Polystyrene Macroinitiator Research Articles

Photochromic Block Copolymer Poly(styrene‐b‐azo monomer) by ATRP

AbstractPhotoactive monomers [(E)‐1(4‐methacryloxyphenyl)‐2‐(nitrophenyl) diazene] (azo 1) and (E)‐1‐(4‐methacryloxyethyl‐phenyl)‐2‐phenyl‐diazene (azo2) were synthesized. The azo 1 monomer showed poor reactivity under the evaluated polymerization method. The Azo 2 monomer was used in the block copolymerization with polystyrene by the normal ATRP methodology. Several polystyrene macroinitiators were prepared with molecular weights of 10, 20 and 30 k g/mol. The end functionality was increased by the addition of 0.1 equivalents of copper II chloride. Block copolymers in 30% yield and low polydispersity were synthesized by ATRP from the polystyrene macroinitiators and the azo monomer. The block copolymer exhibits good photochromic activity.

Silicon‐Based and Fluorinated Polymeric Surfactants for Nitroxide Mediated Dispersion Polymerization in Supercritical Carbon Dioxide

AbstractBlock copolymers based on siloxanes and fluorinated block copolymers were synthesized and tested as surfactants for nitroxide mediated polymerizations (NMP) in supercritical carbon dioxide. Styrene was polymerized in the presence of TEMPO at 130 °C using various surfactants. Siloxane‐based surfactants were synthesized by a new route based on NMP; the perfluorinated surfactants were also synthesized by NMP. The dispersion polymerizations of styrene in scCO2 reveal conversions of up to 35% in 4 hours at 19.1 MPa. The resulting polydispersity indices lie in the range 1.2–1.4. The best results are obtained using a perfluorinated surfactant. Preliminary copolymerization experiments of the polystyrene macroinitiator in scCO2 have shown successful chain‐extension with butyl acrylate (BuA) resulting in the formation of a poly (St‐b‐BuA) block copolymer.

Tailored surface properties of semi-fluorinated block copolymers by electrospinning

Diblock copolymers based on polystyrene (PS) macroinitiators and four different fluorinated monomers (perfluorooctyl ethyl methacrylate (FMA), pentafluorostyrene (FS), perfluorooctyl-ethylene oxymethyl styrene (EMS), 2,3,5,6-tetrafluoro-4-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecaoxy)styrene (FSF)) were synthesized via atom transfer radical polymerization (ATRP). The lengths of the PS and fluorinated blocks were altered and the surface and self-assembling properties of the polymers were compared with respect to the fluorinated monomer used and the fluorine content. The surface properties, contact angles and surface tension, were enhanced by the existence of the CF3 groups at the end of the alkyl chains compared with poly(pentafluorostyrene). Hydrophobicity of the surfaces was further enhanced by electrospinning the polymer solutions, which yielded superhydrophobic surfaces with water contact angles >150° for polymers having CF3 groups.

Preparation and kinetic analysis of PS‐b‐PBA block copolymer by 4‐oxo‐TEMPO capped polystyrene macroinitiators

AbstractPolystyrene‐block‐poly(n‐butyl acrylate) block copolymers were prepared from 4‐oxo‐2,2,6,6‐tetramethylpiperidinooxy (4‐oxo‐TEMPO) capped polystyrene macroinitiators at a high temperature, 165°C. It was found that the number‐average molecular weight of PBA chains in block copolymers could reach above 10,000 rapidly at early stage of polymerization with a narrow polydispersity index of 1.2–1.4, but after that, the polymerization seemed to be retarded. Furthermore, according to the kinetic analysis, the concentration of 4‐oxo‐TEMPO was increased mainly by the hydrogen transfer reaction of hydroxylamine (4‐oxo‐TEMPOH) to growing radicals during polymerization. This increase in 4‐oxo‐TEMPO concentration could retard the growth of polymer chains. The rate constant of the hydrogen transfer reaction of 4‐oxo‐TEMPOH to growing radicals, kH, estimated by the kinetic model is about 9.33 × 104M‐1s−1 at 165°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis of Well-Defined Miktoarm Star Copolymers of Aromatic Polyether and Polystyrene by Chain-Growth Condensation Polymerization and Atom Transfer Radical Polymerization

