A new class of poly(1,6-heptadiyne)-based photorefractive materials by metathesis polymerization

SUMMARY: We utilized the first metathesis reaction to synthesize a new type of photorefractive polymers that contain both a carbazole moiety as a hole transporter and NLO chromophores. These polymers have a long tail band at above 700 nm, indicating the formation of intramolecular charge transfer complexes between the carbazole groups and the conjugated double bonds in the polymer backbone. Also, these polymers show two maximum values of photocurrent around 350 and 700 nm. The electro-optic coefficient (r ₃₃) at the wavelength of 1.3 μm for polymer thin films poled around the 85°C were in the range of 1.6 ∼6.3 pm/V. The hyperpolarizabilities, <γ>, of the resulting polymers were ca. 2.9 × 10⁻³² esu. at the incident wavelength of 1.907 μm. Received: 1 June 1998/Revised version: 27 July 1998/Accepted: 5 August 1998     

Guest-host ferroelectric side-chain liquid crystalline polymeric materials with improved electro-optical properties

A ferroelectric side-chain liquid crystalline polysiloxane (FLCP) containing azobenzene dyes as guest molecules for electro-optics has been investigated. The intensity and frequency of the Goldstone mode for the FLCP were increased remarkably after doping with azobenzene dyes. Larger fluctuation of the spontaneous polarization vector in each smectic layer under an applied electric field can be brought about with the addition of a strong dipole-moment guest molecule. This leads to a larger spontaneous polarization and shorter response time. It was found that the doping of a suitable amount of a strong dipole-moment azobenzene dye in the LC phase of the FLCP is helpful for the improvement of the electro-optical properties.     

Synthesis and characterization of polyimides from 1,4-bis[4-(n-alkyloxy)phenyloxy]pyromellitic dianhydrides and 4,4'-oxydianiline

Summary New pyromellitic dianhydrides having (n-alkyloxy)phenyloxy (-O-Ph-O-n-C_mH_2m+1, m=1,4,8,12) side chains were synthesized and polymerized with 4,4'-oxydianiline (ODA) in NMP at room temperature. Imidization was carried out using triethylamine and acetic anhydride. The synthesized polyimides (C_m-OPIs) were characterized and their properties were measured and discussed in respect to the effects of side chains. Inherent viscosities of the polymers were in the 0.46 – 0.68 dL/g range. All the polymers were highly soluble in N-methylpyrrolidinone (NMP) and slightly soluble in DMSO, m-cresol, DMF and concentrated H₂SO₄ at room temperature. TGA pyrograms showed two-step degradation. In DSC thermograms the polymers exhibited T_g's between 219°C and 305°C and melting points near 350°C were observed in C₈- and C₁₂-OPIs. Wide-angle X-ray diffractometry for as-polymerized samples revealed very low crystallinities and layered structures which were better developed in the polymers with longer side chains. Received: 11 November 1997/Revised version: 4 December 1997/Accepted: 9 December 1997     

Stable carbon dioxide reforming of methane over modified Ni/Al2O3 catalysts

CO₂ reforming of methane was studied over modified Ni/Al₂O₃ catalysts. The metal modifiers were Co, Cu, Zr, Mn, Mo, Ti, Ag and Sn. Relative to unmodified Ni/Al₂O₃, catalysts modified with Co, Cu and Zr showed slightly improved activity, while other promoters reduced the activity of CO₂ reforming. Mn-promoted catalyst showed a remarkable reduction in coke deposition, while entailing only a small reduction in catalytic activity compared to unmodified catalyst. The catalysts prepared at high calcination temperatures showed higher activity than those prepared at low calcination temperature. The Mn-promoted catalyst showed very low coke deposition even in the absence of diluent gas and the activity changed only slightly during 100 h operation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Oxidation characteristics of phthalic and adipic acids by supercritical water

Supercritical water oxidation (SCWO) was carried out in a flow-type reactor for modeling of waste-water containing phthalic or adipic acid. For each acid, the reaction order and rate constant, k, were determined over a wide range of experimental conditions : temperatures from 633.15 to 713.15 K, pressures from 18 to 29 MPa, excess amounts of hydrogen peroxide from zero to 800 percent, and the mean residence time in the reactor from 1.1 to 49.1 seconds. The concentration of both acids in model wastewater was set by 500 ppm. For phthalic acid, we found that the orders of decomposition reaction with respect to the reactant concentrations were 0.56 for phthalic acid, 0.31 for hydrogen peroxide, and 0.53 for water. For adipic acid, the orders of oxidation were 0.78 for adipic acid, 0.53 for hydrogen peroxide, and 0.74 for water. Then measured activation energy for phthalic acid was 33.08 kcal/mol and that for adipic acid was 19.51 kcal/mol, respectively.     

Characterization of enzymatically synthesized structured lipids containing eicosapentaenoic, docosahexaenoic, and caprylic acids

Structured lipids (SL) containing n-3 polyunsaturated (eicosapentaenoic or docosahexaenoic) and mediumchain (caprylic) fatty acids were synthesized in gram quantities and characterized. Tricaprylin was mixed with n-3-rich polyunsaturated fatty acids in a 1:2 molar ratio and transesterified by incubating at 55°C in hexane with SP 435 lipase (10% by wt of total substrates) in a 125-mL Erlenmeyer flask as the bioreactor. After several batches of reaction, the products were pooled and hexane was evaporated. Short-path distillation was used for purification of synthesized SL. The distillation conditions were 1.1 Torr and 170°C at a feed flow rate of 3 mL/min. Up to 240 g of SL was isolated and deacidified by alkaline extraction or ethanol-water solvents. The fatty acid profile, free fatty acid value, saponification number, iodine value, peroxide value, thiobarbituric acid, and conjugated diene contents were determined. Oxidation stability, with α-tocopherol as antioxidant, and the oxidative stability index were also determined.     

