Controlled Free Radical Polymerization Research Articles

Frieder Jäkle

Angewandte Chemie International EditionVolume 57, Issue 41 p. 13378-13378 Author ProfileFree Access Frieder Jäkle First published: 04 June 2018 https://doi.org/10.1002/anie.201805615AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “My not-so-secret passion is a delicious piece of French cheese. I would have liked to have discovered ”frustrated“ Lewis pairs …” Find out more about Frieder Jäkle in his Author Profile. Frieder Jäkle The author presented on this page has recently published his 10th article in Angewandte Chemie in the last 10 years: “p-π Conjugated Polymers Based on Stable Triarylborane with n-Type Behavior in Optoelectronic Devices”: B. Meng, Y. Ren, J. Liu, F. Jäkle, L. Wang, Angew. Chem. Int. Ed. 2018, 57, 2183; Angew. Chem. 2018, 130, 2205. The work of F. Jäkle has been featured on the inside cover of Angewandte Chemie: “Regioregular Synthesis of Azaborine Oligomers and a Polymer with a syn Conformation Stabilized by N–H⋅⋅⋅π Interactions”: A. W. Baggett, F. Guo, B. Li, S. Liu, F. Jäkle, Angew. Chem. Int. Ed. 2015, 54, 11191; Angew. Chem. 2015, 127, 11343. Date of birth: April 11, 1969 Position: Distinguished Professor, Rutgers University, Newark E-mail: fjaekle@newark.rutgers.edu Homepage: http://andromeda.rutgers.edu/∼fjaekle/index.htm ORCID: 0000-0001-8031-9254 Education: 1995 Diploma in chemistry, Technische Universität München (TUM) 1997 Dr. rer. nat. supervised by Prof. Matthias Wagner, TUM 1997–2000, DFG postdoctoral fellow with Prof. Ian Manners, University of Toronto Awards: 2004 NSF Career Award; 2006 Alfred P. Sloan Fellowship, 2009 Friedrich Wilhelm Bessel Award, Alexander von Humboldt Foundation; 2012 ACS Akron Section Award; 2012 Boron in the Americas Award; 2017 Rutgers Board of Trustees Research Award Current research interests: Organoborane Lewis acids and Lewis pairs; conjugated polymers; organometallic polymers; optoelectronic materials; chemical sensors; supported catalysts Hobbies: Hiking, traveling, enjoying fine cuisine with my wife My not-so-secret passion is a delicious piece of French cheese. I would have liked to have discovered “frustrated” Lewis pairs. If I won the lottery, I would expand my research group and otherwise stay true to my “Swabian” upbringing. My favorite place on earth is the Munich beer gardens on a nice summer day, or maybe a hard-to-reach mountain top. I chose chemistry as a career because my soccer skills were not good enough, and I guess I like to play with fire. So what better than to have fun every day! If I were not a scientist, I would be making tons of money on Wall Street while driving a taxi in Manhattan for fun. The most important thing I learned from my parents is to be modest and enjoy a good glass of wine. My greatest achievement has been passing the physics “Vordiplom” (intermediate diploma). My worst nightmare is a lab accident involving one of my students. If I could go back in time and do any experiment, it would be … I prefer to look to the future. I celebrate success by opening a bottle of champagne when my students graduate. My piece of music is Modest Mussorgski's Pictures at an Exhibition. My 5 top papers: 1“Well-Defined Boron-Containing Polymeric Lewis Acids”: Y. Qin, G. Cheng, A. Sundararaman, F. Jäkle, J. Am. Chem. Soc. 2002, 124, 12672. (A selective borylation method that has enabled access to many new materials over the years.) 2“Reversible Expansion and Contraction of a 1,2-Diborylated Ferrocene Dimer Promoted by Redox Chemistry and Nucleophile Binding”: K. Venkatasubbaiah, L. N. Zakharov, W. S. Kassel, A. L. Rheingold, F. Jäkle, Angew. Chem. Int. Ed. 2005, 44, 5428; Angew. Chem. 2005, 117, 5564. (A redox-active analogue of diborabenzene undergoes unique structural changes when applying external stimuli.) 3“π-Expanded Borazine: An Ambipolar Conjugated B–π–N Macrocycle”: P. Chen, R. A. Lalancette, F. Jäkle, Angew. Chem. Int. Ed. 2012, 51, 7994; Angew. Chem. 2012, 124, 8118. (A boron-containing donor–acceptor macrocycle that we succeeded to structurally characterize by X-ray analysis.) 4“Electron-Deficient Triarylborane Block Copolymers: Synthesis by Controlled Free Radical Polymerization and Application in the Detection of Fluoride Ions”: F. Cheng, E. M. Bonder, F. Jäkle, J. Am. Chem. Soc. 2013, 135, 17286. (Polymer effects and block copolymer self-assembly allow for fluoride ion detection in aqueous solutions at extremely low concentrations.) 5“B–N Lewis Pair Functionalization of Anthracene: Structural Dynamics, Optoelectronic Properties, and O2 Sensitization”: K. Liu, R. A. Lalancette, F. Jäkle, J. Am. Chem. Soc. 2017, 139, 18170. (A new class of “contorted” conjugated hybrid materials.) Volume57, Issue41October 8, 2018Pages 13378-13378 ReferencesRelatedInformation

