Nanostructured Interpenetrating Polymer Network (IPN) Precursor Ultrathin Films a Paralee Waenkaew, Prasad Taranekar, Guoqian Jiang, Cheng Yu Huang, Timothy Fulghum, Derek Patton, Lalithya Jayarathna, Sukon Phanichphant, Rigoberto C. Advincula* Introduction Ultrathin films of p-conjugated and conducting polymers have varied applications such as polymer light-emitting diodes (PLEDs), sensors, and field effect transistors (FETs). [1] The formation of morphologically smooth and electro- optically homogeneous ultrathin films of these polymers are essential for sandwich-type device applications. The Layer-by-Layer (LbL) alternate polyelectrolyte deposition approach has been investigated for polymer thin film formation primarily on substrates such as glass, indium tin oxide (ITO), quartz, silicon, Au-coated glass, etc. [2–5] These flat surfaces are amenable to a variety of surface-sensitive spectroscopic and microscopic analysis methods, where electrically conducting substrates such as ITO or Au also allows for electrochemical experimentation. The LbL layers themselves are held together by intermolecular forces of interaction such as electrostatic forces, hydrogen-bonding, charge-transfer interaction, and coordination bonding. [2–5] Thus, the films can be prepared in a nanostructured and sequential manner to provide functional group density and interaction in a very controlled and quantitative fashion. [4] In other words, LbL films not only results in a quantitative increase in thickness, but also in a quantitative amount of functional group increase from each layer. [5] Substituted polythiophenes [6] and polycarbazoles [7] are materials of great interest as charge-carrier transport materials and have been utilized in PLED and FET applications. It can be blended with light-emitting poly- Full Paper R. C. Advincula, P. Taranekar, G. Jiang, C. Y. Huang, T. Fulghum, D. Patton, L. Jayarathna Department of Chemistry, University of Houston, Houston, Texas 772004-5003, USA Fax: 713-743-1755; E-mail: radvincula@uh.edu R. C. Advincula, P. Taranekar, G. Jiang, C. Y. Huang, T. Fulghum, D. Patton, L. Jayarathna Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 772004-5003, USA P. Waenkaew, S. Phanichphant Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand a Supporting Information is available from the Wiley Online Library or from the author The formation of a nanostructured interpenetrating polymer network (IPN) via electropoly- merization is described. The electro-copolymerization of alternate layer-by-layer (LbL) self- assembled polyelectrolytes with thiophene and carbazole pendant monomers was demon- strated facilitating IPN formation of p-conjugated polymers or conjugated polymer network (CPN) films. UV–Vis spectroscopy, QCM, and ellipsometry confirmed linear nanostructured LbL film growth. Electrochemical crosslinking by cyclic voltammetry (CV) manifested highly regular peak current increases with successive cycles. A quantitative correlation of the LbL layer number with the cathodic charge and scan rate was observed. Electroche- mical impedance analysis confirmed CPN film formation and the change in capacitance behavior. Macromol. Chem. Phys. 2011, 212, 1039–1049 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com DOI: 10.1002/macp.201100002 1039