(176d) Properties of Surface-Anisotropic Polystyrene Particles

     Recently, the fabrication of particles with anisotropic surfaces has become of great interest because of their interesting properties such as the amphiphilic character, large dipole moment, and directional reactivity. Most synthetic methods that are known to date with a few exceptions yield particles with highly isotropic surfaces. Subsequent modification of these particles by chemical means usually leads to non-directional growth or shrinkage of the particles.

      Several groups^1-5 have reported successful anisotropic decoration of particles. The surface modification is usually achieved by either employing shadowing effects or templating methods and in a few cases through controlled nucleation and epitaxial growth. We have developed a method based on partial embedment of particles into a polymer film and subsequent modification using electroless deposition resulting in silver capped micrometer sized particles.

     Our method consists of three subsequent steps; (i) assembly of a particle monolayer, (ii) partial embedment of the particle monolayer into a polymer film, and (iii) particle modification by electroless silver deposition onto the templated particles. We have employed this method for sulfonated polystyrene particles in the range from 100 nm to 2.4 µm.

     The paper will discuss the electroless deposition mechanism as well as the physical properties of these surface-anisotropic polystyrene particles. Tests of the effect of electric fields on the self-assembly of these particles and Raman as well as IR characterization are underway.

(1) Lu, Y.; Xiong, H.; Jiang, X.; Xia, Y.; Prentiss, M.; Whitesides, G. M. J. Am. Chem. Soc. 2003, 125, 12724 - 12725.

(2) Choi, J.; Zhao, Y.; Zhang, D.; Chien, S.; Lo, Y.-H. Nano Lett. 2003, 3, 995 - 1000.

(3) Paunov, V. N.; Cayre, O. J. Adv. Mat. 2004, 16, 788-791.

(4) Snyder, C. E.; Yake, A. M.; Feick, J. D.; Velegol, D. Langmuir 2005, 21, 4813-4815.

(5) Yu, H.; Chen, M.; Rice, P. M.; Wang, S. X.; White, R. L.; Sun, S. Nano Lett. 2005, 5, 379 - 382.