, , Adrienne K. Blevins, Masoud Aghajani, , Yifu Ding
Interfacially polymerized polyamide (PA) layers dictate the permselective performance of thin film composite (TFC) membranes. Extensive effort has been focused on understanding and ultimately controlling the structure and morphology of the PA layers on micro- and macro-porous supports. In this study, we demonstrated that controlled growth of PA layers could be achieved at the oil/water interface presented at the surface of hydrogels, where the PA layer was formed through the reaction of trimesoyl chloride (TMC) with 1,3-phenylenediamine (MPD) or piperazine (PIP). In both cases, diffusion-limited, continuous growth of the PA layers was observed on a homogenous hydrogel (PHEMA hydrogel) and a heterogeneous hydrogel (PAAm hydrogel), where both thickness and roughness of the PA layers increased with reaction time. We observed a key morphological difference between the two monomer systems in the gel-liquid interfacial polymerization (GLIP) process: TMC/MPD produced a ridge-and-valley surface morphology whereas TMC/PIP produced nodule/granular structures on the surface of the gels. Compared with PHEMA hydrogels, PAAm hydrogels produced thicker and more porous PA layers that could be easily separated from the hydrogels. The chemical, mechanical and transport properties of select PA layers prepared using the GLIP process were systematically characterized. As reaction substrates, PHEMA and PAAm hydrogels possess pore size below and above conventional porous support (i.e. polysulfone) used in TFC membranes, correspondingly, which could shed more light on the complex growth mechanism of PA barrier layers.
Macromolecular Chemistry and Physics
interfacial polymerization, hydrogel, polyamide, barrier layer, thin film composite, membranes