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1.
Chun Tian Peng Wang Yuanyuan Ni Lifen Zhang Zhenping Cheng Xiulin Zhu 《Angewandte Chemie (International ed. in English)》2020,59(10):3910-3916
Herein, near‐infrared (NIR) photocontrolled iodide‐mediated reversible‐deactivation radical polymerization (RDRP) of methacrylates, without an external photocatalyst, was developed using an alkyl iodide (e.g., 2‐iodo‐2‐methylpropionitrile) as the initiator at room temperature. This example is the first use of a series of special solvents containing carbonyl groups (e.g., 1,3‐dimethyl‐2‐imidazolidinone) as both solvent and catalyst for photocontrolled RDRP using long‐wavelength (λmax=730 nm) irradiation. The polymerization system comprises monomer, alkyl iodide initiator, and solvent. Well‐defined polymers were synthesized with excellent control over the molecular weights and molecular weight distributions (Mw/Mn<1.21). The living features of this system were confirmed by polymerization kinetics, multiple controlled “on‐off” light switching cycles, and chain extension experiments. Importantly, the polymerizations proceeded successfully with various barriers (pork skin and A4 paper), demonstrating the advantage of high‐penetration NIR light. 相似文献
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Huyan Zhou Lu Zhang Peng Wen Yang Zhou Yucheng Zhao Qiaoqiao Zhao Yu Gu Prof. Dr. Ruopeng Bai Prof. Dr. Mao Chen 《Angewandte Chemie (International ed. in English)》2023,62(27):e202304461
Organocatalyzed reversible-deactivation radical polymerizations (RDRPs) are attractive for many applications. Here, we developed photoredox-mediated RDRP by activating (hetero)aryl sulfonyl chloride (ArSO2Cl) initiators with pyridines and designing a novel bis(phenothiazine)arene catalyst. The in situ formed sulfonyl pyridinium intermediates effectively promote controlled chain-growth from ArSO2Cl, enabling access to various well-defined polymers with high initiation efficiencies and controlled dispersities under mild conditions. This versatile method allows “ON/OFF” temporal control, chain-extension, facile synthesis of different polymer brushes via organocatalyzed grafting reactions from linear chains. Time-resolved fluorescence decay studies and calculations support the reaction mechanism. This work provides a transition-metal-free RDRP to tailor polymers with readily available aromatic initiators, and will promote the design of polymerization leveraged from photoredox catalysis. 相似文献
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Richard Whitfield Kostas Parkatzidis Manon Rolland Nghia P. Truong Athina Anastasaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(38):13457-13462
Dispersity significantly affects the properties of polymers. However, current methods for controlling the polymer dispersity are limited to bimodal molecular weight distributions, adulterated polymer chains, or low end‐group fidelity and rely on feeding reagents, flow‐based, or multicomponent systems. To overcome these limitations, we report a simple batch system whereby photoinduced atom transfer radical polymerisation is exploited as a convenient and versatile technique to control dispersity of both homopolymers and block copolymers. By varying the concentration of the copper complex, a wide range of monomodal molecular weight distributions can be obtained (?=1.05–1.75). In all cases, high end‐group fidelity was confirmed by MALDI‐ToF‐MS and exemplified by efficient block copolymer formation (monomodal, ?=1.1–1.5). Importantly, our approach utilises ppm levels of copper (as low as 4 ppm), can be tolerant to oxygen and exhibits perfect temporal control, representing a major step forward in tuning polymer dispersity for various applications. 相似文献
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Di Liu Alvaro D. Sponza Dandan Yang Melanie Chiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16356-16362
Deterministic methods for tuning polymer dispersity are rare, especially for nonradical polymerizations. Reported here is the first example of photomodulating dispersity in controlled cationic polymerizations of vinyl ethers using carboxy‐functionalized dithienylethene initiators. Reversible photoisomerization of these initiators induces changes in their acidities by up to an order of magnitude. Using the more acidic, ring‐closed isomers as initiators results in polymers with lower dispersities. The degree of light‐induced pKa change in the initiators correlates with the degree of dispersity change in polymers derived from the isomeric initiators. The polymerizations are controlled, and dynamic photoswitching of dispersity during the polymerization reaction was demonstrated. This work provides a framework for photomodulating dispersity in other controlled polymerizations and developing one‐pot block copolymerization reactions in which the dispersities of component blocks can be controlled using light. 相似文献
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Zilong Wu Dr. Kenward Jung Prof. Cyrille Boyer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(5):2029-2033
