Determination of Total Styrene in Styrene/Butadiene Block Copolymers by Process NMR and Chemometrics Modeling

A new method involving the use of chemometric techniques was developed on a process nuclear magnetic resonance (NMR) spectrometer for measurement of total styrene in styrene/butadiene (Sty/BD) block copolymers. The method uses partial least-squares (PLS) regression to correlate the total styrene data produced by solutions H-1 NMR to the data produced by process NMR. The new method has comparable accuracy and precision to the solution NMR method, but it is much faster and easier to perform. It also has the additional capability of being selective for a specific process and/or polymer. The NMR method and chemometrics models are discussed, and results for validation of the models and prediction of the total styrene in unknown samples are presented.