Vijitha Mohan and Keisha Walters. Dave C. Swalm School of Chemical Engineering, Mississippi State University, 330 Swalm Chemical Engineering Building, P.O. Box 9595, MS State, MS 39762
A rapidly expanding area of materials research involves tethered, surface-modifying layers that respond to external stimuli such as pH. These materials undergo significant structural/morphological changes due to the application of appropriate external stimuli. Although still considered novel materials, pH-responsive polymers are currently being used in a wide range of applications from drug delivery to microfluidic control. We are synthesizing and characterizing tethered (surface bound) pH-responsive polymer layers and have previously looked at the pH response of polyacids. Amine-terminated silane self-assembled monolayers (SAMs) were deposited onto silicon wafers and the amine reaction sites were used to graft end-functionalized poly(tert-butyl acrylate) (PtBuA). The pendant tert-butyl ester groups were then converted to amide/amine functionalities. A series of diamines were used to investigate the effect of pendant group chemistry on the pH-responsiveness of the grafted polyamine layer. Use of silicon as a substrate allowed for investigation of layer thickness change in situ using ellipsometry. The samples were also characterized using FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), and static contact angle goniometry. Synthesis, chemical characterization, and in situ response behavior of a series of tertiary amine polybases will be presented.