Amphiphilic oligo(2-ethyl-2-oxazoline)s via straightforward synthesis and their self-assembly behaviour

The synthesis of poly(2-oxazoline)s offers an unparalleled degree of functionalization when fabricating smart, functional polymers for biomedical uses. The termination of 2-oxazoline polymerisations by direct endcapping can be exploited to introduce a wide variety of end groups and could potentially offer an easier synthetic route to amphiphilic polymers that usually block copolymer synthesis. Herein, we report a facile one-pot synthesis and preparation of dodecyl-end capped oligo(2-ethyl-2-oxazoline)s via direct endcapping and thiol-yne click chemistry. A small set of propargyl tosylate initiated PEtOx oligomers were synthesised and subsequently functionalized with varying equivalents of dodecanethiol. GPC, NMR and MALDI-ToF were utilised for molecular weight analysis and determination of end-group fidelity. Film rehydration was employed to prepare self-assembled nanoparticles due the inexpensive set-up and practical simplicity of the technique. DLS, SAXS and TEM revealed that mono- and di-functionalized PEtOx self-assembled into micelles around 10 nm in diameter whereas tri-functionalized PEtOx was too hydrophobic and precipitated in aqueous solution. All oligomers were screened for their ability to encapsulate a model hydrophobic drug, curcumin, and UV-Vis spectrometry was utilized to determine the encapsulation efficiencies and drug loading capacities. Di-functionalized PEtOx provided the greatest drug loading capacity (8 wt%) of this study.