Separation systems utilizing silver(I) ion-olefin complexation have limitations since silver(I) ions can be poisoned or reduced to metallic silver. Ionic liquids (ILs) are used as solvents for silver(I) ions to facilitate separations since their physico-chemical properties can be easily tuned. To develop separation systems with sustainable olefin selectivity, factors that affect silver(I) ion stability need to be understood. In this study, a total of 13 silver salt/IL mixtures were examined by inverse gas chromatography to identify the effects of silver salt anion and IL cation/anion combination on silver(I) ion stability. The effects of temperature and three different exposure gases on silver(I) ion stability were systematically studied. Exposing silver salt/IL mixtures to hydrogen at high temperatures had a greater effect on decreasing silver(I) ion-olefin complexation. Silver(I) ions from the silver bis[(trifluoromethyl)sulfonyl]imide ([NTf 2 − ]) salt were more stable in [NTf 2 − ]-containing ILs than in [BF 4 − ]-containing ILs. Optimum mixtures exhibited high olefin selectivity and were stable beyond 90 h when exposed to hydrogen gas.

A versatile Raman spectroscopic method to determine the contents of carbon nanotubes (CNTs) in CNT/polydimethylsiloxane (PDMS) composites is demonstrated, and important issues directly related to the accuracy of the measurement have been investigated. Initially, Raman microscopic mappings over an area of 6.0 × 6.0 mm were carried out on CNT/PDMS composites, which revealed the existence of the partial localization of CNTs on a microscopic scale. Therefore, a laser illumination scheme covering a large sample area of 28.3 mm was employed to acquire a sample spectrum representative of the whole CNT concentration. The peak area ratio between the CNT and PDMS peaks clearly varied with the CNT concentration, whereas the reproducibility of measurements was degraded for the composites containing more than 3.0 wt% CNTs because of the decreased Raman sampling volume arising from the absorption of laser radiation by the CNTs. The laser penetration depth was semi-quantitatively investigated by observing the spectra of thin-sliced samples collected by positioning a Teflon disk behind the sample, and Monte Carlo simulations were employed to examine the internal photon propagation as well as explain the experimental observation. In summary, the fundamental issues affecting the Raman measurement of the CNT containing polymer matrix have been clearly addressed, and the finding here will be a beneficial basis for successful Raman spectroscopic analysis of different CNT-containing composites.

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