Dependence of Performance of Poly(Sulfone‐co‐Amide) Membranes on Compositional Variation of Casting Solution and Coagulation Media—Development of Reverse Osmosis and Nano Filtration Membranes

Influence of Differential Distribution of Piperazine Conformers in Copolyamides on the Formation and Ion Separation Behaviors of Charged Nanofiltration Membranes

“…The structural aspects and the related effects are illustrated schematically in Scheme 1, representing the structural contributions of PIP and DABSA in response to their interaction with acyl chloride and depicted through TPC monomer as happened in n-CPA. The formation of secondary amide groups, as revealed by the FTIR spectra, is confirmed here by the lowintensity 13 C signals for carbonyl carbon, appearing at δ of 179.2 and 178.5 ppm for n-CPA and c-CPA, respectively. 42 Strong 13 C signals appearing at δ of 168.6 and 172.1 ppm are attributed to the carbonyl carbon of tertiary amide groups in n-CPA and c-CPA, respectively.…”

“…The formation of secondary amide groups, as revealed by the FTIR spectra, is confirmed here by the lowintensity 13 C signals for carbonyl carbon, appearing at δ of 179.2 and 178.5 ppm for n-CPA and c-CPA, respectively. 42 Strong 13 C signals appearing at δ of 168.6 and 172.1 ppm are attributed to the carbonyl carbon of tertiary amide groups in n-CPA and c-CPA, respectively. 41 It is observed that the carbonyl carbon of the secondary amide shifts downfield compared with that of tertiary amide.…”

“…42 Furthermore, intramolecular H-bondings between −NH groups and the nonbonding electrons of the carbonyl oxygen residing in close proximity make the carbonyl carbon even more electron deficient and hence get further deshielded. These two effects together result in a downfield shift of the 13 C signals of secondary amide groups in both n-CPA and c-CPA, as presented in peak "d" of Figure 1a,b, respectively. The signals for methine carbons of the two aromatic benzene rings contributed to the copolyamide structures appear with moderate intensities between the δ values of 120−140 ppm.…”

“…The solid-state 13 C CP/MAS NMR spectra of the representative pure polymers, that is, n-CPA and c-CPA, are presented in panels a and b, respectively, of Figure 1. The structural aspects and the related effects are illustrated schematically in Scheme 1, representing the structural contributions of PIP and DABSA in response to their interaction with acyl chloride and depicted through TPC monomer as happened in n-CPA.…”

“…For evaluation of spectral information, 100 scans were taken at a resolution of 2 cm −1 , recording the spectra in transmittance mode over a wavenumber range of 600−4000 cm −1 at ambient condition. Solid-state 13 C NMR spectroscopy of the pure polymers was performed at ambient temperature using a BRUKER AVANCE 500 MHz FT-NMR spectrometer. The NMR spectra were obtained using the technique of cross-polarization (CP) with magic angle spinning (MAS) and dipolar decoupling.…”