This contribution details an efficient and controlled photopolymerization regulated by far-red (λ=680 nm) and NIR (λ=780 and 850 nm) light in the presence of aluminium phthalocyanine and aluminium naphthalocyanine. Initiating radicals are generated by photosensitization of peroxides affording an effective strategy that provides controlled polymerization of a variety of monomers with excellent living characteristics. Critically, long wavelength irradiation provides penetration through thick barriers, affording unprecedented rates of controlled polymerization that can open new and exciting applications. Furthermore, a more optimized approach to performing solar syntheses is presented. By combining the narrow Q-bands of these photocatalysts with others possessing complementary absorptions, layered, independent polymerizations and organic transformations may be performed in parallel under a single broadband emission source, such as sunlight. 相似文献
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Weijia Fan Shigeru Yamago 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7187-7190
Controlled polymerization of acyclic N‐vinylamides, that is, N‐methyl‐N‐vinylacetamide (NMVA), N‐vinylacetamide (NVA), and N‐vinylformamide (NVF), by organotellurium‐mediated radical polymerization (TERP) is reported. The corresponding poly(N‐vinylamide)s with controlled molecular weight and low dispersity (Ð<1.25) were obtained with high monomer conversion in all cases. This is the first report on the controlled polymerization of NVF. Hydrolysis of the polymers, in particular PNVF, occurred quantitatively under mild reaction conditions, giving structurally controlled poly(vinylamine)s. Block copolymers containing poly(N‐vinylamide) and poly(vinylamine) segments were also synthesized in a controlled manner. 相似文献
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Hao Sun Wonmin Choi Nanzhi Zang Claudia Battistella Matthew P. Thompson Wei Cao Xuhao Zhou Christopher Forman Nathan C. Gianneschi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17520-17525
Harnessing metal‐free photoinduced reversible‐deactivation radical polymerization (photo‐RDRP) in organic and aqueous phases, we report a synthetic approach to enzyme‐responsive and pro‐apoptotic peptide brush polymers. Thermolysin‐responsive peptide‐based polymeric amphiphiles assembled into spherical micellar nanoparticles that undergo a morphology transition to worm‐like micelles upon enzyme‐triggered cleavage of coronal peptide sidechains. Moreover, pro‐apoptotic polypeptide brushes show enhanced cell uptake over individual peptide chains of the same sequence, resulting in a significant increase in cytotoxicity to cancer cells. Critically, increased grafting density of pro‐apoptotic peptides on brush polymers correlates with increased uptake efficiency and concurrently, cytotoxicity. The mild synthetic conditions afforded by photo‐RDRP, make it possible to access well‐defined peptide‐based polymer bioconjugate structures with tunable bioactivity. 相似文献
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Organocatalyzed Photocontrolled Radical Polymerization of Semifluorinated (Meth)acrylates Driven by Visible Light 下载免费PDF全文
Dr. Honghong Gong Yucheng Zhao Xianwang Shen Prof. Dr. Jun Lin Prof. Dr. Mao Chen 《Angewandte Chemie (International ed. in English)》2018,57(1):333-337
Fluorinated polymers are important materials that are widely used in many areas. Herein, we report the development of a metal‐free photocontrolled radical polymerization of semifluorinated (meth)acrylates with a new visible‐light‐absorbing organocatalyst. This method enabled the production of a variety of semifluorinated polymers with narrow molar‐weight distributions from semifluorinated trithiocarbonates or perfluoroalkyl iodides. The high performance of “ON/OFF” control and chain‐extension experiments further demonstrate the utility and reliability of this method. Furthermore, to streamline the preparation of semifluorinated polymers, a scalable continuous‐flow approach has been developed. Given the broad interest in fluorinated materials and photopolymerization, we expect that this method will facilitate the development of advanced materials with unique properties. 相似文献
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Dr. Honghong Gong Yu Gu Yucheng Zhao Qinzhi Quan Shantao Han Prof. Dr. Mao Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(2):929-937
Ultra-high-molecular-weight (UHMW) polymers display outstanding properties and hold potential for wide applications. However, their precise synthesis remains challenging. Herein, we developed a novel reversible-deactivation radical polymerization based on the strong and selective fluorine–fluorine interaction, allowing chain-transfer agents to spontaneously differentiate into two groups that take charge of the chain growth and reversible deactivation of the growing chains, respectively. This method enables dramatically improved livingness of propagation, providing UHMW polymers with a surprisingly narrow molecular weight distribution (Đ≈1.1) from a variety of fluorinated (meth)acrylates and acrylamide at quantitative conversions under visible-light irradiation. In situ chain-end extensions from UHMW polymers facilitated the synthesis of well-defined block copolymers, revealing the excellent chain-end fidelity achieved by this method. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):11055-11059
A redox‐neutral intermolecular dicarbofunctionalization of styrenes with CO2 at atmospheric pressure and carbon‐centered radicals is described. This mild protocol results in multiple C−C bond‐forming reactions from simple precursors in the absence of stoichiometric reductants, thus exploiting a previously unrecognized opportunity that complements existing catalytic carboxylation events. 相似文献
