Ubiquitous applications of biopolymer blends require a broader range of accurate information about their behaviour. For this purpose, macro attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and spectroscopic imaging are the main characterisation methods of choice to provide reliable information for both qualitative and quantitative analysis. The main objective of this project is to realise their full potential to investigate biopolymers and biopolymer blends with and without high-pressure CO2.
In situ high-pressure ATR-FTIR spectroscopic imaging was applied to visualize the dynamic process of phase separation in biopolymer Polycaprolactone (PCL)/Poly (lactic acid) (PLA) blends under high-pressure CO2. It was demonstrated that the extent of phase separation in PCL/PLA blends under high-pressure CO2 is enhanced with increasing exposure time, CO2 pressure and temperature.
The mechanisms of polymer-polymer interactions were investigated using 2D correlation analysis and 2D disrelation mapping. Evidence of the break of some of the existing inter- and intramolecular dipole-dipole interaction (C=O···C=O) between polymer molecules under high-pressure CO2 was provided.
The simultaneous visualization of crystallization and phase separation in Poly (3-hydroxybutyrate) PHB/PLA blends has been realized for the first time through utilizing in situ ATR-FTIR spectroscopic imaging. Decreasing the annealing temperature is proved to be an effective method to constrain phase separation between these two blend components and tailor the final morphology in upper critical solution temperature (UCST) crystallizable polymer blends for practical applications.
Spectroscopic images based on the band position were successfully used to investigate changes in intra- and intermolecular interactions in PHB/PLA blends. During the isothermal melt crystallization, the disappearance of the intermolecular interaction between PHB and PLA and the appearance of the inter- and intramolecular interactions within the PHB crystal were both visualized.
Overall, this thesis has demonstrated further the use of ATR-FTIR spectroscopy and macro ATR-FTIR spectroscopic imaging as a valuable analytical approach to investigate biopolymers and biopolymer blends with and without high-pressure CO2, which can aid the design of biopolymer products and biopolymer process.