Tuning structure and dynamics of segmented ionenes with added spherical nanoparticles

Segmented ionenes can be synthesized such that short ion-containing segments alternate with uncharged segments. By changing the ratio of relatively soft and hard uncharged segment types, material properties can be easily tuned. Incorporating nanoparticles may allow for further manipulation of structure and mechanical behavior. However, the multiple length/time scales involved, the large parameter space, and the nanoparticles’ tendency to aggregate complicates material design. Using efficient coarse-grained molecular dynamics simulations, we aim to establish architecture-structure-property relationships to guide synthetic efforts.
Inspired by experimental ammonium ionenes with short polyethylene segments and long, soft segments (such as polyethylene oxide), we study segmented ionenes and spherical nanoparticles using a simple bead-spring model. Soft segment length, the ratio of the two polymer types, and nanoparticle surface chemistry is tuned and structure and dynamics analyzed. We find weight fraction dependent local microphase segregation of soft and hard polymer segments. We also determine the nanoparticle's impact on the local structure as a function of weight fraction and chemistry.