Atom Transfer Radical Polymerization Of Styrene Research Articles

A new strategy for the preparation of multiarm star-shaped polystyrene via a combination of atom transfer radical polymerization and cationic ring-opening polymerization

A multiarm star-shaped polystyrene (PS) was prepared from polystyrene-block-poly(glycidyl methacrylate) (PS-b-PGMA) by combination of atom transfer radical polymerization (ATRP) and cationic-ring opening polymerization (CROP). First, ATRP of styrene was carried out using ethyl 2-bromoisobutyrate (EIBr) as the initiator and copper halide (CuBr) with N,N,N′, N″, N″-pentamethyldiethylenetriamine (PMDETA) as the catalyst system in bulk at 110°C. Then, previously obtained PS was used as a macroinitiator for ATRP of glycidyl methcrylate (GMA) using CuCl/PMDETA as the catalyst system in anisole at 60°C. This produced an AB-type di-block co-polymer (PS-b-PGMA) with a controlled molecular weight and low polydispersity (M w/M n = 1.15). As a third step, CROP of pendant oxirane rings of PS-b-PGMA di-block co-polymer led to a multiarm star-shaped PS in a novel approach. The obtained polymers were characterized by gel-permeation chromatography and 1H-NMR.

A new approach to multiblock copolymers using atom transfer radical coupling

AbstractAtom transfer radical coupling (ATRC) is a method for chain extension of styrene homopolymers prepared by atom transfer radical polymerization (ATRP). This concept is used to produce multiblock copolymers from block copolymers prepared via ATRP of styrene using various macroinitiators. ATRC comprises the reactivation of the dormant species at the chain ends. In the absence of monomer, the active radical species recombine to give chain extension (from polystyrene, PS) or multiblock copolymers (from block copolymers). The application of ATRC to PSblock- poly(bisphenol A carbonate)-block-PS (PS-b-PC-b-PS) was not successful because chain degradation of the PC block occurs. However, poly(phenylene oxide)-block-PS (PPO-b-PS) and PS-b-PPO-b-PS were successfully transformed into tri- and multiblock copolymers by ATRC, although the coupling efficiency is not as high as observed for PS oligomers under similar conditions.

Atom transfer radical polymerization of styrene initiated by the novel initiator 2-bromo-2-nitropropane

AbstractHeterogeneous atom transfer radical polymerization (ATRP) of styrene initiated by 2-bromo-2-nitropropane in bulk was carried out with CuCl/2,2′-bipyridine as the catalyst. The kinetics was first order in monomer and the numberaverage molecular weight of the polymer increased linearly with monomer conversion, indicating the ‘living’/controlled nature of the polymerization. However, the number-average molecular weight was usually higher than the theoretical one. The nitro group might react with the Cu complex, resulting in insufficient initiation. The amount of catalyst has no effect on the controllability of this catalyst system for the ATRP of styrene. The presence of a halide end group in the obtained polymer was confirmed by both 1H NMR and chain-extension reaction.

Synthesis and characterization of mid‐ and end‐chain functional telechelics by controlled polymerization methods and coupling processes

AbstractWell‐defined polystyrene‐ (PSt) or poly(ε‐caprolactone) (PCL)‐based polymers containing mid‐ or end‐chain 2,5 or 3,5‐ dibromobenzene moieties were prepared by controlled polymerization methods, such as atom transfer radical polymerization (ATRP) or ring opening polymerization (ROP). 1,4‐Dibromo‐2‐(bromomethyl)benzene, 1,3‐dibromo‐5‐(bromomethyl)benzene, and 1,4‐dibromo‐2,5‐di(bromomethyl)benzene were used as initiators in ATRP of styrene (St) in conjunction with CuBr/2,2′‐bipyridine as catalyst. 2,5‐Dibromo‐1,4‐(dihydroxymethyl)benzene initiated the ROP of ε‐caprolactone (CL) in the presence of stannous octoate (Sn(Oct)2) catalyst. The reaction of these polymers with amino‐ or aldehyde‐functionalized monoboronic acids, in Suzuki‐type couplings, afforded the corresponding telechelics. Further functionalization with oxidable groups such as 2‐pyrrolyl or 1‐naphthyl was attained by condensation reactions of the amino or aldehyde groups with low molecular weight aldehydes or amines, respectively, with the formation of azomethine linkages. Preliminary attempts for the synthesis of fully conjugated poly(Schiff base) with polymeric segments as substituents, by oxidative polymerization of the macromonomers, are presented. All the starting, intermediate, or final polymers were structurally analyzed by spectral methods (1H NMR, 13C NMR, and IR). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 727–743, 2006

