Synthesis of Nanophase-Separated Poly(urethane-co-acrylic acid) Network Films and Their Application for Magnetic Nanoparticle Synthesis Ju-Young Kim, 1 Dong-Hyun Shin, 1 Jee-Hyun Ryu, 2 Gyung-Hyun Choi, 3 Kyung-Do Suh 2 1 Department of Advanced Materials Engineering, Samcheok National University, Samchok 245-711, South Korea 2 Division of Chemical Engineering, College of Engineering, Hanyang University, Seoul 133-791, South Korea 3 Department of Industrial Engineering, College of Engineering, Hanyang University, Seoul 133-791, South Korea Received 3 June 2003; accepted 25 August 2003 ABSTRACT: Poly(urethane-co-acrylic acid) films were synthesized by the copolymerization of urethane acrylate nonionomer (UAN) and acrylic acid (AA) under different conditions. Poly(urethane-co-acrylic acid) films exhibited very different mechanical properties, attributed to the mi- crostructural difference with the type of solvents used in the film preparation. The film synthesized using UAN/AA/ water mixture had a relatively highly nanophase separated structure compared to that of the other films prepared using UAN/AA/dioxane mixture, resulting in higher mechanical property and glass-transition temperature. The nanostruc- tural differences could be also confirmed by atomic force microscopy measurements. Magnetic nanocomposite films synthesized based on UAN/AA/water and UAN/AA/di- oxane mixtures showed different sizes of magnetic nanopar- ticles, attributed to the differences of size of hydrophilic nanodomains. The higher the degree of nanophase separa- tion within poly(urethane-co-acrylic acid) films, the larger the size of hydrophilic nanodomains, resulting in formation of larger nanoparticles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3549 –3556, 2004 Key words: poly(urethane-co-acrylic acid) film; urethane ac- rylate nonionomer (UAN); nanophase separation; magnetic nanoparticle; hydrophilic nanodomain INTRODUCTION Recently, a number of investigations on nanoparticles dispersed within polymer matrix have been carried out because these materials can provide various new properties that result from the combination of proper- ties both from inorganic components and polymers. The polymeric matrix provides the processability and the flexibility, whereas, at the same time, inorganic nanosized particles confer unique properties that dif- fer from their bulk materials and atoms. As a conse- quence, nanocomposite films having novel catalytic, magnetic, and optical properties can be obtained. 1–18 Most of polymers used in the synthesis of nanocom- posite films have hydrophilic segments and hydro- phobic segments at the same molecules (amphiphilic polymer). Hydrophilic segments can solubilize or ad- here to inorganic materials through dipolar interac- tion, hydrogen bonding, complex formation, or cova- lent bonding and stabilize the formed nanosized par- ticles through steric or electrosteric stabilization. 1–5 Hydrophobic segments can lead to smaller particle size with narrow size distributions and high colloidal stability. There are several types of amphiphilic poly- mers used in the nanocomposite matrix such as non- ionic, anionic, or cationic homopolymers, random co- polymer, and diblock copolymer. The use of am- phiphilic block becomes increasingly attractive because methods of synthesizing nanoparticles in microphase-separated diblock copolymer provide greater control over particle formation. 3–10,17,18 How- ever, amphiphilic block copolymers, which are very expensive materials, can be obtained only by an ex- tremely difficult synthetic process, and some am- phiphilic homopolymers lack desirable mechanical properties, leading to limiting the application of poly- mer films containing metal nanoparticles. Although amphiphilic urethane acrylate chains hav- ing hydrophilic moieties, such as carboxylic, sulfonic acid, amino groups, and polyoxyethylene (POE) groups, have been widely used as water-borne UV coatings, 19,20 little work has been reported on the use of these chains as nanocomposite matrix. In our pre- vious works, we could synthesize nanophase-sepa- rated amphiphilic polyurethane networks through crosslinking polymerization of urethane acrylate non- ionomers (UANs) as well as magnetic nanoparticles within these polyurethane networks. 21,22 Morphology and size of magnetic nanoparticles formed within these networks were largely changed with type of solvent used in the synthesis of networks. Correspondence to: K.-D. Suh (kdsuh@hanyang.ac.kr). Contract grant sponsor: Hanyang University, Seoul; con- tract grant number: HY-2001. Journal of Applied Polymer Science, Vol. 91, 3549 –3556 (2004) © 2004 Wiley Periodicals, Inc.