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Trans content in atactic polystyrene estimated by double-quantum solid-state NMR.

M G Dunbar·B M Novak·K Schmidt-Rohr
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Abstract

The conformational statistics of atactic polystyrene have been investigated by solid-state NMR, on a sample labeled with 25% 13CH2 groups. Double-quantum pulse sequences are used to select statistically formed 13C-13C spin pairs. An experiment correlating the 13C-13C internuclear vector with the 13C chemical-shift anisotropy determines the conformational statistics of a single backbone torsion angle. Double-quantum experiments correlating the 13CH2 chemical-shift anisotropies of two adjacent segments provide information on two consecutive torsion angles. The analysis of the spectra yields a trans content of 68% (+/-10%). This represents the first direct experimental estimate of the trans/gauche ratio in atactic polystyrene. The trans content found here agrees well with rotational-isomeric-state models but is inconsistent with results from more elaborate atomistic models that take packing effects into account.

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AnisotropyMagnetic Resonance SpectroscopyMolecular ConformationPolystyrenesProbabilityQuantum TheoryRotationStereoisomerismTorsion AbnormalityJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.

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M G Dunbar, B M Novak, K Schmidt-Rohr. 1998. Trans content in atactic polystyrene estimated by double-quantum solid-state NMR.. https://doi.org/10.1016/s0926-2040(98)00062-9

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