title: Reversible monolayer-to-crystalline phase transition in amphiphilic silsesquioxane at the air-water interface.
abstract: We report on the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface using synchrotron x-ray scattering measurements. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition. The measured x-ray scattering data of the non-equilibrium crystalline phase on the air-water interface could be explained with a model that assumes periodic stacking of the TBPOSS dimers. These crystalline stacking relaxes upon decompression and the TBPOSS layer retains its initial monolayer state. The existence of these crystals in compressed phase is confirmed by atomic force microscopy measurements by lifting the materials on a solid substrate.
authors: Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064, India.
authors: R
authors: R
authors: Banerjee
authors: Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064, India.
authors: M K
authors: MK
authors: Sanyal
authors: Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064, India.
authors: M K
authors: MK
authors: Bera
authors: LUNAM, IMMM, Faculté de Sciences, Université du Maine, UMR 6283 CNRS, Le Mans Cedex 9, 72085 France.
authors: A
authors: A
authors: Gibaud
authors: Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637, USA.
authors: B
authors: B
authors: Lin
authors: Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637, USA.
authors: M
authors: M
authors: Meron