Design of Soft Interfaces through Biomimetic Approach

Speaker: Atsushi Takahara, Kyushu University, Japan

When: July 31, 2009 (Fri), 03:00PM to 04:00PM (add to my calendar)
Location: SCI 352
Hosted by: Ophelia Tsui

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract:
Since surfaces and interfaces of soft materials (“soft interface”) play an important role in various technological applications and biointerfaces, precise control of soft interfaces would greatly promote the innovation of future science and technology. In this study, methods for design of soft interfaces by biomimetic approach such as nano-texturing of polymer thin films, and high-density polymer brush immobilization are presented.

Nano-imprinting is a promising method for surface nano-texturing. The line pattern was imprinted onto poly(fluoroalkyl acrylate) with long crystalline fluoroalkyl group thin film, and nano-imprinting characteristics of poly(2-pefluorooctylethyl acrylate) (PFA-C8) thin film was investigated. We found out that PFA-C8 could be nano-imprinted even at room temperature because of the weak interaction among fluoroalkyl groups in crystallite at room temperature. The lateral resolution of imprinted pattern was ca.100nm. The nano-textured PFA-C8 with orthogonal line patterns exhibited lotus effect.

Super hydrophilic polymer brushes were prepared on the silicon wafer by surface-initiated atom transfer radical polymerization (ATRP) of 2-methacryloyloxyehtyl phosphorylcholine (MPC) with phosphocholine group. In the case of PMPC, the swollen brush structure at the water interface was characterized by neutron reflectivity (NR). PMPC brush surface showed super hydrophilicity and the air bubble is hardly attached to the PMPC brush surface in the hydrated state. The salt concentration dependence of the polymer chain conformation was not observed for PMPC brush because of the net charge of PMPC is negligible. On the other hand, poly(3-dimethyl(methacryloxyethyl)ammonium propane sulfonate) (PDMAPS) brush exhibited quite different characteristics. Large dependence of the brush thickness on salt concentration was confirmed by NR and atomic force microscopy (AFM). PDMAPS chains showed shrunk conformation in pure water due to the strong interchain association, while PDMAPS adopted highly extended chain conformation in a 0.5M NaCl solution because salt ions in aqueous solution screen the net attractive electrostatic interaction between PDMAPS chains.

1.K. Honda, M. Morita, A. Takahara, Soft Matter, 4,1400-1402 (2008).
2.M. Kobayashi, Y. Terayama, M. Kaido, A. Suzuki, K. Ishihara, A. Takahara, Soft Matter, 3, 740-746(2007).
3.Y. Matsuda, M. Kobayashi, M. Annaka, K. Ishihara, A. Takahara, Langmuir, 24, 8772-8778 (2008).
4.S.. Horiuchi, T. Hanada, M. Ebisawa, Y. Matsuda, M. Kobayashi, A. Takahara, ACS Nano, 3, 1297–1304(2009).