Investigation of fine-structure of polyamide thin-film composite membrane under swelling effect by positron annihilation lifetime spectroscopy and molecular dynamics simulation

Positron annihilation lifetime spectroscopy (PALS) and molecular dynamics (MD) simulation analyses were adopted for an in-depth understanding at the molecular scale of the variation in the fine-structure of polyamide active layers of thin-film composite (TFC) membranes in the dry or the wet condition. The interfacial polymerization reaction between 1,3-diaminopropane (DAPE) and succinyl chloride (SCC) or between DAPE and trans-3,6-endomethylene-1,2,3,6-tetrahydrophthaloyl chloride (tNBDC) on the surface of a modified polyacrylonitrile (mPAN) membrane was carried out to fabricate DAPE-SCC/mPAN or DAPE-tNBDC/mPAN TFC membranes. PALS and MD simulation experimental results were highly consistent with each other.