Reversible deactivation radical polymerization Puns

Topology influences properties and applications of polymers. Consequently, considerable efforts have been made to control topological structures. In this work, we developed a photoorganocatalyzed divergent synthetic approach based on reversible deactivation radical polymerization (RDRP) that enables the preparation of both linear and branched fluoropolymers of low Ð , tunable degree of branching and high chain‐end fidelity by exposing to LED light irradiation under metal‐free conditions. This method promotes the generation of complicated structures (e.g., necklace‐like and mop‐like fluoropolymers) via chain‐extension photo‐RDRP, and provides a novel and versatile platform to access fluoropolymer electrolytes with high Li‐ion transference number and good ionic conductivity, which should create improved opportunities for advanced material engineering.

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Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c10359

Qi Zhang, Da-Hui Qu, Ben L. Feringa, and He Tian

https://ift.tt/31AOZiA

Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c11501

Xun Zhang, Zan Yang, Yu Jiang, and Saihu Liao

https://ift.tt/32uTb3X

https://doi.org/10.1021/acs.macromol.1c02103

Thank you.

It may be a silly question, but why does the cumulative degree of polymerization (DPn or Xn) decrease over time during radical polymerization without a transfer agent? Considering that we are in AEQS conditions.

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c10014

Claire A. L. Lidston, Brooks A. Abel, and Geoffrey W. Coates

https://ift.tt/3kpEZMz

A novel broad-wavelength-absorbing photoinitiator based on phenacyl phenothiazinium hexafluroantimonate (P-PTh) possessing both phenacyl and phenothiazine chromophoric groups was reported. P-PTh absorbs light at UV, Visible and Near-IR region. Photophysical, photochemical, and computational investigations revealed that P-PTh in solution decomposes at all wavelengths by homolytic and heterolytic cleavages and generates cationic and radical species, which could efficiently initiate cationic and free radical polymerizations. It is anticipated that the photoinitiator with such wavelength flexibility may open up new pathways in curing applications of formulations of pigment systems.

https://ift.tt/3vwPzYs

Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c00279

Aditi Bhattacherjee, Mahima Sneha, Luke Lewis-Borrell, Giordano Amoruso, Thomas A.A. Oliver, Jasper Tyler, Ian P. Clark, and Andrew J. Orr-Ewing

https://ift.tt/3utKJei

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c01016

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Does this mean the mononer should be used in the mechanism three times? I just saw this theory & im confused. It involves the radical polymerization of ethene to form polyethylene.

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c10673

Mitchell D. Nothling, Hanwei Cao, Thomas G. McKenzie, Dianna M. Hocking, Richard A. Strugnell, and Greg G. Qiao

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NIR sensitized cationic polymerization proceeded with good efficiency as studied with epoxides, vinyl ether, and oxetanes.  A heptacyanine functioned as sensitizer while iodonium salts served as coinitiator.  The anion uptakes a special function as concluded by a series selected from fluorinated phosphates (a: [PF6]‐, b: [PF3(C2F5)3]‐, c: [PF3(n‐C4F9)3]), aluminates (d: [Al(O‐t‐C4F9)4]‐, e: [Al(O(C3F6)CH3)4]‐ , and methide [C(O‐SO2CF3)3]‐ (f).  Vinyl ether showed the best cationic polymerization efficiency followed by oxetanes and oxiranes.  Density functional theory calculations provided a rough pattern regarding the electrostatic potential of each anion where d exhibited a rather better performance compared to e.  The more efficient shielding of all CF3‐groups can explain these findings.  Anion d also better performed as b, which was introduced as alternative to a.  In addition, formation of interpenetrating polymer networks (IPNs) using trimethylpropane triacrylate and either oxetane or epoxide‐based monomer successfully proceeded in the case of NIR sensitized polymerization were anion d served as anion for the sensitizer and the iodonium salt.  No successful IPN formation occurred in the case of UV‐LED initiation using the same monomers but the photoinitiating system comprised of thioxanthone/iodonium salt.  Exposure was carried out with new NIR‐LED devices emitting at either 805 nm or 870 nm.

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Solid‐state ATRP : An atom transfer radical polymerization (ATRP) was performed in the solid‐state. The reaction is promoted by ball milling, found to proceed in a controlled fashion and facilitates access to copolymers that are challenging to prepare via solution‐state methods.

