Tuning the properties of polysulfides using functionalised cardanol crosslinkers†

This study presents the synthesis, characterisation, and property analysis of surface-functionalised polysulfides synthesised via inverse vulcanisation of elemental sulfur with cardanol and its silane-functionalised derivatives. Three polysulfide formulations, poly-(S-r-C), poly-(S-r-C_APS), and poly-(S-r-C_TMS), were prepared to investigate the impact of functional groups on the crosslinked polysulfide's properties. Reacting the cardanol hydroxy group with either 3-aminopropyltriethoxysilane (APTES) or chlorotrimethylsilane (TMS) enabled the modification of the polysulfide networks. Characterisation, including NMR spectroscopy, FTIR spectroscopy, SEM, contact angle measurements, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and ASTM D3359 cross-hatch adhesion testing, was conducted. Poly-(S-r-C) and poly-(S-r-C_APS) demonstrated strong adhesion to glass substrates and higher thermal stability, attributed to hydrogen bonding and the formation of Si–O–Si networks, respectively. In contrast, poly-(S-r-C_TMS), bearing nonpolar trimethylsilyl groups, exhibited weaker adhesion and lower thermal residue. The results highlight how chemical functionality governs adhesion, wettability, solubility, and thermal behavior. This work demonstrates the potential of renewable cardanol-based monomers in designing sustainable sulfur-rich materials for applications in coatings and adhesives.