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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