Ellipsometric study of adsorption on nanopatterned block copolymer substrates.

We report ellipsometrically obtained adsorption isotherms for a carefully chosen test liquid on block copolymer films of Kraton G1650, compared with adsorption isotherms on homogeneous films of the constituent polymers. Standard atomic force microscopy images imply the outer surface of Kraton G1650 is chemically patterned on the nanoscale, but this could instead be a reflection of structure buried beneath a 10 nm layer of the lower energy component. Our test liquid was chosen on the basis that it did not dissolve in either component and in addition that it was nonwetting on the lower energy polymer while forming thick adsorbed films on pure substrates of the higher energy component. Our ellipsometry data for Kraton G1650 rule out the presence of segregation by the lower energy constituent to the outer surface, implying a mixed surface consistent with Cassie's law. We discuss implications of our findings and related work for the outer surface structures of block copolymer films.

Surface energy of ethylene-co-1-butene copolymers determined by contact angle methods.

Wilhelmy plate measurements of contact angles with a series of test liquids are used to calculate the surface energies of two poly(ethylene-co-1-butene) random copolymers. Results from five methods of calculation are reported: one-liquid (Good-Girifalco and Neumann), two-liquid (harmonic mean and geometric mean), and three-liquid (Lifshitz-van der Waals acid-base) methods. We find that all five methods are sensitive to the choice of test liquids used for contact angle measurements, as previously reported, but consistent results are obtained if recommended combinations of liquids are used. The mean results of the three-liquid acid-base method are judged to be the most reliable and informative, leading to surface energies of 30.8 mJ/m2 for poly(ethylene-co-1-butene) copolymer composed of 92 mol% ethylene and 30.2 mJ/m2 for copolymer composed of 88 mol% ethylene.