Determining the vinyl alcohol distribution in poly(vinyl butyral) using normal-phase gradient polymer elution chromatography.

The vinyl alcohol (VOH) functionality in poly(vinyl butyral) is known to be responsible for a number of important end-use properties, such as controlling adhesion to surfaces, influencing cross-linking behavior, etc. In order to determine the distribution of the VOH percentage in PVB, with the associated averages and polydispersity, we have developed a normal-phase gradient polymer elution chromatography (NP-GPEC) method which relies on both precipitation-redissolution as well as on sorptive interactions between the polymer and the column packing. The method is shown to operate in the linear region of detector response with respect to key operational parameters and is demonstrated to be independent of chemical composition distribution, molar mass, or polydispersity in either molar mass or VOH content. Several examples are given, including where NP-GPEC readily allows visualization of differences between samples that appear identical when analyzed by standard methods.