| A systematic study of the polymer dynamics on patterned surfaces and bilayer thin films is studied. Two common polymers, Polystyrene (PS) and Poly methylmethacrylate (PMMA) were used in the study. The attenuation of corrugated roughness on thick polymer films was studied as a function of time, temperature, frequency, molecular weight and imprinting time using atomic force microscopy. The corrugation maintained its original square waveform as its amplitude decreased. Rapid relaxation was also observed far below Tg. Elastic relaxation, which occurs mostly via segmental motion independent of molecular weight, appears to be the dominant mechanism driving the attenuation. The rate of attenuation also depends upon the processing conditions of the samples.; For the second part of the study I determined the dewetting velocity could be used to accurately determine the viscosity of a polymer coating on a surface. The extracted viscosity is in excellent agreement with previous bulk measurements. We also explored the effects of the large shear in producing melt fracture and slip-stick phenomena when the dewetting velocity exceeds the natural reptation time (τ). It was determined that melt fracture can be significantly minimized by screening the interactions with the substrate.; Finally, I synthesized C18 functionalized gold and palladium particles with average radii of 12nm and 3nm respectively and carried out a systematic study of the effect of nanoscale metallic fillers on the dewetting dynamics. X-ray reflectivity and TEM microscopy were used to study the distribution of the particles within the film and shows that no interfacial segregation or clustering of these particles occurs. The results indicate that the dynamics are a sensitive function of the ratio between the filler and the polymer radii of gyration. Shear Modulation Force Microscopy (SMFM) measurements as a function of temperature indicated that Tg was depressed by 12°C relative to the bulk value for large particle and bulk like for smaller particles. The results were interpreted in terms of an increase in the local excluded volume and elastic distortion of the gaussian chain conformations within the films. The effects presented here promise to be an important means of controlling thin film stability. |
