Photomechanik flüssigkristalliner Elastomere und anderer Polymere

Abstract

Muskeln können chemische Energie in mechanische Arbeit umsetzen. Zur Entwicklung künstlicher Muskeln eignen sich weiche Materialien mit hoher mechanischer Flexibilität und Lebensdauer besser als harte Materialien wie Metalle. Für wirksame muskelähnliche Bewegungen sollten die Materialien Schichtstrukturen und einen hohen molekularen Ordnungsgrad aufweisen. Flüssigkristalline Elastomere (liquid‐crystalline elastomers, LCE) sind diesbezüglich überlegene weiche Materialien, die die Ordnung von Flüssigkristallen und – da sie Polymernetzwerke enthalten – die Elastizität von Elastomeren in sich vereinen. Mit LCEs lassen sich kleine Mengen externer Energie in makroskopisch messbare mechanische Arbeit umwandeln. In diesem Aufsatz konzentrieren wir uns auf Licht als Energiequelle und beschreiben die neuesten Fortschritte auf dem Gebiet weicher Materialien, die Licht direkt in mechanische Arbeit umwandeln können (photomechanischer Effekt), insbesondere die photomechanischen Effekte von LCEs unter dem Blickwinkel der Anwendungsentwicklung lichtgetriebener Aktuatoren.

Photomobile Polymer Materials: Towards Light‐Driven Plastic Motors

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As light is a good energy source that can be controlled remotely, instantly, and precisely, light-driven soft actuators could play an important role for novel applications in wideranging industrial and medical fields. [4][5][6][7][8][9][10][11][12] Herein we demonstrate new sophisticated motions of LCEs and their composite materials: a plastic motor driven only by light.If materials absorb light and change their shape or volume, they can convert light energy directly into mechanical work (the photomechanical effect) and could be very efficient as a single-step energy conversion. [4][5][6][7][8][9][10][11][12] Herein we demonstrate new sophisticated motions of LCEs and their composite materials: a plastic motor driven only by light.

If materials absorb light and change their shape or volume, they can convert light energy directly into mechanical work (the photomechanical effect) and could be very efficient as a single-step energy conversion.

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“…Furthermore, these photomobile materials would be widely applicable because they can be controlled remotely just by manipulating the irradiation conditions. [4][5][6][7][8][9][10][11][12] Although the photoinduced deformation of LCEs previously reported is large and interesting, it is limited to contraction/expansion and bending, preventing them from being used for actual applications. [1,[13][14][15][16][17][18] The expansion and contraction is due to the microscopic change in alignment of mesogens, followed by the significant macroscopic change in order through the cooperative movement of mesogens and polymer segments.…”

trans–cis Photoisomerization of Azobenzene‐Conjugated Dithiolato‐Bipyridine Platinum(II) Complexes: Extension of Photoresponse to Longer Wavelengths and Photocontrollable Tristability

“…These features have led to its valuable use in the fields of biochemistry, [2] surface chemistry, [3] liquid crystals, [4] polymer materials, [5] and molecular devices, [6] among others. Its utility is limited, however, by the photoresponse below 500 nm, as evidenced in its electronic spectra.…”

Photoinduced Curling of Organic Molecular Crystal Nanowires

“…[1,2] The use of molecular crystals as photomechanical materials is challenging, since strain between reacted and unreacted crystal phases often leads to fracture and crystal disintegration. Photomechanical materials usually consist of photoreactive molecules assembled in an ordered matrix, for example a liquid crystal polymer.…”