Bulk Atom Transfer Radical Polymerization Research Articles

Identifying the essential roles of light and sonication in dual‐stimuli regulated bulk atom transfer radical polymerization by multiscale simulation

AbstractMore and more attention has been paid to the important roles of external fields in controlled radical polymerization (CRP). However, their essential roles have not been studied thoroughly yet, which hinders the in‐depth understanding of the mechanism and kinetics. Herein, a strategy combining quantum chemical calculations (QCC) and kinetic modeling was adopted to identify the essential roles of light and ultrasonication in the dual‐stimuli regulated bulk atom transfer radical polymerization (ATRP). At the molecular level, the impact of light on Cu‐catalyzed ATRP was investigated. The CuIIBr/Me6TREN has high absorbance at an experimental wavelength of 365 nm (main excitation S0 → D7 accounts for 84.93%). Electron transfer reactions involving Me6TREN are more favorable paths for photochemical reactions, and the mechanism of the copper activation/deactivation pathway is inner sphere electron transfer. At the micro‐scale, a kinetic model based on the method of moment was established with a “series” encounter pair model to consider the influence of ultrasound on diffusional limitation. Simulation results show that the changes of the reaction rate coefficients ka, kda, and kt at high conversion reflect the degree of diffusional limitation by ultrasound. The multiscale modeling strategy applied in this study identifies the essential roles of photo and ultrasonication in dual‐stimuli regulated model systems, which can be extended to other external‐field regulated CRP to improve the mechanistic understanding.

Synthesis of PS-b-PPOA-b-PS triblock copolymer via sequential free radical polymerization and ATRP

A novel ABA triblock copolymer comprising double-bond-containing poly(phenoxyallene) (PPOA) and polystyrene (PS) segments was synthesized by sequential conventional free radical polymerization and atom transfer radical polymerization (ATRP) via the site transformation strategy. A new bifunctional initiator containing azo and Br-containing ATRP initiating groups was prepared using 2-bromopropionyl chloride, hydroquinone, and 4,4′-azobis(4-cyanopentanoic acid) as starting materials. Conventional free radical homopolymerization of phenoxyallene with cumulated double bond was performed in toluene to provide a polyallene-based macroinitiator bearing ATRP initiating groups at both ends, which is stable under UV irradiation and free radical circumstances. PS-b-PPOA-b-PS triblock copolymer was then obtained by bulk ATRP of styrene initiated by PPOA-based macroinitiator. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1366–1372

Kinetic Studies on Bulk Atom Transfer Radical Polymerization of Styrene

The long chain vinyl end-functional polystyrene has been synthesized in bulk polymerization method using atom transfer radical polymerization (ATRP) with Undecenyl-2-Bromopropionate (UnBP) and CuCl/bypyridine catalytic system. The polymerizations demonstrate an increase in molecular weight and conversion in direct proportion to the polymerization time by consumed monomer which exhibited first-order kinetics. This study concludes the simple kinetics of polystyrene synthesized by ATRP using initiator and ligand-to-copper(I) halide was found to be 1:2:1, which tentatively indicates that the coordination sphere of the active copper(I) center contains two bipyridine ligands. The propagation rate has been investigated for long range of time for ensuring that the rate of radical combination or disproportionation is sufficiently less.

Ultrasonically enhanced bulk ATRP of methyl methacrylate at high conversion with good livingness and control

A great challenge in controlled radical polymerization such as atom transfer radical polymerization (ATRP) has been related to keep the livingness and molecular weight control of the reaction at high conversion, especially in bulk polymerization. The objective of this work is to investigate the effects of ultrasound power on the polymerization at high conversion. The initiator for continuous activator regeneration ATRP is used for bulk polymerization of methyl methacrylate (MMA) as the model system. Good livingness and control up to high conversion are obtained through employing ultrasonic waves. By this method, MMA is polymerized in bulk up to “glass state” (88%) at 70°C with polydispersity about 1.2 under an operating frequency of 40 kHz and output power of 100 W. Chain extension reaction proves the livingness of the synthesized polymers at glassy state. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1683–1687, 2016

Modeling the Influence of Diffusion-Controlled Reactions and Residual Termination and Deactivation on the Rate and Control of Bulk ATRP at High Conversions

