Dicyanate ester/polycyanurate thermosetting polymers are a relatively new class of high-performance materials used in electronic and composite applications, because of their excellent dielectric properties. This research program will investigate the effect of network parameters on the properties of these materials. A series of oligomers of bisphenol A dicyanate (trimer, pentamer, etc.) will be synthesized, and conversion- versus-property relationships will be compared with that of the monomer. Since the relationships between conversion of cyanate and network parameters will differ when different size oligomers are reacted, and since the structure at full conversion is identical for the different oligomers, the effects of network parameters can be determined. This novel approach overcomes complications generally encountered when studying the effects of network parameters in thermosetting systems that arise when the structure of the repeat unit is charged. The properties examined will include the glass-transition temperature and the volume. The conversion at gelation for the reaction of the various oligomers will yield information concerning the magnitude of ring formation in the reaction. Experimental techniques will include differential scanning calorimetry, dilatometry, nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, and gel permeation chromatography. %%% This work will help our understanding of the origins of free volume in the glassy state. This is particularly important for dicyanate ester materials since moisture absorption, which is related to free volume, appears to adversely affect their thermal stability. The proposed work is also important for the optimization of thermosetting properties and for the development of models which predict the time and temperature dependence of glassy thermosetting materials of potential use in composite materials.
