NEW 3D NMR PULSE SEQUENCES FOR CHARACTERIZATION OF POLYMER-CHAIN END STRUCTURES

A series of three-dimensional (3D) nuclear magnetic resonance (NMR) pu lse sequences, utilizing pulsed-field gradients (PFG) techniques, were developed or adapted from biological experiments for applications in the characterization of the structures of polymers and other heteroato m-containing organic materials, in much the same way that the data fro m multiple 3D NMR experiments have been used in biological structure d etermination. This initial Communication describes variations of an H- 1/X/Y chemical shift correlation (HXY) experiment, and an HCX sequence (Y = C-13) is combined with C-13 homonuclear isotropic mixing to gene rate new pulse sequences which provide additional structural informati on. Spectra of polystyrene and poly(alpha,beta-C-13(2)-styrene) (PS) p repared by diphenylphosphinyl radical (DPPR) initiated polymerization of alpha,beta-C-13(2)-styrene are used to illustrate the application o f these techniques for characterization of polymer chain end structure s. While polymers are used to illustrate the applications of these pul se sequences, they can just as easily be used to study other organic s tructures containing an NMR-active X nucleus. Organometallic chemistry is especially suited for applications of these NMR experiments. (C) 1 998 Academic Press.