The Effect of Surface Chemistry on the Glass Transition of Polycarbonate Inside Cylindrical Nanopores

The effect of surface chemistry on the glass transition of polycarbonate (PC) inside cylindrical nanopores is studied. Polycarbonate is melt-wetted into nanoporous anodic aluminum oxide (AAO) treated with hydrophobic alkyl- and fluorosilanes of varying length. The curvature observed at the nanowire tips is consistent with a contact angle descriptive of polycarbonate-AAO surface interactions. Differential scanning calorimetry (DSC) thermograms reveal a distinct broadening of the T_g that is related to the motion of polymer chains at the nanopore wall as well as at the core. DSC and thermal gravimetric analysis (TGA) show that polycarbonate infiltrated into a naked AAO template (without silane treatment) degrades upon heating, suggestive of a surface-catalyzed degradation mechanism. It is further shown that silane treatment largely prevents PC thermal degradation.