Synthesis and characterizations of well‐defined branched polymers with AB2 branches by combination of RAFT polymerization and ROP as well as ATRP

AbstractA well‐defined branched copolymer with PLLA‐b‐PS2 branches was prepared by combination of reversible addition‐fragmentation transfer (RAFT) polymerization, ring‐opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA‐co‐HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA‐co‐HEA)‐g‐PLLAOH with divergent agent, the macro initiator, poly(MA‐co‐HEA)‐g‐PLLABr2 was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS2). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their 1H NMR and GPC measurements. DSC results show one T = 3 °C for the poly(MA‐co‐HEA), T = −5 °C, T= 122 °C, and T = 157 °C for the branched copolymers (poly(MA‐co‐HEA)‐g‐PLLA), and T = 51 °C, T = 116 °C, and T = 162 °C for poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS2). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 549–560, 2006

Synthesis of heteroarm star-shaped (polystyrene) n–[poly(ethyl acrylate)] m via atom transfer radical polymerization

Heteroarm star-shaped polymer, (polystyrene) n –[poly(ethyl acrylate)] m [(PS) n –(PEA) m ], was synthesized in three steps. In the first step, star-shaped polystyrene, (PS) n , was synthesized by the arm-first method via atom transfer radical polymerization (ATRP) using a preformed PS macroinitiator, which was obtained by ATRP of styrene with ethyl 2-bromoisobutyrate as the initiator, in the presence of divinyl benzene (DVB). In the microgel core of (PS) n , there were not only a number of active initiating sites for ATRP, but also some unreacted vinyl groups. Then, in the second step, the residual vinyl groups were converted to 1-bromoethylbenzene groups by hydrobromination. In the last step, heteroarm star-shaped polymer, (PS) n –(PEA) m , where the arm number of PEA was greater than that of PS, was prepared by ATRP of ethyl acrylate using the hydrobrominated (PS) n as the macroinitiator from 1-bromoethylbenzene initiating sites, obtained by both the addition of linear PS macroinitiators to vinyl groups of DVB and the hydrobromination of residual vinyl groups.

Atom transfer radical polymerization of styrene using the novel initiator ethyl 2‐N,N‐(diethylamino)dithiocarbamoyl‐butyrate

AbstractThe atom transfer radical polymerizations (ATRPs) of styrene initiated by a novel initiator, ethyl 2‐N,N‐(diethylamino)dithiocarbamoyl‐butyrate (EDDCB), in both bulk and solution were successfully carried out in the presence of copper(I) bromide (CuBr) and N,N,N′,N″,N″‐pentamethyldiethylenetriamine at 115 °C. The polymerization rate was first‐order with respect to the monomer concentration, and the molecular weights of the obtained polymers increased linearly with the monomer conversions with very narrow molecular weight distributions (as low as 1.17) up to higher conversions in both bulk and solution. The polymerization rate was influenced by various solvents in different degrees in the order of cyclohexanone > dimethylformamide > toluene. The molecular weight distributions of the produced polymers in cyclohexanone were higher than those in dimethylformamide and toluene. The results of 1H NMR analysis and chain extension confirmed that well‐defined polystyrene bearing a photo‐labile N,N‐(diethylamino)dithiocarbamoyl group was obtained via ATRP of styrene with EDDCB as an initiator. The polymerization mechanism for this novel initiation system is a common ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 32–41, 2006

Synthesis of block copolymers with thermodynamically compatible chain segments: di‐ and triblock copolymers of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

AbstractMono‐ and bifunctional poly(phenylene oxide) (PPO) macroinitiators for atom transfer radical polymerization (ATRP) were prepared by esterification of mono‐ and bishydroxy telechelic PPO with 2‐bromoisobutyryl bromide. The macroinitiators were used for ATRP of styrene to give block copolymers with PPO and polystyrene (PS) segments, namely PPO‐block‐PS and PS‐block‐PPO‐block‐PS. Various ligands were studied in combination with CuBr as ATRP catalysts. Kinetic investigations revealed controlled polymerization processes for certain ligands and temperature ranges. Thermal analysis of the block copolymers by means of DSC revealed only one glass transition temperature as a result of the compatibility of the PS and PPO chain segments and the formation of a single phase; this glass transition temperature can be adjusted over a wide temperature range (ca 100–199 °C), depending on the composition of the block copolymer. Copyright © 2005 Society of Chemical Industry

Synthesis and characterization of diblock copolymer by enzymatic ring-opening polymerization and ATRP from a novel bifunctional initiator

A new method is reported for synthesizing AB-type diblock copolymer polycaprolactone-block-polystyrene (PCL-b-PSt) from a novel bifunctional initiator 2.2.2-trichloroethanol (TCE) by combining two different polymerization techniques: enzymatic ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Trichloromethyl terminated PCL was prepared by enzymatic ROP of e-caprolactone (e-CL) in the presence of Novozyme-435 and TCE as biocatalyst and initiator, respectively, and subsequently employed in ATRP of styrene (St) using CuCl/2, 2′-bipyridine (bpy) as the catalyst system. The GPC and NMR analysis indicated the formation of the diblock copolymer including the biodegradable PCL block and the well-defined PSt block.

