Mechanical Properties and UV Curing Behavior of Poly(N-Isopropylacrylamide) in Phosphonium-Based Ionic Liquids

N‐isopropylacrylamide (NIPAM) is photopolymerized in a range of phosphonium‐based ionic liquids (ILs). The curing behaviour of polymer‐IL solutions (linear pNIPAM) and ionogels (crosslinked pNIPAM) is studied using rheometry, DSC, and GPC. It is found that the IL influences the mechanical properties, the rate of polymerization, and the LCST of the resulting pNIPAM ionogels. Ionogels made in trihexyl‐tetradecyl phosphonium dicyanamide show an order of magnitude smaller ratio of loss/storage moduli compared to that of trihexyl‐tetradecyl phosphonium chloride, and a doubling of the UV polymerization rate. Temperature‐ramp rheology scans of the water‐swollen ionogels show that upon LCST transition the moduli of the polymer network exhibit anion dependent increases. N‐isopropylacrylamide is photopolymerized in a selection of phosphonium‐based ionic liquids to form linear polymer solutions and crosslinked ionogels. Rheological monitoring of the polymerization together with DSC measurements and SEC chromatography show that the choice of IL dramatically influences the kinetics of polymerization, the viscoelasticity of the ionogels, and their lower critical solution temperature (LCST) actuation behaviour.