Effect of surface freezing on meniscus relaxation in side chain comb polymers.

We have observed a sharp slowing down of the relaxation of the liquid meniscus for poly(n-alkyl acrylate) at temperatures where there are no abrupt changes in bulk viscosity or surface tension. This slowing down is due to the formation of a surface-ordered monolayer above the bulk melting temperatures. X-ray photon correlation spectroscopy measurements reveal that the surface capillary fluctuations are also significantly slower due to the formation of the ordered monolayer for film thicknesses comparable to that of the precursor films. The slowing down of the precursor film dynamics is responsible for slower meniscus relaxation below the surface ordering transition temperature.