Binbin Xu

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.

Development of highly efficient and versatile strategies for functionalization of commodity polymers direct from carbon-hydrogen (C-H) bonds has attracted growing interest due to the ubiquity of C-H bonds in various commodity polymers and the great desire for upcycle of commodity polymers. However, the efficiency of C-H activation is usually low (<20%) and only one (potential) functional unit was introduced into each activated C-H bond. The low content of introduced functional units could be one great hindrance to the improvement of performance of resulting polymers. Herein we report a photocatalytic hydrogen atom transfer reversible addition-fragmentation chain transfer (HAT-RAFT) grafting polymerization strategy to introduce polymeric side chains of activated pentafluorophenyl esters (PFEs) into commodity polymers of poly(ethylene glycol), poly(propylene oxide), polybutylene, polypropylene, and poly(vinylpyrrolidone) by using the C-H bonds of commodity polymers as the initiating sites. The grafting polymerization of pentafluorophenyl acrylate (PFA) exhibits living/controlled features and temporal controllability. With the amplification effect of grafting polymerization, each activated C-H bond allows to the introduction of tens of PFEs, leading to a high content of PFE groups. Owing to the high reactivity of PFEs toward amino- and hydroxyl-containing molecules under mild conditions with excellent efficiency and group tolerance, the introduced PFEs of PPFA chains enable quantitative transesterification and amidation for efficient functionalization of commodity polymers via PFE-ligation chemistry.

Crystallization-driven self-assembly (CDSA) of π-conjugated homopolymers/oligomers has emerged as a versatile strategy to generate various nanostructures without an extra polymer corona layer. However, this field remains in its infancy, with rare reports concerning this topic. To get an in-depth understanding of how the structure of π-conjugated homopolymers/oligomers affects CDSA behavior, in this contribution, a series of oligo(p-phenylenevinylene) derivatives (OPV_n, where the subscript represents the number of repeat units) with different chain lengths (n = 3, 4, or 5) and chain end groups of aldehyde (CHO) and cyano/carboxyl (CN/COOH) were synthesized. The influence of the chain length and structure of the chain end groups of OPV on CDSA behavior was examined in detail. It was found that the increase in the chain length of OPV would increase the stacking strength of OPV units for both CHO- and CN/COOH-terminated OPV. In addition, the introduction of more electron-deficient CN/COOH units would lead to a more pronounced electron pull-push effect, which not only resulted in the red shift of the UV/vis absorbance and fluorescence bands of OPV but also increased the stacking strength of OPV units as a consequence of the enhancement of charge transfer interactions. CHO-terminated OPV₃-CHO and OPV₄-CHO and CN/COOH-terminated OPV₃-COOH remained in unimolecularly dissolved states in n-butanol at 25 °C. On the contrary, OPV₅-CHO formed ribbon-like micelles with widths in the range from ∼20 to ∼150 nm and lengths up to several micrometers, and OPV₄-COOH formed ribbon-like micelles with a width of ∼20 nm under the same conditions. Interestingly, tube-like micelles with a length of tens of micrometers could be formed for OPV₅-COOH. By virtue of acid-base interactions, amino-based porphyrins can be immobilized onto the surface of the micelles of OPV₅-COOH. This work demonstrates a vital role of the chemical structure of π-conjugated oligomers/polymers in determining CDSA behavior, which will be beneficial to extending CDSA toward the creation of various functional π-conjugated nanostructures.

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.

