AVS 51st International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS+BI-WeA

Paper AS+BI-WeA6
Synthesis, Characterization and Modeling of Tethered Poly (N-isopropylacrylamide)

Wednesday, November 17, 2004, 3:40 pm, Room 210A

Session: Biological Applications of Surface Analysis
Presenter: S. Mendez, The University of New Mexico
Authors: S. Mendez, The University of New Mexico
G.P. Lopez, The University of New Mexico
H. Yim, Sandia National Laboratories
M.S. Kent, Sandia National Laboratories
J.G. Curro, Sandia National Laboratories
J.D. McCoy, New Mexico Tech
Correspondent: Click to Email
Tethered polymers are widely used to control surface properties such as adhesion and wettability. By making thin films out of polymers that are thermo-responsive, we can modulate surface properties with changes in temperature. Specifically, we use poly(N-isopropylacrylamide) (PNIPAM) since this exhibits lower critical solution temperature (LCST) behavior near 32 degrees Celsius in water. At temperatures below the LCST, the polymer is hydrated and swollen, whereas above the LCST, the polymer collapses, and when tethered, the surface becomes more hydrophobic. We report a method of growing PNIPAM from mixed self-assembled monoloyers (SAMs) using atom transfer radical polymerization. The use of two-component SAMs with varying composition permits for the control of polymer surface coverage, and the molecular weight can be controlled by the polymerization time. We have used both surface plasmon resonance and neutron reflectivity techniques to make direct measurements of the polymer brush structure at temperatures above and below the solution LCST. The effects of polymer surface coverage and molecular weight on the polymer structure were investigated. To model the temperature-induced structural changes of these brushes, we employed self-consistent field (SCF) theory using as input the chi parameter extracted from the experimental polymer solution phase diagram. The brush structure as predicted by SCF theory is in qualitative agreement with experimental data.