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The composition and structure of polymers have great influence on their performances.

Polymerization-induced self-assembly (PISA) has been demonstrated to be a powerful strategy to produce polymeric nano-objects of various morphologies.

Worm-like micelles have attracted great interest due to their anisotropic structures. However, the experimental conditions for obtaining worm-like micelles are very restricted, which usually causes seriously poor reproducibility. In this work, significantly enhanced accessibility of worm-like micelles is realized by in situ crosslinking polymerization-induced self-assembly (PISA). The reproducibility of worm-like micelles is greatly improved due to the significantly enlarged experimental windows of worm-like micelles in the morphology diagram. Moreover, the reliability of the methodology to enhance the accessibility of worm-like micelles has been demonstrated in various in situ crosslinking PISA systems. The greatly enhanced accessibility and reproducibility of worm-like micelles is undoubtedly cost-effective especially in scale-up production, which paves the way for further application of worm-like micelles with various compositions and functionalities.

Polymerization-induced self-assembly (PISA) has been established as an efficient method to fabricate polymeric vesicles. In most PISA cases, the formation of vesicles is solely driven by the solvop...

In comparison with the post-polymerization cross-linking strategy, in situ cross-linking by divinyl comonomers in polymerization-induced self-assembly (PISA) is a more straightforward and convenient approach to produce structurally stabilized nano-objects. However, cross-linking usually lowers the chain mobility and hence prevents morphology transition, so formation of higher order morphologies (worm-like micelles or vesicles) by the in situ cross-linking strategy in PISA has always been a great challenge. In this work, not only cross-linked structures but also a promoting effect on morphology transition has been observed during the in situ cross-linking PISA. Worm-like micelles, lamella and vesicles with stabilized (cross-linked) structures are produced by RAFT dispersion copolymerization of 2-(diisopropylamino)ethyl methacrylate (DIPEMA) and the divinyl comonomer cystaminebismethacrylamide (CBMA). The morphology transition is not prevented due to the slower consumption of CBMA than that of the DIPEMA, and the cross-linking process is mostly delayed to the late stage of polymerization. What is surprising, compared with RAFT dispersion polymerization of DIPEMA in the absence of CBMA, is that polymeric nano-objects with higher order morphologies are generated in most cases of the RAFT dispersion copolymerization of DIPEMA and CBMA. The slower consumption of CBMA generates branched structures of the solvophobic blocks, which significantly promote the morphology transition. Cleavage of the cross-linkers (disulfide linkage) by incubating with glutathione (GSH) leads to the morphology transition of the nano-objects to the lower order ones, which further demonstrates the promoting effect on morphology transition in in situ cross-linking PISA.

A multicyclic polymer with a hyperbranched structure was successfully synthesized. A tailored initiator containing a protected alkynyl group was prepared and used to initiate the atom transfer radical polymerization (ATRP) of styrene. By the combination of a click reaction, a UV-induced coupling reaction and post-modification, an AB2 type cyclic polystyrene with a protected alkynyl group and two azide groups was obtained, and after deprotection, the clickable cyclic polymer was used as a macromonomer to prepare a multicyclic polymer with a hyperbranched structure by click polymerization via the AB2 strategy. Gel permeation chromatography (GPC) results showed that the obtained hyperbranched multicyclic polymer contained 47 cyclic units on average.

In this study, a bead-like multicyclic polymer was synthesized by the UV-induced coupling reaction of an anthracene-telechelic monocyclic precursor and the reversible topological transformation between the monocyclic polymer and the multicyclic polymer was realized. Poly(ethylene oxide) (PEO) containing bromine and anthryl groups at both ends was used as a macroinitiator for the atom transfer radical polymerization (ATRP) of styrene to afford a linear block polymer (PS-PEO-Br). After azidation, the azide-terminated linear polymer (PEO-PS-N3) underwent bimolecular ring-closure using sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) as a bifunctional linker via a self-accelerating click reaction, and the corresponding monocyclic polymer with two pendant anthryl groups (C(PEO-PS)-ant) was synthesized. Considering the photo-responsive nature of anthracene, the monocyclic polymer was taken as a macromonomer for synthesizing a bead-like multicyclic polymer through the dimerization reaction of anthryl groups under 365 nm UV irradiation. The obtained polymers were characterized by NMR, FT-IR and GPC. According to the result of GPC, there were about 14 “monocyclic units” in the bead-like multicyclic polymer on average. Moreover, the bead-like multicyclic polymer could be cleaved at the nodal points and converted back to the monocyclic structure when exposed to 254 nm UV light.

