We have investigated the dynamics of thin block copolymer films of poly(styrene)-b-poly(dimethylsiloxane) using X-ray Photon Correlation Spectroscopy (XPCS). The films were prepared on Si substrates and examined at melt (170℃-210℃). The incident angle ...

We have investigated the dynamics of thin block copolymer films of poly(styrene)-b-poly(dimethylsiloxane) using X-ray Photon Correlation Spectroscopy (XPCS). The films were prepared on Si substrates and examined at melt (170℃-210℃). The incident angles were chosen at 0.14° and 0.2° for studying selectively dynamics from surface and micelles in films. The results was compared with the theory of over-damped thermal capillary waves on polystyrene films.
Among the thickness (500Å~4000Å) and temperature (150℃~220℃), we observed variations of surface tension and viscosity on block copolymer films.

We obtained fellowing the results from the thickness dependence as function of temperature of surface tension at same molecular weight and molecular weight dependence for similar thicknesses. It is interesting to observe that both results show small v ...

We obtained fellowing the results from the thickness dependence as function of temperature of surface tension at same molecular weight and molecular weight dependence for similar thicknesses. It is interesting to observe that both results show small value of surface tension than bulk value of PS (~30 mN/m) but they are close to the surface tension of PDMS at room temperature (~20 mN/m) without clear temperature dependence. From these result, one might speculate that the PDMS micelles exits on the surface of PS-b-PDMS films. The surface tension from the static diffuse scattering is used for dynamics analysis. The relaxation time becoms faster with increasing temperature and with increasing in-plane wavevector. This behavior is qualitatively similar to that obtained for polystyrene films. We obtained the viscosities as function of temperature. Compared to the viscosities of similar molecular weight of PS, viscosities obtained from the films of PS-b-PDMS with various thicknesses are larger than thoes of PS. The results meaured with different molecular weight of each block and the different ratio of them also show higher viscosities than those of similar molecular weight of PS. This behavior of viscosities can be interpreted that the surface dynamics slows down due to interaction of the micelles of PDMS inside the block copolymer films.