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01/04/2004

Topology of Grafted Polymers

Research on the topology of tethered polymers focuses on developing a fundamental understanding of the relationship between the conditions at which terminally anchored polymer chains are formed (e.g., reaction conditions) and the resulting surface (e.g., aerial uniformity, chain density, structure of surface features and surface elevation). 

Information on the structure of grafted polymer surfaces is essential to optimizing surfaces of modified membranes, chemical sensors and in forming low friction surfaces. Atomic force microscopy is the main tool used to image polymer and silylated ceramic surfaces. Such surfaces are also characterized by FTIR, TGA and contact angle measurements.

In the present work, the topology of graft polymerized surfaces is being studied using model surfaces. Grafting onto the surface of flat oxidized silicon wafers and is accomplished using a two-step modification procedure in which the first step involves silylation while the second step consists of a surface polymerization process.  

Tapping mode atomic force microscopy (AFM) was performed to examine the topology of unmodified, silylated, and graft polymerized wafers. 

AFM images for the silylated layer suggest the formation of “island” structures. Grafted chains in the surface polymer layer are typically found to form similar structures depending on the conditions of the graft reaction. The distribution of height of polymer grafted features is consistent with the chain size distribution expected for free radical graft polymerization and also agrees with polymer graft yields obtained by experiments on inorganic oxide particles.