Temperature Effect on Interfacial Structure and Dynamics Properties in Polymer/Single-Chain Nanoparticle Composite

Interface structure and dynamics properties in an all-polystyrene composite composed of linear chains and one single-chain nanoparticle (SCNP) are investigated by using large-scale molecular dynamics simulations at both coarse-grained and full atomistic level. It is demonstrated that the SCNP adopts a crumpled globular state in composite; it has layered internal structures especially at low temperatures. When temperature decreases, its interior phenyl rings (iPRs) are parallel to each other and scaffold cross-linking bonds undergo a "loose-to-tight" transition, leading to a "soft-to-hard" transition of the SCNP. Such transition provides more interior free volume and therefore results in faster rotational relaxation of inner layer iPRs at low temperature. It also facilitates the infiltration of the matrix monomers, resulting in an enhanced interfacial correlation and therefore a stronger deceleration effect in diffusion of matrix monomers at low temperatures. These results provide new insights into unique structure and dynamics properties at the polymer/SCNP interface region.