Lanying Zhang

Syntheses of 5′-O-glycosylnucleosides

Abstract A general synthetic approach to 2,3-unsaturated glycosides connecting with nucleosides involving Ferrier rearrangements of glycals is discussed. The new compounds were identified by NMR and MS (HRFAB + ). The hydroxylation of the resulting 2,3-unsaturated glycosides was completed using OsO 4 to give 5′- O -glycosylnucleosides in good yield.

A novel soft matter composite material for energy-saving smart windows: from preparation to device application

Nowadays, with the increasing energy consumption of buildings and the continuous improvement of human living standards, use of architectural glass with multi-functional features of large-scale manufacturing, safety and energy saving has become the mainstream trend. In this paper, a series of cholesteric side-chain liquid crystal polymers (ChSCLCPs) are designed and synthesized to composite with a widely used laminating material for safety glasses, ethylene-vinyl acetate (EVA), to endow the windows with IR light shielding property. The synthesized ChSCLCPs have the desired reflection wavelengths and thermal stability. Preparation methods of EVA/ChSCLCP composite materials are investigated and different ratios of the contents and various film treatment conditions are attempted. Interestingly, when the contents of EVA and ChSCLCP are equal, “sky-blue” areas are found under polarized optical microscopy (POM) and the film exhibits stronger light scattering and selective reflection properties. Taking advantages of this phenomenon, a new type of IR shielding film is manufactured by the powder blending method and it not only performs broadband reflection, but also exhibits a strong light scattering. Then, model buildings equipped with and without the film are set up and an energy conservation efficiency of up to 40.4% is obtained, which proves the films practical applications in energy-saving smart windows.

Synthesis and properties of highly birefringent liquid crystalline materials: 2,5-bis(5-alkyl-2-butadinylthiophene-yl) styrene monomers

In order to obtain liquid crystals with high birefringence (Δn), a series of new liquid crystals monomers incorporating styrene, a 2,5-disubstituted thiophene ring and diacetylenes, which were highly conjugated along the molecular long axis, were synthesized. Their physical properties were evaluated. As expected, they exhibited high Δn values of 0.4–0.7 and a low melting point and were of potential use for polymer-dispersed liquid crystal displays (PDLCDs), cholesteric displays and laser beam steering applications.

Multi-shape-memory effects in a wavelength-selective multicomposite

Utilizing the distinct photoresponsive behaviour of p-aminodiphenylimide and multi-walled carbon nanotubes, we design a wavelength-selective multicomposite featuring remotely controlled, micro-localized and photo-manipulatable shape-memory behaviors based on three typical segments that are neat epoxy, and the p-aminodiphenylimide/epoxy and multi-walled carbon nanotube/epoxy composites. Herein, p-aminodiphenylimide and multi-walled carbon nanotubes not only act as photoabsorbers and heat sources to induce the shape-memory effect but also as functional components to manipulate shape-memory behavior. In our concept, the quantity of temporary shapes and shape recovery process in the shape-memory cycle can be accurately controlled by a photo-manipulation procedure. Moreover, only one switching domain with sharp thermal transition and a simple shape programming process, similar to those for thermal-responsive dual-shape shape-memory polymers, are required to enable the wavelength-selective multicomposite to present triple- or multi-shape-memory effects. This strategy can be put forward for applications of shape-memory polymers and can be applied in other stimulus-responsive systems to generate complex structures.

Synthesis of 3-deoxy-3-nucleobase-2,5-anhydro-d-mannitol: a novel class of hydroxymethyl-branched isonucleosides

Abstract A concise synthesis of 3-deoxy-3-nucleobase-2,5-anhydro- d -mannitol 6 ( a – d ) has been achieved, using the deamination of 2-amino-2-deoxy- d -glucose to construct in one step the sugar skeleton with the desired sense of chirality at each asymmetric center. The selective dibenzoylation of 2,5-anhydro- d -mannitol 9 was investigated, and the key epoxide intermediate 13 was obtained in good yield via an intramolecular Mitsunobu reaction. The process of opening of epoxide 13 by nucleobases appeared to be regioselective.

