| 초록 |
Anomalous swelling phenomena of polymer thin films in supercritical CO2 will be presented, which is associated with CO2 density fluctuation ridge that forms along the extension of the coexistence curve of gas and liquid in the P–T phase diagram. The anomalous swelling is found to scale with the polymer radius of gyration, Rg and extends to a distance approximately 10 Rg . The plasticization effect of the swollen films induced by the density fluctuations was found to enhance the polymer inter-diffusion by 2 orders of magnitude on the ridge, where the diffusion coefficients scale as M2 and can be approximated by an effective William-Landel-Ferry (WLF) equation. Experiments have been done using in-situ neutron scattering through a high pressure chamber. Few applications also will be presented. For an example, the swollen structures are frozen by flash evaporation of CO2 and then be used to produce uniform low-density films, e.g., low dielectric constant films. |
