Self-assembly and photo-cross-linking of eight-armed PEG-PTMC star block copolymers.

Eight-armed poly(ethylene glycol)-poly(trimethylene carbonate) star block copolymers (PEG-(PTMC)(8)) linked by a carbamate group between the PEG core and the PTMC blocks were synthesized by the metal-free, HCl-catalyzed ring-opening polymerization of trimethylene carbonate using an amine-terminated eight-armed star PEG in dichloromethane. Although dye solubilization experiments, nuclear magnetic resonance spectroscopy, and dynamic light scattering clearly indicated the presence of aggregates in aqueous dispersions of the copolymers, no physical gelation was observed up to high concentrations. PEG-(PTMC(9))(8) was end-group-functionalized using acryloyl chloride and photopolymerized in the presence of Irgacure 2959.

Levels of essential and toxic elements in Porphyra columbina and Ulva sp. from San Jorge Gulf, Patagonia Argentina.

Baseline concentration levels of As, B, Ca, Cd, Cr, Cu, Co, Fe, Mg, Mn, Mo, Ni, P, Pb, Se, V, and Zn were determined for Porphyra columbina and Ulva sp. collected from three locations along San Jorge Gulf, in Patagonia Argentina. Elements were quantified by inductively coupled plasma-optical emission spectrometry, with the exception of lead and cadmium in some samples which were determined by electrothermal atomic absorption spectrometry.