Abstract

Poly(2‐vinylnaphthalene) was synthesized in the solid‐state by ball milling a mixture of the corresponding monomer, a Cu‐based catalyst, and an activated haloalkane as the polymerization initiator. Various reaction conditions, including milling time, milling frequency and added reductant to accelerate the polymerization were optimized. Monomer conversion and the evolution of polymer molecular weight were monitored over time using 1H NMR spectroscopy and size exclusion chromatography, respectively, and linear correlations were observed. While the polymer molecular weight was effectively tuned by changing the initial monomer‐to‐initiator ratio, the experimentally measured values were found to be lower than their theoretical values. The difference was attributed to premature mechanical decomposition and modeled to accurately account for the decrement. Random copolymers of two monomers with orthogonal solubilities, sodium styrene sulfonate and 2‐vinylnaphthalene, were also synthesized in the solid‐state. Inspection of the data revealed that the solid‐state polymerization reaction was controlled, followed a mechanism similar to that described for solution‐state atom transfer radical polymerizations, and may be used to prepare polymers that are inaccessible via solution‐state methods.

https://ift.tt/2LBesfY

A tripyridinium–triazine molecule featuring multiple redox centers was developed with a capacity as high as six electrons per molecule. The electronic coupling between the pyridinium and triazine units can effectively delocalize the charge of the radicals, thereby stabilizing the reactive intermediate and enabling reversible storage of multiple electrons.

Abstract

A novel organic molecule, 2,4,6-tris[1-(trimethylamonium)propyl-4-pyridiniumyl]-1,3,5-triazine hexachloride, was developed as a reversible six-electron storage electrolyte for use in an aqueous redox flow battery (ARFB). Physicochemical characterization reveals that the molecule evolves from a radical to a biradical and finally to a quinoid structure upon accepting four electrons. Both the diffusion coefficient and the rate constant were sufficiently high to run a flow battery with low concentration and kinetics polarization losses. In a demonstration unit, the assembled flow battery affords a high specific capacity of 33.0 Ah L−1 and a peak power density of 273 mW cm−2. This work highlights the rational design of electroactive organics that can manipulate multi-electron transfer in a reversible way, which will pave the way to development of energy-dense, manageable and low-cost ARFBs.

https://ift.tt/2UuFzl7

Cryo‐electron micrography was used to precisely determine the three‐dimensional structure of nanocomposite microgels and to provide insights into the interactions between small hydrophobic molecules and the microgels. As explained by K. Murata, D. Suzuki, et al. in their Communication (DOI: https://doi.org/10.1002/anie.20200349310.1002/anie.202003493), styrene monomers recognize molecular‐scale differences in polarity within the microgels during emulsion polymerization. This discovery enabled the synthesis of multilayer nanocomposite microgels in one step by free radical seed emulsion polymerization.

https://ift.tt/3cVuOvJ

Nature Chemistry, Published online: 18 May 2020; doi:10.1038/s41557-020-0460-1

Oxygen is a potent inhibitor of radical polymerization reactions, but the facultative bacterium Shewanella oneidensis has now been shown to facilitate aerobic radical polymerizations by first consuming dissolved oxygen and then directing extracellular electron flux to a metal catalyst. Aerobic polymerization activity is dependent on the S. oneidensis genotype and can be initiated using lyophilized or spent cells.

https://ift.tt/3cK2QDk

Liquid vinyl monomers were converted to solid crystals via halogen bonding and underwent solid‐phase radical polymerizations through heating at 40 °C or ultraviolet photo‐irradiation (250−385 nm). The X‐ray crystallography analysis showed the high degree of monomer alignment in the crystals. The polymerizations of the solid monomer crystals yielded polymers with high molecular weights and relatively low dispersities because of the high degree of the monomer alignment in the crystal. As a unique application of this system, the crystalized monomers were assembled to pre‐determined structures, followed by solid‐phase polymerization, to obtain a two‐layer polymer sheet and a three‐dimensional house‐shaped polymer material. The two‐layer sheet contained a unique asymmetric pore structure and exhibited a solvent‐responsive shape memory property and may find applications to asymmetric membranes and polymer actuators.

https://ift.tt/2wdIRgs

I work with polyester and vinyl ester resins initiated by organic peroxides to make fiberglass by means of pultrusion and open molding. I am looking for a deep understanding on free radical polymerization since it will help me come up with original ideas and ways to troubleshoot.

