Nanocomposites based on natural rubber latex as the matrix and naturally occurring tubular shaped nanoclay, halloysite nanotubes (HNTs) as the reinforcing phase were prepared through co-coagulation method. XRD, morphology, mechanical, and solvent transport properties of the nanocomposites with special reference to weight percentage of nanoclay were analyzed and discussed in detail. Matrix-filler interaction was estimated from Kraus, Cunneen-Russell, and Lorentz-Park plots. Theoretical estimation of reinforcement effect revealed a better interaction between rubber and filler at lower concentration of filler. At higher loading properties decreased due to the formation of filler-filler networks than polymer-filler networks resulting in the reduction of aspect ratio of fillers. Properties of nanocomposites depend on the aspect ratio and volume fraction of reinforcing filler. Morphological analyses of the nanocomposites were done in detail from scanning electron micrographs. Theoretical modulus of nanocomposites was computed using different composite theories by varying the aspect ratio of filler and compared with experimental data. A good agreement between experimental and theoretical values was observed at lower concentration of filler. Solvent transport properties of nanocomposites were found to decrease at lower concentration of HNT because of the tortuosity of the path. POLYM. COMPOS.,

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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.

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.

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Summary: Organically modified halloysite nanotube (HNT) containing polysulfone (PSU) membranes were fabricated by the wet phase inversion method. Organic modification of HNT was carried out using telehelic polyetheramine inorder to overcome the poor dispersion of HNT in PSU matrix. Telehelic polyetheramine acts as a dispersing agent and a hydrophilic modifier. FTIR results revealed the hydrogen bond formation between -SO 2 of PSU and -NH 2 of modified HNT. Based on the obtained results of contact angle measurements, the wettability of membranes were found to increase with the weight percentage of HNT in the presence of polyetheramine. At higher loading of filler the water uptake was found to be increasing due to the aggregation of nanotubes. Porosity values substantiate the results obtained for contact angle and water uptake measurements. Thermogravimetric results showed that the thermal stability of polysulfone (PSU)/HNT nanocomposite membranes decreased when compared to neat PSU due to the presence of aliphatic chain of polyetheramine.

The present work reports the effect of various organically functionalized polyhedral oligomeric silsesquioxane (POSS) particles on the gas transport properties (N 2 , O 2 , and CO 2 molecules) in poly(vinyl alcohol) (PVA) membranes. The incorporation of polyethylene glycol-POSS (PEG-POSS), octa-tetramethylammonium-POSS (Octa-TMA-POSS) and m-POSS (Octa-TMA-POSS molecule was modified using cetyltrimethyl ammonium bromide) led to the enhancement in CO 2 separation performance of PVA, among which, PEG-POSS exhibited highest CO 2 separation due to the dipole-quadrupolar interaction of CO 2 with ethylene oxide group in POSS. Octa-TMA-POSS and m-POSS reduced the O 2 and N 2 permeability of the PVA membrane due to the reduction in the number of permeating pathways as compared to pure PVA. Free volume of the membranes was evaluated by positron annihilation lifetime spectroscopic (PALS) and coincidence Doppler broadening measurements. PALS confirms the increase in polymer free volume in PVA/POSS system due to the presence of rigid and spherical POSS molecule, which could enter in the polymer chain and provide viable pathway for molecular transport. Maxwel-Wagner-Sillar and Higuchi models were applied for the theoretical prediction of permeability of the fabricated membranes.

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