Studies of polymer ball type polymer dispersed liquid crystal films

'Reverse' or 'polymer ball' polymer dispersed liquid crystal (PDLC) samples were prepared by a photopolymerization induced phase separation method. A detailed study of the effects of the sample preparation parameters, such as curing time, curing intensity, and liquid crystal concentration are reported. It was found that by adjusting these parameters, we were able to change the morphology of these 'polymer ball' PDLC samples and thus change their optical characteristics. Incomplete polymerization of the PDLC samples results in a higher threshold voltage and a lower ON state transmission. When the amount of monomer is too low, the shape of the resulting polymer ball becomes irregular, and the sample has a larger threshold voltage and a larger saturation voltage.     

Anti-stokes Raman scattering from DODCI solutions

A clearly resolved anti-Stokes peak was observed in the Raman scattering of He-Ne laser radiation from room temperature solutions of DODCI in ethanol and ethylene glycol, but not from solutions of DODCI in glycerol. A slight red-shift and broadening of the Raman-active vibrational mode was noted in ethylene glycol compared to ethanol. Evidence is presented that solutions of DODCI in glycerol have photochemical instabilities.     

Electrically controllable smart window with greyscale based on polymer-stabilised cholesteric texture films

The study reports a novel liquid crystal (LC) film that can be applied on the transmissive substrates or stuck on existing casement window to upgrade the shield. The shadow area and transmittance can be adjusted according to the condition of the outer sunshine. The window is energy saving for which maintains the transmittance after a once-off operation of pulse amplitude modulation (PAM) electric driving. Such a film can be applied in smart curtain, display frame edge and other transmissive electro-optical devices.     

Chromatographic selectivity of poly(alkyl methacrylate-co-divinylbenzene) monolithic columns for polar aromatic compounds by pressure-driven capillary liquid chromatography

In this study, divinylbenzene (DVB) was used as the cross-linker to prepare alkyl methacrylate (AlMA) monoliths for incorporating π-π interactions between the aromatic analytes and AlMA-DVB monolithic stationary phases in capillary LC analysis. Various AlMA/DVB ratios were investigated to prepare a series of 30% AlMA-DVB monolithic stationary phases in fused-silica capillaries (250-μm i.d.). The physical properties (such as porosity, permeability, and column efficiency) of the synthesized AlMA-DVB monolithic columns were investigated for characterization. Isocratic elution of phenol derivatives was first employed to evaluate the suitability of the prepared AlMA-DVB columns for small molecule separation. The run-to-run (0.16–1.20%, RSD; n = 3) and column-to-column (0.26–2.95%, RSD; n = 3) repeatabilities on retention times were also examined using the selected AlMA-DVB monolithic columns. The π-π interactions between the aromatic ring and the DVB-based stationary phase offered better recognition on polar analytes with aromatic moieties, which resulted in better separation resolution of aromatic analytes on the AlMA-DVB monolithic columns. In order to demonstrate the capability of potential environmental and/or food safety applications, eight phenylurea herbicides with single benzene ring and seven sulfonamide antibiotics with polyaromatic moieties were analyzed using the selected AlMA-DVB monolithic columns.     

Multimode lasing from the microcavity of an octagonal quasi-crystal based on holographic polymer-dispersed liquid crystals

An eightfold photonic quasi-crystal (PQC) sample is fabricated holographically using two-beam interference with multi-exposure based on polymer-dispersed liquid crystals. The transmission spectra from the finite-difference time-domain (FDTD) simulation prove the photonic stop band of the rotational symmetry structure of the sample. The resonant mode of the circular microcavity formed in the PQC is calculated. Amplified spontaneous emission and multimode lasing action are demonstrated from the pumped laser-dye-doped PQC microcavity using a Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) pulse laser.     

An efficient and convenient transformation of α-haloketones to α-hydroxyketones using cesium formate

A new safe and convenient transformation has been developed. In the presence of cesium formate in dry MeOH solution, α-haloketones underwent direct conversion reaction to afford α-hydroxyketone in excellent yields. Furthermore, this methodology can be extended and applied in 2-chloro-N-(1,3-diphenyl-1H-pyrazol-5-yl)acetamide, 2-chloro-N-(2,6-dimethylphen-yl)acetamide, 1-(bromomethylsulfonyl)benzene, and N-(bromomethyl)phthalimide to give the corresponding products in moderate to excellent yields.     

Relaxation time of polymer ball type PDLC films

“Polymer ball” polymer dispersed liquid crystal (PDLC) samples were fabricated by the photo-polymerization induced phase separation method and their relaxation behaviour was studied. It was found that upon removal of the applied electric field, the transmittance of the “polymer ball” PDLC sample decays exponentially from T_on to T_memo with a relaxation time constant in the order of msec. It was found that the measured relaxation time constant decreases as the curing time increases and the LC concentration increases.     

Impurity analysis of 1,4-dioxane in nonionic surfactants and cosmetics using headspace solid-phase microextraction coupled with gas chromatography and gas chromatography-mass spectrometry

1,4-Dioxane impurity in nonionic surfactants and cosmetics were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Experimental results show that there is no significant difference using SPME-GC and SPME-GC-MS for analysis of 1,4-dioxane in three types of nonionic surfactants at the 95% confidence level. The relative standard deviation (R.S.D.) values of each analytical method were smaller than 3%. The amount of 1,4-dioxane was found to vary from 11.6 +/- 0.3 ppm to 73.5 +/- 0.5 ppm in 30% of nonionic surfactants from manufacturers in Taiwan. These methods were linear over the studied range of 3-150 ppm with correlation coefficients higher than 0.995. The recoveries of 1,4-dioxane for these nonionic surfactants following SPME were all higher than 96 +/- 1% (n = 3). The detection limits of 1,4-dioxane for these nonionic surfactants following SPME were from 0.06 ppm to 0.51 ppm. The experimentally determined level of 1,4-dioxane in cosmetics from manufacturers in Taiwan varied from 4.2 +/- 0.1 ppm to 41.1 +/- 0.6 ppm in 22% of daily used cosmetics following SPME coupled with GC and GC-MS. Conventional solvent extraction takes around 1 h for extraction and reconcentration but SPME takes only around 10 min. SPME provides better analyses of 1,4-dioxane in nonionic surfactants and cosmetics than conventional solvent extraction and head space pretreatments in term of simplicity, speed, precision, detection limit, and solvent consumption.