Neutron reflectivity measurements indicate that as the number of arms increases (arm MW decreases) the mobility of polymer chains increases. Diffusion coefficients for 4-arm and 8-arm star PS chains do not change much when the film thickness is varied from 1Rg to 4 Rg. This behaviour is quite different than the behaviour of their linear counterparts for which diffusion coefficient becomes larger as the film thickness is reduced from 4Rg to 1 Rg.
展开▼
