Molecular Hybridization of Polydimethylsiloxane with Zirconia for Highly Gas Permeable Membranes

Inorganic–organic nanocomposite hybrids containing zirconium dioxide (ZrO 2 ) as inorganic cross-linker/filler and polydimethylsiloxane (PDMS) as a polymeric matrix have been synthesized using the in situ sol–gel reaction between silanol-terminated PDMS and zirconium normal butoxide (Zr(OC 4 H 9 ) 4 ). Hybrid materials were used to fabricate gas separation membranes which were characterized by scanning electron microscopy, dynamic scanning calorimetry, nanoindentation, ATR-FTIR, and XPS spectroscopies. Amorphous structure of incorporated ZrO 2 fillers was verified by X-ray diffraction. Small gases (He, H 2, O 2, N 2, and CO 2 ) permeability experiments were carried out to study the effect of the inorganic component amount on the properties of the ZrO 2 @PDMS hybrids. The permeability of the developed hybrids considerably exceeded the permeability of conventional PDMS which is known as “gold standard” highly gas-permeable rubbery polymer. Depending on the ZrO 2 content, fabricated hybrids demonstrated increased permeability for all gases with improvement inversely proportional to the kinetic diameter of gas molecules, that is, highest permeability increase (relatively to PDMS) was observed for H 2 and lowest for N 2 . Such behavior suggests the formation of the size-sieving amorphous zirconia domains within PDMS which do not impede gas transport due to the nanosize of the fillers. As a result, gas separation membranes prepared using the developed materials demonstrated better separation performance for CO 2 /N 2, H 2 /N 2, and O 2 /N 2 pairs compared to the conventional PDMS.