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M. Kansiz, A. Domínguez-Vidal, D. McNaughton, B. Lendl:
"Fourier-transform infrared (FTIR) spectroscopy for monitoring and determining the degree of crystallisation of polyhydroxyalkanoates (PHAs)";
Analytical and Bioanalytical Chemistry, 388 (2007), S. 1207 - 1213.

FTIR spectroscopy has been used to monitor and det. the degree of crystn. in a sample of polyhydroxybutyrate-co-14%valerate (PHB-co-14%HV). Time series spectra of soln.-cast films of the polymer revealed spectral changes attributed to the onset of crystn. Curve fitting was used to obtain an abs. measure of crystallinity. Mean centered principal-component anal. (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 cryst. and amorphous phases. These features were opposite in sign, indicating that changes in the spectra with the onset of crystn. are simultaneous and opposite in direction, i.e. as the cryst. 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 examn. of the loadings of higher factors in the PCA model. PCA has been shown to be suitable for detg. the no. of dynamic spectral features and has enabled relative and objective monitoring of crystn. kinetics.