Macromolecules, Vol.42, No.20, 7945-7952, 2009
Fractionation of Poly(vinyl acetate) and the Phase Behavior of End-Group Modified Oligo(vinyl acetate)s in CO2
Poly(vinyl acetate) (PVAc) is an inexpensive, high-tonnage bulk commodity polymer which, unlike most vinyl polymers, is moderately biodegradable. PVAc has been shown to exhibit anomalously high solubility in CO2 with respect to other vinyl hydrocarbon polymers. Understanding the phase behavior of PVAc in CO2 and its variation with structure is very important for its potential application as suitable surfactant, ligand, or phase transfer agent in a CO2 solvent process. In this article, PVAc has been fractionated using a supercritical fluid extraction method (SCFE) to provide low molecular weight fractions with narrow polydispersity. The phase behavior of hydroxyl terminated poly(vinyl acetate)s (PVAc-OH) were determined by a high throughput gravimetric extraction (HTGE) screening method and a cloud-point pressure method using a variable volume view cell (VVVC). The solubility of PVAc in CO2 strongly depends on the molecular weight, Oligomer PVAc-OH (M-w < 3000 g . mol(-1)) is Soluble in CO2 at low pressures but decreases in solubility with increasing molecular weight. End-group modification of oligomer PVAc-OH alters the phase behavior of the oligomers.