Exact calculation of the NMR spectrum of a twelve spin 1/2 system : application to the structure of the aromatic core of a main-chain nematic polymer

The anisotropic proton NMR spectrum of the 2,2'-dimethylazoxybenzene moiety, a twelve spin 1/2 system, is calculated exactly and compared to the experimental spectra of (i) 4,4'-diacetoxy-2,2'-dimethylazoxybenzene deuterated on the methyl groups and dissolved in the nematic phase of perdeuterated p-azoxyanisole and (ii) deuterated main-chain thermotropic nematic azoxy polymers [Ph(Me)-N=N(O)-Ph(Me)OCO(CH 2 ) m COO] n (m= 7,10) in their bulk nematic phase. Modeling in terms of the single conformation model allows satisfactory fits of the experimental data