Synthesis of 2-C-(4-aminocarbonyl-2-thiazoyl)-1,4-anhydro-l-xylitols and their fluoro derivatives

Abstract 3,5-O-Benzylidene-2-C-cyano-1,4-anhydro- l -xylitol 7 was synthesized stereoselectively from d -xylose in 7 steps. 2-C-(4-Aminocarbonyl-2-thiazoyl)-1,4-anhydro- l -xylitols and their fluoro derivatives were synthesized from the cyanohydrin 7. Fluorination of compound 9 proceeded with retention of configuration using diethylaminosulfur trifluoride (DAST).

Studies on the electro-optical and the light-scattering properties of PDLC films with the size gradient of the LC droplets

Polymer dispersed liquid crystal (PDLC) films with the size gradient of the LC droplets were prepared based on the epoxy/acrylate hybrid polymer matrix. The ultraviolet (UV) intensity gradient was induced by the UV-absorbing dye over the thickness of the samples. Taking advantage of the difference between the epoxy monomers and acrylate monomers in polymerisation rates and the UV intensity gradient, the gradient distribution of the LC droplet size was formed in PDLC films. The effect of the size gradient of the LC droplets on the electro-optical and the light-scattering properties of PDLC films was investigated. The results showed that due to the size gradient distribution of the LC droplets, PDLC films could exhibit the strong light scattering in the UV-visible-near infrared (VIS-NIR) region. Consequently, it provides a potential approach for modulating NIR light transmittance.

Preparation and properties of highly birefringent liquid crystalline materials: styrene monomers with acetylenes, naphthyl, and isothiocyanate groups

Two new series of styrene monomers with different alkyl chain length were successfully synthesised. The chemical structures of synthetic intermediates and monomers were confirmed by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis. Their thermal stability, transition temperatures and phase sequences were investigated by polarised light microscopy, thermogravimetric analysis, differential scanning calorimetry and one-dimensional wide-angle X-ray diffraction. The birefringent and photoelectric properties, UV–vis and fluorescence spectroscopy were also measured using Abbe refractometer and fluorescent apparatus. The results indicated that all the monomers exhibited a liquid crystalline phase at higher temperature, high birefringence values between 0.4 and 0.7, and good photoluminescence properties. Optical anisotropy of homologous molecules was reduced with the increase of alkyl chain length due to the decrease of molecular polarisation. Moreover, a significant effect of the chemical structure on the photoluminescence properties was also found and discussed according to the length of π-conjugation.

A temperature and electric field-responsive flexible smart film with full broadband optical modulation

This study provides a new procedure for the preparation of a flexible multi-responsive smart film containing tin-doped indium oxide nanocrystals and a phase-separated liquid crystal-polymer. This film can reversibly control the passage of visible light in response to temperature and electric field and also screen near infrared light.

Preparation of a Thermally Light-Transmittance-Controllable Film from a Coexistent System of Polymer-Dispersed and Polymer-Stabilized Liquid Crystals

Polymer-dispersed liquid crystal (PDLC) and polymer-stabilized liquid crystal (PSLC) systems are the two primary distinct systems in the field of liquid crystal (LC) technology, and they are differentiated by their unique microstructures. Here, we present a novel coexistent system of polymer-dispersed and polymer-stabilized liquid crystals (PD&SLCs), which forms a homeotropically aligned polymer network (HAPN) within the LC droplets after a microphase separation between the LC and polymer matrix and combines the advantages of both the PDLC and PSLC systems. Then, we prepare a novel thermally light-transmittance-controllable (TLTC) film from the PD&SLC system, where the transmittance can be reversibly changed through thermal control from a transparent to a light-scattering state. The film also combines the advantageous features of flexibility and a potential for large-scale manufacturing, and it shows significant promise in future applications from smart windows to temperature sensors.