Surface fluctuations of polymer brushes probed by diffuse x-ray scattering
Abstract
The effect of tethering on the surface fluctuations of polymer brushes has been probed using diffuse X-ray scattering. Long wavelength fluctuations are suppressed more strongly on the surface of a polystyrene (PS) brush than on the surface of a film of untethered PS chains of comparable thickness, so that even in films of thickness, d, such that d/Rg > 5 clear evidence of the suppression of fluctuations can still be seen in the experimentally available range of qx. Fluctuations are suppressed for qx less than a lower wavevector cutoff, ql,c, which changes with film thickness, though much more weakly than for films of free chains. For values of d/Rg < 4, where Rg is the unperturbed radius of gyration of a comparable free chain, ql,c drops as d increases. For d/Rg > 4 ql,c begins to increase with d, indicative of a transition to a true brush state in which stretching of the chains makes longer wavelength fluctuations at the surface unfavorable. Measurements with poly(n-butylacrylate) brushes having Tg substantially below room temperature confirm these trends.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARV31006K