Designing a Polymer Blend with Phase Separation Tunable by Visible Light for Computer-Assisted Irradiation Experiments Soh Ishino, 1 Hideyuki Nakanishi, 1 Tomohisa Norisuye, 1 Qui Tran-Cong-Miyata,* 1 Yasuhiro Awatsuji 2 1 Department of Polymer Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Kyoto 606-8585, Japan E-mail: qui@kit.ac.jp 2 Department of Electronics and Information Science, Kyoto Institute of Technology, Matsugasaki, Kyoto 606-8585, Japan Received: February 1, 2006; Revised: February 23, 2006; Accepted: March 3, 2006; DOI: 10.1002/marc.200600076 Keywords: computer-assisted irradiation; phase separation; photosensitizer; polymer blends; spatio-temporal manipulation Introduction Controlling phase separation of polymer blends is practi- cally important because the physical properties of multi- phase polymeric materials are greatly affected by their phase-separated structures. [1] Among a wide variety of morphologies, considerable attention has been focused on the co-continuous structures of multiphase polymers because their mechanical [2] as well as conducting proper- ties [3] are superior to those with random structures. In the past decades, there have been a large number of studies on generation and control of these co-continuous structures by using chemical reactions. Most of them are concentrated on inducing phase separation processes of polymer blends via the spinodal decomposition mechanism and subsequently freezing the morphological development by either poly- merization or cross-linking reaction. [4–6] From the view- point of controlling the spinodal decomposition kinetics, thermally activated reactions may have some drawbacks under certain experimental conditions because the heat used to activate these reactions occasionally interfere with the temperature governing the miscibility of the blends. To avoid such an undesirable interference, we have utilized photochemical reactions to control the spinodal decom- position process of polymer blends. [7,8] The main motiva- tion of using light for these purposes is to minimize the above-mentioned interference by taking advantage of the independence of the reaction initiation and termination Summary: A mixture of poly(vinyl methyl ether) (PVME) and a polystyrene derivative bearing cinnamate groups (PSC) was chemically designed so that its phase separation can be tunable by visible light for computer-assisted irradiation (CAI) experiments. This PSC/PVME blend exhibits a lower critical solution temperature (LCST) and undergoes phase separation upon irradiation with 405 nm visible light. The phase separation was induced by photodimerization of the cinnamate moieties in the presence of 5-nitroacenaph- thene used as a photosensitizer. It was found that for visible light with high intensity, phase separation process was almost frozen by photodimerization of the cinnamate groups which act as a photo-cross-linker for the PSC component. It is demonstrated in this work that by using this PSC/PVME blend, phase separation restricted to the micrometer scales can be induced and manipulated by irradiation using a computer-controlled digital projector. These preli- minary results open a new route for spatio-temporal manipulation of phase separation in photo-reactive polymer blends. Computer-assisted irradiation method for a polymer blend with phase separation drivable by visible light. Macromol. Rapid Commun. 2006, 27, 758–762 ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 758 DOI: 10.1002/marc.200600076 Communication