| Popis: |
Posed with the challenge of engineering and characterising nanoscaled objects, this thesis reports on the development of self assembling (cyclic peptide)-polymer conjugates as a versatile supramolecular route to complex nanostructures. A variety of conjugates was synthesised by microwave assisted copper(i)-catalysed azide-alkyne cycloaddition, covalently coupling alt(d,l) α cyclic peptides with synthetic polymers. The product of self assembly was then characterised in solution by small angle neutron scattering. Manipulating the grafted polymer and the chemical functionality of the peptide influenced the stability of the assembly, but was observed to be dependent on the solvating media. H-bonding and solvation strengths of a variety of solvents and mixtures produced nanotubes with lengths >110 nm or as short as 10 nm. Partially N methylated cyclic peptides (NMeCPs) and NMeCP-polymer conjugates were explored as compounds to limit self assembly. While the dimerisation of NMeCPs could be observed by size exclusion chromatography, lateral aggregation was also observed. NMeCP-polymer conjugates formed large (~400 nm) extended structures with small (~1 nm) domains as characterised by differential scanning calorimetry, light and neutron scattering. Monotopic NMeCP species were then investigated as chain stoppers for nanotubes, with the intent of controlling the nanotube length and adding functionality to the tube ends. No change to the geometry of the assembly could be observed, even up to a molar ratio of 1:4 ([CP]/[NMeCP], 80 % NMeCP). To gain insight into this discrepancy, a thermodynamic model was developed to describe the bicomponent system. It is put forward that the decreased availability of NMeCP in monomeric form, due to the lateral aggregation of NMeCP species, could explain the observed inefficiencies in chain stopping. |
