Related Experiment Videos
Control of moisture at buried polymer/alumina interfaces through substrate surface modification
Bryan D Vogt1, Vivek M Prabhu, Christopher L Soles
1Polymers Division and Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA. bryan.vogt@nist.gov
Langmuir : the ACS Journal of Surfaces and Colloids
|March 9, 2005
Summary
Water absorption in poly(4-tert-butoxycarbonyloxystyrene) (PBOCSt) films causes swelling, especially in ultrathin layers. Surface treatments on aluminum oxide (Al2O3) substrates can reduce this moisture accumulation and subsequent swelling.
Area of Science:
- Materials Science
- Polymer Science
- Surface Chemistry
Background:
- Polymer films on substrates are susceptible to moisture absorption.
- Interfacial water accumulation can significantly impact polymer film properties, such as swelling.
- Understanding moisture behavior is crucial for applications involving thin polymer films.
Purpose of the Study:
- To quantify moisture absorption and swelling in poly(4-tert-butoxycarbonyloxystyrene) (PBOCSt) films.
- To investigate the effect of the Al(2)O(3) substrate and its surface treatments on interfacial water accumulation.
- To develop a model describing thickness-dependent swelling.
Main Methods:
- Neutron and X-ray reflectivity were employed to measure moisture absorption.
- Ultrathin PBOCSt films on Al(2)O(3) coated silicon wafers were studied.
- Four different Al(2)O(3) surface treatments were compared: bare, tert-butylphosphonic acid, phenylphosphonic acid, and n-octyltrichlorosilane.
Main Results:
- Ultrathin PBOCSt films exhibit thickness-dependent swelling due to interfacial water accumulation.
- Films on Al(2)O(3) show less swelling than those on SiO(x) for thicknesses below 20 nm, attributed to reduced interfacial moisture.
- Phenyl and octyl surface treatments effectively decrease water accumulation at the Al(2)O(3)/PBOCSt interface.
- Tert-butyl treatment showed no significant reduction in interfacial water concentration.
Conclusions:
- A quantitative model explains the observed swelling behavior based on interfacial water and bulk swelling.
- Surface modification of Al(2)O(3) substrates can control moisture absorption at the polymer-interface.
- Strategic surface treatments offer a method to mitigate unwanted swelling in polymer films.