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High-Resolution Solid-State 13C NMR Studies of Poly[(R)-3-hydroxybutyric] Acid

✍ Scribed by Farhod Nozirov; Zbigniew Fojud; Jacek Klinowski; Stefan Jurga

Publisher
Elsevier Science
Year
2002
Tongue
English
Weight
161 KB
Volume
21
Category
Article
ISSN
0926-2040

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✦ Synopsis

Solid poly[(R)-3-hydroxybutyric] acid was examined by high-resolution 13C MAS NMR, differential scanning calorimetry and infrared spectroscopy. The 13C methyl group resonance consists of three components: the rigid amorphous phase, the crystalline phase and the mobile amorphous phase. Spectral deconvolution, using the Lorentz function, reveals the relative amounts as 62% crystalline and 38% amorphous at 333 K, and 42% crystalline, 40% pure amorphous and 18% beta-orthorhombic at 413 K. NMR indicates a large difference in molecular mobility between the crystalline and amorphous regions of the sample. Infrared spectroscopy shows that the stretching at 1725 cm(-1) (characteristic of the alpha-form) comes from the crystalline region, and the bands at 1744 cm(-1) (characteristic of the beta-form) and 1800 cm(-1) come from the amorphous region.

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