Examination of the Molecular Mass of Polyhydroxypolyamides

The work described in this thesis investigated the use of size exclusion chromatography (SEC) to fractionate a variety of different polyhydroxypolyamide (PHPA) samples for analysis by matrix assisted laser desorption ionisation-time of flight spectrometry (MALDI-TOF). The molecular weights obtained via MALDI-TOF were then compared to those obtained by 1H nuclear magnetic resonance (NMR) end-group analysis. Deionised water was used as the solvent for SEC fractionation using KS sugar columns KS-804 and 805 in series. An issue with PHPA is the possibility that they may hydrolyse in water and also under elevated temperature. Since deionised water was used to prepare each sample and they were run through columns which were under elevated temperatures (50˚C) hydrolysis could occur during fractionation by SEC. Through 1H NMR degradation experiments at room temperature and at 50˚C, it was observed that degradation would not be a problem. Analysis of each PHPA sample on each KS sugar column showed fractions in the V0 region. These fractions make up the majority of the composition of unfractionated PHPA samples. There are two possible explanations for these fractions in this region, these are; 1) smaller ionised molecular weight PHPA polymers and 2) extremely high molecular weight PHPA polymer fractions. From the resulting SEC, MALDI and 1H NMR T2 relaxation rate measurements, it was concluded that these fractions are extremely high molecular weight polymer fractions. The size of these PHPA fractions means molecular weights cannot be determined for these fractions and for unfractionated PHPA samples due to the limitations of MALDI-TOF spectrometry and 1H NMR end group analysis. However MALDI-TOF and 1H NMR end-group analysis do give good predictions for low molecular weight PHPA fractions which are in agreement with each other