Synthesis of UV-curable polyurethane-acrylate hybrids with tuneable hardness and viscoelastic properties on-demand

Abstract

Currently, there is an unmet need for possessing a deeper understanding between the chemical structure and the exhibited properties of more polymers. Moreover, thanks to the development of technologies allowing an unprecedented level of personalization, researchers are aiming towards the generation of polymers tailored for specific applications. In the present work, a series of soft, transparent, and UV-photopolymerizable polyurethane-acrylate (PUA) hybrids were synthesized via a two-step polymerization route, followed by a UV-curing process and maintaining two constant ratios of a soft/hard segment in the polyurethane (PU) structure as well as using three different acrylate segment types at three concentrations in the overall polymeric structure (2.5, 5 and 7.5 wt%). The success of the synthesis procedure, the molecular weight, the transparency, the thermal behaviour, the viscoelastic response and the softness of the synthesized PUA were studied by analytical methods. Using these techniques, it was possible to quantify gradual values between the different generated materials showing up to a 50% difference in the molecular weight, variations reaching 15 °C in the thermal transition or modifications of a thermal stability of 50 °C, changes of even a 90% in the viscoelastic response and, additionally, a range of hardness going from extra-soft to medium-hard. Through this work, it is possible to predict how the different variables affect some of the most relevant properties of the synthesized materials and therefore select the most suitable variables for each specific application. These results are expected to guide further developments in materials in applications ranging from UV-curable coatings to in situ 3D-printing for biomedical applications.