title: Deciphering the three-dimensional morphology of free-standing block copolymer thin films by transmission electron microscopy.
abstract: Block copolymer thin films with distinct morphologies are prepared by spin casting a nominally lamellar assay of poly(styrene-block-ethylene oxide) from a variety of solvents with and without salt doping. The 3-D morphologies of free-standing thin-film regions, which are obtained by casting directly onto holey substrates, are investigated in detail using various energy-filtering transmission electron microscopy techniques and by electron tomography. Surface characterization is achieved by atomic force microscopy. Our results demonstrate that in order to fully characterize the unique 3-D morphologies of the block copolymer thin films, a multi-method approach is required. When casting from a binary solvent, an unexpected layered honeycomb-type morphology is revealed, which likely results from an expansion of the poly(ethylene oxide) phase. A dramatic effect of selective cation coordination on the morphology of the as-cast block copolymer films is also directly observed.
authors.affiliation: National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 94720-8250, USA. FIAllen@lbl.gov
authors.forename: Frances I
authors.initials: FI
authors.lastname: Allen
authors.forename: Peter
authors.initials: P
authors.lastname: Ercius
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Modestino
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Segalman
authors.forename: Nitash P
authors.initials: NP
authors.lastname: Balsara
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Minor