Modulation of the Lower Critical Solution Temperature of Thermoresponsive Poly(-vinylcaprolactam) Utilizing Hydrophilic and Hydrophobic Monomers.

Four-dimensional printing is primarily based on the concept of 3D printing technology. However, it requires additional stimulus and stimulus-responsive materials. Poly--vinylcaprolactam is a temperature-sensitive polymer. Unique characteristics of poly--vinylcaprolactam -based hydrogels offer the possibility of employing them in 4D printing. The main aim of this study is to alter the phase transition temperature of poly--vinylcaprolactam hydrogels. This research focuses primarily on incorporating two additional monomers with poly--vinylcaprolactam: Vinylacetate and -vinylpyrrolidone. This work contributes to this growing area of research by altering (increasing and decreasing) the lower critical solution temperature of -vinylcaprolactam through photopolymerisation. Poly--vinylcaprolactam exhibits a lower critical solution temperature close to the physiological temperature range of 34-37 °C. The copolymers were analysed using various characterisation techniques, such as FTIR, DSC, and UV-spectrometry. The main findings show that the inclusion of -vinylpyrrolidone into poly--vinylcaprolactam increased the lower critical solution temperature above the physiological temperature. By incorporating vinylacetate, the lower critical solution temperature dropped to 21 °C, allowing for potential self-assembly of 4D-printed objects at room temperature. In this case, altering the lower critical solution temperature of the material can potentially permit the transformation of the 4D-printed object at a particular temperature.