Permeation across thin films can be retarded when the films contain aligned flakes of a less permeable material, but aligning these flakes can be difficult. In this research, we measure transport across less permeable flakes which self-assemble from a triblock copolymer. Elasticity is most influenced by an isoprene block but permeability is dominated by a lactide block. The permeability of this lamellar composite for helium, oxygen, and nitrogen is about 20% smaller than that expected from estimates based on resistances in series, implying good alignment. However, the permeability of the triblock is still around 10-7 cm2/s, so that better barriers will require different polymers.
Bibliographical noteFunding Information:
The authors are grateful to Professor Richard D. Noble for help in the polyisoprene permeability experiments. Nancy K. Lape held a National Science Foundation Graduate Research Fellowship. This work was largely supported by the Air Force Office of Scientific Research (grant F49620-01-1-0333). Other support came from the Department of Energy (grant DE-FG07-02ER63509), the Petroleum Research Fund (grant 39083-AC9), the David and Lucile Packard Foundation, and the National Science Foundation (grant CTS 0322882).
- Barrier films
- Triblock copolymer