cis,cis-1,3,5-Triaminocyclohexane (TAC) was synthesized and used to prepare composite nanofiltration (NF) membranes by interfacial polymerization with trimesoyl chloride (TMC). The surface elemental composition, morphology, and hydrophilicity of the prepared NF membranes were characterized. The separation performances were examined with various salts and polyethylene glycol (PEG400, PEG600) solutions. The effects of preparation conditions were also systematically studied. The NF membrane was negatively charged and exhibited a salt rejection in the order Na₂SO₄ (98.2%) > MgSO₄ (90.8%) > MgCl₂ (84.5%) > NaCl (54.6%). The water permeability was 1.56 L m⁻² h⁻¹ bar⁻¹, and the molecular weight cutoff was 600 Da. The TAC/TMC membrane exhibited some characteristics that were different from the ones made from common diamines such as m-phenylenediamine: (1) the surface was smoother, without a ridge-and-valley structure; (2) there were two kinds of crosslinking points in the polyamide chains; (3) the active layer was formed faster (only 5 seconds was required to reach a Na₂SO₄ rejection of 98%). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43511.

The poly(2-hydroxyethyl methacrylate) grafted titanium dioxide nanoparticles were synthesized and added to the substrate of flat-sheet thin film composite forward osmosis (TFC-FO) membranes. The hydrophilicity of substrate was improved, which was advantageous to enhance the water flux of TFC-FO membranes. The membranes containing a 3 wt % TiO₂-PHEMA in the substrate exhibited a finger-like structure combined with sponge-like structure, while those with lower or without TiO₂-PHEMA content showed fully finger-like structures. As for FO performance, the TFC-FO membranes with 3 wt % TiO₂-PHEMA content achieved the highest water flux of 42.8 LMH and 24.2 LMH against the DI water using 2M NaCl as the draw solution tested under the active layer against draw solution (AL-DS) mode and active layer against feed solution (AL-FS) mode, respectively. It was proven that the hydrophilic property of membrane substrates was a strong factor influencing the water flux in FO tests. Furthermore, the structural parameter was remarkably decreased with an increase of TiO₂-PHEMA content in membrane substrate, indicating the reducing of internal concentration polarization. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43719.

Polytetrafluoroethylene (PTFE) porous hollow-fiber membranes were prepared by a method involving billet preform, paste extrusion, stretching, and sintering. The influence of stretching parameters including stretching ratio, temperature, and speed was systematically investigated. The structure and properties of these membranes were characterized by field emission scanning electron microscopy, filtration performance, and mechanical strength test. The results indicate that the stretching ratio is the most significant influencing factor for the formation of various regions in the stress-strain curve. With increasing stretching ratio, the porosity, maximum pore size, and ethanol flux increase remarkably while bovine serum albumin rejection is reduced. These findings have the potential to facilitate PTFE membrane fabrication with finely tuned microporous structure for various application processes.

A simple two-step surface modification method of polyamide nanofiltration membrane, involving the activation of amide groups by formaldehyde and the subsequent cerium [Ce (IV)]-induced graft polymerization of zwitterionic 3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide) (MPDSAH) monomers, was employed to improve membrane antifouling property. The membranes before and after modification were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy, and atomic force microscopy. The changes in both surface chemical composition and morphology of membranes confirmed the successful graft polymerizations of MPDSAH onto polyamide nanofiltration membrane. The static water contact angle measurements showed that surface hydrophilicity of the modified membranes was significantly enhanced. As the MPDSAH concentration increased, the water flux of grafted membrane decreased gradually, while salt rejection increased slightly. The fouling experiments with bovine serum albumin solution demonstrated that modified membranes exhibited better resistance to protein fouling. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41144.