Well-defined AB2 and A2B type miktoarm star copolymers consisting of aromatic polyether arms as the A segment and polystyrene arms as the B segment were synthesized from trifunctional initiators. Atom transfer radical polymerization (ATRP) of styrene was carried out in the presence of 3,5-bis(1-bromoethyl)-4′-fluorobenzophenone as a trifunctional initiator, and then the terminal C−Br bond of the polymer was reduced with Bu3SnH. The obtained polystyrene macroinitiators were used for aromatic polyether segment construction via chain-growth condensation polymerization (CGCP). The GPC trace showed a clear shift toward the higher-molecular-weight region with retention of low polydispersity, and no peak was detected in the lower-molecular-weight region. Accordingly, the target AB2 type miktoarm star copolymers were synthesized without step-growth polycondensation. The synthesis of A2B type miktoarm star copolymers was carried out similarly using 1-bromomethyl-3,5-bis(4-fluorobenzoyl)benzene as a trifunctional i...

Influence of DMF on the polymerization of tert‐butyl acrylate initiated by 4‐oxo‐TEMPO‐capped polystyrene macroinitiator

AbstractBACKGROUND: In a number of studies it has been shown that 2,2,6,6‐tetramethylpiperidinooxy (TEMPO)‐mediated polymerization of acrylates is not facile. Therefore, the object of the study reported here was to prepare poly[styrene‐block‐(tert‐butyl acrylate)] (PS‐b‐PtBA) block copolymers using 4‐oxo‐TEMPO‐capped polystyrene macroinitiator as an initiator, in the presence of small amounts of N,N‐dimethylformamide (DMF). The kinetic analysis and the effect of DMF on the reaction mechanism are also discussed.RESULTS: PS‐b‐PtBA block copolymer was prepared through polymerization of tert‐butyl acrylate (tBA) initiated by 4‐oxo‐TEMPO‐capped polystyrene macroinitiator at 135 °C. The polymerization rate of tBA could be increased by adding a small amount of DMF, and the number average molecular weight of the PtBA block in PS‐b‐PtBA reached 10 000 g mol−1 with narrow polydispersity. The activation rate constant kact−tBA of alkoxyamine increased and the recombination rate constant krec−tBA decreased with increasing DMF concentration.CONCLUSION: DMF was shown to be a rate‐enhancing additive for the polymerization of tBA using a 4‐oxo‐TEMPO‐capped polystyrene macroinitiator. From the kinetic analysis, it was concluded that the improvement of polymerization with the addition of DMF was due to an increase in kact−tBA and a decrease in krec−tBA. Copyright © 2008 Society of Chemical Industry

Compartmentalization in TEMPO-Mediated Styrene Miniemulsion Polymerization

TEMPO-mediated styrene miniemulsion polymerizations were conducted at varying particle sizes (∼50, 90, and 180 nm) to study possible effects of compartmentalization. Polymerizations were initiated using a TEMPO-terminated polystyrene macroinitiator that also acted as costabilizer for the miniemulsion. A bulk polymerization was conducted as a control. Conversion, molecular weight distribution, and the chain livingness were measured to assess the effects of particle size. Decreasing particle size resulted in lower rates of polymerization; after 6 h of polymerization, conversions were 59% for ∼180 nm particles and 43% for ∼50 nm particles. More importantly, large differences in the polymer chain livingness were observed, with smaller particles exhibiting superior livingness at equivalent conversions. Minor effects were also observed on molecular weight; decreasing particle size resulted in higher Mn at a specified conversion, signifying lower chain concentrations in smaller particles.

Successful Chain Extension of Polyacrylate and Polystyrene Macroinitiators with Methacrylates in an ARGET and ICAR ATRP

Well-defined block copolymers poly(n-butyl acrylate)-b-poly(methyl methacrylate-co-styrene) and polystyrene-b-poly(methyl methacrylate-co-styrene) were synthesized using activators regenerated by electron transfer (ARGET) and initiators for continuous activator regeneration (ICAR) for atom transfer radical polymerization (ATRP). In order to overcome the poor initiation efficiency of polystyrene and poly(n-butyl acrylate) macroinitiators during chain extension with methacrylates, a small amount of styrene was used as a comonomer in the second block. To determine the percentage of styrene necessary for efficient chain extension, studies with low molecular weight alkyl halide initiators that model the poly(n-butyl acrylate) and polystyrene macroinitiators, respectively, were performed. Extension from the macroinitiators was then conducted using the appropriate methyl methacrylate/styrene comonomer mixture to obtain well-defined block copolymers, for example, starting from poly(n-butyl acrylate) macroinitiato...

