Entropy-driven segregation of nanoparticles in polymer melts

We present a Monte Carlo study of the dispersibility of nanoparticles in polymer melts based on the relative entropic contributions of particles and polymer chains. Our model predictions are in terms of the particle diameter d and the chain statistical segment length ℓ. In the limit of small (d=ℓ) particles, a good dispersion is predicted, as the high entropy contribution of the small particles largely offsets the loss in polymer chain entropy. This is not the case, however, at larger d ≈ 3ℓ and particle segregation at the surfaces of thin polymer films is observed. That model prediction is in good agreement with experimental observation for systems with little or no enthalpic interaction between polymer and particles.