화학공학소재연구정보센터
Solid State Ionics, Vol.176, No.13-14, 1291-1299, 2005
Self-assembly and flow alignment of protonically conducting complexes of polystyrene-block-poly(4-vinylpyridine) diblock copolymer with phosphoric acid
Phosphoric acid (H3PO4) is selectively swollen in polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer within its P4VP domains to achieve protonically conducting self-assembled acid-base complexes. Shear flow is imposed to macroscopically align the local self-assembled structures. The materials are characterized using Fourier transformation infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), dynamic theology, and impedance spectroscopy. Homopolymeric NVP(H3PO4), (where x denotes the nominal number of H3PO4 molecules vs. repeat units of P4VP) reaches the conductivity value ca. 5*10(-3) S/cm at 100 degrees C when x approaches the values x=2.0(...)2.5. By incorporating a P4VP(H3PO4)(2.2) block within PS-block-NVP (with the block lengths 35.5 and 3.6 kD for PS and P4VP, respectively; polydispersity 1.06), lamellar protonically conducting nanochannels are formed with periodicity of ca. 450 A based on SAXS. Large-amplitude oscillatory shear flow is applied, which leads to macroscopically rather highly aligned lamellar nanochannels based on SAXS. Surprisingly, this leads to only slightly anisotropic conductivities. For example, at 100 degrees C conductivity of 5 * 10(-6) S/cm along the channels and 7 * 10(-7) S/cm in the perpendicular direction are obtained. The observations indicate that defects, potentially involving "dead-end channels" may control the transport properties in self-assembled and aligned materials across macroscopic dimensions. (c) 2005 Elsevier B.V. All rights reserved.