Synthesis of amphiphilic copolymers by ATRP initiated with a bifunctional initiator containing trichloromethyl groups

Bifunctional polystyrene macroinitiators, having various molecular weights, were prepared by atom transfer radical polymerization (ATRP), initiated with bifunctional initiator 1,3-bis{1-methyl-1[(2,2,2-trichloroethoxy) carbonylamino]ethyl}benzene in conjunction with CuCl catalyst and polyamine ligands. These macroinitiators were subsequently used for ATRP of tert-butyl acrylate ( t-BuA), giving BAB triblocks poly[( t-BuA)- b-(Sty)- b-( t-BuA)] as precursors of amphiphilic copolymers. Both the polymerization steps proceeded as controlled processes with linear semi-logarithmic conversion plots and lengths of the blocks following theoretical predictions. Hydrolysis of outer poly( t-BuA) blocks led to triblock copolymers with the central polystyrene block and outer blocks of poly(acrylic acid), the molecular weights of which ranged from ca. 5 × 10 3 to almost 1 × 10 5 Da.

Synthesis of Well-Defined Polystyrene-b-Aromatic Polyether Using an Orthogonal Initiator for Atom Transfer Radical Polymerization and Chain-Growth Condensation Polymerization

Well-defined diblock copolymers of polystyrene and aromatic polyether were synthesized by the combination of atom transfer radical polymerization (ATRP) and chain-growth condensation polymerization (CGCP) from an orthogonal initiator. A polystyrene macroinitiator was first synthesized by the ATRP of styrene in the presence of 4-fluorobenzenesulfonyl chloride (FBS−Cl) as an orthogonal initiator, then the terminal chlorine of the polystyrene was dehalogenated with Et3SiH/Pd(OAc)2. The CGCP of potassium 5-cyano-4-fluoro-2-propylphenolate (1) was then carried out with the polystyrene macroinitiator in sulfolane at 150 °C. However, not only polystyrene-b-aromatic polyether but also macrocycles of 1 were obtained, due to transetherification of the p-sulfonylphenyl ether linkage of the macroinitiator with 1. In contrast, the CGCP of 1 from another polystyrene macroinitiator bearing a keto group, which was prepared similarly by the ATRP of styrene with 4-(1-bromoethyl)-4‘-fluorobenzophenone (FBP−Br) as an orthogo...

Synthesis of controlled rod–coil block copolymers by a macroinitiator method: Chain‐growth polycondensation for an aromatic polyamide from a polystyrene macroinitiator

Synthesis of controlled rod–coil block copolymers by a macroinitiator method: Chain‐growth polycondensation for an aromatic polyamide from a polystyrene macroinitiator

Atom transfer radical polymerization of styrene initiated by bromoacetylated syndiotactic polystyrene macroinitiator

AbstractAtom transfer radical polymerization of styrene was conducted with bromoacetylated syndiotactic polystyrene as macroinitiator and copper bromide combined with N,N,N′,N′,N′‐pentamethyldiethylenetriamine as catalyst. A two‐stage process has been developed to synthesize the macroinitiator. First, syndiotactic polystyrene (sPS) was functionalized in the side phenyl rings with acetyl groups using the Friedel–Crafts reaction; second, the acetyl groups were converted to bromoacetyl groups by an acid‐catalyzed halogenation reaction. The initiator was found to be active in the polymerization of styrene, leading to the production of graft chains with well‐defined structure. The molecular weight and molecular weight distribution of the graft chains were determined using gel permeation chromatography after cleaving from the sPS backbone using peroxide acid oxidation followed by hydrazine‐catalyzed hydrolysis. The results indicated that the polymerization process was characteristic of a ‘living’ nature. Copyright © 2007 Society of Chemical Industry

Graft copolymers and high‐molecular‐weight star‐like polymers by atom transfer radical polymerization

