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° 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.