Xinfeng Tao

Photodynamic therapy (PDT) is a noninvasive, spatiotemporally selective modality that affords rapid healing with negligible scarring, but its clinical efficacy is severely limited by tumor hypoxia and aggregation-induced quenching of photosensitizers. Perfluorocarbons possess excellent oxygen dissolution and transport capacities and have been widely employed to construct oxygen-enriched microenvironments. In addition, the heavy-atom effect enhances intersystem crossing by promoting spin-orbit coupling, thereby increasing singlet oxygen generation. Herein, we synthesized a series of amphiphilic bottlebrush polymers (BBPs) covalently grafted with porphyrin photosensitizers, featuring tunable fluorine-containing side chains and iodine functionalization. Distinct from conventional polymeric PDT systems that primarily serve as photosensitizer carriers, the BBP architecture provides a confined multifunctional microenvironment that simultaneously regulates photosensitizer aggregation, oxygen availability, and intersystem crossing. The strong steric repulsion between neighboring side chains prevents undesired photosensitizer aggregation and preserves their photoactivity, while the fluorine-rich domains and iodine substituents cooperatively promote singlet oxygen generation through oxygen enrichment and external heavy-atom effects, respectively. Consequently, polymer vesicles assembled from these fluorinated and iodinated BBPs exhibit significantly enhanced PDT efficacy. This work establishes a cooperative molecular-design strategy that integrates aggregation suppression, oxygen regulation, and heavy-atom-enhanced intersystem crossing within a single bottlebrush polymer platform for improved PDT.

Alternating azopolymers are notable in smart material design for their unique self-assembly behavior, which stems from the precisely controlled hydrophilic-hydrophobic balance and stimuli-responsiveness. Herein, we report the facile synthesis of light- and pH-responsive alternating copolymers, namely P(Azo-alt-PyEG₂tBu), via Ugi multicomponent polymerization using commercially available azobenzene and pyridine derivatives. P(Azo-alt-PyEG₂tBu) specifically self-assembled into polymersomes with ultrathin membranes (∼2.0 nm) through a folded chain model, serving as potential fluorescent probes when end groups are dye-modified. These polymersomes exhibit reversible morphological transitions between vesicles and micelles under alternating UV and blue light irradiation, driven by the azobenzene isomerization. Similarly, acidic pH triggers disassembly of the polymersomes due to protonation of pyridine groups. Light- and pH-triggered cargo-release studies reveal efficient encapsulation and controlled release of hydrophilic cargos. We have established a versatile strategy for constructing dual-responsive nanocarriers with tailored morphologies and stimuli-adaptive functionalities, advancing smart material applications in drug delivery and bioimaging.

To synthesize functional polypeptoids, the most straightforward strategy involves designing tailored amino acids to generate corresponding N-substituted glycine N-carboxyanhydrides (NNCAs) or N-substituted glycine N-thiocarboxyanhydrides (NNTAs). An alternative route is offered by postpolymerization modification. However, the potential method of modifying NNCA and NNTA monomers to produce functional polypeptoids has received scant attention. Herein, we employed N-allylglycine N-thiocarboxyanhydride (NAG-NTA) as a versatile platform for the convenient synthesis of thioether-functionalized NNTAs via thiol-ene photoaddition. Controlled polymerizations of these thioether-functionalized NNTAs were achieved in CH₂Cl₂ at room temperature, catalyzed by benzoic acid and initiated by a primary amine, yielding well-defined thiopolypeptoids with relatively low dispersities (Đ < 1.29) and predictable molecular weights. The thermal properties and oxidation responsiveness of the thiopolypeptoids were investigated. Poly(ethylene glycol)-b-thiopolypeptoid self-assembled into micelles in water, whose size and morphologies could be tuned by treatment with H₂O₂, showing promise in the fields of bionics and biomedicine due to their excellent biocompatibility.

Hierarchical structures with enhanced performances are of growing importance in many fields, but their preparation suffers from tedious and multistep procedures. There remain challenges to transfer and magnify the molecular functions in hierarchical structures to pursue more unique applications. Herein, a facile one‐step approach for the fabrication of hierarchical structures assembling from amphiphilic copolymers, poly(ethylene glycol)‐ block ‐poly(6‐(4‐(4‐pyridyazo)phenoxy)hexyl methacrylate) (PEG‐ b ‐PAzoPy) with controlled morphologies and enhanced functions, is reported. Various hierarchical structures including three‐dimensional raspberry‐like assemblies, worm networks (WNs), and large compound vesicles are obtained through a heating‐cooling‐aging process in THF/ethanol. The fluorescence detection of p ‐nitrophenol at ultralow concentrations (10 ⁻¹² m ) is realized by the formation of nonfluorescent nitrophenol‐WNs complexes, taking advantage of the high surface area and unique cavities of WNs. Furthermore, a highly efficient nanofiltration composite membrane is constructed by assembling WNs on the surface of a commercial polypropylene membrane. More interestingly, using simple 2H,2H,3H,3H‐perfluoroundecanoic acid as the H‐bond donor and PEG‐ b ‐PAzoPy as the acceptor, they can form H‐bond complexes and further assemble into nanowires with highly ordered liquid crystalline stripes. This study not only offers a facile strategy for the design of hierarchical structures but also facilitates the application of advanced hierarchical materials in various fields.