AbstractGrafting of tert‐butyl acrylate (tBuA), methyl methacrylate (MMA), and styrene (St) monomers (M) by Cu(I)‐mediated ATRP from polystyrene (PSt) macroinitiator (Mn = 5620, polydispersity index, PDI = 1.12), containing initiating 2‐bromopropionyloxy groups (I) (bound to 34% of aromatic cores; 11 groups per backbone), was performed using conditions suitable for the respective homopolymerizations. The preparation of PSt‐g‐PtBuA in bulk using an initial molar ratio [M]0/[I]0 = 140 had a controlled character up to Mn = (132–148) × 103 (PDI = 1.08–1.16). With MMA and St and using the same [M]0/[I]0, preliminary experiments were made; the higher the monomer conversion, the broader was the distribution of molecular weight of the products. Graft copolymerizations of all these monomers at [M]0/[I]0 = 840 or 1680 were successfully conducted up to high conversions. Low‐polydispersity copolymers, with very long side chains, in fact star‐like copolymers, were obtained mainly by tuning the deactivator amount in the reaction mixture. (PSt‐g‐PtBuA, DPn,sc (DP of side chain) = 665, PDI = 1.24; PSt‐g‐PMMA, DPn,sc = 670, PDI = 1.43; PSt‐g‐PSt, DPn,sc = 324, PDI = 1.11). Total suppression of intermolecular coupling was achieved here. However, the low concentrations of initiator required long reaction times, leading sometimes to formation of a small amount (∼5%) of low‐molecular‐weight polymer fraction. This concomitant process is discussed, and some measures for its prevention are proposed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3662–3672, 2006

Azeotropic Atom Transfer Radical Polymerization of Hydroxyethyl Methacrylate and (Dimethylamino)ethyl Methacrylate Statistical Copolymers and Block Copolymers with Polystyrene

Statistical copolymers of hydroxyethyl methacrylate (HEMA) and (dimethylamino)ethyl methacrylate (DMAEMA) were synthesized by atom transfer radical polymerization (ATRP) at the azeotrope in N,N-dimethylformamide (DMF) with controlled molecular weights and molecular weight distributions (generally <1.2). Since the polymerization takes place at the azeotrope, the polymer composition is fixed at the monomer feed composition (HEMA molar composition = 0.718), and there is little compositional drift with total monomer conversion. Poly(HEMA-co-DMAEMA) copolymers were also successfully synthesized from a polystyrene macroinitiator previously made by ATRP. Solution-cast thin films of polystyrene-b-poly(HEMA-co-DMAEMA) amphiphilic diblock copolymers exhibit ordered and periodic nanoscale structures with morphologies that depend on the relative volume fractions and casting solvent used.

Nonspherical Assemblies Generated from Polystyrene-b-poly(l-lysine) Polyelectrolyte Block Copolymers

This report describes the aqueous solution self-assembly of a series of polystyrene(m)-b-poly(L-lysine)n block copolymers (m = 8-10; n = 10-70). The polymers are prepared by ring-opening polymerization of epsilon-benzyloxycarbonyl-L-lysine N-carboxyanhydride using amine terminated polystyrene macroinitiators, followed by removal of the benzyloxycarbonyl side chain protecting groups. The critical micelle concentration of the block copolymers determined using the pyrene probe technique shows a parabolic dependence on peptide block length exhibiting a maximum at n = approximately 20 (m = 8) or n = approximately 60 (m = 10). The shape and size of the aggregates has been studied by dynamic and static light scattering, small-angle neutron scattering (SANS), and analytical ultracentrifugation (AUC). Surprisingly, Holtzer and Kratky analysis of the static light scattering results indicates the presence of nonspherical, presumably cylindrical objects independent of the poly(L-lysine)n block length. This is supported by SANS data, which can be fitted well by assuming cylindrical scattering objects. AUC analysis allows the molecular weight of the aggregates to be estimated as several million g/mol, corresponding to aggregation numbers of several 10s to 100s. These aggregation numbers agree with those that can be estimated from the length and diameter of the cylinders obtained from the scattering results.

