Computational design of nucleating agents of poly (methyl methacrylate) microcellular foams: "savanna-like" surface structures and their effects on foaming

To further the computational design of polymer foaming, this work investigated the interactions between polymer and nucleating agents by evaluating the removal forces needed to remove the polymer from the nucleating agent using molecular dynamics simulations. Silica nanoparticles modified with different organic groups and different surface modification ratios represented model nucleating agents and poly methyl methacrylate (PMMA), a model polymer. Modified organic groups with a certain length and flexibility grafted sparsely on the silica surface, creating a "savanna-like" structure, increased the interaction between PMMA and the silica nanoparticle. The simulation results predicted the effects of the modified organic group and surface modification ratio R of the silica nanoparticle seen in actual batch foaming experiments using CO2 and PMMA with modified silica nanoparticles. Cell size shows a minimum and cell nucleation density a maximum in the foamed polymer under certain conditions, which correlate with the simulation results for the interactions between the polymer and nucleating agent. Based on the correspondence between the simulation and the experimental results, the effectiveness of such simulations for the design of nucleation agents appeared promising.HighlightsComputational design of nucleating agents for microcellular foams.Evaluation of the interaction of polymers with various nucleating agents.Large interactions due to the "savanna-like" structure of nucleating agents.Demonstration of polymer foaming with designed nucleating agents. To further the computational design of polymer foaming, this work investigated the interactions between polymer and nucleating agents using molecular dynamics simulations. Actual batch foaming experiments using CO2 and poly (methyl methacrylate) with modified silica nanoparticles were performed to compare with the simulation results. Based on the correspondence between the simulation and the experimental results, the effectiveness of such simulations for the design of nucleation agents were shown.image