화학공학소재연구정보센터
Macromolecules, Vol.40, No.3, 588-597, 2007
Surface properties of poly[2-(perfluorooctyl)ethyl acrylate] deposited from liquid CO2 high-pressure free meniscus coating
The surface characteristics of poly[2-(perfluorooctyl)ethyl acrylate] (PFOEA) films deposited using a high-pressure free meniscus coating (hFMC) process with liquid CO2 (l-CO2) as the coating solvent on 12.5 cm diameter silicon wafer substrates were investigated using contact angle measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy. The results were compared with surface property measurements of PFOEA films deposited from 1,1,2-trichlorotrifluoroethane (Freon 113) under normal dip coating conditions at atmospheric pressure. NEXAFS measurements showed that perfluoroalkyl groups in the films from l-CO2 and Freon 113 were well-organized and oriented normal to the substrate at the air/polymer interface. AFM images and XPS measurements revealed that a terrace-like structure of the PFOEA film from l-CO2 resulted in carbonyl group exposure at the air/polymer interface. This leads to smaller contact angles on the films cast from l-CO2 relative to the specimens deposited from Freon 113. Annealing the films deposited from the solvents resulted in droplet formation on the surface due to dewetting. The critical surface tension (gamma(c)) after annealing the film prepared from Freon 113 increased from 6.5 to 8.5 mJ/m(2), whereas gamma(c) of the film deposited from l-CO2 decreased slightly from 9.7 to 8.9 mJ/m(2). We discuss how surface morphology changes before and after annealing play a role in the variation of gamma(c).