Abstract:The polymer class of poly(2-oxazoline)s currently is under intensive investigation due to the versatile properties that can be tailor-made by the variation and manipulation of the functional groups they bear. In particular their utilization in the biomedic(in)al field is the subject of numerous studies. Given the mechanism of the cationic ring-opening polymerization, a plethora of synthetic strategies exists for the preparation of poly(2-oxazoline)s with dedicated functionality patterns, comprising among others the functionalization by telechelic end-groups, the incorporation of substituted monomers into (co)poly(2-oxazoline)s, and polymeranalogous reactions. This review summarizes the current state-of-the-art of poly(2-oxazoline) preparation and showcases prominent examples of poly(2-oxazoline)-based materials, which are retraced to the desktop-planned synthetic strategy and the variability of their properties for dedicated applications.

The customized fabrication of soft active devices with self-healing function is demonstrated by 3D printing with vitrimeric thiol–acrylate photopolymers.

Vitrimers are covalent adaptable polymer networks, which are able to rearrange their topology in response to an external stimulus. Below the topological freezing temperature (Tv) they behave like a classic...

Vitrimers exhibit a covalently crosslinked network structure, as is characteristic of classic thermosetting polymers. However, they are capable of rearranging their network topology by thermo‐activated associative exchange reactions when the topology freezing transition temperature (Tv) is exceeded. Despite the vast number of developed vitrimers, there is a serious lack of methods that enable a (spatially) controlled onset of these rearrangement reactions above Tv. Herein, we highlight the localized release of the efficient transesterification catalyst 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) by the UV‐induced cleavage of a photolatent base within a covalently crosslinked thiol–epoxy network. Demonstrated with stress relaxation measurements conducted well above the network's Tv, only the controlled release of TBD facilitates the immediate onset of transesterification in terms of a viscoelastic flow. Moreover, the spatially resolved UV‐mediated photoactivation of vitrimeric properties is confirmed by permanent shape changes induced locally in the material.

Copoly(2-oxazoline)-based photoresists are prepared from pEtOx(80) Bu(=) Ox(20) and pPhOx(80) Dc(=) Ox(20) , respectively, a tetrathiol, and a photosensitive initiator. It is possible to prepare copoly(2-oxazoline)s bearing unsaturated side chains in a microwave reactor on a decagram scale in reaction times of 100 min or shorter. UV irradiation of dried polymer films through a quartz mask induces the thiol-ene reaction in the illuminated areas. Subsequent development of the polymer films in halogen-free solvents reproduces the negative pattern of the mask with a resolution of 2 μm. The pEtOx(80) Bu(=) Ox(20) -derived photoresists can also be developed in water.

Polymers with light-responsive groups have gained increased attention in the design of functional materials, as they allow changes in polymers properties, on demand, and simply by light exposure. For the synthesis of polymers and polymer networks with photolabile properties, the introduction o-nitrobenzyl alcohol (o-NB) derivatives as light-responsive chromophores has become a convenient and powerful route. Although o-NB groups were successfully exploited in numerous applications, this review pays particular attention to the studies in which they were included as photo-responsive moieties in thin polymer films and functional polymer coatings. The review is divided into four different sections according to the chemical structure of the polymer networks: (i) acrylate and methacrylate; (ii) thiol-click; (iii) epoxy; and (iv) polydimethylsiloxane. We conclude with an outlook of the present challenges and future perspectives of the versatile and unique features of o-NB chemistry.

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Poly(2-oxazoline) networks with varying swelling degrees and varying hydrophilicity can be synthesized from 2-ethyl-2-oxazoline, 2-nonyl-2-oxazoline, 2-9'-decenyl-2-oxazoline and 2,2'-tetramethylene-bis-2-oxazoline in one-pot/one-step strategies. These gels can be loaded with organic molecules, such as fluorescein isothiocyanate, either during the polymerization (covalent attachment of the dye) or according to post-synthetic swelling/deswelling strategies (physical inclusion of the dye). Surface functionalization of ground gels by thiol-ene reactions with cysteine-bearing peptides exhibiting the arginine-glycine-aspartic acid (RGD) motif yields microparticles with enhanced recognition of human cancer cells compared to healthy endothelial cells.