Self-Assembly of Rod-Like Copolymers into Monolayers: A Simple Theoretical Estimate of Molecular Recognition Quality Anatoly V. Berezkin, * Alexei A. Lazutin Introduction Synthetic rigid copolymers of the ‘‘rod-coil’’ type stand out from the variety of synthetic macromolecules capable of self-assembly due to molecular recognition. These copoly- mers consist of flexible fragments and rigid blocks, which are usually p-conjugated. Conjugation imparts unique properties to the polymers so that they can be used as polymer electrodes (including biocompatible and cataly- tically active ones), conductors and semiconductors for microelectronics, electroluminescent materials for light- emitting diodes and piezoelectrics. Because of the essential difference in conformational behavior of flexible and rigid blocks, ‘‘rod-coil’’ copolymers undergo microphase separation much more easily than flexible block-copolymers. Usually these separations are accompanied by crystallization of rigid fragments. The formation of nanocrystallites notably increases hole and electron conductivity and the intensity of electro- and photo-luminescence. Thus, investigation of self-assembly in ‘‘rod-coil’’ copolymers is of practical interest, as well as purely scientific, interest. The basics of self-assembly are summed up in mono- graphs. [1,2] The first theoretical investigations of copoly- mers with flexible and rigid fragments were initiated by Semenov, Vasilenko and Subbotin, [3–5] who studied the formation of nematic and smectic mesophases and transitions between them. Halperin [6,7] , Raphael and de Gennes [8] described the behavior of ‘‘rod-coil’’ copolymers in selective solvents using a scaling method. Williams and Fredrickson theoretically predicted the existence of lamellar structures (the so called ‘‘hockey puck’’). [9] A phase diagram for rod-coil copolymers was constructed in the same paper. Mu " ller and Schick used self-consistent field theory [10] to demonstrate the possibility for lamella to bend into more complex morphologies, such as spiral stripes and nanotubes observed in experiments. The same method was used in ref. [11,12] to construct corresponding phase diagrams. Ref. [13–15] should also be Full Paper A. V. Berezkin, A. A. Lazutin A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova str. 28, 119991, Moscow, Russia Fax: þ7 (495) 135-5085; E-mail: berezkin.anatoly@rambler.ru A discrete model of a monolayer, consisting of identical rod-like copolymer molecules, is suggested. The influence of the copolymer’s composition and sequence on its self-assembly was studied. Thermodynamic quantities of monolayers were calculated. It is shown that the system undergoes an ‘‘order-disorder’’ transition upon temperature increase. The most regular monolayers are formed by copolymers with quasi-random sequences. Nevertheless, the monomer composition of such ‘‘good’’ sequences can vary over a wide range. It is shown that homopolymers, copolymers with a predominance of one- type monomer units and copolymers consisting of a small number of large blocks have a reduced ability to self-assembly. 410 Macromol. Theory Simul. 2008, 17, 410–420 ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mats.200800018