8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P9.13Evolution of dynamics and structure formation inresorcinol - formaldehyde polymer gelOrsolya Czakkel, 1 Anders Madsen, 2 and Beatrice Ruta 31 European Synchrotron Radiation Facility, 6. rue Jules Horowitz, 38000, Grenoble,France2 European XFEL, Hamburg, Germany3 European Synchrotron Radiation Facility, 6. rue Jules Horowitz, F38043, Grenoble,FranceNon-equilibrium processes that display significant structural and dynamical changes at thenanometer scale are very difficult to characterize experimentally. In addition, such processes areoften of non-ergodic nature which means that the experimental data must be ensemble averagedand also sufficiently time-resolved to follow the evolution of structure and dynamics in detail.Scattering with coherent light is one of the few methods that can fulfill the above criteria andaccess structure and dynamics simultaneously; in particular coherent X-ray scattering is uniquewhen it comes to the study of materials at nanometric length scales. Owing to the combinationof the time-resolved multi-speckle XPCS [1] and Small-Angle X-ray Scattering (SAXS) we wereable to follow the evolution and interplay between structure and structural dynamics during theformation of a cross-linked polymer gel and were for the first time able to give a detailed picture.We observed a fast, non-ergodic relaxation stemming from localized motions of polymer clustersindicates a stiffening network on the nano-scale as a signature of the gelation. A second, muchslower relaxation that restores ergodicity is due to the dynamics of the gel network. Spatialanisotropy develops in the network dynamics but without any signs of dynamical heterogeneity.This distinguishes the observed dynamics from that of typical jammed systems where dynamicalheterogeneity is a hallmark.[1] Madsen A., Leheny R. L., Guo H., Sprung M. and Czakkel O., New J. Phys., 12 (2010)055001.13