Molecular dynamics simulations were used to study dynamics of single molecules within systems chosen as simple models of bitumen used in paving asphalts.  Analyses of rotation time via orientation time correlation functions and of diffusion coefficient via mean-squared displacement revealed that rotation and diffusion decouple to different extents for molecules that differ in size and/or polarity within a multicomponent system.  The rotation-diffusion product at low temperature increases most for asphaltenes, indicating dynamical decoupling such that rotations control viscosity and mechanical behavior.  For resins the increase depends on size and polarity.

Decoupled rotation and translation across molecule sizes and polarities in 
a model bitumen

240th National Meeting (2010)

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Decoupled rotation and translation across molecule sizes and polarities in a model bitumen