In this article, we reported the hybrid copolymerization of ethylene and cyclic ketene acetals (CKAs) mediated by dithiocarbamate, in which the propagating radicals could open the rings of CKAs to incorporate cleavable ester units into the polyethylene backbone. The molecular weights and ester incorporation in the produced copolymers could be easily regulated. Furthermore, lipase could degrade the ester-containing polyethylene (PE)-based copolymers into short fragments effectively.

Black phosphorus (BP) has exhibited excellent biocompatibility and high photothermal conversion efficiency under near-infrared light, which makes it very promising for photothermal therapy. However, practical applications are highly hampered because it lacks a targeting property and rapidly degrades in cancer cells, especially in response to strong intracellular oxidative stress. Here, we reported that the mitochondrial targeting peptide functionalized black phosphorus nanosheets covered with an acid-labile polymer shell (doubly functionalized black phosphorus (DFBP) nanosheets) exhibited good stability. DFBP nanosheets not only have excellent ability of accumulating in tumor tissue via surface charge switching but also can target mitochondria. The doubly functionalized black phosphorus nanosheets resulted in robust cancer cell uptake but very poor normal cell accumulation.

In nature, the chemical energy and electrons stored in ATP and NADPH generated during irradiation can facilitate biochemical reactions under dark conditions. However, in artificial photoreaction systems, it is still very difficult to perform photoreactions under dark conditions due to the fact that the photogenerated charge pairs can recombine immediately upon ceasing the irradiation. Preventing the recombination of photogenerated charge pairs still constitutes a major challenge at present. Here, it is reported that functionalized carbon nitride nanomaterials having many heptazine rings with a positive charge distribution, which can tightly trap photogenerated electrons, efficiently prevent the recombination of photogenerated charges. These stored charges are exceedingly long-lived (up to months) and can drive photopolymerization without light irradiation, even after one month. The system introduced here demonstrates a new approach for storing light energy as long-lived radicals, enabling photoreactions under dark conditions.

Ti2C(OH)2 can relieve the hypoxia in tumors via generating O2 from endogenous H2O2 and inhibiting mitochondrial respiratory in cancer cell.

Mitochondrial malfunction is considered to be a decisive signal of apoptosis. It would be a promising strategy to target mitochondria in cancer cells to generate reactive oxygen species (ROS), thus directly inducing mitochondrial damage. We herein reported a mitochondria-targeted, photo-responsive polymer (Mito-PNBE), which can self-assemble into nanoparticles (Fe–CO@Mito-PNBE) encapsulated with diphenylcyclopropenone (light-responsive CO prodrugs) and aminoferrocene-based prodrugs via hydrophobic interactions. Upon UV-irradiation, the rapid release of CO and aminoferrocene-based prodrugs caused by disassembly was observed. On one hand, the released carbon monoxide in mitochondria could enhance ROS generation and accelerate oxidative metabolism. On the other hand, the aminoferrocene-based prodrugs will release Fe3+/Fe2+ ions in the tumor microenvironment, thus triggering the Fenton reaction, which generates more ROS and damages the mitochondria. Thus, the synergistic effect of the two drugs produces enough amounts of ROS in the mitochondria, leading to mitochondrial collapse with an enhanced cancer therapeutic effect. This multifunctional platform has potential in precision cancer therapy.

The development of controlled/“living” polymerization greatly stimulated the prosperity of the fabrication and application of block copolymer nano-objects. Controlled/“living” polymerization was later extended to the scope of polymerization-induced self-assembly (PISA), in which a linear increase of the solvophobic blocks resulted in systemic variation of the packing parameter and almost ergodic morphology transitions. PISA combines polymerization and self-assembly in a much concentrated solution, which has been demonstrated to be a powerful strategy for fabricating block copolymer nano-objects. Various controlled/“living” polymerization techniques, such as reversible addition–fragmentation chain transfer (RAFT) polymerization, nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP), “living” anionic polymerization, and ring-opening metathesis polymerization (ROMP), have been used in PISA to date. In this review, we summarize the developments of polymerization techniques in PISA, which complementarily enlarge the scope of PISA to a broad range of reaction conditions and monomer families.

