Two-Dimensional Melting and Phase Change of Binary Mixtures of CCl4 and CHCl3 Confined in ACF Nanospace Studied Using Solid-State 1H NMR

Abstract

Abstract Two-dimensional melting and phase changes of binary mixtures of CCl4 and CHCl3 confined in activated carbon fiber were examined using differential thermal analysis and 1H wide-line NMR. Molecular assembly of CCl4 confined in ACF nanospace with a slit width of 1.1 nm showed succeeding thermal anomalies corresponding to crystal–hexatic and hexatic–liquid transitions. Results showed that these thermal anomalies did not occur in a mixture of CHCl3 and CCl4. This behavior differed greatly from the phase diagram for the bulk mixture between CHCl3 and CCl4. Furthermore, the dynamic features of CHCl3 molecule were examined using the 1H wide-line NMR spectrum. The activation energy of the hopping motion changed from 7 kJ mol−1 for pure CHCl3 to 13 kJ mol−1 for CHCl3 with a 0.016 molar ratio in CCl4. In particular, a drastic increase in the activation energy was observed for doping with a trace amount of CHCl3, suggesting that molecular self-assembly of CCl4 takes place in the ACF nanoslit because of the effective intermolecular interaction between CCl4 molecules. The existence of CHCl3 in CCl4 brings about the remarkable impurity effect on two-dimensional melting and phase transition of CCl4 confined in ACF nanospace.