Dynamics of End-Functionalized Weakly Entangled Polyethylene-Oxide in the Melt

High Resolution Image Download MS PowerPoint Slide Extending an earlier study on short unentangled telechelic poly(ethylene oxide) (PEO2K) chains by Monkenbusch et al. ( Phys Rev Lett 2016, 117 (14), 147802), we present investigations on the association dynamics of weakly entangled PEO8K using pulsed field gradient nuclear magnetic resonance (PFG-NMR), small angle neutron scattering (SANS) and neutron spin echo (NSE). From PFG-NMR we obtain the average Fickian diffusion coefficients. With increasing temperature, they approach those from the neat unfunctionalized melt indicating diminishing aggregation. A random phase approximation (RPA) evaluation of SANS data results in much weaker aggregation compared to the PEO2K counterpart in agreement with the prediction of Caruthers’ law. The picture of mode amplitude suppression as proposed by Monkenbusch et al. is supported. As a consequence of the rather long terminal times of PEO8K compared to the bond lifetimes, the NSE spectra from the functionalized melt may be well approximated by a product of the internal relaxation spectrum of the building block and the modified diffusion dynamics of the aggregates. Finally, the average center of mass diffusion of the ensemble of aggregates is quantitatively described in terms of the structural SANS results and the aggregation statistics extrapolated from earlier work.