Synthesis and characterization of multifunctional copolyimide incorporating triarylamine and NLO chromophore in backbone

Presents the synthesis of Copolyimide containing triarylamine and NLO chromophore in backbone by azo coupling of 4 nitrobenzenediazonium tetrafloroborate to copoly(amic acid) in organic solvent and characterized by IR and UV Vis spectra, which had high glass transition temperatrue and big second order nonlinear optical coefficient  x (2) .

Asymmetric copolyimide membranes fabricated by nonsolvent-induced phase separation for He/CH_(4) and He/N_(2) separation

Membrane gas separation is considered an energy-saving technique to extract He from natural gas due to no phase change and room temperature operation.However,the membrane performance was strongly limited by the trade-off between permeance and selectivity.Herein,novel 4,4′-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)-2,2′-bis(3-amino-4-hydroxyphenyl)hexafluoropropane(APAF)-5-amino-2-(4-aminobenzene)benzimidazole(BIA)asymmetric membranes with a thickness of 300 nm were successfully prepared by the non-solvent induced phase separation method.The membrane performance was modulated by regulating dope solution compositions(e.g.,tetrahydrofuran and polymer concentration).The ideal He/CH_(4) selectivity was 124 and the optimized He permeance reached 87 GPU,beyond the current upper bound.He/CH_(4) selectivity was 75 and He permeance was 73 GPU for the binary mixture feed containing 0.2 mol%He.The membrane showed good resistance to CO_(2) and C_(2)H_(6),which are the typical impurities in natural gas.The 6FDA-APAF-BIA membranes have good stability(>160 h),which can provide great potential in He extraction from natural gas.

Synthesis and Characterization of Sulfonated Polyimides Containing Trifluoromethyl Groups as Proton Exchange Membranes

A novel sulfonated diamine, 4,4＇-bis（4-amino-3-trifluoromethylphenoxy） biphenyl 3,3＇-disulfonic acid （F-BAPBDS）, was successfully synthesized by nucleophilic aromatic substitution of 4,4＇-dihydroxybiphenyl with 2-chloro-5-nitrobenzotrifluoride, followed by reduction and sulfonation. A series of sulfonated polyimides of high molecular weight （SPI-x, x represents the molar percentage of the sulfonated monomer） were prepared hy copoty- merization of 1,4,5,8-naphathlenetetracarhoxylic dianhydride （NTDA） with F-BAPBDS and nonsulfonated diamine Flexible and tough membranes of high mechanical strength were obtained by solution casting and the electrolyte properties of the polymers were intensively investigated. The copolyrner membranes exhibited excellent oxidative stability due to the introducing of the CF3 groups. The SPI membranes displayed desirable proton conductivity （0.52× 10^-1-0.97 × 10^-1 S.cm^-1） and low methanol permeability （less than 2.8×10^-7 cm2.s i）. The highest proton conductivity （1.89× 10^-1 S·cm^-1） was obtained for the SPI-90 membrane at 80℃, with an IEC of 2.12 mequiv/g. This value is higher than that of Nafion 117 （1.7 × 10^-1 S·cm^-1）. Furthermore, the hydrolytic stability of the obtained SPIs is better than the BDSA and ODADS based SPIs due to the hydrophobic CF3 groups which protect the imide ring from being attacked by water molecules, in spite of its strong electron-withdrawing behaviors.