Free volume in layered organosilicate-polystyrene nanocomposites

Experimental studies by Positron Annihilation Lifetime Spectroscopy of free volume in a layered Organosilicate-Polystyrene nanocomposite are reported. Specifically, the intensity (I₃) and lifetime (τ₃) of orthopositronium annihilation were determined for an organically-modified mica-type silicate(OMTS), an atactic polystyrene specimen (M_w), and an OMTS/Polystyrene nanocomposite. The neat OMTS material is produced by a cation exchange reaction between the mica-like silicate and an alkylammonium salt, and has a structure which consists of weakly-cohesive silicate layers connected by galleries with an average spacing of 2.253 nm. The presence of the complexed alkylammonium cations in the galleries between the silicate layers renders the material hydrophobic. On forming the nanocomposite, the interlayer spacing increases to 3.031 nm. PAL analysis of the nanocomposite will be presented and the o-Ps annihilation characteristics, as well as the mean lifetime behaviors, are discussed. Moreover, a comparison of the nanocomposite behavior with the that of the Organosilicate and the bulk polymer is done, in order to unveil the behavior of the confined polystyrene.