13C NMR Assignments of Polyolefines and Olefine Copolymers Based on the 13C NMR Chemical Shift Calculations and 2D INADEQUATE NMR

Abstract

This chapter discusses the 13 C NMR assignments of polyolefines and olefin copolymers in the solution based on 13 C NMR chemical shift calculations and 2D incredible natural abundance double quantum transfer experimen methods (INADEQUATE). Emphasis is placed on revealing the primary structures, such as stereochemical configuration, branching, regioregularity, and comonomer sequence. Two approaches for the assignment of the 13 C NMR spectra of polymers are discussed in this chapter. One is 13 C NMR chemical shift calculations on the basis of the γ-effect on the 13 C chemical shift, using the RIS (rotational isomeric state) model and the other is the 2D INADEQUATE method. The calculation of 13 C chemical shifts on the basis of the γ-effects and the RIS model have also been successfully applied to the 12 C NMR tacticity assignments of other polymers, such as poly(viny1 chloride) and polystyrene. These calculations clarify the origin of the peak splitting due to the tacticity of the polymer in solution and provide methods to examine the tacticity dependent- and time-averaged local conformations calculated with the RIS model. The solid-state 13 C NMR spectra of polyolefines are also well interpreted in terms of the γ-effect. On the other hand, another method, 2D INADEQUATE is especially useful for the sequence analysis of polyolefines and, hereafter, this will be used for the tacticity assignments in addition to the chemical shift calculations.