Luke M. Geever

The design and manufacturing of objects in various industries have been fundamentally altered by the introduction of D-dimensional (3D) and four-dimensional (4D) printing technologies. Four-dimensional printing, a relatively new technique, has emerged as a result of the ongoing development and advancements in 3D printing. In this study, a stimulus-responsive material, N-Vinylcaprolactam-co-DEGDA (NVCL-co-DEGDA) resin, was synthesised by Stereolithography (SLA) 3D printing technique. The N-Vinylcaprolactam-co-DEGDA resins were initiated by the Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiator. A range of Di(ethylene glycol) diacrylate (DEGDA) concentrations in the NVCL-co-DEGDA resin was explored, ranging from 5 wt% to 40 wt%. The structural properties of the 3D printed objects were investigated by conducting Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR-FTIR). Additionally, the 3D printed samples underwent further characterisation through differential scanning calorimetry (DSC) and swelling analysis. The results revealed an inverse relationship between DEGDA concentration and Tg values, indicating that higher concentrations of DEGDA resulted in lower Tg values. Additionally, the pulsatile swelling studies demonstrated that increasing DEGDA concentration prolonged the time required to reach the maximum swelling ratio. These findings highlight the influence of DEGDA concentration on both the thermal properties and swelling behaviour of 3D printed samples.