Liquid crystal coating for SAW sensors

This paper presents results on measurements of surface acoustic wave (SAW) sensor, using polymer liquid crystal layer. The sensitivity and response time for different test probes have been studied. The sensitivity of the order of 4 Hz/ppm or higher, towards such compounds as N,N-dimethylacetamide (DMA), dimethyl methylphosphonate and dibutyl sulphide, was found. The results show that the very high sensitivity towards DMA results from interaction of DMA with structurally ordered liquid crystalline material

An experimental and theoretical study of the C-13 and P-31 chemical shielding tensors in solid O-phosphorylated amino acids

International audiencexx

X-ray, 31P CP/MAS, and single-crystal NMR studies, and 31P DFT GIAO calculations of inclusion complexes of bis[6-O,6-O'-(1,2:3,4- diisopropylidene-alpha-D-galactopyranosyl)thiophosphoryl] disulfide: the importance of C-H...S=P contacts in the solid state.

Bis[6-O,6-O′-(1,2:3,4-diisopropylidene-α-D-galactopyranosyl)thiophosphoryl] disulfide shows a strong tendency to form inclusion compounds. The crystal and molecular structure of eight different solvates was established by X-ray analysis. The results indicate three different types of disulfide arrangements in the crystal lattice. By means of 31P CP/MAS NMR experiments the principal values δ11, δ22, and δ33 of the 31P chemical shift tensor were obtained for each form. The orientation of its principal axes with respect to a molecular frame was investigated by means of 31P CP and single-crystal NMR for the complex with propan-2-ol. The principal axis 1 of both chemically equivalent phosphorus atoms is nearly parallel to the P[BOND]S bond and the principal axis 3 is very close to the P[DOUBLE BOND]S bond. DFT GIAO calculations of the model compound (EtO)2(S)P1SSP2(S)(OEt)2 allowed assignment of the experimental chemical shift curves to the magnetically nonequivalent atoms P1 and P2. The maximum difference between calculated angles (∢ i[BOND]P[BOND]X)calcd and experimental angles (∢ i[BOND]P[BOND]X)exptl is 8.3° and the rms distance 3.8° (i=principal axes 1, 2, 3; X=S, -S-, -O1-, -O2-). The influence of C[BOND]H⋅⋅⋅S weak hydrogen bonding on phosphorus shielding was tested theoretically (31P DFT GIAO) employing the dimethoxythiophosphoryl disulfide⋅CH4 complex as a model compound. The sensitivity of 31P δii parameters to intermolecular forces is demonstrated

Temperature‐Responsive Photonic Devices Based on Cholesteric Liquid Crystals

Cholesteric liquid crystals (CLCs) are a major class of photonic materials that display selective reflection properties arising from their helical ordering. The temperature response of CLCs, comprising of dynamic reflection color changes upon variation of temperature, can be exploited using material systems consisting of small mesogenic molecules, polymer‐dispersed liquid crystals (PDLCs), polymer‐stabilized liquid crystals (PSLCs), or liquid‐crystalline polymers. Taking advantage of the easy processability and flexibility of the molecular design, these temperature‐responsive CLCs have been fabricated into different forms of photonic devices, including cells, coatings, free‐standing films, and three‐dimensional objects. Temperature‐responsive devices developed from CLCs could be integrated for application in temperature sensors, energy‐saving smart windows, smart labels, actuators, and adding aesthetically pleasing features to common objects. This review summarizes the device capabilities of the different material systems of temperature‐responsive CLCs: small mesogenic molecules, PDLCs, PSLCs, and CLC polymers. For each system, examples of different device forms are presented, with their temperature responsiveness and the underlying mechanisms discussed. Additionally, the potential of each material system for future device applications and product developments is envisioned