Synthesis of Soluble Anion-Exchange Copolyimides and Nanofiltration Membrane Performances

Abstract

Novel soluble anion-exchange copolyimides were synthesized by the two-step method.Copolyimides had inherent viscosities between 0.35 and 0.42 dL/g. Ion exchange capacity (IEC) of the polyimides was 0.18-0.33 mequiv/g. These IEC values were well explained with the degree of substitution. All polyimides were soluble in polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide and showed amorphous patterns in X-ray diffraction studies. Soluble copolyimides synthesized in this study had glass transition temperatures between 220 and 265 °C. All unmodified polyimides were thermally stable below 560 °C. 10% weight loss temperatures were recorded in the range 560-600 °C in nitrogen. However, the 2-hydroxypropyl group of anion-exchange copolyimides was degraded at around 260 °C. The anion-exchange copolyimide nanofiltration membranes prepared from a cosolvent of diethylene glycol dimethyl ether and N-methyl-2-pyrrolidone showed better salt removal behavior than that of neutral copolyimides nanofiltration membranes.

High-Flux Nanofiltration Membranes Prepared by Adsorption of Multilayer Polyelectrolyte Membranes on Polymeric Supports

“…In both RO and NF, membranes consist of a selective skin layer on a highly permeable support because the minimal thickness of the skin layer allows a reasonable flux despite its dense nature. Typical procedures for creating such membrane structures include phase inversion and formation of composite membranes by interfacial polymerization, grafting, or film deposition on a preformed porous support. ,− Composite membranes are particularly attractive because they require only small amounts of the potentially expensive skin material.…”

Direct di- and triamination of polyfluoropyridines in anhydrous ammonia

“…Typical procedure for the reaction of polyhalopyridines with liquid NH 3 Polyhalopyridine was placed into a steel autoclave, the required amount of liquid NH 3 was added through a measuring funnel with back pressure and the autoclave was sealed. The reaction mixture was heated up to the given temperature upon stirring by rotation Entries 2,5,6,7,[9][10][11] Purity of the crude products in Entries 1, 3, 5, 7-11 is >95%, in Entries 2, 4, 6 is >90% ( 19 F NMR data). c Preparation of compounds 1b, 2b and 4b has been reported in [1].…”

“…The purpose of this study is the development of aminodefluorination of polychlorofluoropyridines in anhydrous ammonia as a selective method for preparation of novel halogenated pyridines containing two and (or) three amino groups, which are bioactive substance precursors [3,4] and building blocks in synthesis of condensation type polymers, in particular, hyperbranched polyimide membranes for gas separation applications [5] and anion-exchange nanofiltration membranes [6].…”

Synthesis and asymmetric nanofiltration membrane performance of heterogeneously sulfonated aromatic polyimides

“…We have synthesized ultrafiltration membranes with very high flux and 20 kDa molecular weight cut‐off (MWCO) using soluble PIs 11, 12. Moreover, anion‐exchange PIs have been prepared by introducing a pyridine ring into the polymer backbone and by modifying with epichlorohydrin 13…”