Observation of multiple phase transitions in n-C22H46 using a high resolution and super-sensitive DSC

The phase transitions of n-C22H46 have been measured by using a high resolution and super-sensitive DSC. The crystal–rotator transition and the rotator–melt transition were observed both in the heating and in the cooling run, although a rotator–rotator transition was observed only in the cooling run. A new peak was found at about 3 K above the ‘bulk’ melting temperature. It is considered to be due to the order–disorder transition of a monolayer on the surface of the liquid alkane. When the cooling rate was below 0.1 mK s−1, the peak due to solidification was separated to give another phase transition.