Application of multivariate analysis of NMR spectra of poly(N-isopropylacrylamide) to assignment of stereostructures and prediction of tacticity distribution

In this paper, we report multivariate analyses, such as principal component analysis (PCA) and partial least-squares (PLS) regression, of NMR spectra of poly(N-isopropylacrylamide)s [poly(NIPAAm)s]. PCA successfully interpreted the assignments of NMR spectra of poly(NIPAAm)s in terms of stereostructures for the methine carbons at triad levels and for the methylene protons at tetrad levels. Furthermore, triad tacticity was successfully predicted by PLS regression of 1H NMR spectra of the methine and methylene groups, although the low resolution of the signals of the methine protons confines determination of tacticities by conventional methods to the diad levels. Consequently, it is assumed that chemometric approaches are useful for assigning NMR spectra in terms of stereostructures and for predicting tacticity distributions.