High-resolution solid-state 13C NMR studies of poly[(R)-3-hydroxybutyric] acid.
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.
Department of Macromolecular Physics, Adam Mickiewicz University, Poznan, Poland.
Farhod
F
Nozirov
Zbigniew
Z
Fojud
Jacek
J
Klinowsk
Stefan
S
Jurga
D002152:Calorimetry, Differential Scanning; D006885:Hydroxybutyrates / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011091:Polyesters / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D000094122:Polyhydroxybutyrates
D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates