The melting behavior of a bacterially synthesized biodegradable polymer, poly(3-hydroxybutyrate) (PHB), was investigated by using generalized two-dimensional infrared (2D IR) correlation spectroscopy. Temperature-dependent spectral variations in the regions of the C-H stretching (3100-2850 cm -1), C=O stretching (1800-1680 cm-1), and C-O-C stretching (1320-1120 cm-1) bands were monitored during the melting process. The asynchronous 2D correlation spectrum for the C=O stretching band region resolved two crystalline bands at 1731 and 1723 cm-1. The intense band at 1723 cm-1 may be due to the highly ordered crystalline part of PHB, and the weak band at 1731 cm-1 possibly arises from the crystalline part with a less ordered structure. These crystalline bands at 1731 and 1723 cm-1 share asynchronous cross peaks with a band at around 1740 cm-1 assignable to the C=O band due to the amorphous component. This observation indicates that the decreases in the crystalline components do not proceed simultaneously with the increase in the amorphous component. In the 3020-2915 cm-1 region where bands due to the asymmetric CH 3 stretching and antisymmetric CH2 stretching modes are expected to appear, eight bands are identified at 3007, 2995, 2985, 2975, 2967, 2938, 2934, and 2929 cm-1. The bands at 2985 and 2938 cm-1 are ascribed to the amorphous part while the rest come from crystal field splitting, which is a characteristic of polymers with a helical structure.
|Number of pages||10|
|Journal||Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy|
|Publication status||Published - Feb 2005|
All Science Journal Classification (ASJC) codes
- Analytical Chemistry
- Atomic and Molecular Physics, and Optics