Extracting the Density Gradient Profile of Polyethylene Glycol from Bulk to Surface

Abstract

In this work the Simha and Somcynsky (SS) lattice hole theory in conjunction with Cahn-Hilliard(CH) model have been used, (SS) theory describes the thermodynamic properties of both low and high molecular weight in terms of hole fraction, On the other hand (CH) describes the free energy profile of polymer surfaces or interfaces as an inhomogeneous mixture. CH consider the energy density to be two fold. The first is the constant free energy density for a homogeneous region of the system and the second is the density gradient contribution to the free energy. Have employed the mentioned theories in derive the new equations to extract in surface tension and surface depth profile in terms of chemical potential by means of SS theory. Starting form the atmospheric pressure to 150Mpa and for temperature range from 313 to 473 K, Then ıt is found the density profile of polyethylene glycol decrease as it is approached to the surfase. PVT characteristic parameters of the SS theory are calculated using the data of polyethylene glycol. the average and maximum value (at polyethylene glycol in different molecular weight