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

Abstract

Polymer membrane based gas transport and pervaporation processes are fast growing areas in separation technology and have received wide attention as areas of 'clean technology'. Mechanically stable novel polyhedral oligomeric silsesquioxane (POSS) embedded poly(vinyl alcohol) (PVA)/poly(ethylene oxide) (PEO) blend membranes were prepared by solution blending followed by casting. The addition of carboxymethyl cellulose enhanced the interfacial activities of the PVA and PEO blends. The peripheral organic substituent on POSS plays a key role in achieving compatibility with polymers whereas the rigid Si-O-Si core of POSS imparts high mechanical strength. Compared to PVA membrane, poly(ethylene glycol) and octa(tetramethylammonium) functionalized POSS embedded PVA/PEO membranes exhibit 680% and 580% enhancement in Young's modulus as well as 130% and 140% improvement in tensile strength respectively. The Einstein, Kerner and Frankel-Acrivos models were applied to compare the experimental and theoretical Young's modulus of PVA-PEO/POSS membranes. The presence of an ethylene oxide tail on POSS as well as PEO in the blend membrane enhances the CO 2 affinity of the membrane. The presence of a hydrophilic functional group on the POSS improves the hydrophilicity of the membrane and produces more binding sites for water molecules in the membrane during the pervaporation separation of a tetrahydrofuran-water azeotropic mixture. The transport properties of the membrane are further elucidated by means of free volume defect analysis carried out by positron annihilation lifetime spectroscopy and coincidence Doppler broadening spectroscopy.

Natural Rubber/Carbon Nanotube/Ionic Liquid Composite Membranes: Vapor Permeation and Gas Permeability Properties

“…[ 13 ] And, attraction of the membrane material towards gas molecules is another factor that determines the transport of gas molecules. [ 36 ] Condensability of oxygen and its interaction with the rubber membranes are greater than those of nitrogen. This also supports its improved permeability.…”

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

“…In the study, positrons are injected from a radioactive source ( 22 Na) to a few‐tenths of mm interior of the polymer. The details were given in one of our previous works 30 …”

“…Poly(etherblock‐amide) (PEBAX® 2533) membrane doped with 30 wt% of PEG‐POSS exhibited simultaneous improvement in selectivity and permeability at 30°C 29 . In our previous work we are reported pervaporation and gas separation performance of PVA‐PEO/POSS membranes 30 . It was observed that PEG‐POSS greatly increased the CO 2 and water selectivity of PVA‐PEO membrane.…”

The State-of-the-Art Functionalized Nanomaterials for Carbon Dioxide Separation Membrane

“…The work by Li et al [225] demonstrated the enhancement in permeability and CO 2 /N 2 selectivity of the resulting nanocomposite from 250 barrer to 710 barrer and from 59 to 62, respectively, by functionalizing GO with PEG. A quadrupole-dipole interaction between CO 2 and polar groups is the main mechanism that contributed to this improvement [196,[226][227][228]. Similarly, a quadrupole-dipole interaction also contributes to the binding of CO 2 with many metallic compounds from the transition group, especially zinc, cobalt, copper and titanium [229][230][231] and nanomaterials that are rich with electronegative groups such as silica, titanium dioxide (TiO 2 ), GO and BN [32,124,208,232,233].…”

“…• commonly conducted via FTIR to detect formation of new bonds between nanofillers and polymer matrix. [192,[194][195][196] 2. visually observe nanofiller-membrane matrix interfaces:…”