Physical properties of molecular nanomaterials in porous silicon films

The effects of nanoconfinement are known to dramatically affect the structural, thermophysical and dynamical properties of molecular phases. Over the past decades, the fundamental questions arising from nanoconfined systems have been addressed by impregnation of molecular fluids within nano/mesoporous silica glasses. For pore sizes smaller than few tens of nanometers, strong interface and finite size effects dominate the physical properties of the confined phase. Different topics of condensed matter physics have been (re-)considered in confined geometry including H-bonded liquids, polymer physics, phase transitions, critical phenomena, and the glass transition. Very recently, we have addressed the case of calamitic liquid-crystal (LC) in nanochannels of silicon and optically transparent silica membranes [1–8]. We have shown that new physical properties, which are qualitative different from the bulk case are observed. An essential effect of the confinement concerns the phase diagram and the nature of the phase transitions [1,7,8]. In addition, glass-like dynamics seems to be a salient feature of nanoconfined LCs (in terms of drastic molecular slowdown, highly non-Debye decays, dynamical heterogeneities, and super-Arrhenius temperature dependence of the average relaxation time) [2–6]. These drastic changes in the overall properties of LCs in nanochannels should have significant implications in molecular self-assembly and flow, which are crucial issues with respect to hybrid nanomaterials and devices comprising rod-like molecules in nanochannels.