Topology-Enabled Simultaneous Enhancement of Mechanical and Healable Properties in Glassy Polymeric Materials Using Larger POSS

Abstract

Mechanically robust yet healable glassy polymeric materials (HGPMs) are poised for use as next-generation structural and protective materials. However, achieving such materials remains a great challenge due to the inherent conflict between good mechanical properties and adequate molecular mobility required for healing. Herein, we investigate the variations of network topology in HGPMs, leading to simultaneously enhanced mechanical and healable properties. The materials (T 8 -UPy 8 , T 10 -UPy 10 , and T 12 -UPy 12 ) are fabricated by combining multiple hydrogen bonds with T 8 , T 10 , and T 12 polyhedral oligomeric silsesquioxanes (POSSs), respectively, which have identical chemical components yet distinct topologies. It is found that the topological effects arising from the POSS cage size and/or symmetry strongly affect the materials' elastic modulus (E), glass transition temperature (T g ), and healing temperature (T h ). Notably, T 10 -UPy 10 and T 12 -UPy 12 exhibit lower T g (59.5 and 65.4 °C) and T h (65 and 70 °C) yet higher E (5.0 and 6.0 GPa) compared to those of T 8 -UPy 8 . Elaborate comparisons underscore the instrumental contribution of larger POSS-based topological structures, revealing that the larger POSSs contribute to higher molecular mobility with tighter internal framework structures. Meanwhile, these materials possess high pencil hardness, transparency, and exceptional flexibility, making them well-suited for robust flexible protective coatings. This work highlights the significance of the topology, particularly a larger POSS, for fabricating advanced HGPMs.

Cage-rearranged and cage-intact syntheses of azido-functionalized larger T10 and T12 POSSs

“…1 Due to their cage-like shape-persistent three-dimensional structures, hybrid characteristics, and diverse functionalities, POSSs have garnered significant attention in the materials chemistry community and find wide-ranging applications in diverse fields such as polymer nanocomposites, 2 self-assembly, 3 biomedicine, 4 catalysis, 5 dielectrics, 6 absorbents, 7 and coatings. 8 Typically, the properties of POSSs are determined by the T n cage and the substituents attached to it. In terms of the T n cage, extensive research has been conducted on T 8 cage ( O h )-based materials to date, while materials based on larger T 10 ( D 5h ) and T 12 ( D 2d ) POSSs are relatively scarce.…”