Poly[2-(hydroxyethyl methacrylate)-co-(sulfobetaine)]s hydrogels: 1. Synthesis and swelling behaviors of the 2-(hydroxyethyl methacrylate)-co-2-(vinyl-1-pyridinium propane sulfonate) hydrogels

A series of the 2-hydroxyethyl methacrylate/2-vinyl-l-pyridinium propane sulfonate (HEMA/VPPS) copolymeric gels have been prepared from HEMA and zwitterionic monomer VPPS of various molar ratios. The influence of the amount of VPPS in copolymeric gels on their swelling behavior in water and various saline solutions at different temperatures was investigated. Results indicate that the PHEMA hydrogels exhibit an overshooting phenomenon in their dynamic swelling behavior. The maximum overshooting value decreases with increasing temperature. The same results are also shown for the lower VPPS content HEMA/VPPS copolymeric gels. In the equilibrium swelling ratio, the PHEMA hydrogel exhibits a minimum swelling ratio at 55 °C. Then, the minimum swelling ratio disappears gradually with increasing VPPS content in HEMA/VPPS copolymeric gels. In the saline solution, the swelling ratios of HEMA/VPPS copolymeric gels increase rapidly with increasing salt concentration, for salts with a smaller ratio of charge/radius.     

Synthesis of highly crosslinked thermally stable poly(vinylethers) by free radical polymerization

Summary 2,4-Di-(2'-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 2,4-di-(2'-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3,4-di-(2'-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl 3,4-di-(2'-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of 2,4-di-(2'-vinyloxyethoxy)benzaldehyde (1) and 3,4-di-(2'-vinyloxyethoxy)benzaldehyde (3) with malononitrile or methyl cyanoacetate, respectively. Trifunctional vinyl ether monomers 2 and 4 were polymerized readily by free radical initiators to give optically transparent swelling poly(vinylethers) 5 and 6. Polymers 5 and 6 were not soluble in common organic solvents such as acetone and DMSO due to crosslinking. Polymers 5 and 6 showed a thermal stability up to 300°C in DSC thermograms. Received: 24 February 1998/Revised version: 7 April 1998/Accepted: 7 April 1998     

Simulation of pervaporation process for ethanol dehydration by using pilot test results

This paper focuses on providing a pervaporation simulation method for ethanol dehydration from a practical point of view. The simulation procedure is performed by setting up simulation equations which describe the pervaporation process, obtaining the necessary data from pervaporation batch mode pilot tests, verifying the simulation tool through simulations of continuous mode pilot tests, and comparing the simulation results with the real pilot test results. We considered the mass and energy balances that describe separating an ethanol/water mixture by a pervaporation membrane. The simulation equations were mathematically expressed into simultaneous non-linear differential equations based on these balances. The necessary data for simulation consist of the thermophysical properties for the ethanol-water mixture and the characteristic data of a PVA composite membrane. The membrane characteristic data are permeation flux and membrane selectivity, which are functions of feed composition and operating conditions. These data were experimentally determined by a batch mode pilot test. The continuous mode pilot tests were simulated and the simulation results were compared to the real test results. The resulte were fairly good.     

Comparison of COD, nitrogen and phosphorus removal between anaerobic/anoxic/aerobic and anoxic/aerobic fixed biofilm reactor using SAC (Synthetic Activated Ceramic) media

In order to remove nitrogen and phosphorus simultaneously and to develop a compact process for retrofitting a conventional activated sludge system, a new fixed-biofilm reactor was designed and tested employing an operation strategy with three and two reaction phases : anaerobic/anoxic/aerobic (Run-1) and anoxic/aerobic (Run-2). Four kinds of HRT (4, 6, 8 and 10 h) were varied to investigate the effect of nitrification and denitrification in each reactor. The results of the experiments are summarized as follows. All removal rates of COD, T-N and T-P in the water treated in Run-1 were higher than those of Run-2. The average values of COD, T-N and T-P in the treated water were reduced to 5.0 mg/L, 5.6 mg/L and 3.1 mg/L in case of Run-1. The COD and T-N removal efficiencies of Run-1 were higher than that of Run-2, but the difference between Run 1 and Run 2 was almost negligible. More than 60 % T-P removal efficiency could be achieved when the HRT was above 8 hour, but the efficiency was sharply decreased to 36% as the HRT was decreased to 4 hour in case of Run-1. Although the removal efficiency of T-P in Run-2 decreased by 56 % compared with that of Run-1, the fixed biofilm reactor using SAC media reduced the volume of reactor, and high-level COD and T-N removal from domestic wastewater was performed ; stable effluent quality was thereby achieved. The performance of Run 2 with no anaerobic reactor was mostly similar to that of Run 1 with an anaerobic reactor, except for T-P removal. Hence, according to these results, anoxic and aerobic processes using SAC media could be possible for removing organics and nutrients from municipal wastewater, in case phosphorus removal is not considered for municipal wastewater with low concentration of phosphorus.