Grafting of N,N-dimethylaminoethyl methacrylate from PE/PP nonwoven fabric via radiation-induced RAFT polymerization and quaternization of the grafts

Radiation induced grafting method is one of the most promising grafting techniques and it works successfully together with the reversible addition fragmentation chain transfer (RAFT) polymerization, one of the most prominent controlled free-radical polymerization (CRP) methods. This study reports grafting of N,N-dimethylaminoethyl methacrylate (DMAEMA) from the surface of polyethylene/polypropylene nonwoven fabric (PE/PP NWF) by the combination of radiation-induced initiation and the RAFT polymerization technique. Effects of monomer concentration, absorbed dose and solvent choice on the grafting yield have been investigated. The grafted NWF's were characterized by ATR–FTIR, XPS, SEM, EDX and thermal analysis methods. The results indicated that surface properties were completely altered after grafting compared to pristine PE/PP even for those with very low degree of PDMAEMA grafting. Free homopolymers in solution have been analyzed by GPC in order to obtain information about the grafts. The PDMAEMA grafts on the fabric surfaces were later quaternized with dimethyl sulfate to yield positively charged surfaces that were tested for antibacterial properties.

Highlight on the Mathematical Modeling of Controlled Free Radical Polymerization

Over the last quarter century, controlled free radical polymerization (CFRP) has received great attention by the researchers of polymer science and engineering. In addition to the experimental studies, many publications in the literature dealt with the modeling of CFRP processes. A review of acknowledged and well-received researches on mathematical modeling in the area of CFRP is presented in this work. Three main categories of CFRP (namely, ATRP, RAFT, and NMP) are taken into consideration in the review. The different techniques used in modeling CFRP processes are also enumerated with more emphasis on Monte Carlo simulation and the method of moments. The review provides a better understanding of the processes and the recent efforts to model CFRP.

Nitroxide-Mediated Controlled Free Radical Polymerization of the Chelate Monomer 4-Styryl-tris(2-pyridyl)borate (StTpyb) and Supramolecular Assembly via Metal Complexation.

The reaction of 4-(dibromoboryl)styrene with 2-pyridylmagnesium chloride resulted in the formation of 4-styryl-tris(2-pyridyl)borate free acid (StTypb), a new polymerizable nonpyrazolyl "scorpionate" ligand. StTypb did not undergo self-initiated polymerization under ambient conditions and proved to slowly polymerize through standard radical polymerization at 90 °C. Nitroxide-mediated polymerization (NMP) of StTypb at 135 °C proceeded with good control, resulting in a polymer of Mn = 27400 and PDI = 1.21. The TEMPO-terminated homopolymer successfully initiated the polymerization of styrene, generating an amphiphilic block copolymer with DPn of 1200 and 78 for the PS and the StTypb block, respectively. A similar block copolymer with DPn of 29 and 20 for the PS and the StTypb block respectively was obtained in a reverse polymerization procedure from a PS macroinitiator. The self-assembly of these block copolymers was examined in selective solvents and preliminary metal complexation studies were performed.

Electron-Deficient Triarylborane Block Copolymers: Synthesis by Controlled Free Radical Polymerization and Application in the Detection of Fluoride Ions

Luminescent triarylborane homo and block copolymers with well-defined chain architectures were synthesized via reversible addition-fragmentation chain transfer polymerization of a vinyl-functionalized borane monomer. The Lewis acid properties of the polymers were exploited in the luminescent detection of fluoride ions. A dual-responsive fluoride sensor was developed by taking advantage of the reversible self-assembly of a PNIPAM-based amphiphilic block copolymer. Anion detection in aqueous solution was realized by introducing positively charged pyridinium moieties along the polymer chain.

