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

Abstract

Four-dimensional printing is primarily based on the concept of 3D printing technology. However, it requires additional stimulus and stimulus-responsive materials. Poly-N-vinylcaprolactam is a temperature-sensitive polymer. Unique characteristics of poly-N-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-N-vinylcaprolactam hydrogels. This research focuses primarily on incorporating two additional monomers with poly-N-vinylcaprolactam: Vinylacetate and N-vinylpyrrolidone. This work contributes to this growing area of research by altering (increasing and decreasing) the lower critical solution temperature of N-vinylcaprolactam through photopolymerisation. Poly-N-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 N-vinylpyrrolidone into poly-N-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.

The Effects of Incorporating Nanoclay in NVCL-NIPAm Hydrogels on Swelling Behaviours and Mechanical Properties

“…All samples were successfully fabricated through photopolymerisation, similar to our previous studies with NVCL-based hydrogels [17,18,23,[29][30][31]. When compared to other polymerisation methods, the photopolymerisation method uses much less time and creates minimal waste of ingredients [32].…”

“…The close-to-physio LCST of both PNIPAm and PNVCL at 32 • C leads to increased interest in applying them in biomedical applications [14,15]. Previous studies have also proven that the LCST of hydrogels can be tuned by incorporating comonomers [17,18]. Moreover, the biocompatibility, biodegradability, swellability, and flexibility of hydrogels allow them to be developed into commercial products in biomedical applications [19].…”

4D Printing: The Development of Responsive Materials Using 3D-Printing Technology

“…PNIPAM-based hydrogels which can be engineered to be light-responsive [ 101 ] and thermo-responsive in a reversible manner were made using 4D-bioprinting technology [ 102 ]. PNVCL is water-soluble and thermally-responsive with a liquid-to-gel transition in the range of 34–37 °C [ 103 ].…”