Fourier-transform infrared (FTIR) spectroscopy for monitoring and determining the degree of crystallisation of polyhydroxyalkanoates (PHAs) |
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Authors: | Mustafa Kansiz Ana Domínguez-Vidal Don McNaughton Bernhard Lendl |
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Institution: | (1) Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164AC, 1060 Vienna, Austria;(2) School of Chemistry and Centre for Green Chemisty, Monash University, Wellington Rd, Clayton, Melbourne, VIC, 3800, Australia |
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Abstract: | FTIR spectroscopy has been used to monitor and determine the degree of crystallisation in a sample of polyhydroxybutyrate-co-14%valerate
(PHB–co-14%HV). Time series spectra of solution-cast films of the polymer revealed spectral changes attributed to the onset
of crystallisation. Curve fitting was used to obtain an absolute measure of crystallinity. Mean centred principal-component
analysis (PCA) revealed that 99.9% of the spectral variance could be attributed to factor 1. The loadings plot for factor
1 contained features attributable to crystalline and amorphous phases. These features were opposite in sign, indicating that
changes in the spectra with the onset of crystallisation are simultaneous and opposite in direction, i.e. as the crystalline
band increases the amorphous band decreases. Cross-peaks in asynchronous 2D correlation maps indicate there are likely to
be very minor components that are changing out of phase. The presence of these minor components is supported by examination
of the loadings of higher factors in the PCA model. PCA has been shown to be suitable for determining the number of dynamic
spectral features and has enabled relative and objective monitoring of crystallisation kinetics. |
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Keywords: | FTIR Polyhydroxyalkanoates (PHA) Crystallinity Principal-component analysis (PCA) Curve fitting 2D correlation analysis |
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