Polymerization-induced self-assembly (PISA) has been established as a robust strategy to synthesize block copolymer nano-objects with various morphologies, sizes, and surface chemistry, which greatly enlarges the library of functional nano-objects for further applications. The structural stability of nano-objects is an important concern when they are used in drug delivery, nanoreactors, Pickering emulsifiers, etc. Generally, chemical cross-linking via either post-polymerization or in situ cross-linking strategies has been demonstrated to be a viable strategy to improve the structural stability of the nano-objects. In this review, we focus on the PISA-generated nano-objects with enhanced structural stability via either post-polymerization or in situ cross-linking strategies and their applications.

A new strategy combing quantitative reactions and reversible-covalent chemistry is proposed for sequential synthesis of a series of sequence-controlled polymers with different sequences. Using a Michael addition reaction between acrylate and thiol, an aminolysis reaction of five-membered cyclic dithiocarbonate and a thiol substitution reaction of bromomaleimide and thiol, AB-, AB'C- and AB'CD-sequenced molecules are synthesized via AB, AB'C and AB'CD sequential monomer additions, respectively. These three molecules all have furan-protected maleimido group at one end, and the other end of AB-, AB'C- and AB'CD-sequenced molecules is amine, thiol and anthracene groups, respectively. Due to the fact that the furan-protected maleimido group can be efficiently transformed to maleimide group at high temperature via retro Diels-Alder reaction, AB-, AB'C- and AB'CD-sequenced molecules polymerize into sequence-controlled polymers with corresponding sequences at 120 °C. Through this strategy, the synthesis of molecular modules does not require separation and purification, and sequence-controlled polymers with specific sequence can be synthesized in a one-pot process via adding different monomers and adjusting reaction condition.

Stimuli-responsive polymeric vesicles have attracted great attention in drug delivery due to their intrinsic hollow structures and “on demand” release of drugs upon environmental stimuli. The drug-release kinetics from polymeric vesicles, which is usually dependent on the stimuli-responsive behaviors of the polymeric vesicle, has great impacts on the therapeutic efficacy. Over the past decade, polymerization-induced self-assembly (PISA) has been demonstrated to be a powerful strategy to prepare the polymeric vesicles. However, fabrication of stimuli-responsive vesicles with adjustable drug release kinetics via PISA has been rarely reported, which may be due to the poor selectivity of functional membrane-forming polymers in the PISA system. Herein, a series of vesicles with different pH-responsive behaviors were fabricated via RAFT dispersion copolymerization of (diisopropylamino)ethyl methacrylate (DIPEMA) and benzyl methacrylate (BzMA). Both the content of DIPEMA units in hydrophobic P(DIPEMA-co-BzMA) bl...

Cyclic polymers possess distinct properties compared with their linear counterparts, such as smaller hydrodynamic volume, lower viscosity, and higher glass-transition temperature, etc. To explore the impact of the cyclic topology on the thermo-induced phase transition behavior of poly(N-acryloylsarcosine methyl ester) (PNASME), the anthracene-terminated telechelic PNASMEs are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of monomer NASME using a bifunctional chain transfer agent (CTA) with two anthryl groups. Subsequently, cyclic PNASMEs are prepared via UV-induced cyclization under 365 nm UV. There are considerable increases (up to 50 °C) for the cloud point temperatures (Tcp s) of cyclic PNASMEs compared with the linear counterparts. In view of the increment, the Tcp of PNASME is tuned by varying the cyclic/linear ratio (the molar ratio between cyclic PNASME and linear PNASME in the product) with different irradiation time.

