Self-Assembly of a Diblock Copolymer with Pendant Disulfide Bonds and Chromophore Groups: A New Platform for Fast Release

An amphiphilic block copolymer comprising poly­(ethylene glycol) (PEG) and poly­(2-(methacryloyl)­oxyethyl-2′-hydroxyethyl disulfide) (PMAOHD) blocks was synthesized by atom transfer radical polymerization (ATRP). Pyrenebutyric acid was conjugated to the block copolymer by esterification, and a block copolymer with pendant disulfide bonds and pyrenyl groups (PEG-<i>b</i>-P­(MAOHD-<i>g</i>-Py)) was obtained. ¹H NMR and gel permeation chromatography (GPC) results demonstrated the successful synthesis of the block copolymer. The cleavage of the disulfide bonds and the degrafting of the pyrenyl groups were investigated in THF and a THF/methanol mixture. Fluorescence spectroscopy, GPC, and ¹H NMR results demonstrated fast cleavage of the disulfide bonds by Bu₃P in THF. Fluorescence results showed the ratio of the intensity of the excimer peak to the monomer peak decreased rapidly within 20 min. GPC traces of the block copolymer moved to a long retention time region after addition of Bu₃P, indicating the cleavage of the disulfide bonds and the degrafting of the pyrenyl groups. PEG-<i>b</i>-P­(MAOHD-<i>g</i>-Py) can self-assemble into micelles with poly­(MAOHD-<i>g</i>-Py) cores and PEG coronae in a mixture of methanol and THF (9:1 by volume). The dissociation of the micelles in the presence of Bu₃P was investigated. After cleavage of the disulfide bonds in the micellar cores, a pyrene-containing small molecular compound and a block copolymer with pendant thiol groups were produced. Transmission electron microscopy (TEM), dynamic light scattering (DLS), and ¹H NMR were employed to track the dissociation of the polymeric micelles. All the techniques demonstrated the dissociation of the micelles and the fast release of pyrenyl groups from the micelles

Stimuli-Responsive Polypropylene for the Sustained Delivery of TPGS and Interaction with Erythrocytes

Hemocompatibility and oxidative stress are significant for blood-contacting devices. In this study, <i>N</i>-isopropylacrylamide (NIPAAm) and <i>N</i>-(3-aminopropyl)­methacrylamide hydrochloride (APMA) were cografted on polypropylene (PP) membrane using ultraviolet grafting to load antioxidative d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and control the release of TPGS. The immobilization of NIPAAm and APMA onto PP membrane was confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Combined with data from platelet adhesion, red blood cell (RBC) attachment, and hemolysis rate, the hemocompatibility of PP was significantly improved. An in-depth characterization using hemolysis rate test, scanning electron microscopy, atomic force microscopy, and confocal laser scanning microscopy was conducted to confirm that the mechanism of the release of TPGS interacted with RBCs was different at different stages. The release of TPGS from the loading PP membranes affected hemolysis at different stages. At the early stage of release, TPGS maintained the tiny (nanometer-sized) tubers on the membrane surface and enhanced the membrane permeabilization by generating nanosized pores on the cell membranes. Afterward, the incorporated TPGS slowed the lipid peroxidation of erythrocytes and filled in the lipid bilayer of erythrocyte to prevent hemolysis. Thus, the approach implemented to graft NIPAAm and APMA and load TPGS was suitable to develop medical device with excellent hemocompatibility and antioxidative property

Fabrication of a Detection Platform with Boronic-Acid-Containing Zwitterionic Polymer Brush

Development of technologies for biomedical detection platform is critical to meet the global challenges of various disease diagnoses, especially for point-of-use applications. Because of its natural simplicity, effectiveness, and easy repeatability, random covalent-binding technique is widely adopted in antibody immobilization. However, its antigen-binding capacity is relatively low when compared to site-specific immobilization of antibody. Herein, we report that a detection platform modified with boronic acid (BA)-containing sulfobetaine-based polymer brush. Mainly because of the advantage of oriented immobilization of antibody endowed with BA-containing three-dimensional polymer brush architecture, the platform had a high antigen-binding capacity. Notably, nonspecific protein adsorption was also suppressed by the zwitterionic pendants, thus greatly enhanced signal-to-noise (S/N) values for antigen recognition. Furthermore, antibodies captured by BA pendants could be released in dissociation media. This new platform is promising for potential applications in immunoassays

Effect of a Long Alkyl Group on Cyclopentadithiophene as a Conjugated Bridge for D–A−π–A Organic Sensitizers: IPCE, Electron Diffusion Length, and Charge Recombination

