right-handed helical ladder geometry. The researchers also measured the optical activity of the molecules.
The newly reported synthesis route will open up the synthesis of nanoscale helical ladder architectures and optically active chiral materials. "We believe that these ladder polymers, which can fall into a new category of helical polymers, represent a promising class of advanced materials for use as nanochannels for molecular/ion transport, organic electronics, specific reaction fields, and functional hosts through further modification of the backbone and pendant units," commented the authors in the paper.
Fraunhofer WKI develops sustainable sandwich elements made from wood foam and textile-reinforced
10.07.2019 | Fraunhofer-Gesellschaft
Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects
08.07.2019 | Universität Bayreuth
For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.
Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...
An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".
The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...
An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.
Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...
The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...
Physicists at the Max Planck Institute for Nuclear Physics in Heidelberg report the first result of the new Alphatrap experiment. They measured the bound-electron g-factor of highly charged (boron-like) argon ions with unprecedented precision of 9 digits. In comparison with a new highly accurate quantum electrodynamic calculation they found an excellent agreement on a level of 7 digits. This paves the way for sensitive tests of QED in strong fields like precision measurements of the fine structure constant α as well as the detection of possible signatures of new physics. [Physical Review Letters, 27 June 2019]
Quantum electrodynamics (QED) describes the interaction of charged particles with electromagnetic fields and is the most precisely tested physical theory. It...
24.06.2019 | Event News
29.04.2019 | Event News
17.04.2019 | Event News
15.07.2019 | Life Sciences
15.07.2019 | Power and Electrical Engineering
15.07.2019 | Life Sciences