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The first aim of this study is to develop a photo‐ATRP process using methyl methacrylate (MMA) by employing a novel perylenediimide derivative (PDI) as photoinitiator. The analysis of the MMA photopolymerization process kinetics is performed in solution and in bulk, demonstrating control over the reaction progress even if the polymerizations display a slow initiation step. The photo‐ATRP process for MMA in suspension is also developed and the obtained PMMA particles are further used to reinitiate the ATRP polymerization of thermoresponsive polymers (different molecular weights poly(ethylene glycol) methyl ether methacrylate and poly(N‐isopropylacrylamide)) (PNIPAM) in solution and surface‐initiated processes. The synthesized polymers by surface‐initiated process display a bimodal molecular weight distribution with a clear modification of the signal areas ratio depending on the grafted monomer and on the reaction conditions. The grafting process can take place on the surface of the polymer particles (Mn2), or it can also involve polymer chains located further at the interior of the polymer particles (Mn1). The lower critical solution temperature (LCST) transition is demonstrated for the PNIPAM functionalized polymer particles. A perylene diimide derivative is synthesized and used as photoinitiator for atom transfer radical polymerization of methyl methacrylate. Surface‐initiated polymerization confirms the controlled characteristic by exploiting the presence of terminal bromine on the surface of the particles obtained by suspension. The poly(N‐isopropylacrylamide) grafts on the surface of the particles lead to an increase of the lower critical solution temperature transition.

Atom transfer radical polymerization (ATRP) has become one of the most implemented methods for polymer synthesis, owing to impressive control over polymer composition and associated properties. However, contamination of the polymer by the metal catalyst remains a major limitation. Organic ATRP photoredox catalysts have been sought to address this difficult challenge but have not achieved the precision performance of metal catalysts. Here, we introduce diaryl dihydrophenazines, identified through computationally directed discovery, as a class of strongly reducing photoredox catalysts. These catalysts achieve high initiator efficiencies through activation by visible light to synthesize polymers with tunable molecular weights and low dispersities.

Ultrasonic agitation is an external stimulus, rapidly developed in recent years in the atom transfer radical polymerization (ATRP) approach. This review presents the current state-of-the-art in the application of ultrasound in ATRP, including an initially-developed, mechanically-initiated solution with the use of piezoelectric nanoparticles, that next goes to the ultrasonication-mediated method utilizing ultrasound as a factor for producing radicals through the homolytic cleavage of polymer chains, or the sonolysis of solvent or other small molecules. Future perspectives in the field of ultrasound in ATRP are presented, focusing on the preparation of more complex architectures with highly predictable molecular weights and versatile properties. The challenges also include biohybrid materials. Recent advances in the ultrasound-mediated ATRP point out this approach as an excellent tool for the synthesis of advanced materials with a wide range of potential industrial applications.

Lignin is a potential natural sunlight protector because its benzene derivative structure can absorb UV rays. Pure lignin is not good enough for sunblock because lignin is not fully dispersed in cream, and the range of absorbed UV rays is not broad. In this work, lignin was modified with polybutyl acrylate (PBA) and self-assembled into microspheres (L-PBA-NPs) to enhance its compatibility in cream, and it was blended with p-coumaric acid (CA) to extend its light absorbance. The hydrophobicity of grafted PBA on lignin and the microsphere of the modified lignin provided an ability to disperse in oily pure cream. To improve the sun protection factor (SPF) of the blended lignin-based sunscreen, CA with different UV absorbing ability was mixed inside the modified lignin to form CA@L-PBA-NPs. When CA and L-PBA-NPs (1:1) were added in cream with 5%, the SPF of the blended lignin sunscreen reached 18.8. After irradiation of the CA@L-PBA-NPs sunscreen under UV for 3 h, the SPF of the blended lignin-based sunscreen increased slightly because of more conjugated structures produced in lignin. The CA@L-PBA-NPs in sunscreens have great potential as a green ingredient to substitute for the small-molecule sunscreen active ingredients in commercial sunscreen products.

We exploited organic photo-redox-catalyzed atom transfer radical polymerization (O-ATRP) to synthesize a thermo-responsive polymer with a narrow molecular weight distribution. Poly(methyl methacrylate) (PMMA) chains were polymerized from a hydroxypropyl cellulose (HPC)-based macroinitiator using metal-free O-ATRP under visible-light irradiation. This O-ATRP is mediated by 1,2,3,5-tetrakis (carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), a photoredox catalyst with a substantial excited-state reduction potential, low cost, and ease of preparation. The synthesis of a series of PMMA-grafted HPC (PMMA-g-HPC) was characterized by various analytical methods, including FTIR spectroscopy, NMR spectroscopy, TGA, and GPC analysis. The lower critical solution temperature (LCST) of the polymers was determined by measuring the transmittance of the polymer solution as a function of the temperature at various pH values. Consequently, we expanded the LCST window of the HPC-based polymers and generated the opposite pH dependency of the LCST by forming PMMA-g-HPCs. Our “grafting-from” synthetic approach and thermo-responsive polymers, which are controllable in full range of physiological conditions, are promising in a variety of biological, electronics, and biosensor applications, particularly in drug delivery systems.

