ONE-DIMENSIONAL PHASE-TRANSITION OF DIPOLAR MOLECULES INSIDE ZEOLITE PORES

The thermodynamic behavior of dipolar molecules in a system of paralle l straight channels (such as para-nitroaniline (pNA) adsorbed in the c hannels of AlPO4-5 molecular sieves) was studied theoretically. The in teraction between the molecules is considered to be a superposition of long range interaction due to all dipoles in the crystal and nearest- neighbor interaction within the individual pore. The dipoles in a pore are regarded as a one-dimensional system. This leads to a van der Waa ls-type equation of state. A phase transition exists below the critica l temperature. For a real system (pNA in AlPO4-5), the isotherms, the critical point, and the coexistence region are calculated.