Measuring the Crystallinity of PHBHx with Varying Amounts of Sidechains on a Benchtop Instrument

Abstract

Current benchtop instruments with edge filters providing Raman spectra down to 50 cm-1 can be used to study the crystallization of PHBHx (polyhydroxybutyrate-hexanoate) without the complexity of larger instruments. By collecting the averaged signal from spherulites, the effects of orientation can be averaged out, enabling the use of multivariate techniques to compare samples. These polymers are being commercialized because they are created by fermentation and are biodegradable, making them an ideal replacement for petroleum-derived polymers that do not biodegrade. In addition, it is understood how to control the polymer’s physical properties by controlling the molecular weight and the percent of sidechains which, in turn, controls the crystallinity. To compare spectra of different samples, it is necessary to remove the effects of polymer chain orientation, which averaging the spectrum of a spherulite will enable.