X-ray reflectivity on perfluoropolyether polymer molecules on amorphous carbon
- 15 March 1990
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 92 (6), 3781-3793
- https://doi.org/10.1063/1.457836
Abstract
The mass density profile from thin (∼25 Å) layers of polymer molecules adsorbed on amorphous carbon thin films is determined from measurements of the specular reflectivity of x rays. Important information on the conformation of the polymer molecules is obtained from the density profile (average density as a function of position above the surface). The polymer is a perfluoropolyether (PFPE) with piperonyl end groups and has a molecular weight of 2000–3000 Daltons. Three samples are measured: a nonbonded sample with an approximately 25 Å layer applied by dipping, a bonded sample with the layer applied by dipping but followed by a process to attach the molecule to the carbon, and a cleaned sample which is the nonbonded sample after the polymer had been removed. The density profile of the nonbonded polymer shows that the density within 10 Å of the carbon surface is ∼1.6 gm/cc, which is smaller than the density in the region between 10 and 25 Å (∼1.8 gm/cc). This indicates that the less dense piperonyl end groups are preferentially adsorbed near the carbon surface, which provides a possible explanation of the observation that the addition of the piperonyl end group to PFPE improves adhesion of the polymer to surfaces. The bulk-like density in the region between 10 and 25 Å and the compactness of the layer suggest that the preponderance of molecules have both end groups preferentially adsorbed; consequently, the PFPE chains remain close to the surface. The data from the bonded and nonbonded polymer layers are essentially the same, which indicates the molecular conformation is not strongly affected by the bonding treatment.Keywords
This publication has 22 references indexed in Scilit:
- Measurements of carbon thin films using x-ray reflectivityJournal of Applied Physics, 1989
- Structure of aqueous decyltrimethylammonium bromide solutions at the air water interface studied by the specular reflection of neutronsThe Journal of Physical Chemistry, 1989
- Capillary waves on the surface of simple liquids measured by x-ray reflectivityPhysical Review A, 1988
- Specular reflectivity of neutrons by thin polymer filmsMacromolecules, 1988
- X-ray and neutron reflectivity from spread monolayersThin Solid Films, 1988
- Multilayer roughness evaluated by X-ray reflectivityJournal of Applied Crystallography, 1988
- Characterization of diamondlike carbon films and their application as overcoats on thin-film media for magnetic recordingJournal of Vacuum Science & Technology A, 1987
- Model-Independent Structure Determination of the InSb(111)2×2 Surface with Use of Synchrotron X-Ray DiffractionPhysical Review Letters, 1985
- Determination of the density profile in the liquid–vapor interface near the triple pointThe Journal of Chemical Physics, 1978
- Surface Studies of Solids by Total Reflection of X-RaysPhysical Review B, 1954