Counterion, pH, and Temperature Effects on Poly(dimethylaminoethyl methacrylate) Thin Films

In this work, covalently attached stimuli responsive polymer (SRP) brushes were polymerized from self-assembled monolayer modified silicon wafers and gold-coated silicon wafers using AGET-ATRP (Activators Generated by Electron Transfer Atom Transfer Radical Polymerization). Presented is the synthesis and systematic characterization of the stimuli response for the SRP polymer brush, poly(dimethylaminoethyl methacrylate) (PDMAEMA). PDMAEMA brushes were characterized using ellipsometry—an analytical technique that uses changes in the polarization of light to determine refractive index and layer height changes—that provide information on the structural changes of these SRP brushes in response to different ambient conditions. In situ spectroscopic ellipsometry and AFM studies were performed using a liquid cell allowing for the collection of real-time data as a function of pH, salt type (NaCl, NaI, NaBr, and NaSO₄), salt concentration, and temperature. The stimuli response behaviors are complex when one or more stimuli are applied simultaneously.  Results for PDMAEMA give insight into the behaviors of amine polybases in general.  These results can be expanded to other polymer brushes, allowing for the development of structure-property relationships to guide the development of SRP applications—such as drug delivery, heavy metal removal, biofilm resistance, membrane separations, and lubricity/viscosity modification.