Two-Dimensional Melting and Phase Change of Binary Mixtures of CCl sub(4) and CHCl sub(3) Confined in ACF Nanospace Studied Using Solid-State super(1)H NMR

Two-dimensional melting and phase changes of binary mixtures of CCl sub(4) and CHCl sub(3) confined in activated carbon fiber were examined using differential thermal analysis and super(1)H wide-line NMR. Molecular assembly of CCl sub(4) 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 CHCl sub(3) and CCl sub(4). This behavior differed greatly from the phase diagram for the bulk mixture between CHCl sub(3) and CCl sub(4). Furthermore, the dynamic features of CHCl sub(3) molecule were examined using the super(1)H wide-line NMR spectrum. The activation energy of the hopping motion changed from 7 kJ mol super(-1) for pure CHCl sub(3) to 13 kJ mol super(-1) for CHCl sub(3) with a 0.016 molar ratio in CCl sub(4). In particular, a drastic increase in the activation energy was observed for doping with a trace amount of CHCl sub(3), suggesting that molecular self-assembly of CCl sub(4) takes place in the ACF nanoslit because of the effective intermolecular interaction between CCl sub(4) molecules. The existence of CHCl sub(3) in CCl sub(4) brings about the remarkable impurity effect on two-dimensional melting and phase transition of CCl sub(4) confined in ACF nanospace.