A novel flow-through column electrolytic cell was proposed as a detector to obtain current signals for supercritical fluid chromatography. The electrochemical cell consisted of two electrodes and its holder, and a working and a counter electrode were fabricated from 192 carbon strings, which were composed of 400 carbon fibers of 10 μm in diameter filled into a heat-shrinkable tube. These electrodes were placed in the center of a holder made from polyether ether ketone blocks and they were separated by polytetrafluoroethylene membrane filters. To evaluate the sensitivity of this cell, a standard solution of ferrocene was injected into the supercritical fluid chromatography system connected to the electrolytic cell. The ferrocene was eluted through a silica gel column using a mixture of a mobile phase of supercritical CO and a modifier of methanol containing ammonium acetate. The current peak area of ferrocene correlated to the ferrocene concentration in the range of 10-400 μmol/L (r = 0.999). Moreover, the limit of detection on the column estimated from a signal-to-noise ratio of 3 was 9.8 × 10 mol.
The preparation condition of poly(L-lactic acid) (PLLA)/ single-wall carbon nanotube (SWNT) composite films with highly dispersed SWNTs from solutions was examined and the thermo-mechanical properties of the resultant composite films were evaluated by tensile tests, DSC measurements and dynamic mechanical analyses. The dispersion of SWNTs in PLLA/SWNT composites significantly affected by the solvents used and the polymer concentrations. The PLLA/SWNT composite with the highest dispersion of SWNTs was obtained from a 5 wt% PLLA solution in chloroform. The tensile modulus and strength increased with increasing the SWNT content. The glass transition temperature shifted higher and the heat resistance remarkably improved with increasing the SWNT content. The PLLA/ SWNT composite (PLLA-5) added with 5 wt% SWNT showed a glass transition temperature of 81+ and a storage modulus of 0.91 GPa at 100+, which were 14+ and 3.3 times higher, respectively, than those pure PLLA film (PLLA-0). It is important to note that the rigid-amorphous fraction determined from the DSC thermogram increased with increasing the SWNT content suggesting the specific interaction between PLLA chains and SWNTs. The tensile modulus of 9.2 GPa for a PLLA-5 film drawn to an EDR of 9 was significantly higher than that of 7.2 GPa for the PLLA-0 drawn to the maximum achieved EDR of 12. These results indicate that the mixing of small amounts of SWNT (< 5 wt%) into a PLLA significantly improves the thermal stability and thermo-mechanical properties of PLLA films.
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