Molecular Assembly of Alkylated Fused Expanded Pyridinium for a Highly Conductive Anion-Exchange Membrane

Alkylated fused expanded pyridinium (CxFEP) with alkyl chain lengths (x) of 0, 6, 12, and 18 was newly synthesized and introduced into polymers as side chains for anion-exchange membrane (AEM) applications. FEP is characterized by a large π cation that offers weak electrostatic interactions with anions such as hydroxide (OH–) ions and therefore leads to high OH– conductivity in AEM. CxFEP shows a synergetic effect between the π–π interactions of FEP and van der Waals interactions of the alkyl chains and forms a strong assembly, particularly for C6FEP. On the other hand, when CxFEP was introduced into the polymers, C12FEP formed an ordered stacking assembly in the films, whereas the other polymers with shorter (C0 and C6) and longer (C18) alkyl chains exhibited no such ordered structure. For the AEM, all of the polymers showed higher ion conductivities than that of commercial ammonium-based AEM, even with their low ion-exchange capacities (IEC), probably because of their characteristic weak interactions between the FEP cation and OH–. In particular, the AEM with C12FEP showed the highest ion conductivity of 143.3 ± 27.3 mS cm–1, even with a very low IEC of 0.41 mmol g–1. In addition to the high level of ion dissociation of FEP, the molecular assembly of FEP provides ionic conduction paths. This study demonstrates the importance of high ion dissociation and the formation of a conduction pathway for AEM with high conductivity

Interface Velocity.

<p>Interface Velocity.</p

Circular dichroism spectrometry in the ultraviolet wavelength range.

<p>The polypeptide solution of 1mg/mL was preheated for one hour at 80°C.</p

Role of the N‑Terminal Amphiphilic Region of Ovalbumin during Heat-Induced Aggregation and Gelation

Ovalbumin (OVA), a major globular protein in egg white, forms semiflexible fibrillar aggregates during heat-induced gelation. The N-terminal amphiphilic region (pN_1–22) of OVA is removed after treatment with pepsin at pH 4 to leave a large OVA fragment (pOVA). The conformation and thermal stability of pOVA and OVA are similar, but the rheological strength of the heat-induced gel of pOVA is much lower compared to that of OVA. The aggregation rate of pOVA, which forms spherical aggregates, was lower than that of OVA. These results suggest that the N-terminal amphiphilic region of OVA facilitates the α-to-β conformational transition, which triggers OVA fibril formation. Heat treatment of OVA in the presence of pN_1–22 consistently resulted in the formation of straight fibrils. The strength of OVA and collagen gels was increased when prepared in the presence of pN_1–22, suggesting that pN_1–22 may be used to control the properties of protein gels

Typical images obtained with the transmission electron microscope.

<p>(a) in the case of the non-preheated solution, ×12,000; (b) in the case of the non-preheated solution, ×40,000; (c) in the case with one-hour preheating at 80°C, ×12,000; and (d) in the case with one-hour preheating at 80°C, ×40,000.</p

Contour maps of brightness for the polypeptide solutions.

<p>(a) non-preheated solution (1mg/mL); (b) preheated solution (1mg/mL) for 1-hour at 80°C. The arrows show the locations of tips of the interface.</p

Typical images with an ice/solution interface captured with a CCD camera.

<p>The black lines on the left-hand side of each image show the element wires of the thermocouple. (a) pure water; (b) HPLC6 solution; (c) polypeptide solution (1mg/mL) at t = t₀ s; (d) polypeptide solution (1mg/mL) at t = t₀+5 s; (e) polypeptide solution in the case with one-hour preheating at 80°C (1mg/mL) at t = t₀ s; (f) polypeptide solution in the case with one-hour preheating at 80°C (1mg/mL) at t = t₀+26 s; (g) polypeptide solution in the case with 5-hour preheating at 80°C (1mg/mL); and (h) polypeptide solution in the case with 24-hour preheating at 80°C (1mg/mL).</p

Details of cooling section.

<p>The solutions were stored in a space of 25 mm × 22 mm × 0.02 mm between parallel cover glasses. The gap between the cover glasses was realized by the presence of a screen, printed on the lower side of the upper cover glass. The transparent cover and plastic film were used to reduce the influence of air-conditioning flow on the measurements.</p

Image-capturing Conditions.

<p>Image-capturing Conditions.</p

Polypeptide and Winter Flounder Antifreeze Protein.

<p>Polypeptide and Winter Flounder Antifreeze Protein.</p