Controlling structure and properties of polyamide nanofilms by varying amines diffusivity in organic phase

Abstract

Optimizing thickness and structure of polyamide (PA) selective layer of thin film composite (TFC) membranes is critical to improve the performance of the membranes. Here, we employed controlled interfacial polymerization to fabricate free-standing PA nanofilms on a thermal-reversible agarose hydrogel. Manipulation of the nanofilms structure was approached by tailoring the amine diffusivity in organic phase composed of benzene and n-hexane mixtures. An UV–vis method was firstly developed to in-situ monitor the diffusion process of amines from aqueous phase to organic phase. The structure and properties of the nanofilms were systematically analyzed by SEM, AFM and ATR-IR. Experimental results revealed that the diffusion kinetics of amines in organic phase is strongly depends on the content of benzene in the mixture solvent and therefore give rise to different thickness and structure of the nanofilms. The amines diffusion rate was accelerated at higher benzene content, causing a rougher surface, thicker thickness and smaller Young's modulus of the resultant nanofilms. Remarkably, with good fitting coefficient of R2 = 0.9936, the thickness of the nanofilms exhibits a linear relationship with their surface roughness.