Molecular Layer Deposition of Polymers
ALD is defined by two sequential, self-limiting surface reactions. ALD is useful for atomic layer controlled growth of inorganic and metallic films such as Al2O3 and W. Similar methods can be applied to grow polymer films. In this case, the reactants contain "molecular fragments" that are incorporated in the growing film. As a result, this extension of ALD is known as molecular layer deposition (MLD).
Two homobifunctional reactants can be employed for the MLD growth of organic polymers such as polyamides [1,2]. In addition, hybrid organic-inorganic polymers can be grown by using inorganic ALD and organic MLD precursors. We recently demonstrated the growth of aluminum alkoxide (alucone) MLD polymers using trimethylaluminum (TMA) and ethylene glycol (EG) as the reactants [3]. Similar zinc alkoxide (zincone) MLD polymers can be grown using diethylzine and EG as the reactants [4].
A large number of hybrid organic-inorganic polymers can also be grown using various heterobifunctional and ring-opening reactants in ternary ABC reaction sequences [5]. One example shown in the accompanying figure is an ABC alucone grown using TMA, ethanolamine and maleic anhydride. These reactants avoid the double reactions that can occur with homobifunctional reactants.
We are currently exploring a variety of different strategies for the MLD of organic and hybrid organic-inorganic polymers. The goal is to develop very robust MLD chemistries that can deposit polymers films with flexibility and tunable mechanical properties. These polymer MLD films are also be used together with inorganic ALD films to fabricate nanolaminate films with adjustable properties for flexible coatings.
1. Y. Du and S.M. George, "Molecular Layer Deposition of Nylon 66 Films Examined Using In Situ FTIR Spectroscopy" J. Phys. Chem. C 111, 8509 (2007).
2. N.M. Adamczyk, A.A. Dameron and S.M. George, "Molecular Layer Deposition of Poly(p-phenylene terephthalamide) Films Using Terephthaloyl Chloride and p-Phenylenediamine", Langmuir 24, 2081 (2008).
3. A.A. Dameron, D. Seghete, B.B. Burton, S.D. Davidson, A.S. Cavanagh, J.A. Bertrand and S.M. George, "Molecular Layer Deposition of Alucone Polymer Films Using Trimethylaluminum and Ethylene Glycol", Chem. Mater. 20, 3315 (2008).
4. B. Yoon, J.L. O'Patchen, D. Seghete, A.S. Cavanagh and S.M. George, "Molecular Layer Deposition of Hybrid Organic-Inorganic Polymer Films Using Diethylzinc and Ethylene Glycol", Chemical Vapor Deposition (In Press).
5. S.M. George, B. Yoon and A.A. Dameron, "Surface Chemistry for Molecular Layer Deposition of Polymers", Acc. Chem. Res. 42, 498 (2009).
