369 research outputs found
Cholesteric liquid crystalline polymer networks as optical sensors
No full textIn the past decade, chiral nematic liquid crystals (LCs) have emerged as an attractive material for the development of stimuli-responsive systems (White et al. 2010; Ge and Yin 2011; Fenzl et al. 2014; Mulder et al. 2014; Stumpel et al. 2014). Due to the periodic alteration of their refractive indices, they act as one-dimensional photonic structures and reect circularly polarized light of same handedness. The reection of light is governed by Bragg’s law: λ θb = nP cos where λb is the wavelength of Bragg reection, n is the average refractive index, and P is the length of the helical pitch. The pitch of a chiral nematic is dened as the length traversed by the molecular director nˆ on 360° rotation (Figure 4.1a). It is inversely proportional to the concentration [C] as well as the helical twisting power
The Interplay between Different Stimuli in a 4D Printed Photo-, Thermal-, and Water-Responsive Liquid Crystal Elastomer Actuator
Full text linkMulti-stimuli responsivity in 3D-printed objects is receiving much attention. However, the simultaneous interplay between different environmental stimuli is largely unexplored. In this work, we demonstrate direct ink writing of an oligomeric ink containing an azobenzene photo-switch with an accessible hydrogen bond allowing triple responsivity to light, heat, and water. The resulting printed liquid crystal elastomer performs multiple actuations, the specific response depending on the environmental conditions. Bilayer films formed by printing on a static substrate can rapidly change shape, bending almost 80 degrees if irradiated in air or undergoing a shrinkage of about 50 % of its length when heated. The bilayer film assumes dramatically different shapes in water depending on combined environmental temperature and lighting conditions
Chiral nematic liquid crystalline sensors containing responsive dopants
No full textIn his 1990 book, Peter Collings refers to liquid crystals (LCs) as “Nature’s delicate phase of matter.”1 This is perhaps most apparent when looking at the use of LCs as sensors. Due to the inherent fragility of the phase, LCs make ideal candidates for sensors, as small disruptions to the localized order are propagated and ampli-ed throughout the bulk material. This responsiveness, coupled with the attractive optical properties of liquid crystalline materials, has been the focus of much of the investigation into the applications of the liquid crystalline phase
Intelligent stimuli-responsive materials : from well-defined nanostructures to applications
Full text linkBook revie
Supramolecular architectures based on porphyrin and receptor molecules: synthesis, characterization, and applications
No full textPolymerized liquid crystals as actuators and sensors
No full textNovel liquid-crystalline polymers that respond to specific stimuli by changing their shape or color can be used as soft actuators and optical sensors for environmental, energy, and biomedical applications
Supramolecular architectures based on porphyrin and receptor molecules: synthesis, characterization, and applications
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mmubn000001_230183921.pdf (Publisher’s version ) (Open Access)Promotores : R. Nolte en M. FeitersVII, 158 p
Energy-transfer efficiency in stacked oligo(p-phenylene vinylene)s; pronounced effect of order
No full textThe supramolecular structure of two types of oligo(p-phenylene vinylene) (OPV) building blocks in dodecane solution is studied. Monofunctional chromophores (MOPV) form well-defined helical assemblies, whereas bifunctional molecules (BOPV) aggregate into so-called frustrated stacks, lacking any higher helical order. This difference in organization has a major influence on the transfer of excitation energy through the assemblies. Energy transfer to supramolecularly incorporated guests (MOPV with lower bandgap) is used to probe the intrinsic differences in exciton mobility in these two types of mixed aggregates. From the observed donor fluorescence quenching, it can be concluded that the helically ordered nature of the MOPV stacks facilitates the transfer of excitation energy, yielding evidence for higher exciton mobility in the well-ordered assemblies than in the frustrated stacks. Finally, the concept of energy transfer in supramolecular assemblies is extended to the solid state by the successful implementation in a light-emitting diode (LED)
Control of aggregation and tuning of the location of porphyrins in synthetic membranes as mimics for cytochrome P450
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10150.pdf (Publisher’s version ) (Open Access
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