In high-conversion atom transfer radical polymerization (ATRP), all the reactions, such as radical termination, radical deactivation, dormant chain activation, monomer propagation, etc. could become diffusion controlled sooner or later, depending on relative diffusivities of the involved reacting species. These diffusion-controlled reactions directly affect the rate of polymerization and the control of polymer molecular weight. A model is developed to investigate the influence of diffusion-controlled reactions on the high conversion ATRP kinetics. Model simulation reveals that diffusion-controlled termination slightly increases the rate, but it is the diffusion-controlled deactivation that causes auto-acceleration in the rate (“gel effect”) and loss of control. At high conversions, radical chains are “trapped” because of high molecular weight. However, radical centers can still migrate through (1) radical deactivation–activation cycles and (2) monomer propagation, which introduce “residual termination” reactions. It is found that the “residual termination” does not have much influence on the polymerization kinetics. The migration of radical centers through propagation can however facilitate catalytic deactivation of radicals, which improves the control of polymer molecular weight to some extent. Dormant chain activation and monomer propagation also become diffusion controlled and finally stop the polymerization when the system approaches its glass state.

Well-defined gels prepared by radical addition-coupling polymerization

A novel radical addition-coupling polymerization method is applied to prepare gels with controlled chain structure and length between branch points. Structure of the chains was varied between rigid or flexible ones by synthesizing different tribromide and dibromide monomers and reacting them with 2-methyl-2-nitrosopropane (MNP) under catalysis of Cu/N,N,N′,N′′,N′′-pentamethyldiethylene-triamine. The carbon radical generated by single electron transfer from the bromides can be efficiently captured by MNP, forming nitroxide radical. The in situ formed nitroxide radical immediately undergoes cross-coupling reaction with another carbon radical, generating gel bridged with alkoxyaime moiety via step-growth mechanism. The tribromide and dibromide monomers were synthesized from different saturated and unsaturated compounds, or by bulk atom transfer radical polymerization of styrene using small bromide as initiator. The rigid gel has better controlled chains between branch points than the flexible ones. Selective dissociation of the ester group in the backbone of chains has been realized, which reserved the weak of NO–C. Flory–Huggins interaction parameter χ of the gels with fixed length between branch points were measured, which solved the difficulty that χ of insoluble polymer cannot be determined by common methods used for soluble polymers.

Achieving High‐Conversion Bulk ATRP with Good Livingness and Well Controlled by Design and Optimization of Polymerization Temperature Profile

AbstractControlled radical polymerization (CRP) such as atom transfer radical polymerization (ATRP) is often conducted in solution processes and stopped at medium monomer conversions to yield well controlled polymer samples. A great challenge lies in running bulk CRP up to high conversions but still retaining system livingness and molecular weight control. In this work, we demonstrate the achievement of good living and well controlled high‐conversion bulk ATRP by means of design and optimizing polymerization thermal histories. The initiator‐for‐continues‐activator‐regeneration (ICAR) ATRP of methyl methacrylate (MMA) is used as a model system. Employing step functions in temperature, MMA conversions are pushed up to 98% and the PMMA samples possess polydispersities <1.3. Chain extension experiments confirm good livingness of synthesized polymers collected at high conversions.

Well‐Defined Iron Complexes as Efficient Catalysts for “Green” Atom‐Transfer Radical Polymerization of Styrene, Methyl Methacrylate, and Butyl Acrylate with Low Catalyst Loadings and Catalyst Recycling

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(μ-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4 b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.

Pressure Dependence of Iron‐Mediated Methyl Methacrylate ATRP in Different Solvent Environments

Iron‐mediated atom‐transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in N‐methylpyrrolidin‐2‐one (NMP) solution is investigated via online VIS/NIR spectroscopy up to 2500 bar. The activation–deactivation equilibrium constant, KATRP, decreases towards higher NMP content due to the formation of catalytically less active FeII/NMP species. The reaction volume increases from 1 to 15 cm3 mol−1 in passing from 16 to 92 mol% NMP. The same effects are observed for monomer‐free model systems with poly(MMA)–Br as the initiator. Investigations into iron‐catalyzed ATRP of MMA in less polar solvents or even without an additional solvent (i.e., for bulk ATRP) yield KATRP values, which are by two to three orders of magnitude higher than in the presence of NMP. image

Synthesis and characterization of polyrotaxanes comprising α-cyclodextrins and poly(ε-caprolactone) end-capped with poly(butyl methacrylate)s

