Solvent-Free and Highly Transparent SiO2 Nanoparticle–Polymer Composite with an Enhanced Moisture Barrier Property

Solvent-free SiO2–poly­(trimethylolpropane triacrylate) (SiO2–PTPT) nanocomposites are successfully fabricated for an encapsulation layer by surface modification of a SiO2 nanoparticle. In order to lead surface-initiated polymerization and introduce structural similarity between a SiO2 surface and polymer, the surface of the SiO2 nanoparticles are modified with [3-(methacryloyloxy)­propyl]­trimethoxysilane. The modified SiO2 nanoparticle dispersed in trimethylolpropane triacrylate (TPT) is converted to a SiO2–PTPT nanocomposite under UV irradiation. Because SiO2 incorporated in a polymer generates a tortuous path and absorbs a water molecule, the SiO2–PTPT nanocomposite shows a considerably lower water vapor transmission rate than PTPT. All of the nanocomposite films are highly transparent (over 98%) in the visible region before and after humidity aging tests. Furthermore, a light-emitting diode encapsulated by a 20 wt % SiO2–PTPT nanocomposite exhibits a considerably longer lifetime in the accelerated aging condition.