Abstract
Certain technologically advanced coating systems for defence use require organic binders with elevated infrared (IR) transparency. This thesis comprises the first phase of a study to try and produce materials which meet these requirements. A materials evaluation programme was completed using preordained selection criteria. An in-depth study was made of one family of the shortlisted candidate materials: linear poly(methoxy-cyanurate)s. These thermally stable polymers were prepared by phase transfer polymerisation of dichlorotriazines with aromatic bisphenois. The samples were analysed by differential scanning calorimetry, thermogravimetric analysis, elemental analysis and nuclear magnetic resonance spectroscopy. The transparency of the materials was determined using a hemispherical directional reflectometer. At thicknesses of 50 mum, the spectral emissivity of the linear poly(methoxy-cyanurate)s was of the order of 0.25 between 3 and 5 mum and 0.65 between 8 and 12 mum. The linear poly(methoxy-cyanurate)s typically underwent major decomposition at temperatures greater than 300 °C in nitrogen and air. These new materials are more transparent and thermally stable than the poly(urethane) binders currently used in many defence coatings. However, spectral data and model compound studies suggest that poly(methoxy-cyanurate)s isomerise at temperatures above 200 °C. This is contrary to the hypotheses of other workers in the field. Computer simulation methods, evaluated in the course of the study, were used as an aid to assignment of IR spectra and to investigate strategies for improving upon the IR transparency of the poly(methoxy-cyanurate)s between 8 and 12 mum. Novel linear poly(methoxy-thiocyanurate)s and terpoly(methoxy-cyanurate-thiocyanurate)s were prepared to try and improve upon the thermochemical stability and spectral transparency of the simple cyanurate polymers. These materials were characterised using the methods listed above. All steps which were taken to try and improve the spectral transparency of the polymers between 8 and 12 mum failed due to problems with overlapping bands. In light of the project findings, certain material selection criteria have been modified. Suggestions for future research based on these new guidelines are made at the end of the thesis.