Characterization of multiblock copolymers by chromatography methods

The aim of this work was to develop analytical methods and tools to characterise the functionality type distribution (FTD) of poly (p-dioxanone)- (PPDO) and poly (caprolactone)-diol (PCL) samples. In addition information on the heterogeneities of multiblock copolymers (MBC) derived by reacting mixtures of the two polymeric diols with diisocyanates was requested. To gain insight into the chemical heterogeneity of the MBCs samples a gradient method was developed. The method allowed separating PPDO-diols and PPDO-multiblock polymers (MBP) from the PCL-diols and the PCL-MBPs. MBPs were derived by linking either PCL- or PPDO-diols with a diisocyanate. The application of the developed gradient to the MBC-samples resulted in two well separated main peaks. The first peak eluted in SEC mode before the start of the gradient in the retention range of the PPDO-diols and the PPDO-MBPs. In order to validate the assignments of the peaks of the gradient chromatography and to find out about the existence of MBC-structures, identification of the peaks was conducted by means of off-line Fourier Transform Infrared (FTIR). The FTIR spectrum of the first peak revealed the characteristic absorption bands of PPDO while the bands characteristic for PCL were absent, indicating the presence of only PPDO-structures. Since the results were rather unexpected, additional proof was aimed for. Pyrolysis gas chromatography/mass spectrometry (Py-GC-MS) was used as an alternative method to FTIR to verify the results. Gradient chromatography was used to fractionate the MBC-sample into two fractions, corresponding to the observed peaks. The resulting fractions were then analyzed by Py-GC-MS. Based on quantitative studies, the first peak of the gradient chromatography of the MBCs contained more than 80 % (wt%) of PPDO content whereas in the second peak of the gradient chromatography of the MBCs, 0-10% (wt%) of PPDO were found. Further characterization of fractions 1 and 2 of the gradient chromatography of the MBCs was performed by proton nuclear magnetic resonance (1H-NMR). Quantitative 1H-NMR-studies conducted on the two fractions showed that the first fraction contains more than 80 % (wt %) of PPDO, while the second fraction contains 20% (wt %) of PPDO