Atom Transfer Radical Polymerization

Matyjaszewski, Krzysztof; Xia, Jianhui

doi:10.1021/cr940534g

Cited by 7,470 publications

(6,507 citation statements)

References 400 publications

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“…Polymers are generally assembled in a single step by methods such as radical, ionic, or ring-opening metathesis polymerization of RE-bearing monomers. [101,[143][144][145][146][147][148][149] Alternatively, REs can be appended to a pre-formed polymeric scaffold. [101,147] Certain polymerization reactions are more tolerant of biologically active functionality than others; thus, the type of epitopes to be incorporated will determine the most effective synthetic strategy.…”

Section: 3dmentioning

confidence: 99%

Synthetic Multivalent Ligands as Probes of Signal Transduction

2006

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Cell surface receptors acquire information from the extracellular environment and coordinate intracellular responses. Evidence from biochemical and structural studies indicates that many receptors do not operate as individual entities, but rather as part of higher-order complexes (e.g. dimers and oligomers). Coupling the functions of multiple receptors may endow signaling pathways with the sensitivity and malleability required to govern cellular responses. Moreover, multireceptor signaling complexes may provide a means of spatially segregating otherwise degenerate signaling cascades. Despite the proposed importance of receptor-receptor processes in cellular signaling, questions concerning the mechanisms, extent, and consequences of receptor co-localization and interreceptor communication remain unanswered.Chemical synthesis can provide a variety of compounds with which to address the role of receptor assembly in signal transduction. The focus of this review is one such approach -the use of synthetic multivalent ligands to characterize receptor function. Multivalent ligands can be generated that possess a variety of sizes, shapes, valencies, orientations, and densities of binding elements. Their unique architectures imbue multivalent ligands with the ability to access binding modes not available to monovalent compounds. Multivalent ligands, therefore, are capable of illuminating aspects of inter-receptor processes that are not readily probed using conventional approaches. We suggest that, as focus shifts from investigations of the function of individual proteins and toward the analysis of multi-receptor signaling complexes, multivalent ligands will become even more valuable tools with which to ask sophisticated mechanistic questions. Further, multivalent ligands may provide new opportunities for manipulating receptor systems for the deconvolution of pathways, diagnosis, and, ultimately, the treatment of disease.

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Section: 3dmentioning

confidence: 99%

Synthetic Multivalent Ligands as Probes of Signal Transduction

2006

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“…[3][4][5][6][7][8][9][10][11][12][13][14] Well-defined ruthenium benzylidene complexes, commonly used as olefin metathesis catalysts, have also been reported to catalyze ATRA and ATRP. 9,[15][16][17][18][19] The ability of ruthenium benzylidene complexes to promote two reactions with such markedly different mechanisms has been utilized in various tandem reactions in which olefin metathesis and ATR reactions take place in one pot.…”

Section: Introductionmentioning

confidence: 99%

In Situ Catalyst Modification in Atom Transfer Radical Reactions with Ruthenium Benzylidene Complexes

et al. 2016

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Ruthenium benzylidene complexes are well known as olefin metathesis catalysts. Several reports have demonstrated the ability of these catalysts to also facilitate atom transfer radical (ATR) reactions, such as atom transfer radical addition (ATRA) and atom transfer radical polymerization (ATRP). However, while the mechanism of olefin metathesis with ruthenium benzylidenes has been well-studied, the mechanism by which ruthenium benzylidenes promote ATR reactions remains unknown. To probe this question, we have analyzed seven different ruthenium benzylidene complexes for ATR reactivity. Kinetic studies by 1 H NMR revealed that ruthenium benzylidene complexes are rapidly converted into new ATRA-active, metathesis-inactive species under typical ATRA conditions. When ruthenium benzylidene complexes were activated prior to substrate addition, the resulting activated species exhibited enhanced kinetic reactivity in ATRA with no significant difference in overall product yield compared to the original complexes. Even at low temperature, where the original intact complexes did not catalyze the reaction, pre-activated catalysts successfully reacted. Only the ruthenium benzylidene complexes that could be rapidly transformed into ATRA-active species could successfully catalyze ATRP, whereas other complexes preferred redox-initiated free radical polymerization. Kinetic measurements along with additional mechanistic and computational studies show that a metathesis-inactive ruthenium species, generated in situ from the ruthenium benzylidene complexes is the active catalyst in ATR reactions. Based on data from 1 H, 13 C, and 31 P NMR spectroscopy, and X-ray crystallography, we suspect that this ATRA-active species is a RuxCly(PCy3)z complex.

