Synthesis and characterization of liquid crystalline copolymers with dual photochromic pendant groups

In order to study the photoreactivity and the optical properties of liquid crystalline copolymers with multiple photochromic groups, a series of novel liquid crystalline binary and ternary polyacrylates consisting of one (CC or NN) or dual (CC and NN) photochromic segments were synthesized and characterized considering their liquid crystalline, optical, and photochromic properties and their thermal stability. Achiral homopolymer P1 shows a smectic A phase (fan-shaped texture), and all chiral copolymers CP1-CP6 exhibit chiral nematic phases (cholesteric, oily streaks textures). The polymers show excellent solubility in common organic solvents such as chloroform, toluene, and THF. These polymers also exhibit good thermal stability, with decomposition temperatures (T_ds) greater than 373 °C at 5% weight loss, and beyond 440 °C at 50% weight loss under nitrogen atmosphere. UV irradiation caused E/Z photoisomerization at NN and CC segments of the synthesized photochromic copolymers leading to reversible and irreversible isomerizations, respectively. The synthesized liquid crystalline ternary copolymer CP6, containing two different photochromic NN and CC groups, is sensitive to different UV wavelengths and is notably interesting from the viewpoint of photochromic copolymers.     

Determination of the interaction within polyester-based solid polymer electrolyte using FTIR spectroscopy

Characterization and interaction behavior between Li⁺ ion and CO groups of a series polyester electrolyte have been thoroughly examined using Fourier transform infrared (FTIR). The “free/Li⁺ bonded” CO absorptivity coefficient of the LiClO₄/polyester can be determined quantitatively using FTIR spectrum ranging from 1800 to 1650 cm⁻¹ at 80 °C. Results from curve fitting show that the “free/Li⁺ bonded” CO absorptivity coefficient is 0.144 ± 0.005. The CO group of polymer electrolyte shows strong interaction with Li⁺ ion and a limit value of 95% “Li⁺ bonded” CO is approached in the polymer electrolyte system when the Li⁺ ion equivalent fraction is about 0.28. The molecular structure of polyester electrolyte does not affect significantly the efficiency of interaction between Li⁺ ion and CO.     

Synthesis and optical properties of three novel functional polyurethanes bearing nonlinear optical chromophoric pendants with different π electron conjugation bridge structure

High molecular weight functional polyurethanes bearing large π electron conjugated chromophoric pendants with different conjugation bridge structure, poly(1a), poly(1b), and poly(1c), were synthesized and characterized by FTIR, ¹H NMR and UV-vis absorption spectra. Their optical properties were evaluated by optical limiting and nonlinear optical analyses. The results show that these polymers possess good optical limiting and large nonlinear optical properties, which are attributed to the long D-π-A conjugated π electron structure of the NLO-chromophoric segment. Poly(1a) with CC double bond as π electron conjugation bridge shows better optical limiting property than poly(1b) and poly(1c) with CN or NN double bond as conjugation bridge structure under the same linear transmittance, while poly(1c) with NN double bond as π electron conjugation bridge of the NLO-chromophoric segment is superior on nonlinear optical properties to poly(1a) and poly(1b) with CC and CN double bonds as π electron conjugation bridge structure, respectively.     

Electrochemical and spectral studies on the catalytic oxidation of nitric oxide and nitrite by high-valent manganese porphyrins at an ITO electrode

Catalytic oxidation of nitric oxide and nitrite by water-soluble manganese(III) meso-tetrakis(N-methylpyridinium-4-yl) porphyrin (Mn(III)(4-TMPyP) was first studied at an indium-tin oxide (ITO) electrode in pH 7.4 phosphate buffer solutions. A stepwise oxidation of Mn(III)(4-TMPyP) through high-valent manganese porphyrin species has been observed by electrochemical and spectroelectrochemical (OTTLE) techniques. The formal potential of 0.63 V for the formation of OMn(IV)(4-TMPyP) has been estimated from OTTLE data. The product, oxoMn(IV) porphyrin, was relatively stable decaying slowly to Mn(III)(4-TMPyP) with a first-order rate constant of 3.7 × 10⁻³ s⁻¹. OMn(IV)(4-TMPyP) has been found to oxidize NO catalytically at potentials about 70 mV more negative than that previously reported for OFe(IV)(4-TMPyP) with good selectivity against nitrite. Nitrite was catalytically oxidized at potentials higher than 1.1 V presumably by OMn(V)(4-TMPyP). OMn(IV)(4-TMPyP) was observed as an intermediate species. Nitrate has been confirmed to be a final product of the electrolysis at 1.2 V, while at 0.8 V nitrite left unchanged, demonstrating that OMn(IV)(4-TMPyP) could not oxidize nitrite. A possible schemes of the catalytic oxidation of NO by OMn^IV(4-TMPyP) and NO₂⁻ by OMn(V)(4-TMPyP) have been proposed.