Chemical and Biomolecular Engineering - Theses
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ItemA novel approach towards dynamic cross-linked hydrogels( 2012)Expanding interest in supramolecular polymer chemistry has allowed access to a wide range of materials with sophisticated molecular architectures. ‘Sliding-ring’ (SR) hydrogels are based on the non-covalent interaction between α-cyclodextrin (CD) and poly(ethylene glycol) (PEG). Intermolecular cross-linking between the CDs results in networks, where the cross-link points are dynamic in nature. Due to the rotational and translational freedom seen in these cross-link points enhanced mechanical properties are observed. However, since their inception the synthetic approach towards these SR networks has not diverged significantly with numerous isolation and purification steps still being required. This thesis presents a facile one-pot route towards the synthesis of SR networks. The innovative approach results in SR networks where a single CD moiety acts not only as the moveable cross-linker, but also as the end-capping agent which prevents the dissociation of the inclusion complex. Network formation is induced via the copper-catalysed azide-alkyne cycloaddition (CuAAC) form of click chemistry between azido functionalised α-CDs and alkyne functionalised PEG. The resultant networks are characterised in terms of their physicochemical properties such as swellability and mechanical strength. Due to the one-pot nature of the synthetic approach and the fact that inclusion complexation is in dynamic equilibrium, the resulting networks possess both SR and covalent cross-link points. Model studies were conducted whereby a series of rotaxanes were synthesised using the same reagents and under similar curing conditions as for the SR networks. From model studies, an estimation of the extent of SR links within the network was obtained.