Eco-Inspired Multifunctional Cyanate Esters Derived from Bio-Phenols and Fossil-Based Phenols for High Thermal and Super Hydrophobic Applications

In the present work an attempt has been made to develop new types of cyanate esters (CEs) from multifunctional phenolic compounds synthesized from bio-phenols and fossil-based phenols through facile synthetic route suitable for high thermal and super hydrophobic applications. The cyanate esters, viz., cardanol/benzaldehyde-based cyanate ester (CBC), cardanol/terephthalaldehyde based cyanate ester (CTC), imidazole bisphenol-based cyanate ester (IMC), and phenol/hydroxybenzaldehyde based cyanate ester (HTC) were synthesized through cyanation reaction of respective phenolic derivatives using cyanogen bromide and triethylamine (TEA). The molecular structure, curing behavior of CEs in the absence/in the presence of catalyst, thermal stability, and moisture resistant behavior of cyanate esters and 50:50 ratio of hybrid blends of cyanate esters has been carried out using different analytical methods. From DSC data, it was inferred that the cyanate ester (CTC) was found to possesses the lowest curing temperature of 173^oC in the absence of catalyst and that of hybrid (50:50 (w/w) ratio) blend of cyanate ester (CTC/HTC) possesses the lowest curing temperature of 132^oC. The developed HTC system was found to be the most thermally stable material with highest char yield of 43% with the highest flame-retardant behavior in terms of LOI value of 34.7%. The cyanate esters are also possessing an exceptional hydrophobic behavior with the water contact angle value of 151^o. The cyanate esters developed using sustainable bio-based precursors as source material in the present work is considered as a new cutting-edge product in the field of cyanate ester technology where applications require high thermal stability and hydrophobic behavior are warranted.