Preparation of functional poly(acrylates and methacrylates) and block copolymers formation based on polystyrene macroinitiator by ATRP

The polymerization by ATRP of hydroxy and amino functional acrylates and methacrylates with tert-butyldimethylsilyl (TBDMS) or tert-butyloxycarbonyl (BOC) protective groups has been studied for the first time achieving high control over molecular weight and polydispersity. Detailed investigation of the ATRP of 2-{[ tert-butyl(dimethyl)silyl]oxy}ethyl acrylate ( M2b) in bulk and 2-[( tert-butoxycarbonyl)amino]ethyl 2-methylacrylate ( M3a) in diphenyl ether (DPE) showed that the type of ligand plays an important role on either the polymerization rate or the degree of control of the polymerization. Among the ligands used, N,N,N,′ N″ N″-pentamethyl diethylenetriamine (PMDETA) was the most suitable ligand for ATRP of all functional acrylates and methacrylates. The kinetics of M2b and M3a polymerization using PMDETA as a ligand was reported and proved the living character of the polymerization. Well-defined block copolymers based on a halogen terminated polystyrene ( Pst) macroinitiator and the functional acrylate and methacrylate monomers were successfully synthesized by ATRP, and subsequent deprotection of the protective groups from the acrylate or methacrylate segment afforded amphiphilic block copolymers with a specific solubility behavior.

Nitroxide‐mediated homo‐ and block copolymerization of styrene and multifunctional acryl‐ and methacryl derivatives

AbstractThe ability of different alkoxyamines (I1, I2, I3, I4, and I5) to initiate controlled radical polymerization of styrene was evaluated. Among them, 2‐hydroxymethyl‐2‐[(2‐methyl‐1‐phenyl‐propyl)‐(1‐phenyl‐ethoxy)‐amino]‐propane‐1,3‐diol (I5) gave the highest polymerization rate of styrene, and the best control over the molecular weight and the molecular weight distribution of polystyrene. Kinetic studies confirmed that with initiator I5 the polymerization of styrene proceeded in a controlled way. The controlled radical homopolymerization of multifunctional acryl‐ and methacryl derivatives using initiator I5 could not be realized as demonstrated by the high polydispersities (PD) obtained. However, it was possible to polymerize multifunctional acryl‐ and methacryl derivatives using a polystyrene macroinitiator (Pst) and, thus, novel amphiphilic block copolymers with a narrow molecular weight distribution were obtained. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1873–1882, 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

Stable Free‐Radical Copolymerization of Styrene with Acrylates Using OH‐TEMPO

AbstractSummary: Stable free‐radical copolymerizations (SFRP) of styrene with N‐acryloyl morpholine (AMo), 2‐ethoxyethyl acrylate (EOEA) and isobornyl acrylate (iBoA), respectively, were carried out under control of the stable nitroxide radical 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl (OH‐TEMPO). The polymerizations were initiated by a polystyrene macroinitiator (PS‐MI). No accelerating agents were used. In contrast to the experiences made with methacrylates there was no decrease in the polymerization rates up to 50 mol‐% of AMo or EOEA in the monomer mixture. This behavior was ascribed to a compensation of the lack of thermal initiation by the high propagation rate constants of the acrylates. The produced AB diblock polymers were successfully employed in block extension reactions in styrene yielding ABA triblock polymers. Copolymerization reactivity ratios (r‐values) and glass transition temperatures have been estimated.Monomer structures.magnified imageMonomer structures.

Synthesis of miktoarm star and miktoarm star block copolymers via a combination of atom transfer radical polymerization and stable free‐radical polymerization

AbstractA trifunctional initiator, 2‐phenyl‐2‐[(2,2,6,6‐tetramethyl)‐1‐piperidinyloxy] ethyl 2,2‐bis[methyl(2‐bromopropionato)] propionate, was synthesized and used for the synthesis of miktoarm star AB2 and miktoarm star block AB2C2 copolymers via a combination of stable free‐radical polymerization (SFRP) and atom transfer radical polymerization (ATRP) in a two‐step or three‐step reaction sequence, respectively. In the first step, a polystyrene (PSt) macroinitiator with dual ω‐bromo functionality was obtained by SFRP of styrene (St) in bulk at 125 °C. Next, this PSt precursor was used as a macroinitiator for ATRP of tert‐butyl acrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80 °C, affording miktoarm star (PSt)(PtBA)2 [where PtBA is poly(tert‐butyl acrylate)]. In the third step, the obtained St(tBA)2 macroinitiator with two terminal bromine groups was further polymerized with methyl methacrylate by ATRP, and this resulted in (PSt)(PtBA)2(PMMA)2‐type miktoarm star block copolymer [where PMMA is poly(methyl methacrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight &lt; 1.38). All polymers were characterized by gel permeation chromatography and 1H NMR. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2542–2548, 2003