Abstract
A microphase-separated structure of a poly(deuterated styrene-block-2-vinylpyridine) (dPS-b-P2VP) block copolymer thin film was studied by neutron reflectivity (NR). The spun-coated dPS-b-P2VP block copolymer (on a Si substrate) showed the coexistence of a minority thin lamellar layer (holes) dispersed in a majority thick layer. The “terraced structure” was formed due to the mismatch between the initial film thickness and the intrinsic lamellar periodicity of the dPS-b-P2VP block copolymer. The amount and height of the holes were evaluated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and transmission electron microtomography (TEMT). The three-dimensional (3D) images obtained from the TEMT experiments clearly showed that the microphase-separated structure inside the thin film was homeotropically aligned. The thickness of the thick and the thin lamellar layers corresponded to (5/2)L0 and (3/2)L0, respectively (L0 is the lamella periodicity in the bulk state). The NR profile from the dPS-b-P2VP thin film, Rexp, showed many distinctive scattering peaks. Based on the structural information obtained from the microscopy, a scattering length density profile along the depth direction, i.e., the direction normal to the film surface, b/vTEMT, was evaluated, which was then used as an initial profile in the conventional model fitting method. An excellent best-fit to Rexp was obtained using b/vTEMT, even though the thin film had the terraced structure. The surface coverage of the holes was estimated from the resulting b/v, which was in good agreement with the estimated value from TEM.
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Niihara, Ki., Matsuwaki, U., Torikai, N. et al. A Neutron Reflectivity Study on a Terraced Lamellar Morphology in a Block Copolymer Thin Film. Polym J 39, 1105–1111 (2007). https://doi.org/10.1295/polymj.PJ2007100
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DOI: https://doi.org/10.1295/polymj.PJ2007100