Providing access to highly diverse polymer structures by multicomponent reactions is highly desirable; efficient Meldrum's acid-based multicomponent reactions, however, have been rarely highlighted in polymer chemistry. Here, the three-component reaction of Meldrum's acid, indole, and aldehyde is introduced into polymer synthesis. Direct multicomponent polymerization of Meldrum's acid, dialdehyde, and diindole can perform under mild conditions, resulting in complex Meldrum's acid-containing polymers with well-defined structures, and high molecular weights. Additionally, nearly quantitative postpolymerization modification can also perform via this Meldrum's acid-based multicomponent reaction. These results indicate that Meldrum's acid-based multicomponent reaction will be a potential tool to prepare novel polymers.

The size and shape of polymeric vesicles have great impact on their physicochemical and biological properties. Polymerization-induced self-assembly (PISA) is an efficient method to fabricate vesicles. In most PISA-cases, the formation of vesicles is driven by the solvophobic interactions which are lack of versatility on finely structural regulation. Herein, controlling vesicular size and shape is realized in PISA aided by aromatic interactions. Aromatic interactions between the membrane-forming blocks contribute to the augments of membrane tension which lead to the formation of smaller vesicles (as small as 70 nm), but overly enhanced aromatic interactions result in vesicle fusion rather than size decreasing. When the membrane tension is dominated by aromatic interactions and meanwhile high enough to overcome the energetic barriers of fusion, the aromatic interactions drive vesicle fusion in a directional manner to form tubular structures. The precise regulation of vesicular size and shape in PISA would pave the way to fabricate vesicles for a series of size/shape-dependent applications.

Polymerization-induced self-assembly has been demonstrated to be a powerful strategy for fabricating polymeric nanoparticles in the last two decades. However, the stringent requirements for the monomers greatly limit the chemical versatility of PISA-based functional nanoparticles and expanding the monomer family of PISA is still highly desirable. Herein, a camptothecin analogue (CPTM) is first used as the monomer in PISA. Prodrug nanoparticles with reduction-responsive camptothecin release behavior are fabricated at 10% solid concentration (100 mg g-1 ). Poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) and poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) are used as the macro RAFT agents to comediate the RAFT dispersion polymerization of CPTM in ethanol to produce the PHPMA/PDEAEMA-stabilized nanoparticles. The PDEAEMA chains become hydrophobic and are in the collapsed state at physiological pH values. In contrast, in the vicinity of an acidic tumor, the tertiary amine groups of PDEAEMA chains are rapidly protonated, leading to fast hydrophobic-hydrophilic transitions and charge reversal. Such fast charge-reversal results in enhanced cancer cell internalization of the prodrug nanoparticles, thus achieving superior anticancer efficacy.

Polymerization-induced self-assembly (PISA) has been established as a powerful strategy for fabrication of polymeric nano-objects in the past decade. However, in comparison with the traditional self-assembly method, PISA is unsatisfactory in preparation of vesicles with chemical versatility of membrane-forming block for tunable membrane properties, which limits the further application of PISA-based vesicles. Besides the stimuli-responsive property, structural integrity of the vesicles is another important concern for material applications. In situ cross-linking in PISA via copolymerization with multivinyl comonomers (cross-linkers) seems to be a straightforward and convenient method to afford stabilized nano-objects. However, it is hard to fabricate vesicles with cross-linked membrane via in situ cross-linking strategy because cross-linking greatly limits chain mobility of the produced copolymers and thus prevents morphology transition to form vesicles. In this article, in situ cross-linking in PISA for f...

Hybrid copolymerization of two or more structurally distinct monomers (e.g., cyclic monomers and vinyl-type monomers) is very interesting because it can produce new types of copolymers and open up new research directions in the field of polymer chemistry. However, it has long been a challenge because the reactivity and polymerization mechanism of different monomers are extremely different. Here, we report a new hybrid copolymerization via an interconvertible living free radical and anion ring-opening polymerization mechanism, in which the copolymerization of cyclic monomers and vinyl-type monomers can be achieved. Via this novel hybrid copolymerization, the cyclic monomers and vinyl monomers, which generally cannot be copolymerized, now can be copolymerized into one polymer chain. Furthermore, the monomer arrangement in the chains could be easily regulated by the interconverting behavior. This new hybrid copolymerization will provide a powerful means for producing materials that have not been accessible by any other means.

