Self-diffusion coefficients of flexible linear polymers with local inhomogeneities at the center of each chain

We put forward a simple, purely geometric, argument to describe selfdiffusi on coefficients of flexible linear polymers with local inhomogeneities at t he center of each chain. Based on the model, these inhomogeneities must be isolated from each other (with a low volume fraction in the whole system); for instance, they can be ring structures such as a pentagon, hexagon, and the like with two chains at different linkage positions on the ring. When t here is only one ring at the center with two chain molecules of equal molec ular weights attached to it, this can be viewed as a two-arm polymer with d ifferent link-age positions at the center ring. Based on the model calculat ions, it was surprisingly found that, by only changing the linkage position s of these two arms, there was a significant variation in the self-diffusio n coefficients of these polymers. This was found experimentally in three tw o-arm poly(ethylene oxide) (PEO) fractions, which possess a phenylene group at the center of the chain with three different linkages at the 1,4-, 1,3- , and 1,2-positions. Numerical calculations showed quantitative agreement w ith the experimental observations.