ABSTRACT
Hydrogels can be prepared using the commercially available Fmoc-phenylalanine or Fmoc-tyrosine as the gelator. Gelation is triggered by careful adjustment of the pH of the solution using glucono-delta-lactone (GdL). Model dyes have been entrapped in the hydrogels, and the release of the dyes from the hydrogels has been monitored. The release ratios indicate that the systems are under Fickian diffusion control. A range of dyes with different radii of gyration diffuse from the Fmoc-phenylalanine hydrogels with similar diffusion coefficients, implying that the network is not specifically retaining even relatively large (5 nm) dyes. On the other hand, the larger dyes are restricted in their diffusion from Fmoc-tyrosine hydrogels. These results correlate with the rheological measurements for the hydrogels, where those formed from Fmoc-tyrosine were shown to have significantly higher storage moduli than those formed from Fmoc-phenylalanine. In addition, the frequency-dependent behavior of the hydrogels demonstrates that Fmoc-tyrosine shows the classic response of a strong gel with a storage modulus that is nearly independent of frequency. However, for Fmoc-phenylalanine, the frequency dependence of moduli is very strong and very similar to that displayed by a transient network, where the interconnections between junction zones in the network are highly flexible and able to withstand large deformations.
Subject(s)
Amino Acids/chemistry , Fluorenes/chemistry , Hydrogels , Coloring Agents/chemistry , Diffusion , Gels , Gluconates/chemistry , Hydrogels/chemistry , Hydrogen-Ion Concentration , Microscopy, Electron, Scanning/methods , Models, Chemical , Molecular Conformation , Particle Size , Phenylalanine/chemistry , Rheology , Tyrosine/chemistryABSTRACT
Poly(aryleneethynylene) networks prepared from tetrahedral monomers are highly microporous and exhibit apparent Brunauer-Emmett-Teller surface areas of up to 1213 m2 g(-1).
ABSTRACT
Water-insoluble organic compounds are often used in aqueous environments in various pharmaceutical and consumer products. To overcome insolubility, the particles are dispersed in a medium during product formation, but large particles that are formed may affect product performance and safety. Many techniques have been used to produce nanodispersions-dispersions with nanometre-scale dimensions-that have properties similar to solutions. However, making nanodispersions requires complex processing, and it is difficult to achieve stability over long periods. Here we report a generic method for producing organic nanoparticles with a combination of modified emulsion-templating and freeze-drying. The dry powder composites formed using this method are highly porous, stable and form nanodispersions upon simple addition of water. Aqueous nanodispersions of Triclosan (a commercial antimicrobial agent) produced with this approach show greater activity than organic/aqueous solutions of Triclosan.
Subject(s)
Nanoparticles/chemistry , Organic Chemicals/chemistry , Water/chemistry , Anti-Infective Agents, Local/pharmacology , Azo Compounds/chemistry , Carbon Dioxide/chemistry , Corynebacterium/drug effects , Corynebacterium/genetics , Emulsions/chemistry , Ethanol/chemistry , Freeze Drying , Inhibitory Concentration 50 , Microbial Sensitivity Tests , Nanoparticles/ultrastructure , Nanospheres/chemistry , Oils/chemistry , Particle Size , Polymers/chemistry , Polyvinyl Alcohol/chemistry , Porosity , Powders/chemistry , Sodium Dodecyl Sulfate/chemistry , Solubility , Solvents/chemistry , Surface-Active Agents/chemistry , Triclosan/pharmacologyABSTRACT
High surface area porous poly(phenylene butadiynylene) networks were obtained (BET surface area up to 842 m(2) g(-1)) by the palladium-catalyzed homocoupling of 1,3,5-triethynylbenzene and 1,4-diethynylbenzene.
ABSTRACT
The cyclotriphosphazene P(3)N(3)Cl(6) reacts with six equivalents of DMAP (4-(dimethylamino)pyridine) in superheated chloroform to form crystals of composition [P(3)N(3)(DMAP)(6)]Cl(6).19CHCl(3) comprising [P(3)N(3)(DMAP)(6)](6+) ions, which host five chloride ions in basket-type cavities on either side of the ring and at equatorial positions via tetradentate ortho-H-donor arrangements.