Multicyclic polymers including bicyclic and tetracyclic polymers were constructed by combining atom transfer radical polymerization (ATRP) and a photo-induced coupling reaction of anthryl groups. First, 4-arm and 8-arm star polystyrenes were synthesized by ATRP using tetrafunctional and octafunctional initiators, respectively. Subsequently, after two-step modification of Br-terminated 4-arm and 8-arm star polystyrenes, including azidation and copper-catalyzed azide–alkyne cycloaddition (CuAAC) reactions with prop-2-yn-1-yl anthracene-9-carboxylate, the precursors with anthryl end groups were obtained. Finally, the photo-induced coupling reaction was conducted upon irradiation at 365 nm in a diluted solution of 4-arm and 8-arm star precursors, to produce bicyclic and tetracyclic polymers, respectively. Besides, the multicyclic polymers can convert back to the original precursors after heating at 150 °C. 1H NMR, FT-IR, GPC and UV-vis analyses were carried out to verify the resultant multicyclic structures and the topological conversion between multicyclic polystyrenes and their precursors.

In order to develop pH- and redox-responsive unimolecular micelles composed of camptothecin (CPT)-conjugated hyperbranched star copolymers via acid-labile β-thiopropionate linkage, a new monomer, methacryloyloxy-3-thiohexanoyl–CPT, is synthesized through conjugation of CPT with methacrylate via β-thiopropionate linkage, and then used in synthesis of the CPT-conjugated hyperbranched star copolymers by two steps of atom transfer radical polymerization (ATRP): self-condensation vinyl polymerization of the CPT-based monomer, 2-hydroxypropyl methacrylate and inimer, and subsequent ATRP of oligo(ethylene glycol) methacrylate using the obtained hyperbranched polymers as the macroinitiator. The obtained polymers dissolve in water to form unimolecular micelles, and their release of CPT in water at various pHs and their anticancer efficacy are studied. The CPT-loaded unimolecular micelles with diameters of 3.56–6.08 nm are quite stable under neutral environment, and are easily triggered by mild acidic pH, such as 6.0 and 5.0. They can be easily internalized by the tumor cells, releasing the CPT. The CPT-conjugated unimolecular micelles via acid-labile β-thiopropionate linkage have potential for application as tumor-targeted drug release systems.

Summary Polyethylene (PE) is one of the most widely used materials in the world, but it is virtually undegradable and quickly accumulates in nature, which may contaminate the environment. We utilized the cobalt-mediated radical copolymerization (CMRP) of ethylene and cyclic ketene acetals (CKAs) to effectively incorporate ester groups into PE backbone as cleavable structures to make PE-based copolymer degradable under mild conditions. The content of ethylene and ester units in the produced copolymer could be finely regulated by CKA concentration or ethylene pressure. Also, the copolymerization of ethylene and CKA with other functional vinyl monomers can produce functional and degradable PE-based copolymer. All the formed PE-based copolymers could degrade in the presence of trimethylamine (Et3N)., Graphical Abstract, Highlights • We report cobalt-mediated copolymerization for inserting ester unit into PE backbone • The molecular weight of degraded product varied from several hundreds to thousands • This method provides access to a diverse range of degradable functional PE materials, Green Chemistry; Organic Chemistry; Polymers

Providing access to diverse polymer structures is highly desirable, which helps to explore new polymer materials. Poly(thioester sulfonamide)s, combining both the advantages of thioesters and amides, however, are rarely available in polymer chemistry. Here, the ring-opening copolymerization (ROCOP) of cyclic thioanhydride with N-sulfonyl aziridine using mild phosphazene base, resulting in well-defined poly(thioester sulfonamide)s with highly alternative structures, high yields, and controlled molecular weights, is reported. Additionally, benefiting from the mild catalytic process, this ROCOP can be combined with ROCOP of N-sulfonyl aziridines with cyclic anhydrides to produce novel block copolymers.

