Osmotically driven membrane processes (ODMPs) such as forward osmosis (FO) and pressure retarded osmosis (PRO) are extensively investigated for utilization in a broad range of applications. In ODMPs, the operating conditions and membrane properties play more critical roles in mass transport and process performance than in pressure-driven membrane processes. Search of the literature reveals that ODMP membranes, especially newly developed ones, are tested under different temperatures, draw solution compositions and concentrations, flow rates, and pressures. In order to compare different membranes, it is important to develop standard protocols for testing of membranes for ODMPs. In this article we present a standard methodology for testing of ODMP membranes based on experience gained and operating conditions used in FO and PRO studies in recent years. A round-robin testing of two commercial membranes in seven independent laboratories revealed that water flux and membrane permeability coefficients were similar when participants performed the experiments and calculations using the same protocols. The thin film composite polyamide membrane exhibited higher water and salt permeability than the asymmetric cellulosebased membrane, but results with the high permeability thin-film composite membrane were more scattered. While salt rejection results in RO mode were relatively similar, salt permeability coefficients for both membranes in FO mode were more varied. Results suggest that high permeability ODMP membranes should be tested at lower hydraulic pressure in RO mode and that RO testing be conducted with the same membrane sample used for testing in FO mode. AbstractOsmotically driven membrane processes (ODMP) such as forward osmosis (FO) and pressure retarded osmosis (PRO) are extensively investigated for utilization in a broad range of applications. In ODMPs, the operating conditions and membrane properties play more critical roles in mass transport and process performance than in pressure-driven membrane processes.Search of the literature reveals that ODMP membranes, especially newly developed ones, are tested under different temperatures, draw solution compositions and concentrations, flowrates, and pressures. In order to compare different membranes, it is important to develop standard protocols for testing of membranes for ODMP. In this article we present a standard methodology for testing of ODMP membranes based on experience gained and operating conditions used in FO and PRO studies in recent years. A round-robin testing of two commercial membranes in seven independent laboratories revealed that water flux and membrane permeability coefficients were similar when participants performed the experiments and calculations using the same protocols. The thin film composite polyamide membrane exhibited higher water and salt permeability than the asymmetric cellulose-based membrane, but results with the high permeability thin-film composite membrane were more scattered. While salt rejection results in RO mode were...

Poly(acry1ic acid), poly(vinylsu1fonate) and poly(styrenesu1fonate) have been incorporated between the positively charged sheets of layered double hydroxides (LDHs) M1 -xA1,(OH)2f (M = Mg, Ca, Co) and Zn,-,M',(OH),+ (M'= Al, Cr) to form layered nanocomposites. The resulting nanocomposites contained the LDH sheet structures separated by 7.6-16.0 A, which is sufficient to accommodate polymer bilayers between the LDH sheets. Preparations were carried out in deaerated aqueous base by a template reaction, involving the formation and precipitation of nanocomposites from metal nitrate-salt precursors in the presence of the dissolved polymer. Structural and compositional details were provided by X-ray diffraction (XRD), FTIR spectroscopy, elemental analysis, differential scanning calorimetry (DSC) and thermogravimetry (TG). Scanning electron microscopy (SEM) indicates that the nanocomposition of LDHs with ionomers significantly alters the particle microstructure from that of the LDH carbonates derived from aqueous precipitation.The layered double hydroxides (LDHs), otherwise called 'anionic clays', and their intercalation compounds have received considerable attention in recent years in view of their potential technological importance as catalysts, ion exchangers, optical hosts, ceramic precursors and antacids.'-'' The LDH structure consists of brucite-like M(OH), sheets, where partial substitution of trivalent for divalent cations results in a positive sheet charge compensated by anions within interlayer galleries. LDHs are represented by the general formula [M111-xM111'x(OH)2]Xt *[(An"-),,,,, -nH,O] with representative examples M = Mg, Zn or Ca; M' = Al, Cr or Fe; An"-=C032-, C1-, OH-, NO3or SO4'-, and x taking values between 0.16 and 0.45.'' Thus, the mineral hydrotalcite can be abbreviated as Mg-A1-C03-LDH with x=O.25, and has the approximate formula unit Paper 5/04853B;

Partially aliphatic, high molecular weight polyimide copolymers were successfully synthesized using an ester−acid high-temperature solution imidization route by which noncrystalline, soluble materials were obtained. Variations in the aliphatic content produced a series of polyimides having different glass transition temperatures and processing characteristics. The ester−acid reaction pathway eliminated the need for anhydrous solvents and overcame the problem of salt formation commonly observed for nucleophilic, more basic, aliphatic amines prepared by the traditional poly(amic acid) synthesis route. Partially aliphatic polyimides containing either a cycloaliphatic diamine or aliphatic diamines with 6 or 12 methylene units were synthesized. Each copolymer was characterized by its molecular weight, glass transition temperature, thermal stability, coefficient of thermal expansion, refractive index, and dielectric constant. Structure−property relationships were established. The γ and β sub-T g viscoelastic relaxations were explored in order to understand their molecular origins.

High molecular weight, soluble, amorphous, partially aliphatic polyimides were successfully synthesized using an ester acid high‐temperature solution imidization route, which allows one to control desired glass‐transition (Tg) and processing temperatures. This method involves the prereaction of aromatic dianhydrides with ethanol and a tertiary amine catalyst to form ester acids, followed by the addition of diamines. Subsequent thermal reaction forms fully cyclized polyimides. This reaction pathway eliminates the need for anhydrous solvents and overcomes the problem of salt formation commonly observed for nucleophilic, more‐basic aliphatic amines when utilizing the traditional polyamic acid synthesis route. The molar ratio of aromatic‐to‐aliphatic diamines was varied to generate a series of copolyimides with the chosen dianhydride and tailor the physical properties for specific adhesive applications. This series of copolyimides was characterized by their molecular weight, Tg, thermal stability, coefficient of thermal expansion, refractive index, and dielectric constant. Structure‐property relationships were established. The γ and β sub‐Tg viscoelastic properties were researched to understand their molecular origins. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1503–1512, 2002

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