Incorporating nanosized particles in a polymer matrix can lead to new materials with significantly improved mechanical, electrical, optical, and thermal properties. This explains the large body of theoretical, modeling and experimental work accumulated recently, in an effort to address the complex interplay between molecular-level parameters and mechanisms in polymer nanocomposites (PNCs), and macroscopically-manifested properties. But there exist many issues still not well understood such as: a) how one can control nanoparticle (NP) dispersion and what are the molecular or thermodynamic parameters controlling the phase behavior of PNCs?; b) how does the presence of NPs alter the conformational and relaxation properties of the polymer?; c) how are the linear and non-linear viscoelastic properties of the pure polymer matrix changed as a function of the volume fraction and size of the added NPs; d) what is the respective role of the size of polymer chains relative to the NP diameter?; e) what are the relevant contributions of enthalpic and entropic effects?; f) how does chain end-grafting onto a spherical NP alter nanoparticle dispersion, thus also the mechanical and rheological properties of the resulting nanocomposite?
We try to address many of these questions through direct simulation efforts preferably through the design of multi-scale methodologies but also through the development of constitutive models based on a minimal set of state variables representative of the system under study.
Properties to be predicted here include: a) For the bulk polymer matrix: the density, characteristic ratio, static structure factor, distribution of torsion angles, relaxation modulus, entanglement length, viscosity, storage and loss moduli, and free volume, all as a function of temperature. b) For the PNC: structure, conformation, volumetric behavior, work of adhesion, interfacial shear strength, elastic moduli, and rheology in linear and non-linear regimes, all as a function of temperature, applied deformation or shear rate, and nanoparticle volume fraction.