A novel methodology of visible light regulated ring opening polymerization in the presence of reversible merocyanine-based photoacid was reported for the first time. In combination with a ...photoinduced radical polymerization technique, a dual wavelength light controlled orthogonal polymerization system was investigated to switch the polymerization between two different monomers and for the preparation of block and graft copolymers in one pot.
The applications of fluorinated molecules in bioengineering and nanotechnology are expanding rapidly with the controlled introduction of fluorine being broadly studied due to the unique properties of ...C–F bonds. This review will focus on the design and utility of C–F containing materials in imaging, therapeutics, and environmental applications with a central theme being the importance of controlling fluorine–fluorine interactions and understanding how such interactions impact biological behavior. Low natural abundance of fluorine is shown to provide sensitivity and background advantages for imaging and detection of a variety of diseases with 19F magnetic resonance imaging, 18F positron emission tomography and ultrasound discussed as illustrative examples. The presence of C–F bonds can also be used to tailor membrane permeability and pharmacokinetic properties of drugs and delivery agents for enhanced cell uptake and therapeutics. A key message of this review is that while the promise of C–F containing materials is significant, a subset of highly fluorinated compounds such as per- and polyfluoroalkyl substances (PFAS), have been identified as posing a potential risk to human health. The unique properties of the C–F bond and the significant potential for fluorine–fluorine interactions in PFAS structures necessitate the development of new strategies for facile and efficient environmental removal and remediation. Recent progress in the development of fluorine-containing compounds as molecular imaging and therapeutic agents will be reviewed and their design features contrasted with environmental and health risks for PFAS systems. Finally, present challenges and future directions in the exploitation of the biological aspects of fluorinated systems will be described.
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IJS, KILJ, NUK, PNG, UL, UM
Here, we exploit the selectivity of photoactivation of thiocarbonylthio compounds to implement two distinct organic and polymer synthetic methodologies: (1) a single unit monomer insertion (SUMI) ...reaction and (2) selective, controlled radical polymerization via a visible-light-mediated photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) process. In the first method, precise single unit monomer insertion into a dithiobenzoate with a high reaction yield (>97%) is reported using an organic photoredox catalyst, pheophorbide a (PheoA), under red light irradiation (λmax = 635 nm, 0.4 mW/cm2). The exceptional selectivity of PheoA toward dithiobenzoate was utilized in combination with another catalyst, zinc tetraphenylporphine (ZnTPP), for the preparation of a complex macromolecular architecture. PheoA was first employed to selectively activate a dithiobenzoate, 4-cyanopentanoic acid dithiobenzoate, for the polymerization of a methacrylate backbone under red light irradiation. Subsequently, metalloporphyrin ZnTPP was utilized to selectively activate pendant trithiocarbonate moieties for the polymerization of acrylates under green light (λmax = 530 nm, 0.6 mW/cm2) to yield well-defined graft co-polymers.
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Thermo and pH dual-controllable oil/water separation materials are successfully fabricated by photo initiated free radical polymerization of dimethylamino ethyl methacrylate (DMAEMA). The PDMAEMA ...hydrogel coated mesh shows superhydrophilicity and underwater superoleophobicity at certain temperature and pH. Due to the double responsiveness of PDMAEMA hydrogel, the as-prepared mesh can selectively separate water from oil/water mixtures and make water and oil permeate through the mesh orderly and be collected separately by adjusting the temperature or pH. Water can pass through the as-prepared mesh under 55 °C (pH 7) and pH less than 13 (T = 25 °C) while oil is kept on the mesh. When the temperature is above 55 °C or pH is larger than 13, the water retention capacity of PDMAEMA hydrogel is significantly reduced and the swelling volume is decreased. Therefore, oil can permeate through the mesh and be collected in situ. Additionally, this material has excellent potential to be used in practical applications and has created a new field for water/oil separation in which the process can be diversified and more intelligent.
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Uniform synthetic polymers with precisely defined molar mass and monomer sequence (primary structure) have many potential high‐value applications. However, a robust and versatile synthetic strategy ...for these materials remains one of the great challenges in polymer synthesis. Herein we describe proof‐of‐principle experiments for a modular strategy to produce discrete oligomers by a visible‐light‐mediated radical chain process. We utilize the high selectivity provided by photo‐induced electron/energy transfer (PET) activation to develop efficient single unit monomer insertion (SUMI) into reversible addition–fragmentation chain‐transfer (RAFT) agents. A variety of discrete oligomers (single unit species, dimers, and, for the first time, trimers) have been synthesized by sequential SUMI in very high yield under mild reaction conditions. The trimers were used as building blocks for the construction of uniform hexamers and graft copolymers with precisely defined branches.