Phosphonium-Containing ABA Triblock Copolymers: Controlled Free Radical Polymerization of Phosphonium Ionic Liquids

Phosphonium ion-containing acrylate triblock (ABA) copolymers were synthesized using nitroxide mediated radical polymerization. The polymerization of styrenic phosphonium-containing ionic liquid monomers using a difunctional alkoxyamine initiator, DEPN2, afforded an ABA triblock copolymer with an n-butyl acrylate soft center block (DP ∼ 400) and symmetric phosphonium-containing external reinforcing blocks (DP < 30). Two phosphonium monomers with different alkyl substituent lengths enabled an investigation of the effects of ionic aggregation of phosphonium cations on the physical properties of ABA block copolymer ionomers. Subsequently, the thermomechanical properties and morphologies of these materials were compared to a noncharged triblock copolymer analogue with neutral polystyrene external blocks. Shortening the alkyl substituents on the phosphonium cation enhanced the hydrophilicity of tributyl-4-vinylbenzyl phosphonium chloride (BPCl) relative to trioctyl-4-vinylbenzyl phosphonium chloride (OPCl). In...

Using dilatometry in the reversible addition fragmentation transfer polymerization of N-(S)-(−)-α-methylbenzyl methacryloylamine

Optically active polymers were prepared using reversible addition-fragmentation chain transfer polymerization (RAFT) of N-(S)-α-methylbenzylmethacryloylamine (N-(S)-α-MBMA), a functional optically active monomer. RAFT polymerizations were carried out at 70 °C in ethanol using AIBN as a thermal initiator and benzyl or (1-phenyl)ethyl dithiobenzoate (BDB and PEDB, respectively) as the RAFT agents. The kinetic study was performed by dilatometry. Plots of conversion vs time indicated that the polymerizations followed first order kinetics. 1H NMR, IR, and UV–vis spectrophotometric studies confirmed the presence of thiocarbonylthio moieties (−SCS-) in the polymer chains. The molecular weight distributions (MWDs) were moderately narrow with polydispersity indices between 1.3 and 1.6, which indicated that the control of the reaction was not completely achievement using BDB or PEDB as RAFT agents. The optical activity [α]D25 measurements of synthesized polymers by RAFT did not show a noticeably linear increase dependence with respect to molecular weight, as was previously reported for another controlled free radical polymerization (CRP) system.

Exfoliation of layered silicates through in situ controlled free radical polymerization mediated by a silicate-anchored initiator

In this study, a new type of controlled free radical polymerization (CFRP) initiators from azetidine-2,4-dione functional groups were synthesized and then embedded within the interlayer spaces of layered silicates to prepare a series of polymer-layered silicate nanohybrids. Kinetics analyses and determination of the molecular weights and distributions of the polymerization products revealed that these CFRP initiators were viable species for 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-mediated stable free radical polymerization. Anchoring the CFRP initiator within the galleries of montmorillonite (MMT) enlarged the d-spacing from 15 to 38 A. The incorporated cationic CFRP initiator (a silicate-anchored TEMPO derivative) provides the initiation functionality for the controlled free radical polymerization within the interlayers. The molecular weights of the resulting polystyrenes varied from 6800 to 85 200 g mol−1, depending on the initiator–MMT/styrene weight ratio, with polydispersities of 1.14–1.45 for the lower-molecular-weight samples and 1.96–2.43 for the higher-molecular-weight samples. X-Ray diffraction patterns and transmission electron microscopy revealed that the growing polymer chains separated the layered silicates, thereby leading to the formation of exfoliated individual nanoplatelets. Thus, in situ controlled polymerization within the two-dimensional MMT platform, mediated by silicate-anchored initiators, is an effective dispersion/exfoliation route toward polymer-layered silicate nanohybrids.

ARGET ATRP of methyl methacrylate with 2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethylamine (OLC) as both ligand and reducing agent in the presence of air

Copper(II)-mediated activators regenerated by electron transfer for atom transfer radical polymerization of methyl methacrylate (MMA) was successfully carried out in a limited amount of air in the presence of 2-(8-heptadecenyl)-4,5-dihydro-1H-Imidazole-1-ethylamine as ligand that served not only as ligand but also as reducing agents. Reduction of Cu(II) to Cu(I) by an excess amount of nitrogen-based ligand was followed by UV–visible spectroscopy. The kinetics of the polymerizations and effect of different polymerization conditions are investigated. It is found that the polymerization of MMA can be conducted well even if the amount of Cu(II) is as low as 1 mol% catalyst relative to initiator. The results of the polymerizations demonstrate the features of “living”/controlled free-radical polymerization, such as the number-average molecular weights being close to their corresponding theoretical values and increasing linearly with monomer conversion, and narrow molecular weight distributions. Chain extension of poly(methyl methacrylate)s with MMA was successful and demonstrated well-maintained end-group functionality.

