In situ neutron reflectivity is used to monitor the effect of soft polystyrene nanoparticles on the interdiffusion of deuterated and protonated polystyrene bilayers. The in situ temperature cell is designed with two separate, individually controlled temperature plates that allow for precise control of the temperature increase from 90C to 130C in less than 15 minutes with no overshoot or fluctuation. Over 18 minute intervals, reflectivity profiles were measured sequentially at 130C over a limited Q range. For a bilayer containing similar molecular weight polystyrenes, the diffusion of the polymers is symmetric. Therefore the time dependence of the interfacial width, w, between the two layers is fit to Fick’s second law to determine the diffusion coefficient of the PS chain. Analysis of the time dependence of the interfacial width shows t1/4 behavior at early times, which changes to t½ behavior in the diffusive regime. When the soft nanoparticles are dispersed homogeneously within both layers of the bilayer to form a nanocomposite, the diffusion coefficient is faster than that of the neat film. In comparison, slower diffusion is observed in bilayers where the layers are composed of pure nanoparticle and deuterated polystyrene.

In situ determination of polymer diffusion in nanocomposites

251st National Meeting (2016)

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