Abstract Atom Transfer Radical Polymerization Research Articles

Mechanistic aspect for the atom transfer radical polymerization of itaconimide monomers with methyl methacrylate: a computational study

Abstract Atom transfer radical polymerization (ATRP) is a versatile & famous technique for the synthesis of well defined molecular architectures. In ATRP, there is a dynamic equilibrium exists between active & dormant species. Therefore, ATRP progress through a sequence of activation & deactivation cycles, ending upon complete monomer consumption & termination reactions are minimized. This paper presents a systematic computational study on kinetics & thermodynamics associates in the ATRP of itaconimide monomers & methyl methacrylate (MMA). For this, the copolymerization system is modeled as a unimer, dimer & trimer of various itaconimides & MMA monomer. The density functional theory with B3LYP functional & 6–31 + G(d)/LanL2DZ basis sets is used in the prediction of geometries & energetics associated with the dissociation of terminal R–X bond present in the unimer, dimer & trimer. The relative equilibrium constant (K ATRP) for the ATRP activation/deactivation steps is calculated from the free energy values associated with dissociation of R–X bond. The relative K ATRP values of dimer & trimer of selected monomers is compared with their respective unimer. From the transition state geometries of the dimeric propagating radical, activation energy is calculated. The gas phase rate coefficients for propagation (k p) (of itaconimides & MMA copolymerization) are calculated using the standard transition state theory. The effect of system parameters such as solvent, temperature & substituent on K ATRP & k p values of dimer is investigated systematically. The change in the initiating system & temperature has significant effect on k p values as compared to solvent & various substituent. The K ATRP values of dimer & trimer dormant species are higher as compared to their respective monomeric species. The neighboring monomer & penultimate monomer plays vital role in kinetics & thermodynamics associated with copolymerization. The obtained initial results show that the mechanism of copolymerization of itaconimide monomers & MMA follows penultimate model.

Cytochrome C catalyzed oxygen tolerant atom-transfer radical polymerization

Atom-transfer radical polymerization (ATRP) is a well-known technique for controlled polymer synthesis. However, the ATRP usually employed toxic heavy metal ionas as the catalyst and was susceptible to molecular oxygen, which made it should be conducted under strictly anoxic condition. Conducting ATRP under ambient and biocompatible conditions is the major challenge. In this study, cytochrome C was explored as an efficient biocatalyst for ATRP under biocompatible conditions. The cytochrome C catalyzed ATRP showed a relatively low polymer dispersity index of 1.19. More interestingly, the cytochrome C catalyzed ATRP showed superior oxygen resistance as it could be performed under aerobic conditions with high dissolved oxygen level. Further analysis suggested that the Fe(II) embed in the cytochrome C might serve as the catalytic center and methyl radical was responsible for the ATRP catalysis. This work explored new biocompatible catalyst for aerobic ATRP, which might open new dimension for practical ATRP and application of cytochrome C protein.Graphical

Atom transfer radical polymerization initiated by activator generated by electron transfer in emulsion media: a review of recent advances and challenges from an engineering perspective

Atom transfer radical polymerization (ATRP) is a powerful initiation technique that has been used successfully to create a variety of advanced materials. ATRP induced by a benign reducing agent (AGET ATRP) is gaining popularity in emulsion media. The use of emulsion AGET ATRP in a two-step experimental procedure opens up new possibilities for developing environmentally friendly, low-cost, and less toxic catalytic systems. However, no study has specifically addressed the difficulties associated with ligand solubility, ligand-surfactant compatibility, and stirring speed when emulsion AGET ATRP is performed. Furthermore, only a few experimental studies have looked for scaling-up emulsion AGET ATRP, and no explicit mathematical model for this particular system has been reported so far. In this review paper, we discuss the experimental work done so far for the emulsion AGET ATRP. In addition, we show the modern technologies that have been used to address the drawbacks of emulsion AGET ATRP. This review paper also discusses the fundamentals and recent advances in empirical and statistical models developed to better understand the complex mechanism of emulsion AGET ATRP.