One by one: A modular strategy produces uniform oligomers via a visible light‐mediated radical‐chain process in the presence of photoredox catalysts and RAFT agents. A variety of short oligomers (trimers) have been successfully synthesized by sequential monomer addition with high yield under mild reaction conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The Ugi reaction, one of the most famous multicomponent reactions, has recently been introduced into polymer chemistry as a novel, efficient and useful tool to prepare multifunctional polymers. In ...this review, the recent progress on the utilization of the Ugi reaction in polymer chemistry, including monomer synthesis, polycondensation, post-polymerization modification (PPM)
etc
. has been summarized. Meanwhile, the applications of the multifunctional polymers synthesized
via
the Ugi reaction and the future development of the Ugi reaction in polymer chemistry have also been discussed.
The well-known Ugi reaction is becoming a novel, efficient and useful tool to prepare multifunctional polymers.
In this communication, we report a catalyst-free methodology for single unit monomer insertion (SUMI) into reversible addition–fragmentation chain transfer (RAFT) agents initiated by low intensity ...visible light. This method is applicable to broad range of monomer families (monosubstituted vinyl monomers) and allows for the preparation of the corresponding single monomer insertion product in high yields (typically >90%; isolated yields after chromatography 60–80%). The fidelity of the end-functional SUMI products is demonstrated with use of the SUMI products in RAFT polymerization and by using the tools of conventional chemistry (thiol–ene and esterification reactions). A uniform oligomer comprising five discrete vinyl monomer repeat units was synthesized by an iterative strategy comprising three consecutive SUMI reactions and two intermediate esterification and thiol–ene steps. We thus demonstrate a new protocol for incorporating the rich functionality of available vinyl monomers into polymers where sequence is precisely defined at the monomer level.
The Ugi reaction has been utilized as a multicomponent click reaction to efficiently synthesize a series of multifunctional PEGylation agents, and those PEG derivatives were successfully conjugated ...on a protein surface to generate corresponding multifunctional protein–polymer conjugates, indicating the promising potential of the Ugi reaction in the field of PEGylation.
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Magnetic resonance imaging (MRI) is recognized as the most powerful clinical imaging modality due to its ability to generate detailed three-dimensional anatomical images with high ...spatial resolution in a non-invasive manner without requiring harmful ionizing radiation. Conventionally, exogenous paramagnetic transition metal ion chelates or iron oxide nanoparticles are used as contrast agents (CAs) to enhance the image contrast of anatomical features. However, despite the wide use of these metal-based CAs, safety concerns have been raised regarding their potential toxic effects resulting from long-term in vivo accumulation. This has driven the development of organic metal-free CAs in various forms for use in MRI. Importantly, functional polymers capable of MRI via different mechanisms represent one of the most promising alternatives to current metal-based MRI CAs due to appealing features such as low toxicity, improved pharmacokinetics and biodistribution profile, and tailored structures and functionalities. Such structural and functional flexibility can enable a myriad of biomedical applications. In this review, we will highlight advances in the development of functional polymers as organic metal-free macromolecular MRI CAs based on different mechanisms including polymeric nitroxide-based 1H MRI CAs, polymeric chemical exchange saturation transfer (CEST) MRI CAs, and polymeric heteronuclei-based MRI CAs. In addition, the review will address the challenges and future opportunities for these promising classes of metal-free polymeric MRI CAs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Medical imaging agents that can report on the biological state are attracting increasing interest. Here we report the development of novel
19
F polymeric imaging agents that are activated by reactive ...oxygen species (ROS). The imaging agents composed of thioether- and fluorine-containing methacrylate monomers were synthesised using atom transfer radical polymerisation (ATRP) from a hydrophilic poly(ethylene glycol)-based initiator. In aqueous solution, the agents self-assemble into nanoparticles with compact hydrophobic cores. The mobility of the fluorinated segments within the cores is greatly restricted, thereby significantly shortening the
19
F
T
2
relaxation times and attenuating the
19
F NMR signal. However, upon treatment with ROS (
i.e.
H
2
O
2
), the hydrophobic thioether groups of the agents are oxidised to hydrophilic sulfoxide groups, resulting in the disassembly of the aggregated nanoparticles. The disassembly of the
19
F MRI agents lengthens the
T
2
relaxation times, and enables an appreciable enhancement of
19
F NMR signal.
19
F MRI of solutions of the polymers before and after oxidation demonstrated a remarkable "OFF-ON" regulation in response to ROS. The sensitivity of the imaging agents was further enhanced by adding a pH switch, resulting in a ROS/pH dual-responsive
19
F MRI agent. The most pronounced change in intensity of the
19
F NMR/MRI signal was achieved in response to the presence of ROS in a mildly acidic environment. The work demonstrates that these novel polymeric
19
F MRI agents hold great potential for improved diagnosis and therapy of diseases presenting high levels of ROS.
Medical imaging agents that can report on the biological state are attracting increasing interest.
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