The era of poly(ethylene glycol) (PEG) brushes as a universal panacea for preventing non-specific protein adsorption and providing lubrication to surfaces is coming to an end. In the functionalization of medical devices and implants, in addition to preventing non-specific protein adsorption and cell adhesion, polymer-brush formulations are often required to generate highly lubricious films. Poly(2-alkyl-2-oxazoline) (PAOXA) brushes meet these requirements, and depending on their side-group composition, they can form films that match, and in some cases surpass, the bioinert and lubricious properties of PEG analogues. Poly(2-methyl-2-oxazine) (PMOZI) provides an additional enhancement of brush hydration and main-chain flexibility, leading to complete bioinertness and a further reduction in friction. These data redefine the combination of structural parameters necessary to design polymer-brush-based biointerfaces, identifying a novel, superior polymer formulation.
Poly(2-alkyl/aryl-2-oxazoline)s (PAOx) have been gaining increasing attention because they combine biocompatibility with so-called stealth behavior, making them ideal candidates for use in a wide variety of biomedical applications. Especially, the possibility of side-chain modification makes them a valuable alternative to poly(ethylene glycol), currently the gold standard amongst biocompatible polymers. Nevertheless, the cationic ring opening polymerization of 2-oxazolines is not compatible with nucleophilic entities, for example hydroxyl and amine moieties. Therefore, the modular approach of 'click chemistry' offers an elegant strategy towards functional PAOx by postpolymerization modification of PAOx that contain clickable groups. This feature describes the synthesis of PAOx with such clickable entities at the chain-end or in the side-chain, as well as their potential (bio)materials applications.
Poly(2-alkyl-2-oxazoline)s (PAOx) are regaining interest for biomedical applications.H owever,t heir full potential is hampered by the inability to synthesise uniform high-molar mass PAOx. In this work, we proposed alternative intrinsic chain transfer mechanisms based on 2-oxazoline and oxazolinium chain-end tautomerisation and derived improved polymerization conditions to suppress chain transfer,allowing the synthesis of highly defined poly(2-ethyl-2-oxazoline)s up to ca. 50 kDa (dispersity () < 1.05) and defined polymers up to at least 300 kDa ( < 1.2). The determination of the chain transfer constants for the polymerisations hinted towards the tautomerisation of the oxazolinium chain end as most plausible cause for chain transfer.Finally,the method was applied for the preparation of up to 60 kDa molar mass copolymers of 2-ethyl-2-oxazoline and 2-methoxycarbonylethyl-2-oxazoline.
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