Fast Nanorod Diffusion through Entangled Polymer Melts
journal contributionposted on 2015-09-15, 00:00 authored by Jihoon Choi, Matteo Cargnello, Christopher B. Murray, Nigel Clarke, Karen I. Winey, Russell J. Composto
Nanorod diffusion in polymer melts is faster than predicted by the continuum model (CM). Rutherford backscattering spectrometry is used to measure the concentration profile of titanium dioxide (TiO2) nanorods (L = 43 nm, d = 5 nm) in a polystyrene (PS) matrix having molecular weights (M) from 9 to 2000 kDa. In the entangled regime, the tracer diffusion coefficients (D) of TiO2 decrease as the M–1.4, whereas the CM predicts DCM ∼ M–3.0 using the measured zero-shear viscosity of TiO2(1 vol %): PS(M) blends. By plotting D/DCM versus M/Me, where Me is the entanglement molecular weight, diffusion is enhanced by a factor of 10–103 as M/Me increases. The faster diffusion is attributed to decoupling of nanorod diffusion from polymer relaxations in the surrounding matrix, which is facilitated by the nanorod dimensions (i.e., L greater than and d less than the entanglement mesh size, 8 nm).
DCMcontinuum modelpolymer relaxationsPSmatrixRutherford backscattering spectrometrytitanium dioxide5 nmEntangled Polymer MeltsNanorod diffusion8 nmnanorod dimensions43 nm2000 kDaCMconcentration profileTiO 2 decreaseFast Nanorod Diffusiontracer diffusion coefficientsnanorod diffusionentanglement mesh size