Multicyclic polystyrene (PS) with hyperbranched structure was constructed in an efficient way. First, a seesaw-type PS was synthesized via atom transfer radical polymerization (ATRP) using a Y-shaped ATRP initiator containing one hydroxyl at center and bromine at each end. After azidation, the anthryl and hydroxyl groups were introduced to the ends of the polymer chain by click reaction with a trifunctional molecule bearing alkynyl, hydroxyl, and anthryl groups (alkynyl-OH-ant). By irradiation with 365 nm UV light in a highly dilute condition, cyclic polymer with three hydroxyl groups (c-PS-(OH)3) can be obtained; then it was converted to a cyclic polymer containing three azides (c-PS-(N3)3) by bromination of the hydroxyl groups and azidation. This “A3” cyclic macromonomer was then used to construct hyperbranched multicyclic polymers via self-accelerating click reaction with sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DBA). The properties of obtained polymer were characterized by NMR, FT-IR, MALDI-TOF MS, a...

In this study, an efficient method is proposed for the synthesis of polymer prodrug with acid-liable linkage via thiol-acrylate Michael addition reaction of the camptothecin with tethering acrylate group and polymer scaffold containing multiple thiol groups. The polymer scaffold P(HEO2MA)- b-P(HEMA-DHLA) is prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of the methacrylate of lipoic acid (HEMA-LA) using poly(2-(2-hydroethoxy) ethyl methacrylate) (PHEO2MA) as macro-RAFT agent followed by reduction of the disulfides in lipoic acid (LA) groups to give polymer scaffold with dihydrolipoic acid (DHLA) pendent groups. Acrylate-tethering camptothecin (ACPT) is connected to P(HEO2MA)- b-P(HEMA-DHLA) via Michael addition reaction between thiol and acrylate with a high coupling efficiency (95%). Amphiphilic polymer prodrug P(HEO2MA)- b-P(HEMA-DHLA-CPT) spontaneously self-assembles into nanoparticles in an aqueous solution and exhibits a CPT loading content as high as 40.1%. The prodrug nanoparticles with the acid-liable β-thiopropionate linkages can release CPT under acidic conditions, and the prodrug nanoparticles show similar cytotoxicity to HeLa cells as free CPT. Overall, the prodrug nanoparticles with high drug loading contents and acid-liable linkages are promising for pH-responsive anticancer therapy.

A hybrid drug delivery system was successfully fabricated by attaching a camptothecin (CPT)-based polymeric prodrug onto the surface of silver nanoparticles (AgNPs). PEG was employed as a macro-RAFT agent in RAFT polymerization to synthesize a branched star copolymer, to which CPT is linked through the photo-responsive o-nitrobenzyl linkage. In vitro tests indicate that the fluorescence of CPT in the polymeric prodrug is quenched by AgNPs based on the nanomaterial surface energy transfer (NSET) effect and the fluorescence recovers when the CPT molecules are released from hybrid nanoparticles. Thus, the variation of fluorescence intensity is bound up with the drug release behaviours, which may enable this AgNP-based drug delivery system to trace the intracellular drug release process and observe the distribution of released CPT in cells.

In this study, an efficient strategy was presented to prepare monocyclic polymers via combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and light-induced cycloaddition reaction, and tadpole-shaped copolymer was further synthesized via ring-opening polymerization (ROP) using cyclic polystyrene (C-PS) as macroinitiator. A series of well-defined α, ω-hetero bifunctional homopolymers with furan-protected maleimide and o-methylbenzaldehyde terminals, including polystyrene (PS), poly (N, N-dimethylacrylamide) (PDMA) and poly (N-isopropylacrylamide) (PNIPAAm) were prepared via RAFT polymerization. After deprotection, highly active maleimide group at the end of linear polymer coupled intramolecularly with photoenol structure (photoisomer of o-methylbenzaldehyde) via Diels-Alder cycloaddition reaction under 365 nm UV irradiation in dilute solution, leading to the formation of cyclic polymer. The monocyclic polymers were characterized with 1H NMR, UV–Vis spectroscopy, gel permeation chromatography (GPC) and MALDI-TOF MS. Furthermore, the C-PS containing hydroxyl group was used as macroinitiator to prepare tadpole-shaped copolymer CPS-b-PCL via the ROP of e-caprolactone.

