The synthesis and characterization of a novel inorganic glass composite membrane consisting of a mixture of phosphotungstic acid and phosphomolybdic acid are reported. Phosphosilicate gels doped with these two proton conducting donor components were derived by a sol−gel method. The influence of the textural properties of the glass composites could be interpreted from N2 adsoption−desorption isotherms. The pore size was less than 6 nm for all glass membranes. These glass membranes were found to be stable up to 400 °C. Fourier transform infrared spectroscopy indicated that the characteristic Keggin anions PW12O40 3- and PMo12O40 3- were present in the glass composite membrane. The highest proton conductivity was measured to 1.01 × 10-1 S cm-1 at 85 °C with 85% relative humidity (RH). Membrane electrode assemblies were prepared and showed good performance, with a maximum power density value of 35 mW/cm2 at 93 mA/cm2 as well as a current density of 137 mA/cm2 when utilized in a H2/O2 fuel cell at 28 °C and 30% RH.

No abstract

No abstract

A series of soluble, benzimidazole‐based polymers containing sulfonic acid groups (SuPBI) has been synthesized. SuPBI membranes resist extensive swelling in water but are poor proton conductors. When blended with high ion exchange capacity (IEC) sulfonated poly(ether ether ketone) (SPEEK), a polymer that has high proton conductivity but poor mechanical integrity, ionic crosslinks form reducing the extent of swelling. The effect of sulfonation of PBI on crosslinking in these blends was gauged through comparison with nonsulfonated analogs. Sulfonic acid groups present in SuPBI compensate for acid groups involved in crosslinking, thereby increasing IEC and proton conductivity of the membrane. When water uptake and proton conductivity were compared to the IEC of blends containing either sulfonated or nonsulfonated PBI, no noticeable distinction between PBI types could be made. Comparisons were also made between these blends and pure SPEEK membranes of similar IEC. Blend membranes exhibit slightly lower maximum proton conductivity than pure SPEEK membranes (60 vs. 75 mS cm−1) but had significantly enhanced dimensional stability upon immersion in water, especially at elevated temperature (80 °C). Elevated temperature measurements in humid environments show increased proton conductivity of the SuPBI membranes when compared with SPEEK‐only membranes of similar IEC (c.f. 55 for the blend vs. 42 mS cm−1 for SPEEK at 80 °C, 90% relative humidity). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3640–3650, 2010

No abstract

The present study is designed to assess the potential benefits of controlled delivery of silver sulfadiazine from collagen scaffold (SSDM-CS) in infected deep partial thickness burn wounds in which epidermis is lost completely and the entire papillary dermis and most of the recticular layer of the dermis is lost. Infection induced by inoculating 10(7) colony forming units (cfu) of Pseudomonas aeruginosa caused significant increase in wound size (20%) till day 15, which decreased significantly from day 9 by SSDM-CS treatment, showing complete healing by day 27 (control > or = 37 days). Early subsidence of infection (<10(2) cfu, day 9) by SSDM-CS resulted in faster epidermal resurfacing and fibroplasia, whereas heavy microbial load (>10(7) cfu, day 9) in controls caused severe inflammatory cellular infiltration. Persistent infection triggered early expression of proinflammatory cytokines intereukin-6, intereukin 1-beta, and tumor necrosis factor-alpha, lasting until day 9, whereas cytokine level decreased in SSDM-CS-treated group by day 6. Infection exacerbated expression of active matrix metalloproteinases (MMPs)-2 and -9 in controls (day 15), while SSDM-CS positively modulated MMP-2 and -9 with faster decline in their levels (day 12). Inherent nature of the dressing to maintain drug level at equilibrium therapeutic concentration (51.2 microg/mL) for prolonged time (72 h), below systemic toxic limits (20 microg/dL, serum level), accelerated the magnitude and sequence of reparative events.

No abstract

No abstract