Effect of the Poly(ethylene glycol) Diacrylate (PEGDA) Molecular Weight on Ionic Conductivities in Solvent-Free Photo-Cross-Linked Solid Polymer Electrolytes.

To obtain safe, high-performance Li-ion batteries, the development of electrolytes with high impact resistance and high ionic conductivity is important. Ionic conductivity at room temperature has been improved by using poly(ethylene glycol) (PEG) diacrylate (PEGDA) to form three-dimensional (3D) networks and solvated ionic liquids. However, the effects of the molecular weight of PEGDA on ionic conductivities and the relationship between ionic conductivities and network structures of cross-linked polymer electrolytes have not been discussed in detail. In this study, the dependence of the ionic conductivity of photo-cross-linked PEG solid electrolytes on the molecular weight of the PEGDA was evaluated. X-ray scattering (XRS) gave detailed information about the dimensions of 3D networks formed by the photo-cross-linking of PEGDA, and the effects of the network structures on the ionic conductivities were discussed.

pH-Responsive Ultrathin Nanoporous SiO2 Films for Selective Ion Permeation.

Ultrathin nanoporous (NP) films are an emerging field for selective and effective ion/molecular separation and electrochemical sensing applications. We describe selective ion permeation in surface-functionalized ultrathin NP SiO2 films (NP SiO2-NH2). The ultrathin NP SiO2 films with ca. 8 nm thickness were prepared from silsesquioxane-containing blend polymer Langmuir-Blodgett films (nanosheets) using the photo-oxidation method. The porous SiO2 surface was modified with a pH-responsive amine-containing silane coupling agent. Selective ion permeation was demonstrated under acidic pH conditions (pH ≤ 6) using two equally sized redox probes: negative (Fe(CN)63-/4-) and positive (Ru(NH3)62+/3+) ions. The current density for Fe(CN)63-/4- decreased as the pH value increased to pH = 6, whereas it increased for Ru(NH3)62+/3+. Control measurements revealed that the probes can penetrate the pores of nonfunctionalized SiO2 films irrespective of pH values, indicating that both the size and the surface charge response contributed to selective ion permeation. Results obtained from this study pave the way for new applications in molecular separation and sensing applications based on ultrathin nanoporous films (<10 nm) and tailored surfaces.

Synthesis and Porous SiO2 Nanofilm Formation of the Silsesquioxane-Containing Amphiphilic Block Copolymer.

We describe the synthesis, Langmuir-Blodgett (LB) film formation, and photo-oxidation of an organic-inorganic hybrid block copolymer consisting of N-dodecyl acrylamide (DDA) and silsesquioxane (SQ) comonomers [p(DDA/SQ26)- b-pDDA]. The copolymer was synthesized by reversible addition fragmentation chain transfer polymerization of DDA and SQ. Higher monolayer stability at the air-water interface was confirmed for p(DDA/SQ26)- b-pDDA. The p(DDA/SQ26)- b-pDDA monolayer was deposited onto solid substrates with a monolayer thickness of 2.3 nm. The photo-oxidized SiO2 nanofilm revealed its porous structure, which reflects phase-separated structures of p(DDA/SQ26)- b-pDDA, as confirmed using atomic force microscopy, quartz crystal microbalance, and cyclic voltammetry measurements. These results demonstrate that this preparation method using photo-oxidation of the organic-inorganic hybrid block copolymer LB film is promising for manipulating pore formations of inorganic oxide nanofilms.