Metal organic frameworks (MOFs) are supposed to be ideal additives for mixed matrix membranes (MMMs). In this article one kind of MOFs, Cu₃(BTC)₂, is synthesized, then directly incorporated into a model polymer (Ultem®1000) using N,N-dimethylacetamide as solvent. Cu₃(BTC)₂ particles are uniformly dispersed and there are no interfacial defects in the prepared MMMs when Cu₃(BTC)₂ loading is not more than 35 wt %, seen in SEM images. Pure gas permeation tests show that gas permeability increases obviously with Cu₃(BTC)₂ loading increase, while ideal selectivities of CO₂/N₂ and CO₂/CH₄ are almost unchanged. For MMM with the best separation property, CO₂ permeability increases about 2.6 times and CO₂/N₂ selectivity remains almost unchanged. Results about gas diffusivity and solubility indicate that gas diffusivity and solubility make contribution to gas permeability increase at the same time but in different ways. Gas permeation properties of MMMs are well predicted by Maxwell or Bruggeman model. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40719.

In this article, three novel polymers based on poly(2,5-benzimidazole) (ABPBI) were synthesized by introducing propyl, isobutyl or n-butyl groups to its side chain through an alkyl substitution reaction. FTIR and ¹³C NMR were applied to confirm the formation of corresponding chemical groups. Their physical properties including crystallinity, thermal stability, mechanical strength, and micro-morphology were also characterized. Their solubility in common solvents were also tested to see if the modification will bring any improvement. Gas permeation properties of three derivative membranes prepared by a casting and solvent-evaporation method were tested with pure gases including H₂, N₂, O_2, CH₄, and CO₂. It has been revealed that gas with a smaller molecular size owned a larger permeability. This means gas permeation in all prepared membranes should be diffusivity selective. Among all three modified ABPBI membranes, isobutyl substitution modified ABPBI (IBABPBI) showed the best selectivity of H₂ over other gases such as N₂ (∼185) and CO₂ (∼6.3) with a comparable permeability (∼9.33 barrer) when tested at 35°C and 3.0 atm. Testing temperature increase facilitated gas permeation for all three membranes obviously; while in term of gas selectivity temperature increase showed diverse alteration because it brought variable impact on gas solubility of different gases. Even so, IBABPBI membrane still owned acceptable selectivity of H₂ over N₂ (∼118) and CO₂ (∼6.3) with an almost doubled permeability (∼17.5 barrer) when tested at 75°C and 3.0 atm. Additional tests showed that running at high pressure did not bring any obvious deterioration to gas separation performance of IBABPBI membrane. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40440.

Poly(acrylic acid) (PAA) was used as an additive to fabricate blended polysulfone (PSF) ultrafiltration (UF) membranes. Hexanediamine was used as a crosslinking agent to react with PAA and formed an active surface with amine group. Then, an end carboxyl group methoxy polyethylene glycol (MPEG) was grafted on the membrane surface via an amidation reaction. Water contact angle measurement indicated that the surface hydrophilicity of PSF/PAA-blended membranes and MPEG-modified membranes remarkably increased. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR) was used to confirm the existence of PAA in the blended membranes and the change of chemical composition. Membrane surface and cross-sectional morphologies were observed by scanning electron microscope. The flux of pure water increased slightly after modification, while the rejection to bovine serum albumin had no obvious change. The improvement of antifouling property for MPEG-modified membrane was accordant with the increase of PAA content in PSF/PAA-blended membranes. Protein UF experiments revealed that membrane fouling, especially irreversible membrane fouling, was remarkably reduced due to the incorporation of MPEG. The long-term protein UF experiment demonstrated the improvement of recycling property and the reliability of modification. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Chitosan hollow fiber membranes (CHFMs) were successfully fabricated by a phase inversion method. The CHFMs obtained by ethanol–hexane exchange drying displayed integrally skinned asymmetric morphologies by field-emission scanning electron microscope observation. The CHFMs could be used for the pervaporation separation of dimethyl carbonate (DMC)/methanol mixtures. Swelling properties of the polymer material were investigated, and the effects of feed composition and operating temperature on the pervaporation separation performance of the CHFMs were evaluated. The relationship of permeation flux and temperature was in agreement with the Arrhenius equation. It was demonstrated that the integrally skinned asymmetric CHFMs exhibited an effective method for the separation of DMC/methanol azeotropic mixtures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010