The effects of catalyst and deactivator species in atom transfer radical polymerization of n-butyl methacrylate

Atom transfer radical polymerization (ATRP) of n-butyl methacrylate (n-BMA) was performed using CuIBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) as catalyst and tosyl chloride (TsCl) as initiator, and different poly(n-butyl methacrylate) samples were prepared by changing the ratios of monomer/initiator and monomer/catalyst. Comparison was made with the data of another ATRP system with 4,4′-di(5-nonanyl)-2,2′-bipyridine (dNbpy) ligand (n-BMA/CuIBr/dNbpy/TsCl). 1H NMR spectroscopy was used successfully to study monomer conversion during polymerization. For lower degree of polymerization (DP) ≤ 200, the corresponding products displayed narrow molecular weight distribution (D ≤ 1.1). Number average molecular weights (Mn) obtained by gel permeation chromatography (GPC) were higher than those calculated (Mn,theory), while in products with higher degree of polymerization (DP = 300), the Mn,theory surpassed Mn,GPC and molecular weight distribution enhanced (D ≤ 1.25). UV–visible spectroscopy was employed to study the probable coordination of monomer to copper bromide and/or ligand. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used for characterization of prepared poly(n-butyl methacrylate)s. Cyclic voltammetry (CV) for CuII/CuI redox couple was performed in solvent mixtures of isobutyl butyrate (saturated form of n-butyl methacrylate) and acetonitrile having different volume fractions (acetonitrile/butyl isobutyrate: 100/0, 80/20, 60/40, 40/60 and 20/80). By introducing moderately nonpolar butyl isobutyrate to polar aprotic acetonitrile, peak-to-peak separation increased. This implied slow electron transfer (lower KET in presence of monomer) that adjusted KATRP.

High water-content thermoresponsive hydrogels via electrostatic macrocrosslinking of cellulose nanofibrils

Atom transfer radical polymerization (ATRP) has been utilized to synthesize tri- and star-block copolymers of poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) and quaternized poly(2-(dim ...

Synthesis and characterization of poly (ethyl methacrylate)-b-poly(dimethyl siloxane)-b-poly(ethyl methacrylate) triblock copolymer: the effect of solvent on morphology

Atom transfer radical polymerization (ATRP) of ethyl methacrylate (EMA) was carried out at 80 °C using poly(dimethyl siloxane) (PDMS) bifunctional macroinitiator, copper chloride (CuCl) catalyst, and N, N, N′, N″, N″-penta methyl diethyl triamine (PMDETA) ligand in toluene solvent. The final microstructure and kinetic of polymerization of the PEMA-b-PDMS-b-PEMA block copolymer were analyzed by 1H-NMR, FT-IR and gel permeation chromatography (GPC) techniques. The effect of solvent on self-assembly and morphology of PEMA-b-PDMS-b-PEMA triblock copolymer is reported. Intrinsic viscosity measurements, UV absorption and thermodynamic properties evaluations were indicated that certain interactions existed between this block copolymer and acetone, toluene and dichloromethane (DCM) solvents before film formation. The effect of solvent on the final morphology of PEMA-b-PDMS-b-PEMA block copolymer was studied by transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses. The morphology of the block copolymer was transformed from circular into cylindrical and branched as the solvent was changed from DCM into the toluene and acetone, respectively.

Kinetic modeling of atom-transfer radical polymerization: inclusion of break reactions in the mechanism

Atom-transfer radical polymerization (ATRP) is a powerful controlled radical polymerization technique for material synthesis with specific properties. Since the emergence of this technique, few studies have been made to develop kinetic models to study the system at high temperatures. This paper presents a new approach of ATRP kinetic modeling: inclusion of some break reaction common at temperatures above 100 °C aiming to make the model more robust to simulate the process at high temperatures. Kinetic modeling was developed by material balances and the method of moments. It was demonstrated that for the styrene ATRP at 110 °C a better reproduction of experimental data was obtained by the modeling proposed in this work, with a reproduction percentage error for conversion of 4 % versus some values higher than 10 % for the common models from the literature. The model proposed in this present work could help future works dealing with analysis of temperature effect, optimization and process scale-up, since it takes into account some common chemical reactions at higher temperature.

Optimization of reaction conditions in functionalized polystyrene synthesis via ATRP by simulations and factorial design

Atom-transfer radical polymerization (ATRP) is a powerful reversible-deactivation radical polymerization technique that provides polymers with several macromolecular architectures. Global optimization of this type of system is often difficult due to the mathematical models complexity. Based on that, the purpose of this paper is to provide a simplified optimization method to determine the best reaction conditions in bulk styrene ATRP initiated by 2,2,2-tribromoethanol. A kinetic model, with experimental validation, was used to generate the response variables in a full 23 factorial design. Thus, an easy statistic modeling was employed to optimize reaction conditions. It was also performed a traditional global dynamic optimization to prove that our approach could be accomplished without considerable errors. Finally, we demonstrated that the optimum conditions can be obtained in an easy and uncomplicated way, allowing extend it to any polymeric system.

