A selenium-containing amphiphilic block copolymer (PEG-PUSe-PEG) with a hydrophobic polyselenide block and two hydrophilic poly(ethylene glycol) (PEG) blocks was synthesized via polymerization of toluene diisocyanate (TDI) with monoselenide-containing diols and subsequent termination with PEG monomethylether. PEG-PUSe-PEG is able to self-assemble in aqueous solution to form block copolymer aggregates. Interestingly, it was found that the aggregates have a good oxidation-responsiveness and undergo a structural dissociation in a mild oxidative environment (such as 0.1% H 2 O 2 v/v) due to the unique sensitivity of selenide groups in presence of oxidants. Compared with the sulfide analogue PEG-PUS-PEG, PEG-PUSe-PEG is more sensitive to oxidants. It is anticipated that selenium-containing block copolymer aggregates may find application in the field of drug delivery systems.

We have fabricated a polymeric superamphiphile based on the electrostatic interaction between the double hydrophilic block copolymer of poly(ethylene glycol)-b-acrylic acid (PEG-b-PAA) and a selenium-containing surfactant (SeQTA). The polymeric superamphiphiles are able to self-assemble to form micelles in solution. The micelles can be disassembled with the addition of 0.1% H(2)O(2) because SeQTA is very sensitive to oxidation. The selenide group in SeQTA is oxidized into selenoxide (SeQTA-Ox) by H(2)O(2), which makes the surfactant more hydrophilic, thus leading to the disassembly of the micelles. In addition, small guest molecules such as fluorescein sodium can be loaded into the micelles made from the polymeric superamphiphiles and released in a controlled way under mild oxidation conditions. This study represents a new way to fabricate stimuli-responsive superamphiphiles for controlled self-assembly and disassembly.

In this paper we report the synthesis and study of a series of side-chain selenium-containing amphiphilic poly(ethylene oxide-b-acrylic acid) block copolymers PEO-b-PAA-Se. These block copolymers can selfassemble in aqueous solution and form spherical micellar aggregates. The selenide group of PEO-b-PAA-Se can change into hydrophilic selenoxide under mild oxidation of 0.1% hydrogen peroxide, leading to the disassembly of the spherical micellar aggregates. Small compounds like Nile Red can be encapsulated into the micellar aggregates and show fast release upon the addition of 0.1% hydrogen peroxide. More interestingly, the oxidation state of selenoxide can be reversed to selenide under reduction of Vitamin C, thus recovering the spherical aggregates. The reversible oxidation and reduction process shows good reversibility and can be repeated at least 7 times. It is hoped that this reversible redox controlled system may function as nanocontainers for potential application in the areas such as responsive drug delivery and anti-oxidation studies. Experimental section MaterialsSelenium powder, sodium borohydride, triethylamine, benzyl bromide, 30% H 2 O 2 , and all other organic solvents used in this

This article reports the synthesis, characterization, and multimorphological aggregation of a series of amphiphilic diblock copolymers bearing strong push-pull azo chromophores. The diblock copolymers (PEG xb-PCN y ), which consist of poly(ethylene glycol) (PEG) and 2-(N-ethyl-N-(4-(4′-cyanophenylazo)phenyl)amino)ethyl methacrylate (PCN) blocks, were synthesized through atom transfer radical polymerization (ATRP) and postpolymerization azo-coupling reaction. PEG x -b-PCN y was prepared to have different hydrophilic/hydrophobic ratios (x ) 122, y ) 24, 62, 129, 224). Self-assembled aggregates were formed by the gradual addition of water to the solutions of the copolymers in THF. The formation process and morphology of the aggregates were characterized by DLS, SLS, SEM, and TEM. Results show that the block polymers start to form aggregates at the critical water content (CWC), which is related to the initial polymer concentration in THF and PCN block length. The morphology of the aggregates formed in the solutions is controlled by the PCN block length and preparation conditions. With the increase in the PCN length, the aggregates show different morphologies such as spherical micelles, rodlike aggregates, hollow nanotubes, and colloidal spheres. In the experimental range, a change in the polymer initial concentration in THF does not show an obvious effect on the aggregate morphology. The water-adding rate in the preparation process shows an important effect on the aggregate morphology. When the water-adding rate increases from 0.5 to 7.2 mL/h, the morphology of PEG 122 -b-PCN 129 aggregates changes from nanotubes to a mixture of giant vesicles and colloidal spheres. Some well-organized aggregates developed from the photoresponsive copolymers could have potential applications in photocontrollable drug delivery and other uses.

A photoresponsive polyelectrolyte multilayer film containing a diselenide functional group is fabricated using an unconventional layer-by-layer method. The polycation backbone is constructed through copolymerization of di-(1-hydroxylundecyl) diselenide and 1,4-bis(2-hydroxyethyl)piperazine with 2,4-diisocyanatotoluene. A common polyanion poly(styrene sulfonate) is selected as the polyanion. The obtained film can be gradually disrupted under the irradiation of mild visible light, and this process can be monitored with UV-vis spectroscopy. The residue of the film is estimated to be 17% after 5 h of irradiation. The intensity of the visible light can be as low as 50 mW cm⁻², which is even weaker than the sunlight. The cytotoxicity of the building blocks is evaluated in MTT assays using human hepatic cell line (L-02), and the results are satisfactory. Further tests show that cells can grow in a regular manner on this film, indicating good biocompatibility. In addition, the film can be used to achieve cargo loading and controlled release. Considering that light can not only trigger controlled release but also act as part of the therapy itself (photodynamic therapy), this system shows hope for further development into a platform for the combination of chemotherapy and photodynamic therapy, especially for applications concerning skin.