Increased gas permeability in thermo-sensitive polyurethane film with TiO2 nanoparticles

• 1、National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065, China

Abstract：Thermo-sensitive polyurethane (TSPU) solution containing different content of TiO2 nanoparticles was prepared using an organic-inorganic hybrid technique, and the final nanocomposite films were formed via solution casting. When the solution casting temperature was lower than the switch temperature of the TSPU, gas permeability/diffusion coefficients of the nanocomposite films were found to increase with increasing nano-TiO2 content. Conventional composite theory could not explain such observation in that filler particles are generally considered to create more tortuous diffusion path in the polymer for penetrants, and thereby should lead to decreased gas permeability. This unusual phenomenon was rationalized by postulating that rigid TSPU chain could not pack efficiently around the TiO2 nanoparticles during solvent casting, resulting in an interfacial area with higher free volume than the bulk polymer region. Indirect evidence supporting such presumption were provided by positron annihilation lifetime spectroscopy that demonstrated increased free-volume size and concentration within TSPU films with increasing TiO2 nanoparticles.

Keywords： polyurethane nanocomposite film gas permeability