Polyelectrolyte Trilayer Combinations Using Spin-Assembly and Ionic Self-Assembly Malkiat S. Johal, † Joanna L. Casson, ‡ Peter A. Chiarelli, §,⊥ Ding-Guo Liu, ⊥ Jennifer A. Shaw, † Jeanne M. Robinson, ‡ and Hsing-Lin Wang* ,⊥ Division of Natural Sciences, New College of Florida, Sarasota, Florida 34243, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, Department of Chemistry, Pomona College, Claremont, California 91711, and Biosciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Received May 8, 2003. In Final Form: July 17, 2003 Water-soluble, cationic, anionic, and neutral polymers are used to form various repeat trilayer films via ionic self-assembly (ISA) and spin-assembly. These multilayer thin films assemble through physical entanglement, electrostatic, and/or H-bonding interactions. Spin assembly has the advantage over ISA in constructing stable multilayers when polyelectrolytes with like charge are assembled in adjacent layers. These multilayers do not desorb in water over a long period of time. In contrast to spin assembly, the ISA method deposits only a minimal amount of polyelectrolyte on top of a like-charged layer. The mechanical entanglement that is responsible for the deposition of like-charged species in spin assembly is probably lacking in ISA. The ability to construct repeated trilayers or multilayers composed of polycations, polyanions, and neutral polymers allows the fabrication of multilayer thin films with the desired interfacial structure and interactions. In this work, polyelectrolytes with NLO chromophores are used because the deposition can be easily monitored through UV-visible spectroscopy and they have potential utility for NLO thin film devices. The adsorption kinetics of an ISA trilayer was studied, and it was found that the adsorption reaches equilibrium in 15 s to 5 min, depending on the structure and specific interaction between layers. Introduction Multilayered films constructed from polyelectrolyte layers in a scheme of alternating charge have received much attention in recent years. The molecular scale order induced during the assembly of the polyelectrolyte films is important to applications in a growing number of areas, including nonlinear optics, 1,2 photonics, 3,4,5 drug delivery, 6-10 and biosensing. 11 These ordered films have been built by using vapor deposition, 12,13 Langmuir- Blodgett deposition, 14,15 and drop-casting. 16 However, each of these methods limits either the dimensions of the films or the materials available for use in the films. Two other methods with fewer restrictions on the deposition of charged polymers are ionic self-assembly 17-20 (ISA) and spin assembly. 21-23 The ISA method has been practiced extensively over the past decade, while polyelectrolyte spin assembly is a relatively new technique. Spin assembly was developed recently to construct thin films of alternating charge composition. As small amounts of dilute polyelectrolyte solution are dropped onto a spinning substrate, layers of repeatable thickness deposit on the surface. In addition to electrostatic forces, spin assembly induces deposition through polymer chain entanglement between the deposited layer and the film’s outer layer. 21,24 The amount of material deposited in spin assembly can be modulated through the adjustment of spin speed or solution concentration. 21,25 Recently, we have found that multiple deposition cycles of a single poly- electrolyte can result in the formation of a film whose thickness grows linearly with each deposition. 21 Such films * To whom correspondence should be addressed. † New College of Florida. ‡ Chemistry Division, Los Alamos National Laboratory. § Pomona College. ⊥ Biosciences Division, Los Alamos National Laboratory. (1) Casson, J. L.; McBranch, D. W.; Robinson, J. M.; Wang, H. L.; Roberts, J. B.; Chiarelli, P. A.; Johal, M. S. J. Phys. Chem. B 2000, 104, 11996. (2) Heflin, J. R.; Liu, Y.; Figura, C.; Marciu, D.; Claus, R. O. Proc. SPIE 1997, 3147, 10. (3) Kajzar, F.; Swalen, J. D., Eds. 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