Water uptake and proton conductivity as a function of temperature were determined for three aromatic‐based, sulfonic acid‐bearing polymers, plus the perfluoroalkyl sulfonic acid Nafion® 117. Water uptake of submerged, equilibrated samples ranged from less than five water molecules per acid group for a high equivalent weight, sulfonated polyethersulfone to almost fifty waters per acid for a low equivalent weight, sulfonated polyetheretherketone. The most conductive aromatic‐based polymer, sulfonated polyphenylquinoxaline (S‐PPQ), had a room temperature conductivity of 9.8×10−3S/normalcm . about an order of magnitude less than that of a perfluoroalkyl sulfonic acid under identical conditions. The slope of the S‐PPQ Arrhenius conductivity plot was sufficiently steep that at 180°C, the proton conductivity, 1.3×10−1S/normalcm , was only a factor of two lower than that of Nafion under similar conditions. The lower conductivity of the aromatic‐based sulfonic acid polymers can be attributed to chain rigidity, lack of ion channels, and lower acidity. © 2000 The Electrochemical Society. All rights reserved.

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The sponge Dendrilla membranosa, a conspicuous member of the Antarctic benthos that appears to be free of predation, produces several norditerpenes, including the previously unreported dendrillin [1], as well as amino acid and nucleotide derivatives. The norditerpenes, previously implicated as chemical defense agents, displayed no deterrent effect toward the chemosensory tube-feet of the major Antarctic sponge predator, the sea star Perknaster fuscus.

Hexane, chloroform, and methanol extracts of 18 species of antarctic sponges were tested for their ability to induce sustained tube-foot retraction in the antarctic spongivorous sea starPerknaster fuscus. Extracts were imbedded in silicone and used to coat the tip of a glass rod, which was allowed to contact an extended tube-foot. Retraction times were measured and compared with three controls: contact with a glass rod coated with a hexane extract of fish (feeding stimulant), contact with the glass rod alone (mechanical control), and contact with the glass rod coated with silicone alone (silicone control). Only extracts of the spongeMycale acerata did not elicit significantly longer tube-foot retraction times than controls for at least one of the three organic extracts. Hexane sponge extracts elicited the lowest levels of significant tube-foot responses, with only 39% of the sponge species tested showing activity in this fraction. In contrast, chloroform and methanol extracts elicited a significant tube-foot retraction response in 73% and 78% of the species tested, respectively. This indicates that in this assay repellent metabolites are generally more polar substances. It remains to be determined that secondary metabolites are responsible for all of the tube-foot retraction responses detected in sea stars exposed to sponge extracts; bioactive secondary metabolites have been isolated from a number of these antarctic sponges. It may be of ecological significance that the two rapidly growing sponges,Homaxinella balfourensis andMycale acerata, were either not repellent or had low repellency, and thatM. acerata is the primary dietary item ofPerknaster fuscus.