Polyurethane/POSS nanocomposites for superior hydrophobicity and high ductility

A novel polyhedral oligomeric silsesquioxane with di-hydroxyl and two triethoxy groups (m-POSS) was synthesized by a facile method. Then it reacted with diisocyanate to prepare aqueous polyurethane (APU)/m-POSS nanocomposites. The di-hydroxyl groups facilitating the m-POSS dispersing into the main chain of the APU, during which two triethoxy groups served as cross-linking sites. The addition of m-POSS had little influence on the viscosity and stability of the APU/m-POSS dispersions. The APU/m-POSS nanocomposite film with 8 wt% m-POSS exhibited superior surface hydrophobicity with water contact angle up to 121 degrees due to the migration of Si element from inner to the surface. Moreover, the Young's modulus and tensile strength of APU/m-POSS composite increased up to 21.8 MPa and 15.3 MPa, respectively, with the elongation at break increased up to 1000%, which was ascribed to the enhancement of the cross-linked m-POSS. The DMA results revealed that the glass transition temperature (T-g) of the APU hard segment increased significantly while a little change was observed for that of soft segments, indicating that the m-POSS preferred to locate in the APU as hard segments. This functionalized m-POSS can endow polymer matrix with superior hydrophobicity and enhanced mechanical properties.