Synthesis and characterization of poly(n‐butyl methacrylate)‐b‐polystyrene diblock copolymers by atom transfer radical emulsion polymerization

AbstractPoly(n‐butyl methacrylate) (PBMA)‐b‐polystyrene (PSt) diblock copolymers were synthesized by emulsion atom transfer radical polymerization (ATRP). PBMA macroinitiators that contained alkyl bromide end groups were obtained by the emulsion ATRP of n‐butyl methacrylate with BrCH3CHCOOC2H5 as the initiator; these were used to initiate the ATRP of styrene (St). The latter procedure was carried out at 85°C with CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as the catalyst and polyoxyethylene(23) lauryl ether as the surfactant. With this technique, PBMA‐b‐PSt diblock copolymers were synthesized. The polymerization was nearly controlled; the ATRP of St from the macroinitiators showed linear increases in number‐average molecular weight with conversion. The block copolymers were characterized with IR spectroscopy, 1H‐NMR, and differential scanning calorimetry. The effects of the molecular weight of the macroinitiators, macroinitiator concentration, catalyst concentration, surfactant concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are also reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2123–2129, 2005

Controlled synthesis of poly(ε-caprolactone)- graft-polystyrene by atom transfer radical polymerization with poly(ε-caprolactone- co-α-bromo-ε-caprolactone) copolymer as macroinitiator

A substituted ε-caprolactone, α-bromo-ε-caprolactone, was synthesized from α-bromocyclohexanone by Baeyer–Villiger reaction using 3-chloroperoxybenzoic acid. The ring-opening copolymerization of this monomer with ε-caprolactone was carried out with aluminum isopropoxide as the initiator, giving poly(ε-caprolactone- co-α-bromo-ε-caprolactone) copolymer. This copolymer was used as the macroinitiator for the controlled atom transfer radical polymerization (ATRP) of styrene for the synthesis of poly(ε-caprolactone)- g-polystyrene graft copolymers. The results showed that all the initiating sites along the macroinitiator chain initiated ATRP of styrene, and that the molecular weights of the graft copolymers increased with styrene conversion and agreed well with the theoretical values.

Synthesis of Star‐Shaped Poly(ϵ‐caprolactone)‐b‐Poly(styrene) Block Copolymer by Combining Ring‐Opening Polymerization and Atom Transfer Radical Polymerization

Newly designed star‐shaped block copolymers made of poly(ϵ‐caprolactone) (PCL) and polystyrene (PS) were synthesized by combining ring‐opening polymerization (ROP) of ϵ‐caprolactone (CL) and atom transfer radical polymerization (ATRP) of styrene (St). The switch from the first to the second mechanism was obtained by selective transformation of “living” radical sites. First, tri‐ and tetrafunctional initiators were used as an initiator for the “living” ring opening polymerization (ROP) of ϵ‐caprolactone producing a hydroxyl terminated three or four arm star‐shaped polymer. Next, the OH end groups of PCL star branches were derivatized into 2‐bromoisobutyrate groups which gave rise to the corresponding tri‐ and tetrabromoester ended‐PCL stars; the latter served as macroinitiators for the ATRP of styrene at 110°C in the presence of CuBr/2,2‐bipyridine (Bipy) catalyst system affording star‐shaped block copolymers PCLn‐b‐PSn (n=3 or 4). The samples obtained were characterizated by 1H‐NMR spectroscopy and GPC (gel permeation chromatograph). These copolymers exhibited the expected structure. The crystallization of star‐shaped block copolymers was studied by DSC (differential scanning calorimetry). The results show that when the content of the PS block increased, the Tm of the star‐shaped block copolymer decreased.

