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.

We show a versatile method for the preparation of a variety of humidity-responsive actuators based on a single sheet of a hydrogen-bonded, uniaxially aligned liquid crystal polymer network. In this approach, the asymmetry in the molecular trigger in the anisotropic polymer film plays a dominant role leading to programmed deformation events. The material is locally treated with a potassium hydroxide solution to create the asymmetry in the responsiveness toward humidity, which allows to prepare actuators that bend, fold, or curl.

This work describes the fabrication, characterization, and modelling of liquid crystalline polymer network films with a multiple patterned 3D nematic director profile, a stimuli‐responsive material that exhibits complex mechanical actuation under change of temperature or pH. These films have a discrete alternating striped or checkerboard director profile in the plane, and a 90‐degree twist through the depth of the film. When actuated via heating, the striped films deform into accordion‐like folds, while the film patterned with a checkerboard microstructure buckles out‐of‐plane. Furthermore, striped films are fabricated so that they also deform into an accordion shaped fold, by a change of pH in an aqueous environment. Three‐dimensional finite element simulations and elasticity analysis provide insight into the dependence of shape evolution on director microstructure and the sample's aspect ratio.

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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.

A crosslinkable, temperature-responsive cholesteric main-chain liquid crystal oligomer was prepared, and used to make patterned coatings.

The copper‐catalyzed azide–alkyne 1,3‐dipolar cycloaddition (CuAAC) is extensively used for the functionalization of well‐defined polymeric materials. However, the necessity for copper, which is inherently toxic, limits the potential applications of these materials in the area of biology and biomedicine. Therefore, the first entirely copper‐free procedure for the synthesis of clickable coatings for the immobilization of functional molecules is reported. In the first step, azide‐functional coatings are prepared by thermal crosslinking of side‐chain azide‐functional polymers and dialkyne linkers. In a second step, three copper‐free click reactions (i.e., the Staudinger ligation, the dibenzocyclooctyne‐based strain‐promoted azide–alkyne [3+2] cycloaddition, and the methyl‐oxanorbornadiene‐based tandem cycloaddition−retro‐Diels−Alder (crDA) reaction) are used to functionalize the azide‐containing surfaces with fluorescent probes, allowing qualitative comparison with the traditional CuAAC.

Cholesteric liquid crystals (CLCs) are chiral photonic materials reflecting only circularly polarized light with the same handedness as the helical polymer structure. Concurrent shape and color changes can be achieved using CLCs, but the fabrication of CLCs with switchable 3D shape, structural color, and hyper‐reflectivity, that is, reflecting both left‐ and right‐handed circularly polarized light simultaneously, has not yet been achieved. Here, CLC elastomer (CLCE) actuators are reported to reflect equal amounts of left‐ and right‐handed circularly polarized light. Hyper‐reflectivity is achieved by uniaxially stretching the partially crosslinked film to induce helix deformation which is then fully crosslinked to fix the deformed helical structure. The shape, structural color, and hyper‐reflectivity of the polymer film are switchable with temperature. At high temperatures, only right‐handed circularly polarized light is reflected and the color is redshifted. The film can be shaped in three dimensions: a structural colored 3D shaped beetle is fabricated using molding, which reflects both left‐ and right‐handed circularly polarized light and shows reversible, temperature responsive structural color and 3D shape changes. Hence, 4D engineered bioinspired multifunctional materials are fabricated, which are interesting for applications ranging from sensing actuators to switchable hyper‐reflective films and objects.