Zhang Gang,Huang Guang-shun,Wang Xiao-jun,Long Sheng-ru,Yang Jie
Two kinds of aromatic dibenzoyl chloride monomer containing thioether unit 4,4′-Bis(4-chloroformylphenylthio)benzophenone (BP-DC) and 4,4′-thiodibenzoyl chloride (T-DC) were synthesized with two steps, which was reacted with diamine monomer containing thioether and amide unit to prepare a new kind of polyamide containing high quantity thio-ether group. The intrinsic viscosity of the polyamides was 0.76–0.90 dl/g obtained with optimum synthesis conditions. The polymers were found to have good optical properties: the optical transmittance of the aromatic polyamide film at 450 nm is higher than 80%, meantime the high quantity thio-ether unit provided the polymer with a high refractive index ranging from 1.691 to 1.696 and low birefringence of 0.007–0.008. At the same time the polymers had excellent thermal performance with glass transition temperature (T g ) of 226 °C–278 °C, initial degradation temperature (T d ) of 427 °C–439 °C. They showed improved solubility in polar aprotic solvents.
A novel tri-acyl chloride monomer containing reductive thioether units (T-TDC) was prepared. It was conducted to partially replace trimesoyl chloride (TMC) and react with m-phenylenediamine (MPD) by interfacial polymerization to prepare a series of T-TDC/TMC/MPD copolymer thin-film-composite reverse-osmosis polyamide membranes. Through this routine, the reductive thioether units was introduced into the film molecular chain to protect amide bonds from being chlorinated by oxidizing during the membrane cleaning process. The enhanced chlorine resistance of these resultant membranes was revealed by FT-IR and XPS characterization: it could be found thioether was prior to amide oxidation, and its oxidation process can be divided into two steps (the thioether units was first converted to sulfoxide groups, and then further oxidized to sulfone groups). Through this routine, the active chlorine was consumed partially, then the amide bond was protected. The experiment result is consistent with the DFT theoretical calculation. The chlorine exposure concentration of the normalized flux and rejection decreased to 1 increased gradually with the addition of copolymerization ratio of T-TDC, especially for the sample 20%-TTDC-TFC, its chlorine exposure concentration was 3 and 4 times higher respectively than that of 0%-TTDC-TFC when its normalized flux and rejection at 1. In addition, it can be found that the polar sulfone and sulfoxide groups can form hydrogen bonds to prevent the membrane from degrading immediately. This method provides an effective way for improving the service life of RO film.
Gang Zhang,Shu-shan Yuan,Zhi-min Li,Sheng-ru Long,Jie Yang
Two kinds of high glass temperature poly(arylene ether sulfone)s containing thioether and biphenyl units (PASSs) have been developed. The polymers were prepared by a polycondensation reaction of 4,4′-bis(4-chlorophenylsulfone)biphenyl (BCPSB) and 4,4′-dimercaptodiphenyl sulfone (DMDPS) (or 4,4′-bis(4-mercaptophenylsulfone)biphenyl (BMPSB)). They showed good thermal properties such as a relatively high glass transition temperature of 263–282 °C and a 5% weight-loss temperature (T5%) of 441–445 °C. The water flux and retention rate of the resultant membranes were 0.61–2.48 L m−2 h−1 and 89.47–94.91%, respectively. Interestingly, we found that the corrosion resistance of the membranes had been largely improved with the oxidization treatment. They were even insoluble in NMP, DMSO, concentrated H2SO4, aqua regia and so on, while the polymers without oxidation were soluble or destroyed in above solvents. In addition, we found the water flux of the oxidized membrane was also improved but the retention rate only decreased a little.
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