Synthesis and Characterization of a Novel Perfluorocyclobutyl Aromatic Ether-Based ABA Triblock Copolymer

A novel perfluorocyclobutyl aromatic ether-based ABA triblock copolymer (A: polystyrene block; B: perfluorocyclobutyl aromatic ether-based fluoropolymer block) was synthesized by combination of atom transfer radical polymerization (ATRP) of styrene and thermal step-growth cycloaddition polymerization of trifluorovinyl monomer. We first synthesized a new ATRP initiator containing the trifluorovinyl group, which can initiate ATRP of styrene in a controlled way to obtain well-defined polystyrene with narrow molecular weight distribution (Mw/Mn < 1.10). The apparent polymerization rate exhibited first-order relation with respect to the concentration of monomer and the molecular weight increases linearly with the conversion of monomer. Second, fluoropolymer containing a perfluorocyclobutyl aromatic ether unit was prepared by solution polymerization and followed by reacting with ATRP initiator containing a trifluorovinyl group to get ATRP macroinitiator with two initiation groups at both ends. The macroinitiator-initiated ATRP of styrene to obtain ABA triblock copolymer. The copolymer shows excellent solubility in conventional solvents.

Star polymers by ATRP of styrene and acrylates employing multifunctional initiators

AbstractMultifunctional initiators for atom transfer radical polymerization (ATRP) are prepared by converting ditrimethylolpropane with four hydroxyl groups, dipentaerythritol with six hydroxyl groups, and poly(3‐ethyl‐3‐hydroxymethyl‐oxetane) with ∼11 hydroxyl groups to the corresponding 2‐bromoisobutyrates or 2‐bromopropionates as obtained by reaction with acid bromides. Star polystyrene (PS) is produced by using these macroinitiators and neat styrene in a controlled manner by ATRP at 110 °C, employing the catalytic system CuBr and bipyridine. Mn up to 51,000 associated with narrow molecular weight distributions (PDI &lt; 1.1) are obtained with conversions up to 32%. Hydrolysis of the star‐PS leads to linear chains having the expected Mn values. The star‐PS polymers based on dipentaerythritol degrade thermally in nitrogen in a two‐step process in which the first low‐temperature step involves scission of the ester linkages and the second step corresponds to the normal PS degradation. Star poly(methyl acrylates) with various cores are likewise prepared in a controlled manner by ATRP of methyl acrylate in bulk and in solution at 60–80 °C with the 1,1,4,7,7‐pentamethyldiethylene triamine ligand. Under these conditions, higher conversions were possible still maintaining low PDI signaling controlled star growth. Multiarm stars of poly(n‐butyl acrylate) and poly(n‐hexyl acrylate) with controlled characteristics have also been prepared. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3748–3759, 2005

Synthesis of poly(ethylene oxide)- block-poly(methyl methacrylate)- block-polystyrene triblock copolymers by two-step atom transfer radical polymerization

The synthesis of ABC triblock copolymer poly(ethylene oxide)- block-poly(methyl methacrylate)- block-polystyrene (PEO- b-PMMA- b-PS) via atom transfer radical polymerization (ATRP) is reported. First, a PEO–Br macroinitiator was synthesized by esterification of PEO with 2-bromoisobutyryl bromide, which was subsequently used in the preparation of halo-terminated poly(ethylene oxide)- block-poly(methyl methacrylate) (PEO- b-PMMA) diblock copolymers under ATRP conditions. Then PEO- b-PMMA- b-PS triblock copolymer was synthesized by ATRP of styrene using PEO- b-PMMA as a macroinitiator. The structures and molecular characteristics of the PEO- b-PMMA- b-PS triblock copolymers were studied by FT-IR, GPC and 1H NMR.

Synthesis and characterization of diblock and triblock copolymer by enzymatic ring-opening polymerization of ε-caprolactone and ATRP of styrene

Diblock and triblock copolymer of e-caprolactone(e-CL) and styrene(St) were obtained by the combination of two different polymerization process, namely enzymatic ring-opening polymerization(ROP) and atom transfer radical polymerization(ATRP) methods. Mono-/di- hydroxyl terminated macromolecules were prepared by enzymatic ROP of e-CL in the presence of Novozyme-435 and methanol/ethylene glycol as biocatalyst and initiator, respectively, and subsequently converted to bromine ended polycaprolactone(PCL) by the esterification of the resulting macromolecules with α-bromopropionyl bromide. The mono- and difunctional macroinitiators were employed in ATRP of styrene using CuCl/2, 2’-bipyridine(bpy) as the catalyst system. The GPC and 1H-NMR analysis indicated a controlled/living radical polymerization which resulted in the formation of block copolymers with narrow polydispersities.

