Formation of Nanonuclei during a Structural Phase Transition in Molecular Crystals of Normal Alkanes

The phase transitions in the homologous series of normal alkanes: hexadecane (C16H34), heptadekane (C17H36), octadekane (C18H38), nonadekane (C19H40), and eicosane (C20H42) have been studied by differential scanning calorimetry. The elimination of methodic errors enables the obtainment of true values of the thermodynamic parameters of these transitions. The quantitative analysis of the profiles of the heat capacity jumps performed for the solid-phase first-order transitions on the base of the blurred phase transition theory allowed the calculation of a new-phase nucleus sizes in the volume of the old phase during the structural phase transition and the consideration of the kinetics of their development. The method of separating asymmetric peaks of the heat capacity into components has been improved, which enables the separation of various stages of developing the solid-phase transitions.