Perfluorocarbon (PFC) nanoemulsions, droplets of fluorous solvent stabilized by surfactants dispersed in water, are simple yet versatile nanomaterials. The orthogonal nature of the fluorous phase promotes the formation of nanoemulsions through a simple, self-assembly process while simultaneously encapsulating fluorous-tagged payloads for various applications. The size, stability, and surface chemistry of PFC nanoemulsions are controlled by the surfactant. Here, we systematically study the effect of the hydrophilic portion of polymer surfactants on PFC nanoemulsions. We find that the hydrophilic block length and identity, the overall polymer hydrophilic/lipophilic balance, and the polymer architecture are all important factors. The ability to modulate these parameters enables control over initial size, stability, payload retention, cellular internalization, and protein adsorption of PFC nanoemulsions. With the insight obtained from this systematic study of polymer amphiphiles stabilizing PFC nanoemulsions, design features required for the optimal material are obtained.
SYNOPSISRed #170 (pigment) polyurea microcapsules have been successfully prepared at our laboratory. Both core and shell of these microcapsules are demonstrated to be red #170 pigment and polyurea, respectively, by infrared ( I R ) spectra. The number-average particle sizes of these microcapsules are seen to decrease with increasing concentration and the ethylene oxide chain length of nonylphenylpolyoxyethylene ether (NP,; n = 6,8, 10, 12, 16) as an emulsifier in the water phase used for making microcapsules. Experimental results indicate that the average particle sizes of red #170 polyurea microcapsules are smaller for the system with NPI6 than for the system with NP4 (in the oil phase) and/or NP16 (in the water phase) and that, in the presence of NP,, these particle sizes are seen to be slightly smaller for use of methylcellulose than for use of sodium carboxymethylcellulose as a protective colloid. It is also interesting to note that the released amounts of red #170 pigment from polyurea microcapsules in di-n-butylphthalate solvent is lower for a system with NP16 than for a system with methylcellulose, as a result of good emulsification leading to decrease the interaction between toluene diisocyanate and water molecules. This may further cause more crosslinkage to take place a t the urea groups, resulting in a decrease in the porosity of the capsules.
Sequential organocatalytic additions of 2-furanone and dihydroxyacetone derivatives to a crotonaldehyde lynchpin provide polyhydroxylated chains reminiscent of lactonized deoxo Kdn type sugars. Further homologation via Kulinkovich ring opening of the butyrolactone and acylation of the zinc homoenolate derived from the incipient cyclopropanol allows assembly of functionalized chain precursors to portimine. Our experiments probe the stability and reactivity of monosubstituted methylidene pyrrolines and generate advanced intermediates useful for exploring the biosynthesis and de novo synthesis of portimine.
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