The structure of bidisperse polyethylene (PE) nanocomposite mixtures of 50:50 (by mole) of long and short chains of C

160

H

322

/C

80

H

162

and C

160

H

322

/C

40

H

82

filled with spherical nanoparticles were investigated by a coarse-grained

on lattice Monte Carlo method using rotational isomeric state theory for short-range and Lennard-Jones for long-range energetic interactions. Simulations were performed to evaluate the effect of wall-to-wall distance between fillers (

D

)

polymer-filler interaction (

w

) and polydispersity (number of short chains in the mixture) on the behavior of the long PE chains. The results indicate that long chain conformation statistics remain Gaussian regardless of the effects of confinement

interaction strength and polydispersity. The various long PE subchain structures (bridges

dangling ends

trains

and loops) are influenced strongly by confinement whereas monomer-filler interaction and polydispersity did not have any impact. In addition

the average number of subchain segments per filler in bidisperse PE nanocomposites decreased by about 50% compared to the nanocomposite system with monodisperse PE chains. The presence of short PE chains in the polymer matrix leads to a reduction of the repeat unit density of long PE chains at the interface suggesting that the interface is preferentially populated by short chains.