Effect of trifunctional planar monomer on the structure and properties of polyamide membranes

Pararosaniline (PAR) was successfully introduced into polyamide network aiming to optimize the structure and properties of polyamide nanofilms. The synthesis of the free-standing polyamide nanofilms was performed on agarose hydrogel supports by interfacial polymerization using 1,3-phenylenediamine (MPD) and PAR as aqueous-phase monomers. The structure and properties of the resultant polyamide nanofilms were systematically analyzed. Atomic force microscopy analysis indicated that PAR can greatly improve the mechanical strength of the polyamide nanofilms. Young's modulus of the polyamide (PA) nanofilms increases about 1.5 times with the introduction of PAR units in the polyamide network. Strikingly, scratching resistance of the composite membranes was obviously improved through incorporating the polyamide nanofilms containing PAR units. The loss in salt rejection of the composite membranes after scratching is approximately three times lower than that of the membranes without using PAR. Both of the nanofilm thickness and contact angle increase with the increase of PAR, while the effect of PAR on the surface roughness behaves opposite. Using porous polysulfone (PS) membranes as supports, composite membranes comprising the polyamide nanofilms prepared from 0.015 wt% PAR shows higher water flux and salt rejection as compared to that of the nanofilms without PAR.