Examining the preparation and characterization of coatings based on linear aromatic terpoly(methoxy-cyanurate-thiocyanurate)s

Two series of terpoly(methoxy-cyanurate-thiocyanurate)s based on thiodiphenol and dithiodiphenyl sulphide, and dihydroxydiphenylether and dithiodiphenyl ether, are prepared in good yield and purity, and fully characterised. Most of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and thermal stability. Two series of terpoly(methoxy-cyanurate-thiocyanurate)s based on thiodiphenol and dithiodiphenyl sulfide and on dihydroxydiphenyl ether and dithiodiphenyl ether, were prepared in good yield and purity and fully characterized. Most of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and thermal stability (some examples suffer practically no mass loss when held isothermally at 190 °C and only display appreciable losses when held continuously at 225 °C). Char yields of 53%-61% are achieved in nitrogen depending on backbone structure. Some problems were encountered with solubility, particularly with copolymers, which limited molecular weight analysis, but values of M_n = 8000-13000 g mol^-1 were obtained for the polymers based on thiodiphenol and dithiodiphenyl sulfide, and M_n = 5000-13000 g mol^-1 for the polymers based on dihydroxydiphenyl ether and dithiodiphenyl ether. DSC reveals polymerization exotherms with maxima at 184-207 °C (ΔH_p = 43-59 kJ mol^-1), which are believed to be due to isomerization of the cyanurate to the isocyanurate (activation energies span 159-195 kJ mol^-1). Molecular simulation shows that diphenylether and diphenylsulfide display very similar conformational energy surfaces and would therefore be expected to adopt similar conformations, but the diphenylsulfide offers less resistance to deformations that increase the proximity of the two phenyl rings and results in more resilient films.