Composition Distributions and Effective Concentration of Miscible Polymer Blends Probed by MD Simulation

Using molecular dynamics we simulate the effects of thermally-driven concentration fluctuations and chain connectivity on segmental dynamics of miscible weakly interacting polymer blends. These naturally lead to local variations in glass transition temperature and hence, a distribution of segmental relaxation times. The self-concentration and pure component limits naturally truncate the Gaussian distribution of compositions surrounding a given segment. The most-probable composition differs considerably from the mean-field estimation of Lodge and McLeish for blend compositions that differ from 50/50, when we consider chain connectivity effects for all chains in the control volume.