Polymeric Phosphorylcholine−Camptothecin Conjugates Prepared by Controlled Free Radical Polymerization and Click Chemistry

Novel polymer-drug conjugates, consisting of zwitterionic poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) as the polymer component, and camptothecin (CPT) as the drug, were prepared by two methods. In one case, CPT was transformed by acylation into a functional initiator for copper catalyzed atom transfer radical polymerization (ATRP), and polyMPC was grown from this therapeutic initiator. In the other case, a one-pot ATRP-"click" conjugation strategy was employed to synthesize novel polyMPC structures containing multiple copies of the drug pendant to the zwitterionic polymer chain. The latter method allows polyMPC-graft-CPT conjugates to be prepared with a high weight percent drug loading (up to 14% CPT) with excellent solubility in pure water (>250 mg/mL). The linkage chemistry chosen between the polyMPC backbone and the pendant drugs proved critically important for assuring drug release within a time frame reasonable to consider these structures as a platform for injectable cancer therapeutics. Liberation of the drug from the polymer backbone was monitored by high-performance liquid chromatography, using size-exclusion and reverse-phase columns, and the toxicity of the polymer-drug conjugates was examined in cell culture against breast (MCF7), ovarian (OVCAR-3), and colorectal (COLO 205) cancer cell lines.

Fe(III)-catalyzed AGET ATRP of styrene using triphenyl phosphine as ligand

Activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) is a new technique for conducting ATRP developed recently. In this work, an iron(III)-mediated AGET ATRP of styrene in bulk was carried out at 110 °C, using benzyl bromide as an initiator, oxidatively stable iron(III) chloride hexahydrate (FeCl3·6H2O) as a catalyst, triphenyl phosphine as a ligand, and ascorbic acid as a reducing agent. The polymerizations demonstrated the features of “living”/controlled free-radical polymerization, such as the number–average molecular weights increasing linearly with monomer conversion and narrow molecular weight distributions (Mw/Mn = 1.14–1.31).

A Highly Active Iron‐Based Catalyst System for the AGET ATRP of Styrene

The atom transfer radical polymerization of styrene using activators generated by electron transfer (AGET ATRP) has been carried out in bulk in a limited amount of air at 110 °C, using 1,3,5-(2'-bromo-2'-methylpropionato)benzene (BMPB) as an initiator and FeCl(3) · 6H(2) O/tris(3,6-dioxaheptyl) amine (TDA-1)/ascorbic acid (VC) as a novel Fe(III) -mediated catalyst system. The results of the polymerizations demonstrate the features of 'living'/controlled free-radical polymerization, such as the number-average molecular weights being close to their corresponding theoretical values and increasing linearly with monomer conversion, and narrow molecular weight distributions ($\overline M _{\rm w} /\overline M _{\rm n}$ = 1.18-1.26). The end functionality of the obtained polymers was confirmed by (1) H and (13) C NMR spectra as well as a chain-extension reaction.

AGET ATRP of methyl methacrylate catalyzed by FeCl3/iminodiacetic acid in the presence of air

The recently developed living free-radical polymerization system, atom transfer radical polymerization using activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP), was used for methyl methacrylate (MMA) polymerization in the presence of a limited amount of air, using a novel catalyst system based on iron (FeCl3) complexes with iminodiacetic acid (IDA) and using ascorbic acid (VC) as a reducing agent. The kinetics of AGET ATRPs of MMA with different amounts of VC in the presence of air was investigated. The results of the polymerizations demonstrated the features of “living”/controlled free-radical polymerization such as the number-average molecular weights increasing linearly with monomer conversion and narrow molecular weight distributions (Mw/Mn=1.31–1.44).

Rapid Polymer Brush Growth by TEMPO-Mediated Controlled Free-Radical Polymerization from Swollen Plasma Deposited Poly(maleic anhydride) Initiator Surfaces

Pulsed plasma-chemical deposition of poly(maleic anhydride) is shown to be a substrate-independent method for functionalizing solid surfaces with initiator sites for nitroxide-mediated controlled free-radical graft polymerization. Swelling of the initiator film via aminolysis can lead to grafted polymer brushes that are 1 order of magnitude thicker than those obtained by existing methods on solid surfaces.

