PhD ceremony: Ms. R. Rachmawati, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen
Dissertation: Inclusion complexes between amylose and polytetrahydrofurans. The supramolecular assembly of homopolymers and block copolymers
Promotor(s): prof. K. Loos
Faculty: Mathematics and Natural Sciences
Amylose is a linear polysaccharide having α -(1 -> 4)-glycosidic linkages. The single helical V-amylose has a hydrophobic cavity that enables it to include guest polymers such as polytetrahydrofuran (PTHF).
Amylose-PTHF complexes were prepared via direct mixing as it is more time- and cost-effective compared to the in situ complexation via “vine-twinning polymerization”. The complexes were formed immediately upon mixing of soluble amylose and emulsified PTHF. The degree of polymerization (DP n ) and the end groups of the guest PTHF influence the complexation as the mechanism seems to proceed via insertion of the guest PTHF rather than wrapping around. The complexes are stable against storage, are yet reduced in organic solvents. Ethanol-washed complexes assembled as round spherulitic structures constructed of vertically stacked round lamellae. The high melting temperature of the complexes (t m 125-145 °C) indicates a high crystallinity. Additionally, X-ray diffraction (XRD) demonstrates that the complexed amylose is in the form of V-amylose with 6 glucose residues per helix turn (V 6 - amylose), possibly a mixture or an intermediate between V 6I - and V 6II -amylose. This structure was also observed for complexation of low DP n PTHF with PTHF-bamylose (t m complexes 120-139 °C). However, the V 6II -amylose which indicates the presence of guest PTHF in between the amylose helices was observed in PTHF-bamylose. This indicates that the structures of the corresponding PTHF-b-[amylose- PTHF complex] seems to be influenced by the organization of the block copolymer as well as by inclusion complex formation. Other polymers such as amylose-b-PTHFb- amylose and three-arm PTHF-b-amylose were synthesized and are also expected to act as host molecules.
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