I can formulate resin systems that work but cannot find the answers to questions like “what families of organic peroxide should I avoid when using metal compounds as a promoter”. Thanks!

Growth potential: Thiol‐ene cationic and radical reactions were achieved not only for 1:1 addition between a thiol and vinyl ether but also for cyclization and step‐growth polymerization between a dithiol and divinyl ether. An organic acid and a radical initiator, respectively, led selectively to the formation of thioacetal and thioether linkages. Concurrent cationic and radical step‐growth polymerization was also realized to afford polymers composed of both thioacetal and thioether linkages in the main chains.

Abstract

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.

https://ift.tt/3bx5sof

Polymers in flow: Organic photoredox catalysis is applied to the controlled synthesis of poly(acrylates). This advancement is enabled by the development of new organic photoredox catalysts, dimethyl dihydroacridines, with unique properties. The use of continuous flow reactors is also key to the success of the method.

Abstract

Development of photocatalysts (PCs) with diverse properties has been essential in the advancement of organocatalyzed atom transfer radical polymerization (O‐ATRP). Dimethyl dihydroacridines are presented here as a new family of organic PCs, for the first time enabling controlled polymerization of challenging acrylate monomers by O‐ATRP. Structure–property relationships for seven PCs are established, demonstrating tunable photochemical and electrochemical properties, and accessing a strongly oxidizing 2PC.+ intermediate for efficient deactivation. In O‐ATRP, the combination of PC, implementation of continuous‐flow reactors, and promotion of deactivation through addition of LiBr are critical to producing well‐defined acrylate polymers with dispersities as low as 1.12. The utility of this approach is established through demonstration of the oxygen‐tolerance of the system and application to diverse acrylate monomers, including the synthesis of well‐defined di‐ and triblock copolymers.

https://ift.tt/33oKK4x

Weird geeky questions but, in APS-TEMED initiated polymerization of acrylamide, APS is described as the initiator and TEMED as the catalyst of APS radical formation. But, according to the mechanisms I've found, the APS-TEMED reaction involves the generation of a radical sulfate ion and a TEMED radical. Does the TEMED radical also act as an initiator? And is it truly a catalyst and if so how is it regenerated? Thanks!

https://pubs.rsc.org/en/content/articlehtml/2015/sm/c5sm01996f#cit26

Amplifying free radical production by chemical dynamic catalysis to cause oxidative damage to cancer cells has received extensive interest for cancer-specific therapy. The major challenge is inevitable negative modulation on the tumor microenvironment (TME) by these species, hindering durable effectiveness. Here we show for the first time an oxygen vacancy - rich Bi-based regulator that allows environment-adaptive free radical catalysis. Specifically, the regulator catalyzes production of highly toxic O 2 •- and • OH in cancer cells via logic enzymatic reactions, yet scavenges accumulation of free radicals and immunosuppressive mediators in TME-associated noncancerous cells. Atomic-level mechanistic studies reveal that such dual-modal regulating behavior is dominated by oxygen vacancies that well fit for free radical catalytic kinetics, along with distinguished cellular fates of this regulator. With this smart regulator, a “two birds with one shot” cancer dynamic therapy can be expected.

https://ift.tt/3wFzHTN

We report a novel orthogonal combination of cationic and radical RAFT polymerizations to synthesize bottlebrush polymers using two distinct RAFT agents. Selective consumption of the first RAFT agent is used to control the cationic RAFT polymerization of a vinyl ether monomer bearing a secondary dormant RAFT agent, which subsequently allows side‐chain polymers to be grafted from the pendant RAFT agent by a radical‐mediated RAFT polymerization of a different monomer, thus completing the synthesis of bottlebrush polymers. The high efficiency and selectivity of the cationic and radical RAFT polymerizations allow both polymerization to be conducted in one‐pot tandem without intermediate purification.

https://ift.tt/3bCfSCZ

A conductive polymer (PEDOT:PSS) and potassium poly(heptazine imide) (K‐PHI) are combined in one hybrid nanocomposite as electron donor and photocatalyst, respectively. The composite represents an example of unconventional photocatalysis: K‐PHI modulates the physicochemical properties of the conductive polymer upon exposure to light and dark in different environments.