Synthesis of Well-Defined Vinyl End-Functional Polystyrene Using Multifunctional Initiator by Atom Transfer Radical Polymerization

Atom Transfer Radical Polymerization (ATRP) has proven to be a powerful technique to obtain polymers with narrow polydispersities and controlled molecular weight. It also offers control over chain-ends. N-allyl-2-bromopropinamide (ABPN) was synthesized by one step reaction which involved on amidification of 2-bromo-propionyl bromide with allyl amine. 1H NMR has confirmed the structure of the ABPN. The well-defined polystyrene was synthesized by using ABPN as initiator in ATRP method. The results of the polymerization were significantly affected by reaction conditions. The vinyl end-functional polystyrene obtained was characterized by Gel Permeation Chromatography (GPC) and NMR analysis.

Urotropine as a highly effective and versatile promoter for atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) is a transition metal complex-catalyzed controlled/‘living’ radical process. Recently, there has been a lot of interest focused on decreasing the catalyst loading and reducing the cost of post-polymerization purification for ATRP. In this work, urotropine was found to significantly enhance the ATRP of methyl acrylate (MA), methyl methacrylate (MMA) and styrene (St) catalyzed by CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) and CuBr/tris(2-(dimethylamino)ethylamine) (Me6TREN). With the addition of 25 times the amount of urotropine relative to CuBr, well-controlled polymerizations of MA, MMA and St were obtained at catalyst-to-initiator ratios of 0.01, 0.05 and 0.05, respectively, producing the corresponding polymers with molecular weights close to theoretical values and low polydispersities. The catalyst concentration could even be reduced to ppm level at a catalyst-to-initiator ratio as low as 0.001 in the polymerization of MA. These results indicate that urotropine is a very effective and versatile promoter for both CuBr/PMDETA and CuBr/Me6TREN. In the presence of urotropine, the catalyst loading could be reduced by as much as 1000 times. As PMDETA is one of the cheapest ATRP ligands, the combination of urotropine with CuBr/PMDETA could substantially reduce the catalyst loading and the cost of post-polymerization purification at the industrial scale and thus is promising for potential industrial applications. © 2014 Society of Chemical Industry

Synthesis and characterization of PSt-b-PVAc diblock copolymers via combination of atom transfer radical polymerization and cobalt-mediated radical polymerization

Atom transfer radical polymerization (ATRP) of styrene (St) initiated with trichloromethyl-terminated poly(vinyl acetate) was performed in the presence of CuCl/PMDETA as a catalyst system at 60 °C. PVAc-CCl3 telomers prepared from radical telomerization (without catalyst) and controlled radical telomerization (in the presence of Co(acac)2/DMF), were used in atom transfer radical polymerization (ATRP) to synthesize polystyrene-b-poly(vinyl acetate) (PSt-b-PVAc) diblock copolymers. The PVAc based block copolymers revealed a significant effect of Co(acac)2/DMF on PVAc macroinitiator which was used in the synthesis of highly ordered diblock copolymer on a well-defined microstructure. Diblock copolymers were characterized by 1H-NMR, DSC and GPC techniques. Reactivity ratios of St and VAc were calculated by the Mayo-Lewis (rSt = 0.563, rVAc = 0.081), Kelen-Todous (rSt = 0.583, rVAc = 0.074) and Finemann-Rose(rSt = 0.569, rVAc = 0.090) methods, which are in a good agreement with those reported for the conventional free-radical copolymerization of St and VAc. The number average molecular weights calculated from 1HNMR spectra were in good agreement with theoretically calculated values for block copolymers.

Synthesis and Characterization of Star Polymer with Comb-like Poly(lauryl methacrylate) Arms by Atom Transfer Radical Polymerization via One-pot ‘Arm-First’ Method

Atom transfer radical polymerization (ATRP) was used to prepare core crosslinked star polymers with comb-like poly (lauryl methacrylate) (LMA) arms by one-pot “arm-first” method, involving the synthesis of comb-like PLMA arms, followed by their crosslinking, using a mixture of LMA monomer and ethylene glycol dimethacrylate (EGDMA) crosslinker. By adjusting the feeding time and level of EGDMA, a series of star-like polymers with various comb-like arms length and number can be obtained. The molecular architecture including radius of gyration (Rg), hydrodynamic radius (Rh) and intrinsic viscosity (ηi) etc. were characterized by a triple-detector gel permeation chromatography (GPC) equipped with a refractive index detector, viscometer detector and a multi-angle static laser light scattering (MALLS) detector. The thermal property and shearing stability of these star-like polymers were also investigated.

