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One of the major challenges in the processing of hydrogels based on poly(ethylene glycol) (PEG) is to create mechanically robust electrospun hydrogel scaffolds without chemical crosslinking postprocessing. In this study, this is achieved by the introduction of physical crosslinks in the form of supramolecular hydrogen bonding ureido‐pyrimidinone (UPy) moieties, resulting in chain‐extended UPy‐PEG polymers (CE‐UPy‐PEG) that can be electrospun from organic solvent. The resultant fibrous meshes are swollen in contact with water and form mechanically stable, elastic hydrogels, while the fibrous morphology remains intact. Mixing up to 30 wt% gelatin with these CE‐UPy‐PEG polymers introduce bioactivity into these scaffolds, without affecting the mechanical properties. Manipulating the electrospinning parameters results in meshes with either small or large fiber diameters, i.e., 0.63 ± 0.36 and 2.14 ± 0.63 µm, respectively. In that order, these meshes provide support for renal epithelial monolayer formation or a niche for the culture of cardiac progenitor cells.

Supramolecular polymers based on ureido‐pyrimidinone (UPy) represent a promising class of biocompatible materials for medical applications. Here, the chemical modification effect of UV irradiation, used to sterilize these materials, is studied. Besides anticipated crosslinking effects, UV irradiation causes telechelic UPy‐polymers to become fluorescent. UPy‐model compounds confirm a relation between UV‐induced changes and the UPy‐moiety. UV‐induced fluorescence and IR‐spectral changes are (partially) reversible by heat and/or solvent treatment. The results indicate the presence of at least two distinct UV‐induced molecular species. UPy‐model compounds with specific tautomeric forms directly relate fluorescence to UPy‐enol tautomers. Photo‐enolization is hypothesized to occur via an excited‐state intermolecular double proton transfer. Changes in UPy‐tautomeric equilibrium and crosslinking are factors that influence the dynamics of UPy‐based materials. Identification and understanding of such factors will aid in the successful application of these materials, for example as biomaterial in tissue engineering applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 81–90

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