Convection in polymeric fluids subjected to vertical temperature gradients

We present a study of convection in thin layers of poly(dimethyl siloxane) (PDMS) oligomers end-terminated with different functional groups. In PDMS, silanol-, and aminopropyl-terminated PDMS, surface-tension-driven convection produces ordered hexagonal patterns with a critical wavenumber k approximate to 2. The onset of convection is close to that predicted by a Linear theory. In thin films of methacryloxypropyl-terminated PDMS (MAOP-PDMS) surface-tension-driven convection is suppressed, despite the fact that macroscopic physical properties favor this type of convection. In thick films of MAOP-PDMS, mixed surface-tension- and buoyancy-driven convection occurs, generating hexagonal and roll-like patterns. We demonstrate that ordered nonequilibrium patterns induced in the fluid MAOP-PDMS films can be trapped in the solid state by photopolymerization.