From fundamental insights to rational (bio)polymer nanocomposite design - Connecting the nanometer to meter scale

Nanoparticle addition has the potential to make bioplastic use mainstream, as the resultant nanocomposite shows improved mechanical, barrier, and thermal properties. It is well established that the architecture and dynamics of the nanoparticle-polymer interphasial region, ∼ 1.5-9 nm from the nanoparticle surface, are crucial for nanocomposite characteristics. Yet, how these molecular phenomena translate to the bulk is still largely unknown. A multi-disciplinary and multi-scale vision is required to capture the full picture and improve materials far beyond what is currently possible. In this review, a first step in bridging the apparent gap between fundamental insights toward observed material properties is made. At the molecular scale, the polymer chain density and dynamics at the nanoparticle surface are governed by a complex interplay between enthalpy and entropy. The resultant interphasial properties can only be propagated to the macroscopic scale effectively when the nanoparticles are well-distributed. This makes the dispersion state a key parameter for which thermodynamic and kinetic insights can be used to prevent nanoparticle aggregation. These insights are linked to material properties relevant to packaging. The outlook section elaborates on the remaining challenges and the steps required to further understand and better design nanocomposite systems.