Synthesis of Dendrimer-Like Polystyrene by Atom Transfer Radical Polymerization and Investigation of Their Viscosity Behavior

The synthesis of dendrimer-like polystyrene (PS) of second and third generations by combination of atom transfer radical polymerization (ATRP) and chain end modifications is reported. Calixarene-based cores were used as initiators for ATRP of styrene yielding star polymers containing precisely 4, 6, or 8 arms. The latter were modified in two steps so as to generate PS stars carrying 8, 12, or 16 terminal bromoisobutyrate groups, respectively. These precursors served as multifunctional macroinitiators for the formation of the second generation of dendrimer-like PS. Reiteration of the aforementioned sequence of reactions allowed to derive dendrimer-like polystyrene of third generation that were constituted of 16, 24, or 32 outer arms, respectively. The chain end modification was monitored by 1H NMR spectroscopy. The dendrimer-like PS were also characterized by size exclusion chromatography equipped with a multiangle laser light scattering detector (SEC/MALLS). The actual polymer architecture and the functio...

Nuclear magnetic resonance monitoring of chain‐end functionality in the atom transfer radical polymerization of styrene

AbstractThe evolution of the bromine end functionality during the bulk atom transfer radical polymerization (ATRP) of styrene [in the presence of the catalyst CuBr/4,4′‐di‐(5‐nonyl)‐2,2′‐bipyridine] was monitored with 600‐MHz 1H NMR. A decrease in the functionality versus the conversion was observed. The loss of functionality was especially significant at very high conversions (&gt;90%). The experimental data were compared with a kinetic model of styrene ATRP. The latter indicated that the loss of chain‐end functionality was partly due to bimolecular terminations but was mainly due to β‐H elimination reactions induced by the copper(II) deactivator. These elimination reactions, which occurred later in the reaction, did not significantly affect the polymer molecular weights and the polydispersity. Therefore, a linear evolution of the molecular weights and low‐polydispersity polymers were still observed, despite a loss of functionality. Understanding these side reactions helped in the selection of the proper conditions for reducing the contribution of the elimination process and for preparing well‐defined polystyrene (number‐average molecular weight ∼10,000 g mol−1; weight‐average molecular weight/number‐average molecular weight ∼1.1) with a high functionality (92%). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 897–910, 2005

Synthesis and characterization of PBMA-b-PSt-b-PBMA triblock copolymers by atom transfer radical emulsion polymerization

Poly(n-butyl methacrylate)-b-polystyrene-b-poly(n-butyl methacrylate) (PBMA-b-PSt-b-PBMA) triblock copolymers were successfully synthesized by emulsion atom transfer radical polymerization (ATRP). Difunctional polystyrene (PSt) macroinitiators that contained alkyl chloride end-groups were prepared by ATRP of styrene (St) with CCl4 as initiator and were used to initiate the ATRP of butyl methacrylate (BMA). The latter procedure was carried out at 85°C with CuCl/4,4-di (5-nonyl)-2,2- bipyridine (dNbpy) as catalyst and polyoxyethylene (23) lauryl ether (Brij35) as surfactant. Using this technique, triblock copolymers consisting of a PSt center block and PBMA terminal blocks were synthesized. The polymerization was nearly controlled, ATRP of St from those macroinitiators showed linear increases in the number average molecular weight (Mn) with conversion. The block copolymers were characterized with infrared (IR) spectroscopy, hydrogen-1 nuclear magnetic resonance (1HNMR), and differential scanning calorimetry (DSC). The effects of the molecular weight of macroinitiators, concentration of macroinitiator, catalyst, emulsion, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP were also reported

Effect of (Pseudo)halide Initiators and Copper Complexes with Non‐halogen Anions on the Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) relies on an activation/deactivation cycle where a lower oxidation state metal, such as Cu(I)YL, abstracts a (pseudo)halogen from an activated alkyl (pseudo)halide, RX, to generate an active radical and the higher oxidation state metal, Cu(II)XYL [L = ligand = 4,4′‐di‐(5‐nonyl)‐2,2′‐bipyridine (dNbpy)]. This investigation focused on the effect of X on the alkyl compound and Y on the copper(I) species in the ATRP of styrene and methyl acrylate. Using either symmetrical combinations of copper species and initiators, where X = Y, or unsymmetrical combinations, where X≠Y, the polymerization kinetics were monitored to determine the difference in reactivity between halogens like chlorine, bromine, or iodine and (pseudo)halogens such as the thiocyanate group (SCN). The results show that pseudo(halogens) can be used to initiate an ATRP reaction, but the polymerization is only controlled in the presence of a copper(I) halide complex. This suggests that there is an exchange between X and Y once the Cu(II)XY complex is formed to generate a CuX species and Y terminated chain end and that the carbon‐centered radical will preferentially bond to a halogen as opposed to the pseudo(halogen). This was confirmed by using Cu(I) species with non‐exchangeable anions like CuPF6, which led to poorly controlled ATRP.