“Living”/Controlled Free Radical Polymerization Using bis(Thionaphthoyl) Disulfide as a Source of RAFT Agent

The reversible addition fragmentation chain transfer (RAFT) bulk polymerization of styrene has been studied using bis(thionaphthoyl) disulfide (BTNDS) and 2,2′‐azobis(isobutyronitrile) (AIBN) to generate RAFT agent (2‐cyanoprop‐2‐yl 1‐dithionaphthalate, CPDN) in situ at 80°C. The results show that the polymerization displays living free radical polymerization characteristics: controlled molecular weight with low polydispersity (PDI = 1.14–1.26) and first order kinetics. The extension polymerization using obtained polystyrene as a macro‐RAFT agent displays controlled polymerization behavior. The RAFT polymerizations of methyl methacrylate (MMA), methacrylate (MA), butyl methacrylate (BMA), and octyl acrylate (OA) were successfully carried out using the same polymerization system.

Novel SG1-Based Water-Soluble Alkoxyamine for Nitroxide-Mediated Controlled Free-Radical Polymerization of Styrene and n-Butyl Acrylate in Miniemulsion

Nitroxide-mediated controlled free-radical polymerizations of n-butyl acrylate and styrene were performed in miniemulsion using, for the first time, a water-soluble SG1-based alkoxyamine as an initiator. For n-butyl acrylate, polymerizations exhibited all the features of a controlled system. In particular, the initiator efficiency was high, indicating an extensive entry in the monomer droplets of all of the oligoradicals generated in the aqueous phase. The efficiency, however, was not high for styrene homopolymerization, which was explained by a highly pronounced persistent radical effect, leading to a large proportion of dead oligomers, to a large concentration of free nitroxide, and thus to a too slow chain growth in the aqueous phase. Nevertheless, the addition of a very small amount of methyl acrylate strongly enhanced the entry rate, as a consequence of a favorable kinetic effect due to appropriate copolymerization conditions.

Initiator‐Grafted Silica Particles for Controlled Free Radical Polymerization: Influence of the Initiator Structure on the Grafting Density

AbstractA series of organic‐inorganic hybrid particles were synthesized by a self‐assembled layer of different initiators, immobilized on silica particles and used for controlled radical polymerization. We use three different initiator systems for atom‐transfer radical polymerization (ATRP), unimolecular nitroxide mediated polymerization (NMP), and bimolecular NMP, for the development of the hybrid inorganic/organic particles. After preliminary qualitative characterization by X‐ray spectroscopy (XPS) and Fourier‐transformed infrared (FT‐IR) measurements, the hybrid nanoparticles were studied by thermogravimetric analysis (TGA) to determine and discuss the initiator graft density in terms of steric hindrance.The coupling agents employed for the various approaches used here: a) NMP1‐bimolecular system, b) NMP2‐unimolecular system, and c) ATRP.magnified imageThe coupling agents employed for the various approaches used here: a) NMP1‐bimolecular system, b) NMP2‐unimolecular system, and c) ATRP.

Controlled Free Radical Polymerization of Styrene Initiated from Alkoxyamine Attached to Polyacrylate Chemisorbed onto Conducting Surfaces

A new inimer that associates an alkoxyamine, which is an initiator/mediator in nitroxide mediated radical polymerization (NMP), and a polymerizable acrylate has been synthesized and used in a two-s...

Homogeneous Controlled Free Radical Polymerization in Aqueous Media

AbstractFor Abstract see ChemInform Abstract in Full Text.

Controlled Free Radical Polymerization in Water-Borne Dispersion Using Reversible Addition−Fragmentation Chain Transfer

A novel approach to conducting controlled free radical polymerization in water-borne organic dispersions using reversible addition−fragmentation chain transfer (RAFT) has been studied. The novel approach in this study focused on eliminating monomer and oligomer transport and comprised two fundamental steps: the synthesis of dithiobenzoate-end-capped styrene oligomers in bulk followed by emulsification of these oligomers to yield a polymerizable water-borne dispersion. Dithioesters that act as chain transfer agents in the RAFT process were synthesized in situ. The free radical polymerization of the dithiobenzoate-end-capped styrene oligomers in the water-borne organic dispersion proceeded in a controlled manner; molar mass increased in a linear fashion with increasing conversion, while polydispersities remained low. The familiar red layer formation associated with RAFT polymerization in conventional emulsions was not observed under these conditions. The effects of changing the costabilizer (hydrophobe) and the degree of polymerization of the emulsified oligomers were investigated. Better control was achieved with a less hydrophilic costabilizer and for the shorter of the oligomers tested.