Meishan Pei

Phase Behavior of Liquid Crystals Formed in [C12mim]CI/H2O and [C12mim]CI/Alcohols Systems

Phase behaviors of different binary systems involving 1-dodecyl-3-methylimidazolium chloride ([C12mim]Cl) and H2O, [C12mim]Cl and different alcohols (1-butanol, 1-pentanol, 1-hexanol and 1-octanol) are investigated at 25 °C. Hexagonal liquid crystal phase (H1) is identified in [C12mim]Cl/H2O system, and lamellar liquid-crystalline (Lα) phase is found in [C12mim]Cl/alcohols systems by using polarized optical microscopy and small-angle X-ray scattering techniques. The formation of such phases is considered as a synergetic result of the solvatophobic force and the hydrogen-bonded network comprising an imidazolium ring, chloride ion and water (or alcohols), which can be confirmed by Fourier transform infrared spectra. It is noticeable that in [C12mim]Cl/1-octanol system, the lattice spacings of lamellar phase increase with increasing C12mimCl concentration, which is opposite to the results of [C12mim]Cl/H2O system. This may result mainly from stronger static repulsion among hydrophilic headgroups of imidazolium salts arranged in the bilayers of lamellar structures. Further measurements by differential scanning calorimetry indicate that the lamellar phase is stable within a wide temperature range above room temperature. However, the lattice spacings decrease with the increase of temperature, which may be due to the softening of the hydrocarbon chain of [C12mim]Cl molecules. In different alcohols systems, it is found that the lamellar lyotropic liquid crystal structure is easier to be formed when the carbon chain length becomes longer.

Synthesis of gold nanogears, nanobelts and nanoplates in hexagonal phase of lyotropic liquid crystal

Abstract Single crystalline planner gold nanostructures, including nanogears, nanobelts and nanoplates, are synthesised in hexagonal lyotropic liquid crystals made of P123/HAuCl4 aqueous solution. The effects of reaction temperature as well as capping agent on the growth of nanoproducts are studied in detail. When cetyltrimethyl ammonium bromide is used as the capping agent, gold nanobelts appear in the products at 45°C, while gold nanogears can be obtained with a large scale at room temperature when poly(N-vinyl-2-pyrrolidone) is the capping agent. Results show that temperature is an important factor that may influence the growth of gold nanoproducts through changing the lyotropic liquid crystal structure and the adsorption process of capping agent on nanocrystal surfaces. The growth mechanism of nanostructures is further certified by the products from the microwave assistant method.

Electrosyntheses of free-standing poly(thiophene-3-acetic acid) film in mixed electrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid

High quality free-standing poly(thiophene-3-acetic acid) (PTAA), a water-soluble polythiophene derivative, was successfully electrosynthesized in boron trifluoride diethyl etherate (BFEE) + 25% (by volume) trifluoroacetic acid (TFA) at lower potential (0.38 V versus Pt). The carboxyl group makes PTAA highly soluble in water, facilitating its potential application as a blue-light-emitting material. PTAA films with conductivity of 7 S cm−1 obtained from this medium showed better redox activity and thermal stability. The structure and morphology of the polymer were studied by UV-Vis, FT-IR, 1H-NMR spectra and scanning electron microscopy, respectively.