The option of using conjugated π-linkers is critical for rational molecular design toward an energy-level strategy for organic sensitizers. To further optimize photovoltaic performance, methyl- and octyl-substituted 4<i>H</i>-cyclopenta­[2,1-<i>b</i>:3,4-<i>b</i>′]­dithiophene (CPDT) are introduced into D–A−π–A featured sensitizers. Along with CPDT, instead of thiophene as conjugated bridge, <b>WS-39</b> and <b>WS-43</b> exhibit an extended spectral response due to the excellent conjugation and coplanarity of CPDT. Specifically, we focused on the critical effect of length of the alkyl group linked to the bridging carbon atoms of CPDT on the photovoltaic performances. Octyl-substituted <b>WS-39</b> shows a broader IPCE onset with an enhanced photovoltage relative to the analogue <b>WS-5</b>. In contrast, <b>WS-43</b>, with methyl substituted on the CPDT moiety, presents a relatively low quantum conversion efficiency within the whole spectral response region, along with low photocurrent density. <b>WS-43</b> displays a distinctly low IPCE platform, predominately arising from the short electron diffusion length with significant electron loss during the electron transport. The relative movement of the conduction band edge (<i>E</i>_CB) and charge transfer resistance as well as lifetime of injected electrons are studied in detail. Under standard AM 1.5 conditions, <b>WS-39</b>-based solar cells show a promising photovoltaic efficiency of 9.07% (<i>J</i>_SC = 16.61 mA cm^–2, <i>V</i>_OC = 770 mV, FF = 0.71). The octyl chains attached on CPDT can provide <i>dual protection</i> and exhibit a high propensity to prevent binding of the iodide–triiodide redox couple, producing an efficient shielding effect to retard the charge recombination and resulting in improvement of <i>V</i>_OC. Our research paves the way to explore more efficient sensitizers through ingenious molecular engineering

Porphyrin Cosensitization for a Photovoltaic Efficiency of 11.5%: A Record for Non-Ruthenium Solar Cells Based on Iodine Electrolyte

Dye-sensitized solar cells (DSSCs) are promising for utilizing solar energy. To achieve high efficiencies, it is vital to synergistically improve the photocurrent (<i>J</i>_sc) and the photovoltage (<i>V</i>_oc). In this respect, conjugation framework extension and cosensitization are effective for improving the absorption and the <i>J</i>_sc, which, however, is usually accompanied by undesirably decreased <i>V</i>_oc. Herein, based on a rationally optimized porphyrin dye, we develop a targeted coadsorption/cosensitization approach for systematically improving the <i>V</i>_oc from 645 to 727, 746, and 760 mV, with synergistical <i>J</i>_sc enhancement from 18.83 to 20.33 mA cm^–2. Thus, the efficiency has been dramatically enhanced to 11.5%, which keeps the record for nonruthenium DSSCs using the I₂/I₃^– electrolyte. These results compose an alternative approach for developing highly efficient DSSCs with relatively high <i>V</i>_oc using traditional iodine electrolyte

Rational Molecular Engineering of Indoline-Based D‑A-π‑A Organic Sensitizers for Long-Wavelength-Responsive Dye-Sensitized Solar Cells

Indoline-based D-A-π-A organic sensitizers are promising candidates for highly efficient and long-term stable dye-sensitized solar cells (DSSCs). In order to further broaden the spectral response of the known indoline dye <b>WS-2</b>, we rationally engineer the molecular structure through enhancing the electron donor and extending the π-bridge, resulting in two novel indoline-based D-A-π-A organic sensitizers <b>WS-92</b> and <b>WS-95</b>. By replacing the 4-methylphenyl group on the indoline donor of <b>WS-2</b> with a more electron-rich carbazole unit, the intramolecular charge transfer (ICT) absorption band of dye <b>WS-92</b> is slightly red-shifted from 550 nm (<b>WS-2</b>) to 554 nm (<b>WS-92</b>). In comparison, the incorporation of a larger π-bridge of cyclopentadithiophene (CPDT) unit in dye <b>WS-95</b> not only greatly bathochromatically tunes the absorption band to 574 nm but also largely enhances the molar extinction coefficients (ε), thus dramatically improving the light-harvesting capability. Under the standard global AM 1.5 solar light condition, the photovoltaic performances of both organic dyes have been evaluated in DSSCs on the basis of the iodide/triiodide electrolyte without any coadsorbent or cosensitizer. The DSSCs based on <b>WS-95</b> display better device performance with power conversion efficiency (η) of 7.69%. The additional coadsorbent in the dye bath of <b>WS-95</b> does not improve the photovoltaic performance, indicative of its negligible dye aggregation, which can be rationalized by the grafted dioctyl chains on the CPDT unit. The cosensitization of <b>WS-95</b> with a short absorption wavelength dye <b>S2</b> enhances the IPCE and improves the η to 9.18%. Our results indicate that extending the π-spacer is more rational than enhancing the electron donor in terms of broadening the spectral response of indoline-based D-A-π-A organic sensitizers