High-Pressure Phase Behavior for Poly(ethylene glycol) and 1,1,1,2-Tetrafluorethane Systems

Abstract

The development of polymeric systems for drug deliveryhas received attention with the aim of producing new systems as an alternative to conventional drug therapy. The design of new systems for this purpose in a compressed medium requires a knowledge of the phase behavior for the polymeric matrix in the high-pressure fluids. This work reports the phase equilibrium experimental data of binary systems involving poly(ethylene glycol) (PEG) with molecular weights of 1000and 2000 g·mol−1 and 1,1,1,2-tetrafluoroethane (HFA-134a). The experimental data were obtained in a high-pressure variable-volume viewing cell based on the static synthetic method at temperatures from 287.4 to 334.2 K, pressures of up to 29.81 MPa, and a PEG concentration in the range of 1 to 7 wt %. Liquid−liquid equilibrium,liquid−liquid−vapor equilibrium, and, in some cases, solid−liquid equilibrium were observed under the experimental conditions of pressure, temperature, and compositions investigated. The experimental results show that temperature and pressure have significant influences on the solubility of PEG in HFA-134a. The solid-phase formation for the system PEG + HFA-134a, in the range of values investigated for temperature, pressure, and compositions, is influenced by the molecular weight of the polymer.