Stimuli-responsive polymers, also referred to as smart polymers undergo changes with respect to their physico-chemical properties or morphology when they are exposed to external stimuli such as temperature, pH and/or light. Thermoresponsive polymers can be primarily categorized into those that exhibit a lower critical solution temperature (LCST), upper critical solution temperature (UCST) or physical gelation. Polymers, which undergo physical gelation have gained great interest because of their potential applications in drug delivery and release, tissue engineering and regenerative medicine, biofabrication, cosmetics and smart coatings. The gelation process is mainly defined by the (reversible) formation and growth of supramolecular structures yielding three-dimensionally, physically crosslinked networks. The molecular interactions defining the network formation may be coulomb interactions, hydrogen bonding or hydrophobic/aromatic interactions. Polymers with UCST behavior reversibly phase separate upon cooling, typically leading to precipitation. In some cases, precipitation does not occur, instead a gel is formed. UCST-type behavior can be observed in solvent mixtures and, though much more rarely, in water. Already in 1979, Wellinghoff et al. described a poly(styrene) and poly(dimethylphenylene oxide) system which forms gels in organic solvents upon rapid cooling. In 2015 a thixotropic poly(glycerol sebacate)-based supramolecular structure with UCST behavior was reported to form a hydrogel at rather low concentrations (5.2 %) with self-healing ability with a storage modulus of 100 kPa. The clear liquid turned into a turbid gel upon cooling. Theato and co-workers described polymers based on vinylcyclopropane and investigated their UCST and physical gelation behavior in ethanol and ethanol-water mixtures at different concentrations. The transition temperature hysteresis between the heating and the cooling phase was very large (about 45 K). Another class of thermoreversible physically crosslinked hydrogels formed from ABA linear triblock copolymers was reported recently. The polymers feature a hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMMA) middle block B and flanking UCST-type thermosensitive poly(acrylamide-co-acrylonitrile) (P(AAm-co-AN)) A blocks. At distinct block lengths, chemical compositions, and polymer concentration, aqueous solutions of these polymers showed cooling-induced, reversible sol-gel transitions in water. Polymers of cyclic imino ethers, in particular poly(2-substituted-2-oxazoline)s (POx) and poly(2-substituted-5,6dihydro-4H-1,3-oxazine)s (poly(2-oxazine)s; POzi) are important classes of thermoresponsive polymers and can be synthesized via living cationic ring-opening polymerization to yield different polymeric architectures and compositions. Over the last decades POx were intensively studied as thermoresponsive materials , surface coatings , but also in biomedical applications and drug delivery. More recently, Bloksma et al. investigated the thermoresponsive behavior of some POzi homopolymers. Interestingly though, only a few reports can be found that show thermogelation in water for pure POx/POzi based systems. In fact, Zahoranova et al. investigated different triblock copolymers mimicking Pluronic-type polymers based on the hydrophilic poly(2-methyl-2-oxazoline) (PMeOx) and the thermoresponsive poly(2-n-propyl-2-oxazoline) (PnPrOx), but no thermogelling could be observed. In contrast, Lorson et al. established a thermogelling (G´ ~ 4 kPa), cytocompatible and printable poly(2-oxazoline)/poly(2-oxazine) (POx/POzi) supramolecular hydrogel. These diblock copolymers, comprising a hydrophilic poly(2-methyl-2-oxazoline) block and a thermoresponsive poly(2-n-propyl-2-oxazine) block of equal or similar block length, undergo thermogelation above a defined sol/gel-temperature. Very recently, Hoogenboom and Monnery reported thermogelling ABA triblock copolymers bearing thermoresponsive poly(2-n-propyl-2-oxazoline) and hydrophilic poly(2-ethyl-2-oxazoline) blocks, but block lengths necessary for thermogelation were extremely high. More recently, Lübtow et al. reported on a different ABA triblock copolymer, again with hydrophilic poly(2-methyl-2-oxazoline) A blocks and a hydrophobic poly(2-iso-butyl-2-oxazoline) B block which forms thermogels, albeit rather weak ones that are barely printable. To the best of our knowledge, there has been no reported case of UCST-type POx/POzi in water, nor inverse gelation of POx/POzi based polymers.