This paper elaborates the preparation of “flower-shaped” tricyclic and hexacyclic polymers by intramolecular cyclization via a “tail-biting” strategy. Multifunctional initiators with equal amounts of alkynyl groups and 2-bromoisobutyrate groups are synthesized by catalyst-free azide-alkynyl click reaction, and then used in atom transfer radical polymerization (ATRP) of styrene to afford multiarm star polystyrenes (PS). After azidation of terminal bromines, multicyclic polymers are prepared by intramolecular cyclization via Cu-catalyzed azide-alkynyl cycloaddition (CuAAc) click reaction between terminal azide groups and interior alkynyl groups. Structures of tricyclic and hexacyclic polystyrenes are characterized by 1H NMR, GPC and FT-IR. Fluorescence emissions of initiators and polymers are observed, and the influence of topology on fluorescence intensity is discussed.

A unique drug delivery system, in which silver nanoparticles (AgNPs) are covered with camptothecin (CPT)-based polymer prodrug, has been developed, and the polymer prodrug, in which the CPT is linked to the polymer side chains via an acid-labile β-thiopropionate bond, is prepared by RAFT polymerization. For poly(2-(2-hydroxyethoxy)ethyl methacrylate-co-methacryloyloxy-3-thiahexanoyl-camptothecin)@AgNPs [P(HEO2MA-co-MACPT)@AgNPs], the polymer thickness on the AgNP surface is around 5.9 nm (TGA method). In vitro tests in buffer solutions at pH = 7.4 reveal that fluorescence of the CPT in the hybrid nanoparticles is quenched due to the nanoparticle surface energy transfer (NSET) effect, but under acidic conditions, the CPT fluorescence is gradually recovered with gradual release of the CPT molecules from the hybrid nanoparticles through cleavage of the acid-labile bond. The NSET “on” and “off” is induced by the CPT–AgNP distance change. This unique property makes it possible to track the CPT delivery and rel...

Intelligent vesicles are fabricated at up to 30% solid content via an approach of polymerization-induced self-assembly and reorganization (PISR). Upon irradiation with UV light (365 nm), light-triggered dimerization of the coumarin moieties anchored in the membrane leads to the membrane cross-linking of the vesicles, which endows the vesicles with superior structural stability. Due to the tertiary amine groups in the membrane, the vesicles go through a swelling/deswelling change upon switching the pH values. In acidic aqueous solution, the pores in the membrane of vesicles are opened, which is beneficial for transmembrane traffic. The pore size in the membrane of vesicles is in accordance with the extent of membrane cross-linking, which can be conveniently regulated by the irradiation time of UV light (365 nm). The size range of the substance for transmembrane traffic is effectively enlarged; even 15 nm gold nanoparticles can be postloaded into the vesicles with lower extents of the membrane cross-linking through the diffusion method. Although the pores in the vesicle membrane are opened in acidic aqueous solution, transmembrane traffic is inhibited for the electropositive substance because of electrostatic repulsion but is allowed for the electronegative substance. These reported vesicles herein may be the smartest artificial vesicles to date due to their multiple selective permeability.

Cyclic polymers have a number of unique physical properties compared with those of their linear counterparts. However, the methods for the synthesis of cyclic polymers are very limited, and some multicyclic polymers are still not accessible now. Here, we found that the five˗membered cyclic structure and electron withdrawing groups make methylene in rhodanine highly active to aldehyde via highly efficient Knoevenagel reaction. Also, rhodanine can act as an initiator for anionic ring-opening polymerization of thiirane to produce cyclic polythioethers. Therefore, rhodanine can serve as both an initiator for ring-opening polymerization and a monomer in Knoevenagel polymerization. Via rhodanine-based Knoevenagel reaction, we can easily incorporate rhodanine moieties in the backbone, side chain, branched chain, etc, and correspondingly could produce cyclic structures in the backbone, side chain, branched chain, etc, via rhodanine˗based anionic ring-opening polymerization. This rhodanine chemistry would provide easy access to a wide variety of complex multicyclic polymers., Cyclic polymers have a number of unique physical properties compared to their linear counterparts but their synthesis is very limited. Here, the authors show a method to form a wide variety of multicyclic polymers by a rhodanine˗based Knoevenagel reaction and ring-opening polymerization.

