Berlin 2015 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Polymer dynamics

CPP 21.8: Talk

Tuesday, March 17, 2015, 11:30–11:45, C 264

Model-free information on polymer dynamics from neutron backscattering — •Felix Roosen-Runge and Tilo Seydel — Institut Laue-Langevin, Grenoble, France

Quasi-elastic and inelastic neutron backscattering is well-suited to study dynamics at time scales of several pico- to nanoseconds and nanometer length scales. Dynamical transitions in polymers versus temperature or time can been monitored via the mean-squared displacement obtained in a model-free way from scans of the elastic scattering at zero neutron energy transfer. Recent instrument updates at the spectrometer IN16B (Institut Laue-Langevin, Grenoble) allow for so-called inelastic fixed window scans (IFWS) at fixed non-zero neutron energy transfer [1]. In combination with the achieved high flux, IFWS allow to monitor dynamics in more detail, e.g. focusing on tunnel spectra. A generalized mean-squared displacement from IFWS can be used as a model-free indicator of confined and anomalous diffusion [2]. We outline the power of the IFWS using analytical results for the measured quantities. Our results allow a direct evaluation of the effect of instrumental resolution on the measured mean-squared displacement. We discuss further application of IFWS such as monitoring dynamical heterogeneities in the sample.

[1] B. Frick et al., Nucl. Instrum. Meth. A 669, 7 (2012)

[2] F. Roosen-Runge, T. Seydel, EPJ Web of Conferences, in press