Yongbin Han

Photosensitized oxidation of alkenes with dendrimers as microreactors: controllable selectivity between energy and electron transfer pathway

Carboxylic acid terminated poly(aryl ether) dendrimers were used as microreactors to conduct the photooxidation of trans-stilbene and trans,trans-1,4-diphenyl-1,3-butadiene (DPB) sensitized by 9,10-dicyanoanthracene (DCA) in aqueous media. The photooxidation pathways can be successfully controlled by encapsulating the substrate and sensitizer molecules in the same or different sets of dendrimers. The singlet oxygen can transfer from one dendrimer to another. After the photoreaction, products could be more easily extracted from a dendrimer than from a micelle or a vesicle, and the dendrimer can be simply recovered by neutralization of the solution and reused.

Stabilized Vesicles Consisting of Small Amphiphiles for Stepwise Photorelease via UV Light

A small amphiphile consisting of hydrophilic tetraethylene glycol monoacrylate and hydrophobic alkyl chain which were connected by an o-nitrobenzyl unit, a photolabile group, was designed and synthesized. The critical aggregate concentration of the synthesized amphiphile was determined to be about 3 × 10(-5) M by the fluorescence probe technique. Nanosized vesicles were prepared and stabilized by in-situ radical polymerization without altering the morphology. The polymeric vesicle was highly stable which retained vesicular shape under dilution or UV irradiation. Hydrophobic guests can be encapsulated within the vesicle membrane and released out of the vesicle by UV stimulus through splitting the amphiphilic structure of the amphiphile. Distinguished dose-controlled photorelease of the polymeric vesicle is achieved due to the maintenance of the vesicular shape integrity which makes the guest release depend on the cleavage amount of amphiphilic structure during UV irradiation. This study provides a promising strategy to develop stable drug delivery systems for sustained and phototriggered release.