Abstract
Attempts have been made to synthesise a novel siloxane-containing dicyanate ester, 1,3-bis(4-cyanatophenyl)-1,1,3,3-tetramethyldisiloxane, commencing from 4-bromophenol or 4-methoxyphenol. Most of these syntheses have involved the use of a Grignard reaction to form a disiloxane group, followed up subsequent cleavage of an alkyl-protecting group to yield a free phenol. Several different ethers have been attempted, but none was successful. The extreme susceptibility of the aryl silicon-carbon bond to cleavage under acidic conditions has been demonstrated by these reactions. A novel phosphazene-containing dicyanate ester, 1,3-bis(4-cyanatophenyl)-1,3,5,5-tetraphenoxycyclotriphosphazene has been successfully synthesised in a four-step procedure with an overall yield of ca. 35%. The cyanate ester has been characterised by differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, thermomechanical analysis (TMA), 1H, 13C and 13P NMR spectroscopy, and Fourier-Transform Infra-red (FT-IR) and Raman spectroscopy. The thermal data collected showed a surprisingly low glass transition temperature (59 °C) and enthalpy of polymerisation (ca. 36-5 kJ mol-1 of cyanate). The former figure was confirmed by TMA and modulated DSC. However, the cured cyanate showed reasonably high thermal stability: no mass loss was observed before 300 °C. Total decomposition did not occur until about 650 °C.