The double-gyroid structure of self-assembling systems is very attractive for a host of potential applications, particularly if after self-assembly one component can be removed to yield a bicontinuous nanoporous structure. Nanoporous materials with this well-defined interconnected pore structure having the Ia3d topology have long been sought due their high surface area and potentially low mass transport resistance. Powders have been synthesized by several techniques, but thin films have proved more difficult. Only two reports are known[1, 2]. Here, we report the synthesis and characterization of highly ordered and oriented double-gyroid block copolymer-silica thin films. The synthesis is based on a new method to control the interaction parameter between the hydrophilic block of the copolymer and the silica oligomers that allows fine tuning of the interfacial curvature necessary to synthesize the double-gyroid phase. The films are synthesized from commercially available reagents at room temperature and normal lab humidity (40%-60% relative humidity) by evaporation induced self-assembly (EISA) from coating solutions that are stable and may be stored at room temperature (after mixing) for up to a month. The films are thermally stable to block copolymer removal and remain highly ordered after calcination. The GISAXS pattern of the (211) oriented films contains 96 spots, all of which have been indexed. While the space group is initially Ia3d, the films contract perpendicular to the substrate and break many of the symmetry elements present in the Ia3d space group. In particular additional peaks observed are due primarily to breaking glide plane symmetry. The observed GISAXS data has interpreted using the Distorted Wave Born Approximation (DWBA). The spot pattern is quantitatively matched using code developed previously by the Hillhouse group[3]. In addition, simulations of the GISAXS pattern intensity match the observed data well. TEM simulations show that while Ia3d symmetry is broken, the topology of the double-gyroid structure is maintained. The details of the film synthesis and controlling interfacial curvature will be discussed in addition to FESEM, TEM & GISAXS characterization of the resulting films.

References [1] V.Z.H. Chan, J. Hoffman, V.Y. Lee, H. Iatrou, A. Avgeropoulos, N. Hadjichristidis, R.D. Miller, and E.L. Thomas, Science, 286, (1999) 1716-1719. [2] R.C. Hayward, P.C.A. Alberius, E.J. Kramer, and B.F. Chmelka, Langmuir, 20, (2004) 5998-6004. [3] M.P. Tate, V.N. Urade, J.D. Kowalski, T.C. Wei, B.D. Hamilton, B.W. Eggiman, and H.W. Hillhouse, Journal of Physical Chemistry B, In press (2006).