Different from conventional synthetic polymers, polypeptides exhibit a distinguishing characteristic of adopting specific secondary structures, including random coils, α-helixes, and β-sheets. The conformation determines the rigidity and solubility of polypeptide chains, which further direct the self-assembly and morphology of the nanostructures. We studied the effect of distinct secondary structures on the self-assembly behavior of polytyrosine (PTyr)-derived amphiphilic copolymers. Two block copolymers of enantiopure poly(ethylene glycol)-b-poly(l-tyrosine) (PEG-b-P(l-Tyr)) and racemic poly(ethylene glycol)-b-poly(dl-tyrosine) (PEG-b-P(dl-Tyr)) were synthesized through the ring-opening polymerization of l-tyrosine N-thiocarboxyanhydride (l-Tyr-NTA) and dl-tyrosine N-thiocarboxyanhydride (dl-Tyr-NTA), respectively, by using poly(ethylene glycol) amine as the initiator. PEG₄₄-b-P(l-Tyr)₁₀ adopts a β-sheet conformation and self-assembles into rectangular nanosheets in aqueous solutions, while PEG₄₄-b-P(dl-Tyr)₉ is primarily in a random coil conformation with a tiny content of β-sheet structures, which self-assembles into sheaf-like nanofibrils. A pH increase results in the ionization of phenolic hydroxyl groups, which decreases the β-sheet content and increases the random coil content of the PTyr segments. Accordingly, PEG₄₄-b-P(l-Tyr)₁₀ and PEG₄₄-b-P(dl-Tyr)₉ self-assemble to form slender nanobelts and twisted nanoribbons, respectively, in alkaline aqueous solutions. The secondary structure-driven self-assembly of PTyr-derived copolymers is promising to construct filamentous nanostructures, which have potential for applications in controlled drug release.

Due to the intrinsic porosity and photo‐regulated pore environment, azobenzene (Azo) functionalized covalent organic frameworks (COFs) show great potential for contaminant removal. However, the stability and degree of functionality of the COFs greatly affect the porosity and subsequent adsorption capacity and selectivity. Herein, a highly stable thiazole‐linked COF containing phenolic hydroxyl groups (OH‐COF) is constructed by using 4,4′,4′‐(1,3,5‐triazine‐2,4,6‐triyl)trianiline and 2,5‐dihydroxyterephthalaldehyde in the presence of sulfur, which shows high crystallinity and specific surface. Azo‐functionalized COFs ((Azo)_x‐COFs) are prepared by grafting different amounts azobenzene groups onto OH‐COF through post‐modification, whose aperture is conveniently tuned by the grafted azobenzene amount. The pore size of (Azo)_x‐COFs also can be reversibly adjusted under UV and visible light irradiation without affecting the crystallinity. Appropriate amount of Azo‐grafted (Azo)_0.1‐COF possessed a high adsorption capacity (1216.93 mg g⁻¹) to Congo red (CR). While the adsorption capacity of (Azo)_1.0‐COF to CR significantly increased 2.9 times to reach 1489.96 mg g⁻¹ after UV irradiation. (Azo)_1.0‐COF also can selectively separate dye molecules with different sizes based on photo‐regulated pore size, showing excellent reversibility and reusability. As such, the ability to photo‐regulate the adsorption and interception of (Azo)_x‐COFs highlights their significance in functioning as smart porous nanomaterials for pollutant removal and water purification.

Hyperbranched poly(α‐amino acid)s have caught great attention due to their excellent biocompatibility, biodegradability, and bioactivity. However, hyperbranched polypeptoids are rarely reported because of the challenge of synthesis. Herein, unique polymerizations of N,N'‐diphenoxycarbonyl‐N,N'‐(1,4‐phenylenebismethylene)–diglycine (di‐NNPC, an A*B*‐A*B*‐type monomer) which uncommonly result in hyperbranched polypeptoids rather than gels after the complete consumption of di‐NNPC are reported. The molecular weights of the hyperbranched polypeptoids are controlled by the degree of branching via tuning the initial concentrations of monomer and basic catalyst. N‐Phenyloxycarbonyl glycine pendant groups plentifully remained on the polymer chains are used for Gd³⁺ complexation and post‐modification, which makes the hyperbranched polypeptoids multifunctional single molecular micelles applicable as magnetic resonance imaging contrast agents and photoluminescence probes.

Stimuli‐responsive photonic crystals (PCs) have attracted increasing attentions owing to the unique optical feature in regulating the propagation of light and tunable structural colors in response to external stimuli, emerging application potential on diverse fields. However, the development of stimuli‐responsive PCs with wide visible light range, broad shift of bandgaps, and adjustable responsive rates for counterfeiting remains challenging. Herein, a simple strategy for the preparation of photo‐responsive azobenzene‐containing inverse opal (AzoIO) films is reported. First, azobenzene‐containing composites are generated by filling functional monomers into voids of silica colloids crystals. Followed by the thermal polymerization and subsequent etching, a series of AzoIO films are successfully fabricated with adjustable structural colors in wide visible wavelength. Upon irradiation with linearly polarized visible light (LPVL), a slowly broad blueshift of bandgaps (≈138 nm, 3200 s) is observed due to the anisotropic shrinkage of the periodic PC structures. However, UV light irradiation contributed to a fast broad blueshift of bandgaps (≈131 nm, 10 s), owing to the photoisomerization merit of azobenzene moiety. The proof‐of‐concept study on the applications in light‐modulated multicolored writable paper, encryption films, and fast writing/erasing demonstrated the potential for information security. This work paves an avenue for developing promising optical anti‐counterfeiting materials.