Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: Interfaces and Thin Films II
CPP 7.1: Vortrag
Montag, 14. März 2011, 14:00–14:15, ZEU 114
Cracking in thin polymer films promoted through physical ageing — •Mithun Chowdhury1, Christophe Calers1, Arnold Chang-Mou Yang3, Ullrich Steiner2,4, and Günter Reiter1,2 — 1Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, 79104, Freiburg, Germany — 2Freiburg Institute for Advanced Studies (FRIAS) — 3Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan — 4Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
Dynamics of polymers in ultrathin films is a long standing yet ever stimulating topic in the arena of polymer physics. Being inspired by occasionally observed cracking of such films during spin-coating, we performed systematic studies on the influence of film preparation and physical ageing at temperatures close but below the glass transition. We observed the growth of cracks after ageing and cooling the films to room temperature. Hierarchical patterns of interconnecting cracks were formed. AFM inspection showed nano/micro-structures of voids and fibrils within the cracks, indicating plastic deformation similar to crazing. We tentatively suggest that physical ageing of such films causes segmental relaxations of non-equilibrated polymer chains, introducing a gradient in lateral tension within the film in the direction normal to the film surface. Considering the possibility of generating strong mechanical tension at the film surface due to the formation of a 'crust' during film preparation, we may have to consider two antagonistic origins for crack growth: gradients in stresses induced by film preparation and amplification of such gradients during physical ageing.