Stereoregular oligomers of methyl methacrylate

Summary Packed column SFC has been found suitable for the rapid and detailed analysis of the isotactic and syndiotactic oligomers of MMA, when the temperature gradient technique was applied and the modifier was employed. Oligomer components from trimer to 20-mer separated completely. The heptamer fraction collected three times by SFC gave the ¹H NMR spectrum of satisfactorily high S/N ratio; the spectrum agreed well with that of the standard sample. Separation by tacticity as well as by molecular weight was observed for the SFC of a mixture of the isotactic and syndiotactic oligomers. The isotactic oligomers had longer retention time than the syndiotactic oligomers of the corresponding degree of polymerization. Part 3: cf. Ute K. Nishimura T, Hatada K, Polym J (1989) 21: 1027     

Application of system identification modelling to solar hybrid systems for predicting radiation, temperature and load

Uncertainties in local solar radiation, ambient temperature and thermal load data have been one of the major factors limiting the reliability and efficiency of solar thermal hybrid systems. In the present paper, moving average auto regressive exogenous (ARX) model based reasoning has been mooted and modified to include moving average method, as an effective tool for predictions of these data. The results show that the method is quite robust and is capable of predicting fairly accurate results, which would make these systems more viable in areas where meteorological data are not available or vague.     

Experimental study and modeling of organic solvent reverse osmosis separations through organosilica membranes

Exceptionally stable, mechanically robust, and highly methanol-selective organosilica membranes, including Bis(triethoxysiyl)acetylene (BTESA), fluorine-doped bis(triethoxysiyl) methane (F-BTESM), and Cetyltrimethylammonium chloride-etched bis(trimethoxysiyl)hexane (CTAC-BTMSH), were prepared and utilized for organic solvent reverse osmosis (OSRO) separations. The BTESA membrane showed optimal separation performance regarding methanol/toluene and possessed the highest levels of both permeation flux and rejection. Continuous measurements were performed to highlight the molecule size/shape discrimination of BTESA membranes using compounds such as methanol/methyl acetate, methanol/dimethyl carbonate (DMC) and methanol/methyl tert-butyl ether (MTBE). Also, a generalized solution-diffusion model was successful in predicting the permeation behaviors through organosilica membranes when used in an OSRO modality, and proved to be capable of accurate predictions on pressure-dependent permeation flux and rejection for a wide range of feed concentrations (0–55 wt%) and pressures (2–14 MPa). This study lends important insight for the development of organosilica membranes and process design for the energy-efficient OSRO separation of organic liquids.     

Application of bis(fluorosulfonyl)imide-based ionic liquid electrolyte to silicon-nickel-carbon composite anode for lithium-ion batteries

An ionic liquid electrolyte containing bis(fluorosulfonyl)imide (FSI) anion without any solvent is applied to a silicon-nickel-carbon (Si-Ni-carbon) composite anode for rechargeable lithium (Li)-ion batteries. The FSI-based ionic liquid electrolyte successfully provides a stable, reversible capacity for the Si-Ni-carbon anode, which is comparable to the performance observed in a typical commercialized solvent-based electrolyte, while a common ionic liquid electrolyte containing bis(trifluoromethanesulfonyl)imide (TFSI) anion without FSI presents no reversible capacity to the anode at all. Ac impedance analysis reveals that the FSI-based electrolyte provides very low interfacial and charge-transfer resistances at the Si-based composite anode, even when compared to the corresponding resistances observed in a typical solvent-based electrolyte. Galvanostatic cycling of the Si-based composite anode in the FSI-based electrolyte with a charge limitation of 800 mAh g⁻¹ is stable and provides a discharge capacity of 790 mAh g⁻¹ at the 50th cycle, corresponding to a cycle efficiency of 98.8%.     

Multilayer Mg-Stainless Steel Sheets,Microstructure, and Mechanical Properties

Different multilayer Mg AZ31 and SS304L steel sheet combinations were prepared with different volume fractions of Mg. Isolated stress–strain curves of the Mg layers showed significant improvements in the strength and elongation of multilayer samples. Results indicated that in the most extreme situation with the lowest Mg volume fraction (V _f  = 0.39), the ultimate strength was increased by 25 pct to 370 MPa and the elongation was improved by 70 pct to 0.34. Investigation of the fracture surface showed that failure occurs by the coalescence of cracks close to the interface region. The improved strength of the multilayer samples was due to the combined effect of surface crack prevention by the steel layer and the higher work-hardening rate caused by the possible increased activity of non-basal systems. It is suggested that the stronger work-hardening behavior and the enhanced activity of non-basal systems in the multilayer samples were due to the formation of new stress components in the transverse direction. The larger the volume fraction of steel in the multilayer, the longer the distance remaining unstrained before the UTS.

     

Molecular orientation induced by high-speed substrate transfer during vacuum vapor deposition of organic films

The authors investigate a relationship between substrate transfer speeds during vacuum vapor deposition and orientation characteristics of organic molecules. Results show that rod-shaped molecules of alpha-sexithiophene (α-6T) are oriented in a substrate transfer direction and an absorption dichroic ratio of 1.44 is obtained from the oriented α-6T molecule film when a high substrate transfer speed of 4 m s⁻¹ is used. By combining the substrate transfer technique with homoepitaxial growth of α-6T molecules on a rubbed surface, the absorption dichroic ratio further increases to 4.29. Polarized electroluminescence (EL) characteristics are investigated using rod-shaped molecules of 4,4′-bis[4-(di-p-tolylamino)styryl]biphenyl (DPAVBi) as a light-emitting hole-transport layer. An EL dichroic ratio of 2.12 is obtained due to an orientation of DPAVBi molecules caused by combining two techniques.