Surface Chemistry Effects on the Reactivity and Properties of Nanoconfined Bisphenol M Dicyanate Ester in Controlled Pore Glass

Abstract

Nanoconfinement has been found to have significant effect on the glass transition behavior of low molecular weight and polymeric glass formers. Here, we investigate the influence of nanoconfinement on the cure kinetics and glass transition temperature of a bisphenol M dicyanate ester/polycyanurate material as a function of surface chemistry and nanoconfinement size in native and silanized controlled pore glasses (CPGs). The glass transition temperature and conversion as a function of cure time are examined using differential scanning calorimetry (DSC). The native CPG surface accelerates the cure of bisphenol M dicyanate to a larger extent compared to the silanized hydrophobic CPG presumably because of the catalytic nature of hydroxyl groups on the CPG wall. Two Tgs are observed for both monomer and polycyanurates confined in the native CPGs. The primary Tg of the “fully cured” polycyanurate is depressed by 60 K at 11.5 nm, and the secondary Tg is 10−33 K above the primary Tg; the values are similar to those found previously in silanized CPGs. The length scale associated with the secondary Tg is ∼0.90 nm assuming that the secondary Tg reflects the material at the CPG wall surface. Based on the measurements of Tg, the total heat capacity change at Tg, and the sol content, all as a function of conversion, the network structure does not change upon nanoconfinement.