Synthesis and characterisation of styrene butadiene styrene-g-N-isopropylacrylamide via UV polymerisation for potential use in biomedical applications

The work undertaken investigates the mechanical and thermal properties of a styrene butadiene styrene (SBS) grafted with N-isopropylacrylamide (NIPAAm) for potential use in the field of biomaterials. SBS-g-NIPAAm was synthesised using UV polymerisation and analytical techniques such as differential scanning calorimetry (DSC), attenuated total reflectance Fourier transform spectrometry (ATR-FTIR), dynamic mechanical thermal analysis (DMTA) and tensile tests were used to characterise the grafted copolymers. The ATR-FTIR spectrum for NIPAAm illustrates bands corresponding to C=O stretching and NH bending for secondary amides at 1655 and 1544 cm⁻¹, respectively. These bands are represented as shoulders in SBS-g-NIPAAm copolymers. In relation to the thermal analysis, the butadiene domain present in the SBS and the grafted SBS copolymers were analysed using DSC. It was evident that all of the grafted samples have a broad thermal transition when compared to the PB domain present in SBS, suggesting that grafting had occurred within each of the SBS-g-NIPAAm copolymers. This was confirmed by the use of DMTA, where the results showed an increase in T _g values from −92 to −74 °C for SBS-g-NIPAAm copolymers.