Biodegradable polyrotaxane-based triblock copolymers were synthesized via the bulk atom transfer radical polymerization (ATRP) of n-butyl methacrylate (BMA) initiated with polypseudo-rotaxanes (PPRs) built from a distal 2-bromoisobutyryl end-capped poly(e-caprolactone) (Br-PCL-Br) with α-cyclodextrins (α-CDs) in the presence of Cu(I)Br/N,N,N′,N″,N″-pentamethyldiethylenetriamine at 45 oC. The structure was characterized in detail by means of 1H NMR, gel permeation chromatography, wide-angle X-ray diffraction, DSC and TGA. When the feed molar ratio of BMA to Br-PCL-Br was changed from 128 to 300, the degree of polymerization of PBMA blocks attached to two ends of the PPRs was in the range 382 − 803. Although about a tenth of the added α-CDs were still threaded onto the PCL chain after the ATRP process, the movable α-CDs made a marked contribution to the mechanical strength enhancement, blood anticoagulation activity and protein adsorption repellency of the resulting copolymers. Meanwhile, they could also protect the copolymers from the attack of H2O and Lipase AK Amano molecules, exhibiting a lower mass loss as evidenced in hydrolytic and enzymatic degradation experiments. © 2013 Society of Chemical Industry

Exploration of the Bulk Atom Transfer Radical Polymerization of Styrene

ABSTRACTThe synthesis of well‐defined polystyrene by atom transfer radical polymerization (ATRP) is reported. The effects of temperature, initiators, catalysts, and ligands on styrene bulk ATRP were investigated in detail. Results indicated that the initiator activity for a given monomer needs careful matching to bring about a match of the chain‐initiation and chain‐propagation rates. The higher activity is not necessarily the better. Thus, the less reactive monomer, styrene, was efficiently initiated by 1‐phenylethyl bromide (1‐PEBr), which only has a moderate initiator activity. Similarly, the catalyst system had to be carefully matched to achieve a real controlled/living radical polymerization. Controlled/living bulk ATRP of styrene was achieved by using 1‐PEBr as initiator, copper(I) bromide as catalyst, and N,N,N′,N′′,N′′‐ pentamethyldiethyllenetriamine as ligand at 90°C. After 4 h, the monomer conversion reached 51.8%, the practical molecular weight of polystyrene coincided well with the theoretical molecular weight of polystyrene, and the molecular weight distribution was 1.15. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21371; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21371

Controlled radical polymerization of tert-butyl acrylate at ambient temperature: Effect of initiator structure and synthesis of amphiphilic block copolymers

Controlled and very rapid ambient temperature polymerization of tert-butyl acrylate (tBA) via atom transfer radical polymerization (ATRP) and single electron transfer living radical polymerization (SET-LRP) conditions is reported. Two initiators, one that would generate a secondary radical and another that would generate a primary radical, upon activation, are used. A very active catalyst CuBr/Me6TREN was found to initiate rapid polymerization whether it was the primary or the secondary initiator. The polymerization was well controlled and very rapid. The initiator that produces secondary initiating site is found to result in more rapid polymerization than the one that produces primary initiating site. To explore the possibility of rapid ambient temperature polymerization through the SET-LRP mechanism, the polymerization was also carried out in the presence of DMSO. It was found that the polymerization was much faster compared to the bulk ATRP, without loss of control. Styrene was block copolymerized from PtBA macroinitiators and vice versa. In both the cases, block copolymers with controlled molecular weights were obtained. The tBA block of the polymer was selectively hydrolyzed to get amphiphilic block copolymers. This amphiphilic block copolymer was found to be useful in preparing stable cadmium sulfide (CdS) nanoparticulate dispersion. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A novel perfluorocyclobutyl aryl ether-based graft copolymer via 2-methyl-1,4-bistrifluorovinyloxybenzene and styrene

A series of novel perfluorocyclobutyl aryl ether-containing graft copolymers with polystyrene side chains were synthesized by the combination of thermal step-growth [2π+2π] cycloaddition polymerization of aryl bistrifluorovinyl ether monomer and atom transfer radical polymerization (ATRP) of styrene. We first synthesized a new aryl bistrifluorovinyl ether monomer of 2-methyl-1,4-bistrifluorovinyloxybenzene in two steps using commercially available 2-methylhydroquinone as starting material and the corresponding perfluorocyclobutyl aryl ether-based homopolymer with methoxyl end groups was prepared through the homopolymerization of this monomer in diphenyl ether. Next, the pendant methyls of this fluoropolymer were mono-brominated by N-bromosuccinimide and benzoyl peroxide so as to be converted to ATRP initiation groups. The targeted poly(2-methyl-1,4-bistrifluorovinyloxybenzene)-g-polystyrene with relatively narrow molecular weight distributions (Mw/Mn≤1.38) was obtained by the combination of bulk ATRP of styrene at 110°C using CuBr/bpy as catalytic system and the grafting-from strategy. These fluorine-containing graft copolymers show excellent solubility in common organic solvents.

