Abstract
In this thesis, two major topics are discussed, namely the synthesis and characterisation of a cyanate ester polymer system based on the poly(arylene ether sulphone) backbone, together with the molecular modelling of this and similar polymeric systems. The molecular modelling studies involve the general modelling of a poly(arylene ether sulphone) oligomer in a vacuum, which has the same repeat unit as UDEL poly(sulphone), originally produced by Union Carbide. The oligomer was characterised by atomistic models of the system using molecular mechanics and molecular dynamics techniques in which the flexibility of the backbone torsional angles were examined. The sulphone torsional angle was identified as the most flexible, followed by the ether torsional angle, with the isopropylidene angle being the most inflexible. Their energy barriers were 1, 4 and 6kcal/mol respectively. The complexity of the polymeric system was then increased to model the above thermoplastic polymer under the influence of bulk conditions. Finally, the thermoset polymer with a poly(arylene ether sulphone) backbone, linked together by cross-linking cyanurate rings was modelled. Conformational properties were obtained of the various linking groups together with the calculation of various mechanical and physical properties, e.g., the Young's moduli and the glass transition temperatures of the simulated polymers. The results obtained from this work were generally in good agreement with experimental calculations. The synthetic work involved making the oligomeric repeat unit which constituted the repeat unit used in the thermoset modelling studies. A poly(arylene ether sulphone) dicyanate ester oligomer was synthesised, which when cured, formed a cyanurate ringed thermoset network via the reaction of three cyanate ester groups to form an s-triazine ring. This polymer was then characterised by classical techniques to obtain various mechanical and physical properties of the networked thermoset polymer. These were then compared with the properties calculated in the modelling studies. Fairly good agreement between the experimental and simulated results were observed, e.g., the simulated Young's modulus and Poisson's ratio were 3.64GPa and 0.35 respectively, whilst the experimental results were 2.50GPa and 0.33 respectively. In essence, the objective of this thesis was to synthesise and simulate via molecular simulation some poly(arylene ether sulphone) based thermoplastic and thermoset polymers and then to compare the various properties obtained from both techniques. The results show that molecular modelling techniques can be used to obtain accurate values of various properties of polymeric systems. This indicates that in the future, molecular modelling in conjunction with synthetic techniques may be used to predict trends and values of various properties of polymeric systems.