Effects of π-π interactions on the rheological and heat-resistant behaviors of silicon-containing arylacetylene resins: A molecular dynamics simulation.

• As the fraction of rings increases, the viscosity and glass transition temperature enhance. • The PSA-VF resin has a weaker diffusion ability compared to the PSA-V and PSNP-V resins. • The PSA-V resin exhibits a relatively discrete structure, whereas the PSNP-V and PSA-VF resins display an ordered structural stacking. • The interactions between the resins are typical π-π stacking interactions. Silicon-containing arylacetylene (PSA) resins are promising high-temperature resistant polymers. But their structure–property relationships at the atomic level are still unknown. In this study, the effects of π-π interactions on the rheological and heat-resistant behaviors of silicon-containing arylacetylene resins containing benzene unit (PSA-V), 2,7-diethynylnaphthalene unit (PSNP-V), and 2,7-diethynyl-9H-fluorene unit (PSA-VF) in main chains were explored using molecular dynamics. Compared to the PSA resin, the PSA-VF resin has stronger π-π stacking interactions, confirmed by interaction region indicator and energy decomposition analysis methods. When the resin has a higher fraction of aromatic ring, the mobility of the molecules decreases and so the diffusion capacity will be reduced. After analyzing the simulated trajectories for different resin systems, the face-to-face stacking between the resins was found. Compared with the PSA-V resin with relatively dispersed aggregate structure, the PSA-VF resin with larger-sized and more regular aggregate structure has higher viscosity and glass transition temperature due to stronger π-π interactions. These results provide a new perspective on the relationship between the π-π interactions and properties of the PSA resins. [ABSTRACT FROM AUTHOR]