Chemodynamic therapy based on Fe2+-catalyzed Fenton reaction holds great promise in cancer treatment. However, low-produced hydroxyl radicals in tumor cells constitute its severe challenges because of the fact that Fe2+ with high catalytic activity could be easily oxidized into Fe3+ with low catalytic activity, greatly lowering Fenton reaction efficacy. Here, we codeliver CuS with the iron-containing prodrug into tumor cells. In tumor cells, the overproduced esterase could cleave the phenolic ester bond in the prodrug to release Fe2+, activating Fenton reaction to produce the hydroxyl radical. Meanwhile, CuS could act as a nanocatalyst for continuously catalyzing the regeneration of high-active Fe2+ from low-active Fe3+ to produce enough hydroxyl radicals to efficiently kill tumor cells as well as a photothermal therapy agent for generating hyperthermia for thermal ablation of tumor cells upon NIR irradiation. The results have exhibited that the approach of photothermal therapy nanomaterials boosting transformation of Fe3+ into Fe2+ in tumor cells can highly improve Fenton reaction for efficient chemodynamic therapy. This strategy was demonstrated to have an excellent antitumor activity both in vitro and in vivo, which provides an innovative perspective to Fenton reaction-based chemodynamic therapy.

A simple and efficient method to construct a hyperbranched multicyclic polymer is introduced. First, a tailored trithiocarbonate with two terminal anthracene units and three azide groups is successfully synthesized, and this multifunctional trithiocarbonate is used as chain transfer agent (CTA) to afford anthracene-telechelic polystyrene (PS) via reversible addition-fragmentation chain transfer (RAFT) polymerization. After that, linear PS is irradiated under 365 nm UV light to achieve the cyclization process. The monocyclic polymer further reacts with sym-dibenzo-1,5-cyclooctadiene-3,7-diyne via "A2 +B3 " strategy based on a self-accelerating click reaction to produce hyperbranched multicyclic polymer. The structures and properties of the polymers are characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), UV-vis spectrophotometry, and triple-detection size-exclusion chromatography (TD-SEC). The number of monocyclic units of the resultant hyperbranched multicyclic polymer reaches about 21 based on multi-angle laser light scattering (MALLS) measurements. The plot of intrinsic viscosity versus molecular weight reveals that the α value of the unique hyperbranched multicyclic polymer is lower than both hyperbranched polymers and cyclic polymers.

Polymerization-induced self-assembly (PISA) is an efficient and robust strategy to fabricate polymeric nano-objects. PISA enables us to prepare polymeric nano-objects in situ during the course of polymerization in concentrated solution (up to 50% w/w), making industrial production of polymeric assemblies in large-scale possible. In this work, reversible addition-fragmentation chain transfer (RAFT) dispersion copolymerization of styrene (St) and N-methacryloxysuccinimide (NMAS) was conducted with poly(2-hydroxyethyl acrylate) (PHEA) as a macro-chain transfer agent (macro-CTA) in methanol. Compared with the PHEA-mediated alcoholic dispersion polymerization of St, RAFT dispersion copolymerization of St and NMAS promoted morphology transition of nano-objects to form higher order morphologies (such as worms and vesicles). Moreover, the introduction of NMAS units into the solvophobic blocks provided functional handles for post-PISA modification of the resultant nano-objects via the active ester-amine reaction. The reaction of 1,6-hexanediamine with NMAS units in P(St-co-NMAS) blocks was conducted to afford cross-linked nano-objects with robust structural stability.

Herein, we report a novel category of optically active hyperbranched polymers (HBPs) that can serve as a recyclable chiral host platform to promote the asymmetric Michael addition reactions in aqueous environments. The chiral hydrophobic cavities within the HBPs provide a chiral microenvironment for the asymmetric Michael addition with a high product yield of up to 89% and satisfactory enantioselectivity. HBPs-6 (prepared with pure D-type chiral monomer) and quinine can work together in a synergistic way, which leads to an enhancement in catalytic stereoselectivity. However, for HBPs-1 (prepared with pure L-type chiral monomer), the catalytic stereoselectivity of quinine within the L-type chiral hydrophobic cavities is slightly suppressed since the quinine units are very likely to be shielded by the polymer chains. The present study not only provides a catalyst scaffold to achieve high yield and enantioselectivity for the asymmetric Michael addition in aqueous environments, but also is of great fundamental value for the rational design of artificial synthetic materials in approximating enzymes.