Abstract

In photocatalysis, small organic molecules are converted into desired products using light responsive materials, electromagnetic radiation, and electron mediators. Substitution of low molecular weight reagents with redox active functional materials may increase the utility of photocatalysis beyond organic synthesis and environmental applications. Guided by the general principles of photocatalysis, we design hybrid nanocomposites composed of n‐type semiconducting potassium poly(heptazine imide) (K‐PHI), and p‐type conducting poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the redox active substrate. Electrical conductivity of the hybrid nanocomposite, possessing optimal K‐PHI content, is reversibly modulated combining a series of external stimuli ranging from visible light under inert conditions and to dark conditions under an O2 atmosphere. Using a conductive polymer as the redox active substrate allows study of the photocatalytic processes mediated by semiconducting photocatalysts through electrical conductivity measurements.

https://ift.tt/3tz0SxX

My pi and I are pursuing a new route to our polymer. Particularly transitioning from condensation polymerization to vinyl based. Our group is small and i haven't much experience with radical polymerization. I'm wondering if there is any insight here for radical polymerization of ion containing monomers. Particularly, to achieve high molecular weight you need to dilute as the ionic polymer becomes very viscous. Solvent will likely result in chain transfer and disproportionate which will kill the polymerization. Does anyone have experience getting around this? I am looking for any general insight or good references to learn more about acceptable additives and polymerization modifications for vinyl based monomers

For a polymer lab I am in, we need to plan our own experiments with a goal in mind.. 30 kDa PMMA, 3 hour half life of initiator, solution*/emulsion/suspension pzn. That's all fine and all; I need a DP of ~300, use Arrhenius eq with initiator to find out what temperature I need the reaction to be at to get the half life I want.. suitable solvent needed of course, toluene.. but the trouble I am having is determining amount of initiator. I have no clue where to find the Kp, Kt, Kctr values. Is there something I'm missing? Or am I just not looking in the right places?

Edit. Uh, so, crisis averted. Polymer Handbook saves lives.

Edit 2. Not quite averted.. Is there a specific frequency value that is generally used? For calculating rate constants at the temperature I am using. Backcalculating from data in the Handbook gives me a range of values.

Edit 3. Ok, I crunched numbers and a couple averages from data in the Polymer Handbook to determine Kd, Kp and Kt. Fun. Now getting to chain transfer, it seems that toluene as a solvent and methyl methacrylate as the monomer provide chain transfer while the AIBN initiator does not.. I found values for Cs and Cm, but I don't really know where to go from there... In the polymer handbook are Cs/p/m values ex. 0.2x10^4 or are they multiplied by 10^4 to get 0.2?? The former gives me impossible numbers for my initiator concentrations. :\

Real quick. As I increase the concentration in a solution-based polymerization the molecular weight of the corresponding polymer will increase, yes? I have a coworker suggesting that it will infact decrease. I think we are both right. If viscosity becomes too high, then the polymerization will result in a higher PDI, lower yield, and low molecular weight. Although, if it is dilute, chain-transfer to solvent will increase and molecular wieght will be reduced. Although, should the concentration be just right, we will get a molecular weight that is not limited by viscosity or chain transfer. Any input is appreciated. Thanks

I know oxygen has 2 unpaired electrons, so it's in a triplet state and can be thought of as a stable (di)radical. But why does this make O₂ so good at reacting with other free radicals?

The polymer to polymerize is methyl methacrylate. I'm trying to find one that DOESN'T involving messy external source (ie- UV, X-ray) and produce no harmful (or easy to remove) by-products.

:3 thanks

A divergent photoorganocatalyzed controlled radical polymerization towards both linear and branched fluoropolymers has been developed, enabling topological control under metal‐free conditions driven by light. This method promotes the synthesis of fluoropolymers with low dispersity, a tunable degree of branching, and high chain‐end fidelity.

Abstract

Topology influences the properties and applications of polymers. Consequently, considerable efforts have been made to control topological structures. In this work, we have developed a photoorganocatalyzed divergent synthetic approach based on reversible‐deactivation radical polymerization (RDRP) that enables the preparation of both linear and branched fluoropolymers of low dispersity (Ð), a tunable degree of branching and high chain‐end fidelity by exposure to LED light irradiation under metal‐free conditions. This method promotes the generation of complicated structures (e.g., necklace‐like and mop‐like fluoropolymers) via chain‐extension photo‐RDRP, and provides a novel and versatile platform to access fluoropolymer electrolytes with high Li‐ion transference number and good ionic conductivity, which should create improved opportunities for advanced material engineering.

