Controllable dimensions and regular geometric architectures from self-assembly of lithium-containing polyhedral oligomeric silsesquioxane: Build for enhancing the fire safety of epoxy resin

Mitigating the fire hazards of epoxy resin (EP) and simultaneously improving mechanical properties have always been a goal pursued by polymeric scientists. Herein, we prepared a lithium-containing hepta-isobutyl-POSS (ibu-T₇-Li-POSS). The chemical structure of ibu-T₇-Li-POSS was well characterized. Just via tuning the ethanol solution concentration, we can obtain zero-dimensional (0D) spherical nanoparticles, two-dimensional (2D) ultrathin mono-layer nanoflakes, three-dimensional (3D) multiple-layered lamellae and hexagonal petal-shaped micron-size crystal based on ibu-T₇-Li-POSS. Regular macroscopic octahedron single crystal of ibu-T₇-Li-POSS was analisized by single crystal X-ray diffraction. The prepared ibu-T₇-Li-POSS was incorporated into EP to improve the mechanical properties and enhance the fire safety. When the ibu-T₇-Li-POSS content was 1 wt%, the flexural strength of EP-1 was enhanced from 81.8 MPa of EP to 110 MPa. The incorporation of ibu-T₇-Li-POSS can apparently decrease the dielectric constant and loss of EP nanocomposites. Moreover, when 5 wt% of ibu-T₇-Li-POSS was incorporated into EP, the reduction of peak of heat release rate (p-HRR), peak of smoke production rate (p-SPR) and peak of CO production rate (p-COP) reached to 34.1%, 38.6% and 40.6%, respectively. Therefore, our findings provide a considerable promotion for the facile preparation of low-dimensional environment-friendly nano-/micron-flame retardants based on metal-containing polyhedral oligomeric silsesquioxane (M-POSS) compounds.