The effect of polymers on the ice nucleation temperature (T f ) was studied in a W/O emulsion using ~ 5m diameter droplets by differential scanning calorimetry (DSC). Four types of polymers were used. Among them, only polyvinyl alcohol (PVA) showed the additional effect of increasing the T f of the aqueous solutions. This increase was logarithmic with the concentration of PVA and the difference in molecular weight did not have any significant effect on T f for the same weight concentration. It was shown that the number of the structural unit (CH 2 CHOH) was the key parameter for the increasing degree of T f .

A series of an ABA triblock copolymer with amorphous polymethacrylate A blocks and a main-chain liquidcrystal (LC) polyester center block were prepared with the molecular weight of the amorphous blocks (M n am ) ranging from 2300 to 10 000 and that of the LC block kept constant at 10 000. Irrespective of asymmetric compositions, all block copolymers invariably formed lamellar microstructures. The LC segments were more extended perpendicular to the interface to form smectic layers parallel to the lamellae and folded to be accommodated in lamellae, whereas the amorphous segments had dimensions similar to those of segments in amorphous block copolymer microdomains. Increases in M n,am enlarge the interfacial area between the amorphous and LC segments and increase the number of folds in LC segments. Thus, LC lamellar thickness decreases and counterbalances the increase in amorphous lamellar thickness so as to suppress the lamellar spacing increase. When the LC segment was in the isotropic phase, the lamellae in the copolymers at asymmetric fractions were disordered and developed on cooling simultaneously with LC formation. The lamellar formation is attributed to the smectic layers that prefer a flat microdomain interface from an energetic perspective.

The catalyst layer (CL) in a proton exchange membrane fuel cell is a critical component that determines the performance of the cell. Although the CL is fabricated using a catalyst ink, there have been no studies concerning the effect of the quality of the ink on the CL structure. In the present work, catalyst ink samples were analyzed using gas chromatography-mass spectrometry. The results indicate the formation of hydrophobic compounds from the alcohol in the solvent, due to catalysis by Pt. These products result in the agglomeration of Pt/C particles, thus initiating cracks in the CL during the drying process.

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The self-assembly of ABA triblock copolymers comprising flexible amorphous poly(ethyl methacrylate) (PEMA, A block) and semiflexible liquid crystal (LC) polyester (B block) was investigated for amorphous block volume fractions (φ) ranging from 20% to 80%. Two copolymer series with different LC block molecular weights (M n,LC) were examined. At φ < 55%, block copolymers with M n,LC = 11 600 formed lamellar microdomains in which LC segments mostly extended along the lamella normal but folded to fit in the lamellae. When φ was augmented, the LC segment fold (N fold) increased to enhance the interface between the LC and amorphous segments and counterbalanced the increase in amorphous lamella thickness by reducing the LC lamella thickness. When φ > 68%, the LC lamellae were divided into cubes, transforming into spheres in the PEMA matrix. When M n,LC decreased to 6300, the copolymers showed similar morphology. However, the lamellae adopted zigzag configurations showing a greater tilting angle between the lamella normal to the LC chain axis with increasing φ. Thus, the LC and PEMA segments enhanced their interface by mutually sliding along the chain axis instead of increasing N fold.