The self-assembly behaviors of rod-coil asymmetric diblock molecular brushes (ADMBs) bearing responsive side chains in a selective solvent are investigated via dissipative particle dynamics simulations. By systematically varying the polymerization degree, copolymer concentration, and side chain length, several morphological phase diagrams were constructed. ADMB assemblies exhibited a rich variety of morphologies, including cylindrical micelles, spherical micelles, nanowires, polyhedral micelles, ellipsoid micelles, and large compound micelles. The structures of the representative nanowires were analyzed in detail. A kinetics study revealed that the one-dimensional growth of nanowires follows the step-growth polymerization mechanism. Besides, by calculating the local order parameter of the rigid chains, we found that increasing the lengths of A and C side chains can promote the ordered arrangement of the rigid chains. Moreover, the rod-to-coil conformation transitions were simulated to explore the stimuli-responsive behaviors of ADMBs with responsive rigid side chains. The simulation results indicated that the volume of the assemblies expanded without the support of the rigid chains. The present work not only provides a comprehensive understanding of the self-assembly behaviors of ADMBs but also provides meaningful theoretical support for the development of novel molecular brush materials.

Living crystallization-driven self-assembly (CDSA) has emerged as an efficient strategy to generate nanofibers of π-conjugated polymers (CPNFs) in a controlled fashion. However, reports of donor-acceptor (D-A) heterojunction CPNFs are extremely rare. The preparation of these materials remains a challenge due to the lack of rational design guidelines for the D-A π-conjugated units. Herein, we report a versatile CDSA strategy based upon carefully designed D-A-co-oligomers in which electron-deficient benzothiadiazole (BT) or dibenzo[b,d]thiophene 5,5-dioxide (FSO) units are attached to the two ends of an oligo(p-phenylene ethynylene) heptamer [BT-OPE₇-BT, FSO-OPE₇-FSO]. This arrangement with the electron-deficient groups at the two ends of the oligomer enhances the stacking interaction of the A-D-A π-conjugated structure. In contrast, D-A-D structures with a single BT in the middle of a string of OPE units disrupt the packing. We employed oligomers with a terminal alkyne to synthesize diblock copolymers BT-OPE₇-BT-b-P2VP and BT-OPE₇-BT-b-PNIPAM (P2VP = poly(2-vinylpyridine), PNIPAM = poly(N-isopropylacrylamide)) and FSO-OPE₇-FSO-b-P2VP and FSO-OPE₇-FSO-b-PNIPAM. CDSA experiments with these copolymers in ethanol were able to generate CPNFs of controlled length by both self-seeding and seeded growth as well as block comicelles with precisely tunable length and composition. Furthermore, the D-A CPNFs with a BT-OPE₇-BT-based core demonstrate photocatalytic activity for the photooxidation of sulfide to sulfoxide and benzylamine to N-benzylidenebenzylamine. Given the scope of the oligomer compositions examined and the range of structures formed, we believe that the living CDSA strategy with D-A-based co-oligomers opens future opportunities for the creation of D-A CPNFs with programmable architectures as well as diverse functionalities and applications.

Heterografted molecular brushes (HMBs) bearing two or more types of side chains have attracted tremendous attention because of their asymmetric structures and multiple functionalities. However, the controlled synthesis of HMBs with three types of side chains remains a challenge. The structure–property–application correlations of HMBs with three types of side chains are still not clear. Herein, based on the multivalent monomer strategy, we report the synthesis of well-defined asymmetric HMBs comprising three different side chains by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization, atom transfer radical polymerization (ATRP), thiol–epoxy coupling reaction, and ring-opening polymerization (ROP). PA-g-PAzo/PEG/PLA with a polyacrylate (PA) backbone, hydrophobic poly(azobenzene-methacrylate) (PAzo) brush, hydrophilic polyethylene glycol (PEG) brush, and hydrophobic polylactide (PLA) brush was synthesized and characterized. The self-assembly behavior of PA-g-PAzo/PEG/PLA with a short backbone and relatively strong intermolecular association in solutions was investigated. Well-defined platelets with tunable morphologies were constructed. Subsequently, PA-g-PFA/PEG/PLA with a fluorophilic poly(pentafluoropropyl acrylate) (PFA) brush, hydrophilic PEG brush, and lipophilic PLA brush was synthesized and further used as an efficient surfactant for the stabilization of different emulsions. Our study offers a platform for exploring the unique properties of asymmetric HMBs.