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Johnny W. Lee Katarzyna N. Lee Ming‐Yu Ngai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11289-11299
Trifluoromethoxy (OCF3) and difluoromethoxy (OCF2H) groups are fluorinated structural motifs that exhibit unique physicochemical characteristics. Incorporation of these substituents into organic molecules is a highly desirable approach used in medicinal chemistry and drug discovery processes to alter the properties of a parent compound. Recently, tri‐ and difluoromethyl ethers have received increasing attention and several innovative strategies to access these valuable functional groups have been developed. The focus of this Minireview is the use of visible‐light photoredox catalysis in the synthesis of tri‐ and difluoromethyl ethers. Recent photocatalytic strategies for the formation of O?CF3, C?OCF3, O?CF2H, and C?OCF2H bonds as well as other transformations leading to the construction of ORF groups are discussed herein. 相似文献
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Dr. Mineto Uchiyama Masahiro Osumi Prof. Dr. Kotaro Satoh Prof. Dr. Masami Kamigaito 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(17):6899-6905
Thiol-ene cationic and radical reactions were conducted for 1:1 addition between a thiol and vinyl ether, and also for cyclization and step-growth polymerization between a dithiol and divinyl ether. p-Toluenesulfonic acid (PTSA) induced a cationic thiol-ene reaction to generate a thioacetal in high yield, whereas 2,2′-azobisisobutyronitrile resulted in a radical thiol-ene reaction to give a thioether, also in high yield. The cationic and radical addition reactions between a dithiol and divinyl ether with oxyethylene units yielded amorphous poly(thioacetal)s and crystalline poly(thioether)s, respectively. Under high-dilution conditions, the cationic and radical reactions resulted in 16- and 18-membered cyclic thioacetal and thioether products, respectively. Furthermore, concurrent cationic and radical step-growth polymerizations were realized using PTSA under UV irradiation to produce polymers having both thioacetal and thioether linkages in the main chain. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(49):15889-15893
Reported herein is a novel visible‐light photoredox system with Pd(PPh3)4 as the sole catalyst for the realization of the first direct cross‐coupling of C(sp3)−H bonds in N‐aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra‐ and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp3)−C(sp3) and C(sp2)−C(sp3) bonds in moderate to excellent yields. These redox‐neutral reactions feature broad substrate scope (>60 examples), good functional‐group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible‐light photocatalyst and radicals are involved in the process. 相似文献
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Facile Fabrication of Concentrated Polymer Brushes with Complex Patterning by Photocontrolled Organocatalyzed Living Radical Polymerization 下载免费PDF全文
Dr. Chen‐Gang Wang Chen Chen Dr. Keita Sakakibara Prof. Dr. Yoshinobu Tsujii Prof. Dr. Atsushi Goto 《Angewandte Chemie (International ed. in English)》2018,57(41):13504-13508
Photocontrolled surface‐initiated reversible complexation mediated polymerization (photo‐SI‐RCMP) was successfully applied to fabricate concentrated polymer brushes with complex patterning structures. Positive‐type patterned polymer brushes were obtained by photo‐SI‐RCMP under visible light (550(±50) nm) using photomasks. A particularly interesting finding was that negative‐type patterned polymer brushes were also obtainable in a facile manner. A nonspecial UV light (250–385 nm) enabled the preparation of pre‐patterned initiator surfaces in a remarkably short time (1 min), leading to negative‐type patterned polymer brushes. Based on this unique selectivity between visible and UV light, the combination of two patterning techniques enabled the preparation of complex patterned brushes, including diblock copolymers, binary polymers, and functional binary polymers, without multistep immobilization of one or more initiators on the surfaces. 相似文献
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Radičević R. Ž. Stoiljković D. M. Budinski-Simendić J. 《Journal of Thermal Analysis and Calorimetry》2000,62(1):237-249
It is well known that the free radical bulk polymerization of lower n-alkyl methacrylates is characterized by autoacceleration after definite conversions of the monomers. The conversion vs.time curves of polymerization have a typical 'S' shape. There are several characteristic points in these curves: the onset
of autoacceleration (point M), the maximum in the polymerization rate (point S) and the end of the polymerization (point K).
We have observed points P and R (maximum and minimum of autoacceleration) as inflection points in the derived polymerization
rate vs. time curve.
In this work, the free radical bulk polymerizations of methyl, ethyl and butyl methacrylates were investigated by differential
scanning calorimetry. The effects of the polymerization temperature and the alkyl group length in the esters on the monomer
conversions at the points M, P, S, R and K were studied. By regression analysis of the experimental results, relations were
developed with which it is possible to predict the positions of the characteristic points, depending on the polymerization
temperature and the alkyl group length.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献