Crystallization behaviors of $n$-nonadecane in confined space: observation of metastable phase induced by surface freezing

Crystallization and phase transition behaviors of $n$-nonadecane in microcapsules was studied with the combination of differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (XRD). As evident from the DSC measurement, a surface freezing monolayer, which is formed in the microcapsules before the bulk crystallization, induces a novel metastable rotator phase (R$_{II})$, which has not been reported anywhere else. We argue that the existence of the surface freezing monolayer decreases the nucleating potential barrier of R$_{II}$ phase and turns the transient R$_{II}$ phase to a `long-lived' metastable phase.