Tailor‐Made Soluble Polymer Supports: Synthesis of a Series of ATRP Initiators Containing Labile Wang Linkers

AbstractA series of functional initiators for atom transfer radical polymerization (ATRP) was prepared. These structures contain an ATRP initiating site, a labile p‐alkoxybenzyl ester Wang linker and a functional end‐group (i.e., COOH, N3, OH, CCH, or NHFmoc). These novel initiators can be utilized for synthesizing well‐defined soluble polymer supports. For instance, the azide‐, alcohol‐, alkyne‐, and NHFmoc‐ derivatives were tested as initiators for the bulk ATRP of styrene. SEC, MALDI‐TOF‐MS, and NMR measurements indicated that well‐defined polystyrene samples with defined end‐groups have been synthesized in this process. Moreover, it was demonstrated that the labile Wang linkers could be easily cleaved with a mild trifluoroacetic acid treatment.magnified image

Preparation of organic–ceramic–metal multihybrid particles and their organized assembly

This paper describes the synthesis and assembly of multihybrid particles having a gold core, silica as an initial shell and polymethylmethacrylate (pMMA) as a second shell (Au@SiO2@pMMA). Multihybrid particles were synthesized in a stepwise manner. First, direct sol–gel coating of silica onto gold nanoparticles was carried out to prepare Au@SiO2 particles. The Au@SiO2 particles were modified with 3-(triethoxysilyl)propyl 2-bromo-2-methylpropanoate (BMPS), which is an initiator for atom transfer radical polymerization (ATRP) of MMA. Finally, bulk ATRP of MMA was conducted using BMPS-coated Au@SiO2 particles. Au@SiO2@pMMA particles formed a closely packed monolayer at the air–water interface. The monolayer can be deposited onto a solid substrate using the Langmuir–Blodgett technique. Atomic force microscopy and scanning electron microscopy images of the deposited film show a uniform and closely packed monolayer film in an area a few tens-of-micrometers in size with no voids. Moreover, a clear Au core, silica shell and pMMA shell structure were observed in a transmission electron microscopy image of the transferred film. It is particularly interesting that the monolayer film shows no clear plasmon absorption of the gold core, as observed in the chloroform solution of the particle. Results show that a thick silica shell masked the monolayer film’s plasmon absorption.

Polymers from renewable resources: Bulk ATRP of fatty alcohol‐derived methacrylates

AbstractCopper‐mediated atom transfer radical polymerization (ATRP) of lauryl methacrylate (LMA) and other long‐chain methacrylates was investigated in bulk at 35 °C by using CuCl/N,N,N′,N′,N′′‐pentamethyldiethylenetriamine (PMDETA)/tricaprylylmethylammonium chloride (Aliquat®336) as the catalyst system and ethyl 2‐bromoisobutyrate (EBIB) as the initiator. The investigated monomers can be derived from fatty alcohols and are therefore an important renewable resource for a sustainable development of our future. The amounts of ligand, Aliquat®336 and CuCl were optimized and the effect of their concentrations on the control of the polymerization and the observed conversions were investigated. It was found that a molar ratio of EBIB/CuCl/Ligand/Aliquat®336 of 1 : 1 : 3 : 1 provided the highest conversions of LMA and the best controlled polymerizations. These optimized conditions allowed for the synthesis of poly(lauryl methcarylate)s with different targeted DP (25, 50, 75, 100, 120, 240, and 500), including high‐molecular‐weight polymers with narrow molecular weight distributions. In addition, methacrylate monomers were prepared from fatty alcohols (capric, myristic, palmitic, stearic) and polymerized using the developed procedure to obtain polymers with the same DP and different chain lengths (C10, C12, C14, C16, and C18) of pending alkyl groups. Finally, the thermal properties of these polymers were examined by differential scanning calorimetry and thermogravimetric analysis.

