Molecular self-assembly is rapidly becoming a method to optimize performance in materials and devices by directing the formation of supramolecular structure. In the area of conjugated (or conducting) organic polymers, self-assembly has been used to build layer by layer1 polymer heterostructures2 and polydiacetylene self-assembled monolayers (SAMs),3 to generate polymers with high electrical conductivities,4a and to create waterbased polymer chemoselective sensors4b and polymers that exhibit highly sensitive, solvent-induced chiral optical effects.5 The Langmuir-Blodgett technique6,7 has been successfully used to prepare thin films of functional molecular surfactants8 as well as nonamphiphilic polymers decorated with alkyl chains.9 Here we present amphiphilic, regioregular polythiophenes that can be processed by the Langmuir-Blodgett technique into nanoscale structures. These amphiphilic polythiophenes selfassemble into π-stacked conjugated chains that form a very stable cell-membrane-like monomolecular layer with a local structure that is optimized for high electrical conductivity. These wellordered polymer monolayers can be transferred to solid supports, forming highly conductive ultrathin films. They can also be micropatterned by chemical means as demonstrated by the fabrication of an electronic microchip replica. The fabrication of the chip structure, producing a pattern of 2.5 nm thick and 1000 nm wide conjugated polymer “wires”, is performed at ambient conditions by purely chemical self-assembly methods.10 The key to the above results lies with the design and synthesis of new regioregular amphiphilic polythiophene copolymers where perfectly alternating hydrophobic and hydrophilic side groups form a rigid rod polymer that has a hydrophobic side and a hydrophilic side. Other studies on the formation and properties of LB films of conducting polymers have started with polymers containing many structural defects (or the polymer was not amphiphilic), rendering the polymer unable to form highly ordered systems. Five new, amphiphilic, regioregular, alternating copolymers of polythiophene have been prepared using modifications of the methods previously developed by McCullough et al.4b,11-13 The synthesis of polythiophenes 4, 5a, 5b, 6, and 10 is shown in Scheme 1. Dimer 3 can be regiospecifically polymerized in excellent yield by a modified Stille coupling recently developed for the synthesis of regioregular, water-soluble carboxylate polymers of polythiophene4b (Scheme 1, top reaction sequence). Polymer 4 bears an oxazoline protecting group as a masked carboxylate and hence allows for the preparation of regioregular, amphiphilic polythiophenes, such as esters 5a and 5b and carboxylate 6. We have also polymerized12 dimer 9 to give amphiphilic 10. From the routes shown in Scheme 1, a diverse array of amphiphilic polythiophenes can be prepared which have novel properties as described below. Chloroform solutions of regioregular, amphiphilic 10 are readily spread onto the water surface of a Langmuir trough. Isothermic compression leads to a close-packed monolayer consisting of oriented polythiophene chains (Figure 1). The pressure-area isotherm for the Langmuir film of 10 shown in Figure 1C reveals a collapse of ∼29 Å2 per polymer repeat unit. This collapse area agrees with the anticipated structure shown in Figure 1D in which efficient π-stacking of adjacent polymers is accomplished by displacing the polymers by one thiophene unit along the backbone, thereby allowing the alkyl chains on one polymer to fill the void space (Figure 1A) between the alkyl chains on the adjacent polymer. The collapse areas for polymers 4, 5a, 5b, and 6 are found to be 30, 29, 30, and 29 Å2, respectively, suggesting that all the regioregular, amphiphilic polythiophenes investigated here form monolayer arrangements roughly similar to that represented for 10. It is important to note that nonamphiphilic poly(3dodecylthiophene) (R ) C12H25, Figure 1C) does not form a monolayer, emphasizing the importance of the amphiphilic nature of the polymer. * Corresponding authors (e-mail: tb@symbion.ki.ku.dk and rm5g@ andrew.cmu.edu). † University of Copenhagen. ‡ RISØ National Laboratory. § Carnegie Mellon University. (1) Decher, G.; Hong, J. D.; Schmitt, J. Thin Solid Films 1992, 210-211, 831. (2) (a) Ferreira, M.; Cheung, J. H.; Rubner, M. F. Thin Solid Films 1994, 244, 806. (b) Cheung, J. H.; Fou, A. C.; Rubner, M. F. Thin Solid Films 1994, 244, 985. (c) Fou, A. C.; Rubner, M. F. Macromolecules 1995, 28, 7115. (d) Ferreira, M.; Rubner, M. F. Macromolecules 1995, 28, 7107. (3) (a) Chan, K. C.; Kim, T.; Schoer, J. K.; Crooks, R. M. J. Am. Chem. Soc. 1995, 117, 5875. (b) Kim, T.; Crooks, R. M.; Tsen, M.; Sun, L. J. Am. Chem. Soc. 1995, 117, 3963. (c) Kim, T.; Chan, K. C.; Crooks, R. M. J. Am. Chem. Soc. 1997, 119, 189. (4) (a) McCullough, R. D.; Tristram-Nagle, S.; Williams, S. P.; Lowe, R. D.; Jayaraman M. J. Am. Chem. Soc. 1993, 115, 4910. (b) McCullough, R. D.; Ewbank, P. C.; Loewe, R. S. J. Am. Chem. Soc. 1997, 119, 637. (5) Bouman, M. M.; Meijer, E. W. AdV. Mater. 1995, 7, 385. (6) Langmuir, I. J. Am. Chem. Soc. 1917, 39, 1848. (7) Blodgett, K. B. J. Am. Chem. Soc. 1935, 57, 1007. (8) See, e.g.: (a) Bryce, M. R.; Petty, M. C. Nature (London) 1995, 374, 771. (b) Garnaes, J.; Larsen, N. B.; Bjørnholm, T.; Jørgensen, M.×e2 Kjaer, K.; Als-Nielsen, J.; Jørgensen, J. F.; Zasadzinski, J. A. Science (Washington, D.C.) 1994, 264, 1301 and references therein. (9) (a) Orthmann, E.; Wegner, G. Angew. Chem., Int. Ed. Engl. 1986, 25, 114. (b) Vahlenkamp, T.; Wegner, G. Macromol. Chem. Phys. 1994, 195, 1933. (c) Neher, D. AdV. Mater. 1995, 7, 691. (d) Rulkens, R.; Wegner, G.; Enkelmann, V.; Schulze, M. Ber. Bunsen-Ges. Phys. Chem. 1996, 100, 707. (10) Kumar, A.; Whitesides, G. M. Appl. Phys. Lett. 1993, 63, 2002. (b) Kumar, A.; Biebuyck, H. A.; Whitesides, G. M. Langmuir 1994, 10, 1498. (11) McCullough, R. D. AdV. Mater. 1998, 10, 1. (12) McCullough, R. D.; Lowe, R. D.; Jayaraman, M.; Anderson, D. L. J. Org. Chem. 1993, 58, 904. (13) Polymers 4, 5a, 5b, 6, and 10 have molecular weights (Mn) of 11K with polydispersity indexes (PDI) of around 2. Preparative fractionation of these polymers can provide PDIs as low as 1.2. The structure and purity of all key intermediates were determined by 1H and 13C NMR, and elemental analysis. The polymers 5, 10, and 6 were characterized by 1H NMR, GPC, and UV-vis. Details are found in the Supporting Information. Scheme 1a