Synthesis and Characterization of Polyacrylates Side-Chain Liquid Crystalline Polymer via Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) of methacrylate liquid crystal monomer M (4-((4-(2-(acryloyloxy)ethoxy)benzoyl)oxy)phenyl 4-propylbenzoate) was carried out using CuBr/PMDETA complex as catalyst and 2-bromo-2-methyl-propionic acid ester as initiator. The obtained monomer M and polymer P was characterized via infrared spectroscopy and1H NMR. The phase behavior and mesomorphism were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and x-ray diffraction (XRD). The molecular weight and the structure of the polymers were identified with gel permeation chromatography and nuclear magnetic resonance.

Atom Transfer Radical Polymerization: A Robust and Versatile Route for Polymer Synthesis

Atom transfer radical polymerization (ATRP) has become an established synthetic methodology to prepare polymers of high molecular weights with narrow molecular weight distributions and living polymerization characteristics. This review is a conceptual overview of ATRP and the components of an ATRP system. Current approaches to reduce the transition metal concentration are then described including activators regenerated by electron transfer (ARGET) ATRP. Finally, a recent polymerization approach, single electron transfer living radical polymerization (SET-LRP), is described.

STUDIES ON A FOUR-ARM POLYSTYRENE GEL BY LASER LIGHT SCATTERING

Atom transfer radical polymerization(ATRP)was used to synthesize narrowly distributed 4-arm-polystyrene star chains(4-PS-Br).Then the bromine end functional groups were further modified to thiol groups(4-PS-SH).Oxidization of each two thiol end groups leads to a disulfide bond(—S—S—),which enables us to slowly crosslink the PS star chains in THF solutions to form polymer clusters,then gels.Static laser light scattering(SLS)shows that in both semidilute solutions and gels the time-average scattered intensity changes little with the sample position,where the sample position is arbitrarily chosen by rotating and lifting the sample cuvette,indicating this chemical gel is homogeneous and speckle-free.Dynamic laser light scattering(DLS)shows that first there is only one fast decay mode of the time-time intensity correlation function in the original semidilute solution.Then the slow modes of the correlation function appear and the contributions of the slow modes increase at the early oxidation stage,indicating the formation of large cross-linked clusters.With oxidation time increase the contribution of the slow mode decreases,finally disappears.The correlation functions of the chemical gel are nearly the same as those of the original semidilute solution.The normalized intermediate scattering function can fully relax to zero,indicating that the gel has no frozen-in static component,and the speckles of other polymer gels originate from large voids inside,not cross-linked chains(clusters).Both SLS and DLS results indicate that this polystyrene gel is a homogeneous chemical gel.

