The glass transition of supported and unsupported polystyrene nanorods using Flash differential scanning calorimetry

Nanoconfinement is known to influence the glass transition temperature (T_g). In the case of polymer ultrathin films supported on neutral surfaces, T_g generally decreases with decreasing film thickness, and the magnitude of the depression increases as cooling rates decreases. Compared to ultrathin films, glass-forming polymeric materials in nanopores have been less well studied. Here, we aim to examine the glass transition behavior of supported and unsupported polystyrene (PS) nanorods over five decades of cooling rates, from 0.1 – 1000 K/s, using Flash differential scanning calorimetry. The samples are prepared by the vacuum infiltration of 2000 kg/mol PS into AAO templates having a thickness of 5 μm and pore diameters of 20, 55 and 350 nm. Preliminary results indicate that T_g increases for supported PS nanorods of all the pore sizes studied; however, bulk behavior is observed for unsupported PS nanorods. The implications of the results are discussed within the context of current work in the field.
Keywords: Nanoconfinement, Flash DSC, nanorods, glass transition, AAO templates