Supramolecular polymerization of poly(2-ethyl-2-oxazoline) functionalized ureido-pyrimidinone monomers

The application of supramolecular polymers as biomaterials is gaining more attention due to the dynamicity and tunability provided by their reversible non-covalent interactions. Poly(ethylene glycol) (PEG) is often employed in supramolecular biomaterials due to its excellent hydrophilicity and biocompatibility. The development of immunogenicity upon repeated exposure to PEG-based biomedicines along with the oxidative degradation of its polyether backbone are encouraging the research of alternative polymers with similar properties. Poly(2-alkyl-2-oxazoline)s are promising candidates as PEG replacement owing to their biocompatibility and stealth properties being similar to those of PEG. Herein, the effect of substituting PEG with poly(2-ethyl-2-oxazoline)s (PEtOx) of varying degree of polymerization (DP) of 10, 20, 50 and 100 on the self-assembly of four novel ureido-pyrimidinone (UPy) supramolecular monomers is investigated to explore their potential as future supramolecular biomaterials. The kinetics, stability and morphology of the assemblies formed by each supramolecular monomer are demonstrated to depend on the DP of the PEtOx. Specifically, supramolecular polymer formation is observed for PEtOx with DP of 10, 20 and 50, while more disordered structures are observed for the PEtOx with the higher DP of 100. Additionally, all the supramolecular monomers exhibit lower critical solution temperature behaviour with a cloud point temperature well above the body temperature, making them ideal for further development as future supramolecular biomaterials.