https://ift.tt/3ak848y

The three‐dimensional structure of nanocomposite microgels was precisely determined by cryo‐electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo‐electron micrography. The obtained three‐dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, i.e., hydrophobic styrene monomers recognize molecular‐scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi‐layered nanocomposite microgels, which promise substantial potential in colloidal applications.

https://ift.tt/2WYlPoO

Poly(2‐vinylnaphthalene) was synthesized in the solid‐state by ball milling a mixture of the corresponding monomer, a Cu‐based catalyst, and an activated haloalkane as the polymerization initiator. Various reaction conditions, including milling time, added reductant to accelerate the polymerization, and milling frequency were optimized. Monomer conversion and polymer molecular weight evolution were monitored over time using 1H NMR spectroscopy and size exclusion chromatography, respectively, and linear correlations were observed. While the polymer molecular weight was effectively tuned by changing the initial monomer‐to‐initiator ratio, the experimentally measured values were found to be lower than their theoretical values. The difference was attributed to premature mechanical decomposition and modeled to accurately account for the decrement. Random copolymers of two monomers with orthogonal solubilities, sodium styrene sulfonate and 2‐vinylnaphthalene, were also synthesized in the solid‐state. Collectively, the data indicated that the solid‐state polymer chemistry is controlled, follows a mechanism similar to that described for solution‐state atom transfer radical polymerizations, and may be used to prepare polymers that are inaccessible via solution‐state methods.

https://ift.tt/2LBesfY

Growth potential: Thiol‐ene cationic and radical reactions were achieved not only for 1:1 addition between a thiol and vinyl ether but also for cyclization and step‐growth polymerization between a dithiol and divinyl ether. An organic acid and a radical initiator, respectively, led selectively to the formation of thioacetal and thioether linkages. Concurrent cationic and radical step‐growth polymerization was also realized to afford polymers composed of both thioacetal and thioether linkages in the main chains.

Abstract

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.

https://ift.tt/3bx5sof

Liquid vinyl monomers were converted into solid crystals via halogen bonding. They underwent solid‐phase radical polymerization, yielding polymers with high molecular weights and relatively low dispersities. The monomer crystals were assembled to pre‐determined structures, followed by solid‐phase polymerization, to yield polymer materials with complex structures.

Abstract

Liquid vinyl monomers were converted into solid crystals via halogen bonding. They underwent solid‐phase radical polymerizations through heating at 40 °C or ultraviolet photo‐irradiation (365 nm). The X‐ray crystallography analysis showed the high degree of monomer alignment in the crystals. The polymerizations of the solid monomer crystals yielded polymers with high molecular weights and relatively low dispersities because of the high degree of the monomer alignment in the crystal. As a unique application of this system, the crystalized monomers were assembled to pre‐determined structures, followed by solid‐phase polymerization, to obtain a two‐layer polymer sheet and a three‐dimensional house‐shaped polymer material. The two‐layer sheet contained a unique asymmetric pore structure and exhibited a solvent‐responsive shape memory property and may find applications to asymmetric membranes and polymer actuators.

https://ift.tt/2wdIRgs

Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c00287

https://ift.tt/32w9Nnh

Thiol‐ene cationic and radical reactions were conducted not only for 1:1 addition between thiol and vinyl ether but also for cyclization and step‐growth polymerization between dithiol and divinyl ether.  An organic acid catalyst such as p ‐toluenesulfonic acid (PTSA) induced the cationic thiol‐ene reaction to generate the thioacetal as the Markovnikov adduct in high yield, whereas organic radical initiators such as 2,2’‐azobisisobutyronitrile (AIBN) caused the radical thiol‐ene reaction to give the thioether as the anti‐Markovnikov adduct, also in high yield.  The cationic and radical addition reactions between dithiol and divinyl ether with oxyethylene units allowed the starting materials to efficiently undergo both cationic step‐growth polymerization in the presence of PTSA and radical polymerization in the presence of AIBN or under UV irradiation to yield amorphous poly(thioacetal)s and crystalline poly(thioether)s, respectively.  In contrast, under high dilution conditions, the cationic and radical reactions resulted in 16‐ and 18‐membered cyclic thioacetal and thioether products, respectively, which have a structure similar to that of crown ether.  Furthermore, concurrent cationic and radical step‐growth polymerizations were realized using PTSA under UV irradiation to produce polymers composed of both thioacetal and thioether linkages in the main chains, where the polymer properties are arbitrarily tunable by the concentration of PTSA or the content of the two linkages.

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