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Dynamics of ¹H-¹³C Cross Polarization in Nuclear Magnetic Resonance of Poly(3-hydroxybutyrate)

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Koval'aková M., Fričová O., Hutníková M., Hronský V., Olčák D.

Acta Physica Polonica A

2017

vol. 131

issue 4

1162-1164

Poly(3-hydroxybutyrate) (PHB) is a semicrystalline biodegradable polymer with chains consisting of methyl (CH₃), methylene (CH₂), methine (CH) and carbonyl (CO) groups. The ¹H-¹³C cross polarization NMR measurements were performed on an as-supplied powder PHB sample at a magic-angle spinning rate of 10 kHz. The measured cross polarization build-up curves and their analysis provided information on the dynamics of ¹H-¹³C NMR cross polarization in functional groups with directly bonded hydrogens. The measurements required setting up the Hartmann-Hahn condition, which was inferred from the Hartmann-Hahn matching profiles measured for each functional group. The cross polarization build-up curves displayed an oscillatory course, which indicates the presence of rigid ¹H-¹³C spin pairs isolated from the lattice. The frequency of the observed oscillations is directly proportional to the ¹H-¹³C dipolar coupling constant, which is related to the C-H distance and its value also reflects the mobility of particular functional groups. The values of dipolar coupling constants were derived from splittings in the Fourier transforms of cross polarization build-up curves. The mobility of particular groups was assessed with the order parameter ⟨S⟩ calculated using experimental and rigid lattice values of dipolar coupling constants.

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1 Acta Physica Polonica A

1 2017

1 Fričová O.

1 Hronský V.

1 Hutníková M.

1 Koval'aková M.

1 Olčák D.

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Dynamics of ¹H-¹³C Cross Polarization in Nuclear Magnetic Resonance of Poly(3-hydroxybutyrate)