Glass transition temperature and reaction kinetics of cyanurates in bulk and under confinement and signatures of structural recovery of polystyrene

The glass transition temperature (Tg) is known to deviate from the bulk when subjected to confinement, increasing, decreasing, or remaining unchanged based on the confinement geometry, surface interactions, and the confining material itself. Previous work from the Simon laboratory has analyzed the effect of nanopore confinement on the Tg of two materials, a low molecular weight cyanurate trimer and a polycyanurate network, with both showing a Tg depression on confinement. In this dissertation an uncrosslinked cyanurate is investigated under nanopore and thin film confinement using conventional and fast scanning calorimetry, respectively. A Tg depression is observed under both confinement geometries and the volume to surface area ratio of the confining mediums is used to collapse the Tg depressions onto a single curve. The relationship between bulk fragility and changes in Tg (ΔTg) due to nanopore confinement for various cyanurates is also analyzed as it has been suggested to be a key factor in determining how the Tg of linear polymers will change on confinement. However, it is found that ΔTg and fragility do not correlate for the cyanurates studied under nanopore confinement here. Furthermore, previous work from the Simon laboratory on the trimerization of cyanate esters found that the reaction kinetics were faster for both a mono- and difunctional monomer under nanopore confinement. The similar extend of reaction acceleration for both monomers was attributed to monomer layering near the pore walls. In this work the monomer layering was disrupted by reacting a mixture of mono- and difunctional cyanate ester monomers, which have different structures and molecular weights. The results showed that the acceleration factor (α) on confinement for the monomer mixtures was four times less than the α of the pure materials. The signatures of structural recovery, the intrinsic isotherm, asymmetry of approach, and memory effect experiments, have been historically difficult to conduct in enthalpy space due to the nature of the calorimetry experiments. In this dissertation, the fast heating and cooling rates offered by fast scanning calorimetry were exploited to obtain the signatures of structural recovery in enthalpy space for the first time; using aging times as short as 0.01 s and relatively high aging temperatures.