Liquid-liquid interfacial polymerization (ll-IP) is conventionally used for manufacturing bulk polymers like nylon, as well as forming barrier layers for reverse osmosis membranes. In this work, we explore the use of gel-liquid infiltration polymerization to modify the surface of polymer networks. We demonstrate this method with polydimethylsiloxane (PDMS) as a model network and a well-known ll-IP monomer system: trimesoylchloride (TMC) and 1, 3- phenylenediamine (MPD). The process involves two simple steps: swelling of PDMS within a TMC/hexane solution, and subsequently reacting the swollen PDMS gel within an aqueous MPD solution. Due to the asymmetry in solubility, MPD diffuses into the PDMS gel and polymerizes with the TMC, forming an aromatic polyamide network at the PDMS surface. The polyamide-PDMS skin layer wrinkles into a series of surface features upon drying of the PDMS. The characteristics of the skin layer can be controlled by adjusting a range of processing parameters: PDMS crosslinking density and degree of swelling, as well as the infiltration polymerization conditions including MPD/TMC concentrations and reaction times. Compared with other surface modification methods, the skin layer formed use this method is a hybrid material with a potential depth concentration gradient, which allows for the formation of crack-free wrinkles with very large true surface area and amplitude, on both flat and topographically patterned surfaces.
Citation: ACS Applied Materials and Interfaces
Pub Type: Journals
interfacial polymerization, xps, afm, membrane