(418bv) Polymer Structure and Rheology at Fluid-Fluid Interfaces

Polymer structure and rheology at interfaces have great consequences in biology and chemistry, and there are many examples where our current knowledge of these systems has commercial applications in products like paints, cosmetics, foods, and advanced materials. At fluid-fluid interfaces polymers have found commercial applications as stabilizers in cosmetic and food products, and there are areas of biology where polymers at fluid-fluid interfaces play an important role. An ongoing debate amongst those investigating polymer structures at fluid-fluid interfaces is whether or not the polymer adopts an entangled structure similar to that in bulk solutions of concentrated polymer above a critical molecular weight, or whether the polymer adopts a non-entangled structure analogous to bulk solutions of polymer chains below a critical molecular weight. We have investigated this by measuring the interfacial rheological properties of two similar polymers: poly(tert-butyl methacrylate) (PtBMA), and poly(tert-butyl acrylate) (PtBA), each at an air-water interface. The results we will present do not support the entanglement theory, and additionally indicate that the discussion of polymer structure at an air-water interface need not be restricted to a debate over polymer microstructure. For example, we will show that PtBA forms large heterogeneities at all levels of surface coverage, and that its interfacial rheological behavior is surprisingly different than that of the PtBMA that forms relatively uniform layers at all surface coverages.

* authors affiliated with both the Department of Chemical Engineering at KU Leuven, and the Department of Materials Science at ETH Zurich.