Abstract

In this work, the inhomogeneous polymer reference interaction site model (PRISM) integral equation theory is extended to investigate the microscopic structure of a new system of nanocomposites with polymer-grafted nanoparticles near solid surface. The chemical and morphologic details of polymers are described by a semiflexible chain model, which can be utilized to capture the intramolecular interactions between different segments. Based on the novel bridge functionals of different segments constructed from the corresponding chemical potentials, the modified hypernetted chain approximation is combined with the inhomogeneous PRISM equation to obtain the detailed density distributions of nanoparticle-polymer blends near substrate. The effects of particle volume fraction, nanoparticle size, attractive interaction strength between different segments and chain stiffness on the density profiles of single tethered polymer nanocomposites (PNCs) near surface are systematically investigated to capture the contribution of the packing and configurational entropies. The end effects of polymer chains and effects of solid wall confinement are also considered. It is found that the particle size and particle volume fraction play the most significant roles in the density profiles of the single tethered PNCs among the present investigated model parameters. The increase of the particle volume fraction leads to a monotonic increasing variation behavior of the density profiles of single tethered nanoparticles as the particle diameter is relatively small. With increasing the nanoparticle size, the intensity of the density profiles of nanoparticles decreases prominently. The detailed packing structure of polymer-nanoparticle blends is also influenced by the polymer chain stiffness and particle-monomer interactions, where these parameters of structure and chemistry can enable the density profiles of the single tethered PNCs to show similar variation trends. The present inhomogeneous PRISM theory can provide a detailed description of packing and conformational entropies on the density profiles of different segments in nanocomposites with polymer-grafted nanoparticles. It could also be easily extended to some real systems with more complicated architecture of polymer-grafted nanoparticles under confinement and anticipated to assist in developing some predictive approaches for design control of PNCs near substrate.

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