Tailoring the alignment of string-like nanoparticle assemblies in a functionalized polymer matrix via steady shear

Abstract

Recent work has shown that nanoparticles (NPs) dispersed in a sequence specific functionalized polymer matrix can be organized into a variety of superstructures, such as strings, sheets, and percolated networks. However, these spontaneously formed structures are generally ordered within the short range. To exploit the use of NPs to their full potential, defect-free, long-range ordered NP organization is usually necessary. The use of a shear field may be an appropriate means to reach this objective due to its well-understood orientation effect. Therefore, the present study seeks to probe the effect of steady shear on the ordering of string-like NP assemblies in a functionalized polymer matrix on the basis of coarse-grained molecular dynamics simulations. We found that by properly tuning shear rate, the shear can induce one-dimensional alignment to the NP strings, and the emerging structures can remain stable after the cessation of shear, which is required for many applications such as the fabrication of nanomaterial arrays. The mechanism for forming such a well-defined structure can be interpreted from the competition among the NP mobility, polymer relaxation, NP-functional group interaction, and external shear effect. It may be expected that the information derived in the present study provides a useful foundation for guiding the design and preparation of tailored PNCs.