Pervaporation separation of an azeotropic mixture of a tetrahydrofuran–water system with nanostructured polyhedral oligomeric silsesquioxane embedded poly(vinyl alcohol)

Abstract

Cage -structured polyhedral oligomeric silsesquioxane (POSS) molecules were used as modifiers in the fabrication of poly (vinyl alcohol) (PVA) membrane for the separation of an azeotropic mixture of tetrahydrofuran (THF) and water system. Poly(ethylene glycol) and anionic octa(tetramethyl ammonium)-functionalized POSS were used for this study. The membranes exhibited excellent water selectivity and permeance because of their preferential interactions toward water molecules in the azeotropic THF-water mixture.In the presence of poly(ethylene glycol)-POSS and anionic octa(tetramethyl ammonium)-POSS, the PVA membrane exhibited a significant increase in selectivity. A modified Maxwell-Stefan equation was used for the computation of the theoretical flux, which was compared with the experimental values.

Free volume defects and transport properties of mechanically stable polyhedral oligomeric silsesquioxane embedded poly(vinyl alcohol)‐poly(ethylene oxide) blend membranes

“…. The surface roughness value ( R q (nm) = 9.5) of pristine PVA was reported in our previous work . Compared to pristine PVA, PEG‐POSS embedded PVA‐PEO blend exhibits reduced surface roughness ( R q (nm) = 7.3).…”

“…Both PEG‐POSS and Octa‐TMA‐POSS act as excellent mechanical reinforcing agents for the PVA‐PEO membrane and CMC enhances the miscibility of PVA‐PEO. In previous work, the mechanical properties of PEG‐POSS and Octa‐TMA‐POSS incorporated PVA were presented and it was observed that the mechanical stability of the PVA membrane increased in the presence of POSS molecules; this was further increased on blending with PEO . The blend membrane exhibits reduced elongation at break and improved stiffness due to good miscibility of the PVA and PEO polymers in the presence of CMC implying that the latter acts as a stabilizer of the PVA‐PEO blend.…”

“…PVA‐PEO/POSS membranes of 16.6 cm 2 circular size were used for the pervaporation separation of a tetrahydrofuran (THF)–water azeotropic mixture. The pervaporation studies were carried out as reported in our previous work …”

Changes in free volume and gas permeation properties of poly(vinyl alcohol) nanocomposite membranes modified using cage‐structured polyhedral oligomeric silsesquioxane

“…AFM images PEG-POSS-, Octa-TMA-POSS-, and m-POSS-incorporated PVA membranes are presented in our previous work. 34,35 The surface roughness parameter is found to be higher in PEG-POSS and m-POSS filled PVA membranes as compared to pure PVA whereas PVA/Octa-TMA-POSS system shows reduced surface roughness. The variation in the surface roughness by changing the functional group in POSS is probably due to the difference in the nature of interaction between the matrix and the filler at the PVA-POSS interfaces, resulting in the reorganization of chains of PVA on surfaces.…”

“…The cross-sectional morphology of PEG-POSS embedded PVA membrane (Figure 2(b)) shows a smooth and dense structure like pure PVA without forming any bulky agglomeration or any noticeable defects at the PVA-POSS interface. [34][35][36][37] This can be attributed to the dominating PEG side group (92 wt%) over the rigid siloxane core in PEG-POSS resulting in good interfacial bonding between polymer and POSS. However, in the case of Octa-TMA-POSS and m-POSS doped PVA membranes, spherical shape of the POSS particle were clearly visible.…”