Block copolymer preparation by atom transfer radical polymerization under emulsion conditions using a nanoprecipitation technique

AbstractLiving‐radical polymerization of acrylates were performed under emulsion atom transfer radical polymerization (ATRP) conditions using latexes prepared by a nanoprecipitation technique previously employed and optimized for the polymerization of styrene. A macroinitiator of poly(n‐butyl acrylate) prepared under bulk ATRP was dissolved in acetone and precipitated in an aqueous solution of Brij 98 to preform latex particles, which were then swollen with monomer and heated. Various monomers (i.e. n‐butyl acrylate, styrene, and tert‐butyl acrylate) were used to swell the particles to prepare homo‐ and block copolymers from the poly(n‐butyl acrylate) macroinitiator. Under these conditions latexes with a relatively good colloidal stability were obtained. Furthermore, amphiphilic block copolymers were prepared by hydrolysis of the tert‐butyl groups and the resulting block copolymers were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The bulk morphologies of the polystyrene‐b‐poly(n‐butyl acrylate) and poly(n‐butyl acrylate)‐b‐poly(acrylic acid) copolymers were investigated by atomic force microscopy (AFM) and small angle X‐ray scattering (SAXS). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 625–635, 2008

Atom transfer radical polymerization (ATRP) of styrene and acrylonitrile with monofunctional and bifunctional initiators

A bifunctional initiator (benzal bromide) was used to initiate the bulk atom transfer radical polymerization of styrene and acrylonitrile at 90°C with CuBr/2,2-bipyridyl. We compared these results with those of a monofunctional initiator of similar structure (1-bromoethyl benzene) under the same polymerization conditions. The monofunctional initiator worked better than the bifunctional initiator when both comonomers were added simultaneously at the beginning of the copolymerization; the bifunctional initiator was only effective when acrylonitrile was added after 20min of polymerization with styrene. The styrene–acrylonitrile copolymers were characterized by gel permeation chromatography, 13C nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and refractometry. Copolymer composition was monitored by both 13C NMR and by the change in the specific refractive index increment.

Synthesis of novel crosslinkable polymers by atom transfer radical polymerization of cardanyl acrylate

AbstractIn this work, the successful application of atom transfer radical polymerization (ATRP) to cardanyl acrylate, a polymerizable monomer derived from a renewable resource cardanol, is reported. Polycardanyl acrylate and poly(methylmethacrylate)‐cardanyl acrylate copolymers were prepared in bulk ATRP, using Copper(I) bromide/N, N, N′, N′, N″‐pentamethyl diethylene triamine (PMDETA) catalyst system at 95 °C in combination with ethyl‐2‐bromo isobutyrate initiator. The copolymers had mol. wt. (Mn) in the range 8300–2400 g/mol and polydispersity index (PDI) 1.27–2.00, depending upon the [M]0/[I]0 ratio. 1H NMR analysis of the copolymer showed that unsaturation in the side chain of cardanyl acrylate is unaffected under the conditions of ATRP. This was further confirmed by studying the curing reaction of polycardanyl acrylate by supported dynamic mechanical thermal analysis (DMTA) in dual cantilever mode. The thermogravimetric analysis shows that the copolymers have improved thermal stability, by about 35 °C, in comparison with pure PMMA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5953–5961, 2005

Kinetics and Molar Mass Evolution during Atom Transfer Radical Polymerization of n-Butyl Acrylate Using Automatic Continuous Online Monitoring

Homogeneous bulk atom transfer radical polymerization (ATRP) of n-butyl acrylate (BA) was monitored by automatic continuous online monitoring of polymerization reactions (ACOMP). This allowed simultaneous monitoring of conversion, weight-average molar mass Mw, and intrinsic viscosity, from which the viscometric average molar mass Mv, and an index of polydispersity Mw/Mv, were also determined. For ATRP of BA, initiated by methyl 2-bromopropionate and catalyzed by copper bromide complexes with 4,4‘-di(5-nonyl)-2,2‘-bipyridine, ACOMP yielded an equilibrium constant, Keq(90 °C) = 5.8 × 10-10. The polymerizations exhibited first-order kinetics with respect to monomer and initiator concentrations, as expected for ATRP. These results set the stage for further detailed understanding of kinetics and mechanisms in ATRP reactions using ACOMP, where temperature and concentration dependences can be readily monitored.