SYNTHESIS, CHARACTERIZATION AND SELF-ASSEMBLY OF AN AZOBENZENE-CONTAINING AMPHIPHILIC ABA TRIBLOCK COPOLYMER

Atom transfer radical polymerization(ATRP) was applied to prepare an amphiphilic azobenzene-containing ABA triblock copolymer PMAA-b-PMAZOCNb-PMAA.In the presence of(4,4′-di(n-nonyl)-2,2′-)bipyridine(bpy9) and CuBr(as the catalyst),the dibromo-initiator butylene di(2-bromoisobutyrate) was reacted with the azobenzene-containing monomer,6-[4-(4′-cyanophenylazo)phenoxy]hexyl methacrylate(MAZOCN),which resulted in the macro-initiator.The absolute molecular weight of the macro-initiator was obtained by GPC-SLS(gel permeation chromatography-static light scattering) method.The dn/dc of the macro-initiator was predetermined as 0.257 mL/g by the refractometer.Then CuCl was used as the catalyst,and the macro-initiator further reacted with the tert-butyl methacrylate to obtain the triblock copolymer PtBMA-b-PMAZOCN-PtBMA as a precursor.From()~1H-NMR,the polymerization of tBMA monomers initiated by the macro-initiator was proved by the presence of a rather strong resonance at δ=1.43 which is corresponding to the tert-butyl group.A single Gaussian peak in the GPC curves further proved the narrow polydispersity of the resultant precursor triblock copolymer.The absolute molecular weight of the triblock copolymer was obtained by combination of the segement molar ratio determined from the characteristic ~1H-NMR peaks and the absolute molecular weight of the macroinitiator.In the final step,the tert-butyl groups were removed by the selective hydrolysis reaction with trifluoroacetic acid at room temperature.~1H-NMR analyses proved that most of the tert-butyl groups were hydrolyzed(conversion 95%),while the ester groups in the azo blocks were retained.These monomers and polymers were then studied with PLM(polarized light microscopy) and DSC(differential scanning calorimetry).The monomer,macro-initiator and the precursor triblock copolymer are all own smectic phase in the liquid crystalline region,while no characteristic liquid crystalline texture could be observed for the amphiphilic triblock copolymers.It is possibly because that,the presence of H-bonds between carboxyl groups hindered the development of the liquid crystalline phase.The amphiphilic ABA triblock copolymer possessed hydrophilic blocks in the outer part and the hydrophobic block in the central part.The vesicular aggregates of the polymer were obtained by gradually adding water,which is the good solvent of the hydrophilic block and the poor solvent of the azobenzene-containing liquid crystalline block,into the stirring THF solution of the amphiphilic copolymer.When the water content was more than 50% volume ratio,an excessive amount of water was added to freeze the assembly of the copolymer.THF was removed from the mixed solvent by dialyzed against ultrapure water for days.The TEM(transmission electron microscopy) observation showed that the amphiphilic block copolymer self-assembled into vesicular aggregates with average diameters from 300 to 500 nm.By using a high-pressure mercury lamp as the light source,the vesicular aggregates transform to the colloidal spheres when irradiated with the ultraviolet light in the solid state.

Synthesis by ATRP and Properties of Liquid Crystalline Three-Armed Star Polymers Containing Azobenzene Chromophores

Atom Transfer Radical Polymerization (ATRP) has been applied to synthesize liquid crystalline methacrylic polymers having three-arms star structure, starting from a central core of C3 symmetry. By just changing the duration of the polymerization process, macromolecules having distinct average chain lengths with low polydispersity values and well defined end-groups have been obtained. All the obtained star-shaped polymers, characterized by differential scanning calorimetry and polarized optical microscopy, exhibit smectic and nematic liquid-crystalline phases on heating, with transition temperatures strongly dependent on the average polymerization degree, and high clearing points. The comparison of these systems with the analogous linear derivatives pointed out higher glass transition temperature values, although they are characterized by lower average polymerization degree. Such behavior can be attributed to the stiffness of the aromatic core, which limits the free movement of chain ends.

Atom Transfer Radical Polymerization of MMA Initiated by 2‐(4‐chloromethyl‐phenyl)‐benzoxazole and Fluorescent Property of PMMA

Atom transfer radical polymerization (ATRP) of MMA was conducted using 2‐(4‐chloromethyl‐phenyl)‐benzoxazole as initiator, CuCl as catalyst, and PMDETA as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (Mn/Mw range from 1.30 to 1.45). The structure of PMMA was analyzed by 1H‐NMR and proved the polymerization could be controlled to some degree. The optical property of the initiator was well preserved in the resulting PMMA, and the end‐functionalized PMMA exhibited fluorescent emission at 360 nm whether in DMF solution or in film state.

Studies on atom transfer radical emulsion polymerization of n-butyl methacrylate

Atom transfer radical polymerization (ATRP) of n-butyl methacrylate (BMA) in water-borne media, catalyzed and initiated by CuCl/4,4-di (5-nonyl)-2,2-bipyridine (dNbpy) and Ethyl 2-bromopropinate (BrCH3CHCOOC2H5) was conducted. The influence of several factors, such as the amount of surfactant, catalyst, initiator and the reaction time, temperature on the stability of the latexes and the control of the polymerization was investigated. The nucleation mechanism of the latexes, thermodynamic data and activation parameters for the ATRP emulsion polymerization of BMA were also reported.

Atom Transfer Radical Polymerization of Styrene with 5‐Chloromethyl‐2‐hydroxy‐benzaldehyde as Initiator

Atom transfer radical polymerization (ATRP) of styrene (St) proceeded using 5‐chloromethyl‐2‐hydroxy‐benzaldehyde as initiator, CuCl as catalyst, and N,N,N′,N′,N′‐pentamethyldiethyltriamine (PMDETA) as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (M n/M w ranges from 1.25 to 1.50). The end structure of PSt was analyzed by 1H‐NMR, and PSt initiated MMA to form block copolymer (PSt‐b‐PMMA), which also proved that the polymerization could be controlled. The effects of reaction temperature and monomer to initiator mole ratio on the polymerization displayed living character were discussed.