Synthesis and characterization of a tertiary amine polymer series from surface-grafted poly(tert-butyl acrylate) via diamine reactions

A sequence of reaction steps was used to graft poly(tert-butyl acrylate) (PtBA) to silicon (Si) wafers and to modify the pendant groups of the tethered PtBA to create chemically tailored surface modifying layers. The Si wafers were first prepared for grafting by the deposition of a self-assembled monolayer (SAM) of N-aminopropyldimethylethoxysilane. The terminal primary amine groups on the SAM provided sites for reaction with carboxy-terminated PtBA. The choice of PtBA as the tethered polymer was due to the ability to substitute the tert-butyl ester groups with other functionalities. In this study, the tert-butyl esters were replaced with various diamines to create a series of polymers with tertiary amine pendant groups. The reactions and surface properties were monitored with external reflectance (ER) and transmission FTIR spectroscopies, ellipsometry, X-ray photoelectron spectroscopy (XPS), and static water contact angle goniometry. Hydrolysis and novel diamine conversion reactions were successfully performed on both neat PtBA homopolymer and end-grafted PtBA (Si-g-PtBA). Changes in static water contact angle confirmed the deposition of the N-aminopropyldimethylethoxysilane SAM and grafting of the end-functionalized PtBA. Reactions of the surface-grafted PtBA with ethylenediamine and dimethylethylenediamine showed the highest conversion yields.