Role of Polymer Chain Architecture in Interparticle Interactions Between Functionalized Nanosheets
In polymer nanocomposites, the incorporation of fillers with at least one dimension comparable to polymer chain size produces composites with extra-ordinary properties due to enhanced surface to volume ratio of the nanofillers. In order to improve the dispersion of nanoparticles, the fillers are functionalized by grafting polymeric chains on the surface inducing steric stabilization preventing particle agglomeration. A comprehensive understanding of the interparticle interaction between these functionalized nanoparticles plays an important role in the synthesis of a stable polymer nanocomposite. In the present study, we address the dispersion of clay nanosheets in polymer matrix. With the help of self-consistent field theory (SCFT), we theoretically construct the polymer mediated interparticle potential for two nanosheets grafted with polymeric chains. The interaction potential is obtained from the inhomogeneous composition field for the polymer segments. First, we examine the interpaticle interaction between two grafted nanosheets immersed in the matrix of polymeric chains of dissimilar chemistry to that of the grafted chains. The interaction potential is repulsive at short separation and shows depletion attraction for moderate separations induced by high grafting density. It is found that the strength of attraction well can be tuned by altering the compatibility between the grafted and the mobile chains. Further, we construct the interaction potential between two functionalized nanosheets dispersed in matrix with polymeric chains of varying architectures, like star polymer and diblock copolymer. For nanosheets in the matrix of star polymer, the role of number of arms in the shape of the interparticle potential curve is examined. Increasing number of arms for a fixed value of degree of polymerization tends to weaken the attraction at intermediate separations.
Keywords- Clay nanosheets, Polymer brush, Polymer nanocomposites, Self-consistent field theory