Distribution Of Molecular Properties Research Articles

Characterization of Poly(Vinyl Alcohol) by Liquid Chromatographic Techniques

Abstract Poly(vinyl alcohol) is a complex, multicomponent material exhibiting a number of broad molecular property distributions and is therefore difficult to characterize by simple analytical techniques. Molecular weight distribution can be measured by aqueous size exclusion chromatography methods but the choice of eluent is critical in eliminating non-size exclusion behavior. Aqueous size exclusion experiments have been carried out using a number of eluents including standard electrolytes and surfactants. The most favorable molecular size separation was obtained using 0.25% w/v sodium lauryl sulfate as eluent. Compositional distributions in copolymer systems can be assessed using high-performance liquid chromatography employing a reversed-phase separation mechanism. For poly(vinyl alcohol), gradient elution with water/tetrahydrofuran (THF) was found to produce a separation according to composition. Fast gradient elution (> 10% THF/min) suggested a broad distribution of composition which was verified using a column packed with nonporous beads. Slower gradient elution (< 1% THF/min) suggested that this was not caused by a gradual composition change, but rather discrete fractions of similarly hydrophobic material.