Surface precrystallization of normal C24 alkane in porous glass

The behavior of the enthalpy and specific heat of normal C24 alkane in the bulk and in porous glasses is investigated using an adiabatic scanning micr ocalorimeter. Enthalpy jumps, which precede a phase transition in the entir e volume of the pores, are found in porous glass with characteristic pore s ize 1000 Angstrom at a transition from the isotropic liquid into the rotato r phase RII. The enthalpy jumps are interpreted as a layerwise growth of a crystal phase on the surface of porous glass. It is also found that porous glass substantially changes the phase behavior of alkanes. (C) 2000 MAIK "N auka/Interperiodica".