Isotopically enriched crosslinked epoxy polymers
The epoxy resin system based on tetraglycidyldiaminodiphenyl- methane (TGDDM) and diaminodiphenylsulfone (DDS) is widely used for high performance aerospace applications. The desirable macroscopic properties of the TGDDM/DDS resin are dependant upon the microscopic network formed during resin curing, but to date work aimed at clarifying the structure of this network has proved inconclusive. This work further investigates the epoxy resin network structure, using the techniques of isotopic labelling and solid state nuclear magnetic resonance (NMR).The synthesis of labelled TGDDM and DDS by known and original protocols has been investigated. A majority of the work was aimed at the unambiguous labelling with carbon-13 and deuterium of TGDDM, the success of which has led to the discovery of a versatile and convenient method of labelling epichlorohydrin. Nitrogen-15 labelled TGDDM and DDS were also synthesised, the latter using an original protocol. Cured epoxy resins containing isotopic labels were produced, and investigated using solid state NMR. The presence of both linear and cyclised structures was observed, and their relative contributions to the network estimated. Unambiguous assignment of the solid state NMR spectrum was also made. Finally, using samples and methodologies from the isotopic labelling syntheses, further small scale studies were carried out. A range of a-ketosulfonate compounds was synthesised to probe the formation reaction. The crystal structures of three related compounds containing different halogen substituents were compared. Two further epoxide compounds were synthesised and evaluated as potential epoxy resin additives. A bis-a-chloroketone was evaluated as a substrate for baker’s yeast reduction, and yielded a diol with a high enantiomeric excess.