| AVS 54th International Symposium | |
| Biomaterial Interfaces | Thursday Sessions |
| Session BI-ThP |
| Session: | Biomaterial Interfaces Poster Session |
| Presenter: | S. Mendez, University of New Mexico |
| Authors: | S. Mendez, University of New Mexico B. Andrzejeweski, University of New Mexico D.H. Keller, University of New Mexico H.E. Canavan, University of New Mexico G.P. Lopez, University of New Mexico J.G. Curro, University of New Mexico J.D. McCoy, New Mexico Tech |
| Correspondent: | Click to Email |
Tethered polymers are widely used to control surface properties such as wettability or cell adhesion. 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-isopropyl acrylamide) (PNIPAM) since this exhibits lower critical solution temperature (LCST) behavior near 32°C 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. In the past we reported on a method of synthesizing thin films of terminally anchored PNIPAM from self-assembled monoloyers using atom transfer radical polymerization.1 We used neutron reflectivity techniques to measure the polymer brush structure at temperatures above and below the solution LCST. To model the temperature-induced structural changes of these brushes, we employed self-consistent field (SCF) theory using as input the Flory-Huggins chi parameter extracted from the experimental polymer solution phase diagram.2 As a continuation of that work, we used the SCF theory to calculate the force between the PNIPAM brush and a test wall as a function of wall separation distance, i.e., we generated force-distance profiles. The parameters that we varied were temperature, polymer surface coverage and molecular weight, and the interaction between the PNIPAM and the test wall. AFM techniques were employed to obtain force-distance profiles of PNIPAM samples. We found that the force-distance profiles predicted by the theory were in qualitative agreement with those from experiment. Our ultimate goal is to employ theoretical predictions to guide future efforts to optimize tethered PNIPAM for cell attachment/detachment applications.
1 Yim et al, Macromolecules 2006, 39, 3420.
2 Mendez et al, Macromolecules 2005, 38, 174.