Migration of liquid polymers on solid surfaces

Migration of very thin (<30 nm) polymeric films on solid surfaces was investigated quantitatively using two techniques—scanning microellipsometry and scanning small spot x-ray photoemission spectroscopy. The surface diffusion coefficient Ds increases as the film thickness decreases down to 1 nm, however, below 1 nm, Ds becomes independent of polymer film thickness. The functional dependence of Ds with molecular weight M is described, over the limited range of M in the unentangled regime, by M−1.7 The activation energy for polymer segment hopping is about 41 kJ/mol, which is similar to values obtained from bulk self-diffusion of other polymers.