Precise compositional analysis of styrene/butyl acrylate/methacrylic acid terpolymer by two-step reactive pyrolysis–gas chromatography with tetramethylammonium acetate

Abstract

Compositional analysis of a styrene (St)/butyl acrylate (BA)/methacrylic acid (MAA) terpolymer, which was quite difficult by conventional pyrolysis–gas chromatography (Py–GC) mainly because of highly polar nature of MAA moiety, was performed by two-step (double-shot) reactive Py–GC. In this method, the MAA units were converted into methyl methacrylate (MMA) ones, which are readily depolymerize, by tetramethylammonium acetate (TMAAc) in the first step in the microfurnace pyrolyzer. Pyrolysis of the derivatized terpolymer sample was then carried out at 600°C. Prior to the measurement, the sample was dissolved in THF and premixed with TMAAc to enhance the derivatization efficiencies between the sample and the reagent. The reaction conditions for derivatization were also settled experimentally at 200°C for 10min. The pyrogram obtained by this procedure showed some major peaks such as butene, butanol, butyl acrylate, and butyl methacrylate for BA, methyl acrylate and methyl methacrylate for MMA, and styrene and α-methylstyrene for St. Based on the relative peak intensities of these characteristic products detected by a flame ionization detector, the terpolymer composition (mol%) was estimated to be St/BA/MAA=29.9/33.1/37.1, which was almost identical with the feed composition (St/BA/MAA=30/33/37) with excellent relative standard deviations less than 0.25%.