Paper TF-MoA1
Inorganic/Organic Interface Structure on ALD Modified Polymer Fibers

Monday, October 18, 2010, 2:00 pm, Room Pecos

Inorganic thin film growth by atomic layer deposition (ALD) on polymer fibers is shown to be significantly affected by the process conditions and materials. Transmission electron microscopy in combination with in situ quartz crystal microbalance analysis shows a strong influence on processing temperature and polymer backbone structure that can lead to varying types of interface modifications between the inorganic and organic polymer. Deposition on cellulose cotton shows conformal surface growth due to the presence of hydroxyl sites, resulting in conformal thin film growth. Polypropylene, which has no reactive sites, does allow for vapor phase diffusion of the ALD precursors, resulting in subsurface growth. The subsurface growth on polypropylene is significantly impeded at lower processing temperatures. The strong temperature dependence of interface modification is ascribed to a relatively large increase in bulk species diffusivity that occurs upon the temperature-driven free volume expansion of the polymer. The interface structure can significantly modify the physical properties of resulting inorganic-coated polymer fibers. For example, we measured the electrical properties of ALD ZnO coatings on polypropylene fiber mesh, and we find that modifying the polymer inorganic interface using low temperature ALD Al₂O₃ before ZnO ALD produces fibers with conductance that is increased by a factor >100x as compared to ZnO coated polypropylene without the interface pretreatment. For a range of polymer materials studied, we find distinct trends between polymer structure, ALD process conditions and resulting interface structure, and these results will be presented and discussed.