AVS 52nd International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS+BI-TuM

Invited Paper AS+BI-TuM1
Synthesis and Characterization of Mixed Polymer Brush Films

Tuesday, November 1, 2005, 8:20 am, Room 206

Session: Surface Characterization of Organic and Biological Systems
Presenter: D.J. Dyer, Southern Illinois University
Authors: D.J. Dyer, Southern Illinois University
J. Feng, Southern Illinois University
R.T. Haasch, University of Illinois-Urbana Champaign
V.-N. Wong, Southern Illinois University
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Chameleons respond to their environment by changing color so that they take on the characteristics of their surroundings. Smart organic films may also respond to environmental perturbations and adapt to their environment. In particular, polymer brush films have shown remarkable switching properties, especially when the films are within the ultra-thin region from 1-100 nm. These so-called polymer brushes are composed of polymers that are tethered to an inorganic substrate and may stretch out away from that substrate. Polymer brushes that are composed of more than one component are referred to as mixed, or binary brushes. Typically, the two different polymers are randomly distributed on the surface and exhibit phase-separation and interfacial morphology that is distinct from that of spin-cast blends of the same composition. This occurs because the brush chains are confined to the substrate and are forced into contact with nearby incompatible chains, whereas in a blend the polymer chains can more easily rearrange during annealing. Here we discuss the synthesis and characterization of mixed polymer brushes on silicon and gold substrates. One of the major challenges we face is the quantification of the bulk film composition as compared to the air/liquid interface. For this we use a tandem XPS/RAIRS strategy. Our paper will place an emphasis on amphiphilic systems where one polymer is hydrophilic and the other is hydrophobic. These results demonstrate that a mixed brush of polystyrene (PS) and polyacrylamide (PAAM) may switch from hydrophobic to hydrophilic in one minute at room temperature. Such rapid switching is highly unusual for mixed brushes.