Reversal of electroosmotic flow in capillary electrophoresis can be achieved by the addition of cationic surfactants to the electrophoretic buffer. This reversal of flow is caused by the formation of a bilayer or hemimicelle at the walls of the capillary, effectively making the wall charge positive. The bilayer can be formed either by adsorption of monomeric surfactants or by admicelles (surfactant pairs), depending on the ionic strength of the buffer and the surface charge at the capillary walls. At concentrations of cationic surfactant sufficient to form the bilayer (i.e., greater than the critical micelle concentration) the electroosmotic flow velocity is independent of pH above a pH of 4. Adjustment of the ionic strength causes minor variations in the reversed electroosmotic flow rate due to the opposing forces of increased concentration of adsorbed surfactant and decreased double layer thickness. The nature of the anionic counterion in solution has a strong effect on the magnitude of the reversed electroosmotic flow observed, analogous to the effect of the buffer cation's effect on normal electroosmotic flow. This effect is explained using a simple ion exchange model.

Two to three pyrene groups were attached to the PCEMA block of polystyrene-block-poly(2-cinnamoylethyl methacrylate) (PS-b-PCEMA) to yield PS-b-PCEMA−Py. Both PS-b-PCEMA and PS-b-PCEMA−Py formed micelles with PCEMA cores and PS shells in THF/cyclopentane (CP) mixtures with sufficiently high CP contents. Mixing such micelles led to chain exchange between different micelles, which increased the pyrene monomer fluorescence intensity at the cost of excimer emission. The data of pyrene monomer fluorescence intensity increase with time and were fitted to a two-exponential-term function. The average lifetime obtained was used to characterize the micelle chain exchange rate. Investigated were the effect of varying solvent composition, temperature, micelle concentration, and the length of both the PS and PCEMA blocks on the chain exchange rate.

Triblock nanospheres with hydroxylated polyisoprene (PHI) coronas, cross-linked poly(2-cinnamoyloxyethyl methacrylate) shells, and poly(acrylic acid) (PAA) cores were prepared following a method described previously. Equilibrating such nanospheres with a PdCl 2 solution in methanol enabled the loading of Pd 2+ into the PAA cores of the nanospheres. After the excess PdCl 2 in the methanol phase was removed, Pd(II) inside the nanosphere cores was reduced with hydrazine to yield Pd nanoparticles. Such encapsulated Pd particles were dispersed in methanol or water, which solubilized PHI. Like Pd black, the nanosphereencapsulated Pd nanoparticles catalyzed the hydrogenation of alkenes. The need for the reactant(s) to diffuse into and products to diffuse out of the encapsulating nanospheres expectedly slowed the catalytic reactions. The more interesting aspect had been in our ability to modify the activity of the Pd catalyst via changing the pH and thus the conformation of the encapsulating polymer chains.

Oil-filled nanocapsules were synthesized using the oil droplets of an O/W microemulsion as templates. A polysiloxane/silicate shell was formed at the surface of the oil droplet by cross-linking n-octadecyltrimethoxysilane and tetramethoxysiloxane. The shell imparted stability to the oil droplets against coalescence. The nanocapsules can be used in a number of applications (i.e., biomedical or environmental) where the free concentration of lipophilic compounds must be reduced. As a proof, the nanocapsules (1.4% w/v oil content in saline) were shown to sequester quinoline (8 μM) from saline in <15 min. The removal process was followed in real time using the UV absorbance of free quinoline in solution. Our primary goal is to produce a system for drug detoxification therapy. As a proof of concept for sequestering drugs, the nanocapsules were used in the removal of free bupivacaine from normal saline solution. The free bupivacaine concentration was determined in the aqueous phase after contact with such nanocapsules using HPLC. The results showed a rapid removal of bupivacaine. The nanocapsules at a concentration of 0.1% w/v oil content showed a maximum removal capacity of ≈1900 μM bupivacaine.

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