3D NMR Studies of C-Centered n-ad Structures in Poly(ethylene-co-n-butylacrylate-co-¹³C-carbon monoxide) (PolyEBC*)

Abstract

Three-dimensional HC A C X and HC A C X -HH-TOCSY NMR experiments (J. Magn. Reson. 2004, 168, 352) at 750 MHz have been used to investigate the resonance assignments and monomer sequence distributions of C-centered triads and pentads in poly(ethylene-co-n-butyl acrylate-co-13 C-carbon monoxide), poly(EBC*) terpolymer prepared from 13 C-labeled carbon monoxide. These experiments provide spectra with correlations among mutually coupled atoms with δ CO plotted along the f 1 dimension and δ CA and δ H of adjoining groups plotted along the f 2 and f 3 dimensions, respectively. The correlation among signals in three planes in a 3D NMR spectrum facilitates selective detection of the resonances from the structure fragments near the 13 C labeled ketone carbonyl groups. Moreover, these experiments provide enormous spectral resolution, permitting the identification of numerous unresolved signals that are overlapped in 2D 1 H-13 C HMBC NMR spectrum. The correlation of resonances involving three different nuclei (δ H , δ CA , and δ CO ) provides unambiguous atomic connectivity information in the polymer backbone that facilitates analysis of comonomer composition, stereo-sequence distribution and branching structures. Occasionally, these experiments provide additional proof of the methods adopted to perform chemical shift assignments from 2D HMBC NMR experiments.

Interplay of Structure and Dynamics in Macromolecular and Supramolecular Systems

“…122 Advantage should be taken, however, of the fact that a general formalism exists, which does not involve the usual assumption of exponential relaxation and can handle locally anisotropic motion. 123 Indeed, in a recent ab initio calculation of 2 H and 17 O relaxation in water, without any empirical parameters or model assumptions a pleasing agreement with experimental data was found. 124 Remarkably, however, the simulated correlation function differs significantly from a simple exponential.…”

“…Thus, the methodologies converge, albeit the technical differences should not be ignored. Indeed, application of NMR spectroscopic methods from protein NMR to study synthetic polymers in solution provides unambiguous atomic connectivity information in the polymer backbone which facilitates analysis of comonomer composition, stereosequence distribution, and branching structures . As several reviews on new developments of NMR on bulk polymers and supramolecular systems are available, − we refrain from describing the techniques in detail again.…”

Solid acid clay mediated copolymerization of methyl acrylate and 1‐octene: 2D NMR substantiation of predominant alternating comonomer sequence

“…NMR is the most widely used technique for the qualitative and quantitative analysis of chain microstructure and polymer composition determination. Two‐dimensional (2D) NMR has been widely accepted and practiced in a large spectrum of polymer characteristics like main chain structure elucidation and identification of chain ends 18–21…”