Exosomes are emerging as ideal drug delivery vehicles due to their biological origin and ability to transfer cargo between cells. However, rapid clearance of exogenous exosomes from the circulation as well as aggregation of exosomes and shedding of surface proteins during storage limit their clinical translation. Here, we demonstrate highly controlled and reversible functionalization of exosome surfaces with well-defined polymers that modulate the exosome’s physiochemical and pharmacokinetic properties. Using cholesterol-modified DNA tethers and complementary DNA block copolymers, exosome surfaces were engineered with different biocompatible polymers. Additionally, polymers were directly grafted from the exosome surface using biocompatible photomediated atom transfer radical polymerization (ATRP). These exosome polymer hybrids (EPHs) exhibited enhanced stability under various storage conditions and in the presence of proteolytic enzymes. Tuning of the polymer length and surface loading allowed precise control over exosome surface interactions, cellular uptake, and preserved bioactivity. EPHs show fourfold higher blood circulation time without altering tissue distribution profiles. Our results highlight the potential of precise nanoengineering of exosomes toward developing advanced drug and therapeutic delivery systems using modern ATRP methods.

The development of polymers that can spontaneously repair themselves after mechanical damage would significantly improve the safety, lifetime, energy efficiency and environmental impact of man-made materials. Most approaches to self-healing materials require the input of external energy, healing agents, solvent or plasticizer. Despite intense research in this area, the synthesis of a stiff material with intrinsic self-healing ability remains a key challenge. Here, we show a design of multiphase supramolecular thermoplastic elastomers that combine high modulus and toughness with spontaneous healing capability. The designed hydrogen-bonding brush polymers self-assemble into a hard–soft microphase-separated system, combining the enhanced stiffness and toughness of nanocomposites with the self-healing capability of dynamic supramolecular assemblies. In contrast to previous self-healing polymers, this new system spontaneously self-heals as a single-component solid material at ambient conditions, without the need for any external stimulus, healing agent, plasticizer or solvent. Polymer materials that could spontaneously heal like tissues in living systems would significantly improve the safety, lifetime, energy efficiency and environmental impact of man-made materials. Now, a general multiphase design of autonomous self-healing elastomeric materials that do not require the input of external energy or healing agents is reported.

Effective separation of oil and water has always been a long-term challenge. Here we introduce a facile and fluorine-free method to fabricate superhydrophobic and superoleophilic filter paper without the decoration of solid particles for robust oil/water separation. After chemically bonding octadecanoyl and α-bromoisobutyryl groups on the surface of filter paper through simultaneous esterification with stearoyl chloride and α-bromoisobutyryl bromide (BiBB) to obtain C18-FP-g-Br, superhydrophobic poly(styrene-co-acrylonitrile) (SAN) grafted filter paper (C18-FP-g-SAN) was fabricated via surface-initiated atom transfer radical polymerization. The obtained C18-FP-g-SAN showed a water contact angle of 153° and achieved a separation efficiency exceeding 98.5% after ten different typical oil/water separation processes due to the synergistically combined contributions of bonded octadecanoyl chain and grafted SAN. C18-FP-g-SAN remained high separation efficiency after 10 cycles of use and treatment with strong acidic or basic solution. The excellent reusability and chemical stability of C18-FP-g-SAN promise its practical applications of continuous oil/water separation and oil spillage cleanup.Graphic abstract

To address the growing demand for environmentally friendly flexible sensors, here, a composite hydrogel of nanocellulose (NC) and polyvinyl alcohol (PVA) was designed and fabricated using Camellia oleifera shells as a sustainable alternative to petroleum-based raw materials. Firstly, NC was extracted from Camellia oleifera shells and modified with 2-chloropropyl chloride to obtain a nanocellulose-based initiator (Init-NC) for atomic transfer radical polymerization (ATRP). Subsequently, sulfonyl betaine methacrylate (SBMA) was polymerized by Init-NC initiating to yield zwitterion-functionalized nanocellulose (NC-PSBMA). Finally, the NC-PSBMA/PVA hydrogel was fabricated by blending NC-PSBMA with PVA. A Fourier transform infrared spectrometer (FT-IR), proton nuclear magnetic resonance spectrometer (1H-NMR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), universal mechanical testing machine, and digital source-meter were used to characterize the chemical structure, surface microstructure, and sensing performance. The results indicated that: (1) FT-IR and 1H NMR confirmed the successful synthesis of NC-PSBMA; (2) SEM, TEM, and alternating current (AC) impedance spectroscopy verified that the NC-PSBMA/PVA hydrogel exhibits a uniform porous structure (pore diameter was 1.1737 μm), resulting in significantly better porosity (15.75%) and ionic conductivity (2.652 S·m−1) compared to the pure PVA hydrogel; and (3) mechanical testing combined with source meter testing showed that the tensile strength of the composite hydrogel increased by 6.4 times compared to the pure PVA hydrogel; meanwhile, it showed a high sensitivity (GF = 1.40, strain range 0–5%; GF = 1.67, strain range 5–20%) and rapid response time (<0.05 s). This study presents a novel approach to developing bio-based, flexible sensing materials.

A cellulose-grafted-poly(N-isopropylacrylamide) (cellulose-g-PNIPAAm) copolymer with thermo-responsivity was synthesized using homogeneous activators regenerated by electron transfer for atom transfer radical polymerization (ARGET-ATRP). The prepared copolymer dispersed at low concentration in water or phosphate-buffered saline (PBS) at 25 °C could self-assembly into micelles at 37 °C. The size and morphology of these micelles were determined by dynamic light scattering and transmission electron microscopy. The copolymer at a concentration over 4.2% by weight in water formed an injectable thermo-responsive hydrogel that was composed of micelles when the temperature increased to 37 °C. This hydrogel was used to load the anticancer drug doxorubicin (DOX). In vitro release studies demonstrated that this hydrogel released DOX in a sustained manner. Furthermore, this cellulose-based injectable thermo-responsive hydrogel was used in cytotoxicity tests, revealing that it was very biocompatible. Based on the above results, this cellulose-g-PNIPAAm injectable thermo-responsive hydrogel has strong potential for application in smart drug delivery systems.