(6cc) Properties of Surfaces and Films from Viscous Liquids to Elastic Solids

Surface deformations during the coalescence of two polymer melt films were studied by use of a surface forces apparatus (SFA). A new type of well-ordered periodic transient surface fingering pattern was observed during the coalescence, which eventually disappeared, leaving smooth polymer-air interfaces. The life-times of the transient well-ordered patterns depend on the viscosities and film thickness of the polymers. These observations are contrast to the conventional understanding that liquid-liquid coalescence usually occurs with the deforming surfaces remaining smoothly curved at all stages, with no abrupt changes or esoteric shape transitions. In further, the transitions and dynamic transients associated with the adhesion and/or coalescence of surfaces ranging from viscous liquids to elastic solids were studied in great details. This talk will address the properties of surfaces and films from liquid-like to solid-like state and types of instabilities observed during their approach, adhesive contact, coalescence and detachment, and discuss common situations where similar effects likely occur.