Rise or fall: Complex-structured freestanding polymer films with molecular order in three dimensions were prepared through photoalignment of polymerizable liquid crystals. The resulting films deform into cone and saddle shapes upon heating.
Functional organic materials are of great interest for a variety of applications. To obtain precise functional properties, well-defined hierarchically ordered supramolecular materials are crucial. The self-assembly of liquid crystals has proven to be an extremely useful tool in the development of well-defined nanostructured materials. We have chosen the illustrative example of photopolymerizable hydrogen-bonding mesogens to show that a wide variety of functional materials can be made from a relatively simple set of building blocks. Upon mixing these compounds with other reactive mesogens, nematic, chiral nematic, and smectic or columnar liquid-crystalline phases can be formed that can be applied as actuators, sensors and responsive reflectors, and nanoporous membranes, respectively.
Auf‐ oder abwärts: Komplex strukturierte freistehende Polymerfilme mit einer dreidimensionalen molekularen Ordnung wurden durch Photoausrichtung polymerisierbarer Flüssigkristalle hergestellt. Die gebildeten Filme verformen sich beim Erhitzen zu Kegel‐ und Sattelformen.
Hydrogen‐bridged, cholesteric liquid‐crystal (CLC) polymer networks are adopted as an optical sensor material to distinguish between ethanol and methanol. Fast uptake of the alcohols is facilitated by an incorporated porosity created by breaking the hydrogen bridges and by a previously removed non‐reactive liquid‐crystal agent. The discrimination between the alcohols is based on the diversity in molecular affinity of ethanol and methanol with the hydrogen‐bridged CLC polymer networks. The CLC networks are molecular‐helix‐based, one‐dimensional bandgap materials with a discrete reflection band in the visible part of the spectrum that depends on the pitch of the molecular helix. The changes in positions of the reflection bands of the CLC network accurately discriminate between the alcohol types and provide information on their ratio in case they are blended.
Irreversible optical sensing of humidity by a doped cholesteric liquid crystal is achieved by using a thin film of nematic host E7 with a binaphthylorthosilicate ester as dopant (guest). The film changes its color from blue (to green to orange to red) to colorless when exposed to humidity as the dopant is hydrolyzed.
Funktionelle organische Materialien sind von großem Interesse für eine Vielzahl von Anwendungen. Um funktionelle Eigenschaften gezielt einstellen zu können, benötigt man wohldefinierte hierarchisch geordnete supramolekulare Materialien. Die Selbstorganisation von Flüssigkristallen hat sich als ein extrem nützliches Werkzeug für die Entwicklung nanostrukturierter Materialien bewährt. Wir wählen das anschauliche Beispiel photopolymerisierbarer wasserstoffverbrückter Mesogene, um zu zeigen, dass eine breite Vielfalt funktioneller Materialien aus einem relativ einfachen Satz von Bausteinen hergestellt werden kann. Durch Umsetzung dieser Verbindungen mit anderen reaktiven Mesogenen können nematische, chirale nematische und smektische oder kolumnare flüssigkristalline Phasen gebildet werden, die als Aktuatoren, Sensoren, responsive Reflektoren und nanoporöse Membranen genutzt werden können.
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