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“…[1][2][3] It has been well-established that the topological structures and chemical composition of nonlinearshaped block copolymers can exhibit dramatic effects on the solution properties and self-assembling morphologies as compared with their linear counterpart. [4][5][6][7][8][9] It is worthy of noting that the developments of a variety of controlled radical polymerization techniques 10 such as atom transfer radical polymerization (ATRP), [11][12][13] reversible addition-fragmentation chain transfer (RAFT) polymerization, [14][15][16] and nitroxide-mediated polymerization (NMP) 17,18 have facilitated the synthesis of nonlinear-shaped polymers with varying chain architectures such as cyclic, 8,9,[19][20][21][22][23] (miktoarm) star, [24][25][26] star block copolymers, 27,28 comb, [29][30][31][32] sun-shaped, [33][34][35] H-shaped, [36][37][38] and θ-shaped 39,40 polymers. Among these nonlinear chain topologies, tadpole-shaped linearcyclic diblock copolymers [41]…”

Section: ' Introductionmentioning

confidence: 99%

Synthesis of Amphiphilic Tadpole-Shaped Linear-Cyclic Diblock Copolymers via Ring-Opening Polymerization Directly Initiating from Cyclic Precursors and Their Application as Drug Nanocarriers

2011

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We report on the facile synthesis of well-defined amphiphilic and thermoresponsive tadpole-shaped linear-cyclic diblock copolymers via ring-opening polymerization (ROP) directly initiating from cyclic precursors, their self-assembling behavior in aqueous solution, and the application of micellar assemblies as controlled release drug nanocarriers. Starting from a trifunctional core molecule containing alkynyl, hydroxyl, and bromine moieties, alkynyl-(OH)-Br, macrocyclic poly(N-isopropylacrylamide) (c-PNIPAM) bearing a single hydroxyl functionality was prepared by atom transfer radical polymerization (ATRP), the subsequent end group transformation into azide functionality, and finally the intramacromolecular ring closure reaction via click chemistry. The target amphiphilic tadpoleshaped linear-cyclic diblock copolymer, (c-PNIPAM)-b-PCL, was then synthesized via the ROP of ε-caprolactone (CL) by directly initiating from the cyclic precursor. In aqueous solution at 20°C, (c-PNIPAM)-b-PCL self-assembles into spherical micelles consisting of hydrophobic PCL cores and well-solvated coronas of cyclic PNIPAM segments. For comparison, linear diblock copolymer with comparable molecular weight and composition, (l-PNIPAM)-b-PCL, was also synthesized. It was found that the thermoresponsive coronas of micelles self-assembled from (c-PNIPAM)-b-PCL exhibit thermoinduced collapse and aggregation at a lower critical thermal phase transition temperature (T c ) compared with those of (l-PNIPAM)-b-PCL. Temperature-dependent drug release profiles from the two types of micelles of (c-PNIPAM)-b-PCL and (l-PNIPAM)-b-PCL loaded with doxorubicin (Dox) were measured, and the underlying mechanism for the observed difference in releasing properties was proposed. Moreover, MTT assays revealed that micelles of (c-PNIPAM)-b-PCL are almost noncytotoxic up to a concentration of 1.0 g/L, whereas at the same polymer concentration, micelles loaded with Dox lead to ∼60% cell death. Overall, chain topologies of thermoresponsive block copolymers, that is, (c-PNIPAM)-b-PCL versus (l-PNIPAM)-b-PCL, play considerable effects on the self-assembling and thermal phase transition properties and their functions as controlled release drug nanocarriers. ' INTRODUCTIONIn the past decades, enduring attention has been paid to explore the intrinsic correlation between the chain topology of block copolymers and their physical properties, self-assembling behavior in selective solvents or in bulk states, and the associated functional applications. 1-3 It has been well-established that the topological structures and chemical composition of nonlinearshaped block copolymers can exhibit dramatic effects on the solution properties and self-assembling morphologies as compared with their linear counterpart. [4][5][6][7][8][9] It is worthy of noting that the developments of a variety of controlled radical polymerization techniques 10 such as atom transfer radical polymerization (ATRP), 11-13 reversible addition-fragmentation chain transfer (RAFT) polymerization, [14][...

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Atom Transfer Radical Polymerization

Cited by 7,470 publications

References 400 publications

Synthetic Multivalent Ligands as Probes of Signal Transduction

Synthetic Multivalent Ligands as Probes of Signal Transduction

In Situ Catalyst Modification in Atom Transfer Radical Reactions with Ruthenium Benzylidene Complexes

Synthesis of Amphiphilic Tadpole-Shaped Linear-Cyclic Diblock Copolymers via Ring-Opening Polymerization Directly Initiating from Cyclic Precursors and Their Application as Drug Nanocarriers

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