Synthesis of densely branched poly(methyl methacrylate)s via ATR copolymerization of methyl methacrylate and ethylene glycol dimethacrylate

Densely branched poly(methyl methacrylate)s have been synthesized by copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) using atom transfer free radical polymerization (ATRP). By employing the phenyl and benzyl esters of 2-bromo-2-methylpropionic acid as the initiators with 2,2-bipyridyl and Cu(I)Cl it has been possible to use high field ¹H nuclear magnetic resonance spectroscopy to evaluate in some detail the composition and structure of the branched PMMAs obtained. Parallel molar mass size exclusion chromatographic analysis using a multi-angle light scattering detector with a refractive index detector (MALS/SEC) has allowed the branched architecture of the products to be confirmed. Rather remarkably, high yields of branched PMMAs can be obtained without crosslinking using MMA/EGDMA molar feed ratios of up to 5/1 by appropriate adjustment of the molar feed of initiator. In particular by maintaining the EGDMA/initiator molar feed ratio ∼1/1 fully soluble products can be obtained that are densely branched since this feed ratio ensures that on average each living primary chain initiated contains on average only one branching EGDMA segment. As might be expected this controlled free radical process offers better control in the synthesis of branched polymer than the corresponding system we have reported using conventional free radical polymerization, and unlike the latter which requires the use of a chain transfer agent, the ATRP system requires no additional chain regulating component. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2375–2386, 2007     

Mesomorphic properties of linear and branched new triphenylene-based poly(ester-ether)s

A series of main chain discotic liquid crystal polymers, synthesized following a new approach based on the incorporation of triphenylene units in both comonomers, show ordered columnar mesophases in a very wide thermal range, including room temperature. The introduction of branching points based on the same kind of triphenylene units increases their thermal range and gives rise to glassy low-temperature phases. Room temperature extrusion of these polymers yields fibers with molecules oriented perpendicular to the mechanical stress, and an orientational order parameter close to 0.5, which slightly increases for branched polymers.     

Synthesis and nonlinear optical properties of a novel indium phthalocyanine highly branched polymer

Due to the well‐known optical limiting properties of indium (III) phthalocyanines (In [III] Pcs) and aiming at extending their conjugation system, a highly branched indium phthalocyanine polymer was prepared. Flash chromatography was used for obtaining a pure polymer of polydispersity index near to the unity. The structure of the prepared polymer was determined using different spectroscopic techniques. Optical limiting and open aperture Z‐scan measurements were carried out according standard procedures. Compared with many other phthalocyanines, the prepared indium‐phthalocyanine polymer shows a high optical limiting performance that is indicated by a relatively low limiting threshold of 430 mJ cm^?2 and a large nonlinear absorption coefficient (α₂ = 3.4 × 10^?8 cmW^?1). Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,characterization, and rheological properties of multiarm stars with poly(glycidol) core and poly(methyl methacrylate) arms by AGET ATRP

Well‐defined multiarm star block copolymers poly(glycidol)‐b‐poly(methyl methacrylate) (PGOHBr‐b‐PMMA_x) with an average number of PMMA arms of 85, 55, and 45 have been prepared. The core‐first approach has been selected as the methodology using atom transfer radical polymerization (ATRP) of MMA from an activated hyperbranched poly(glycidol) as the core. These activated hyperbranched macroinitiators were prepared by esterification of hyperbranched poly(glycidol) (PGOH) with 2‐bromoisobutyryl bromide. The effect of monomer/initiator ratio, catalyst concentration, time, temperature, and solvent on the growing of the arms has been studied in detail in order to optimize the process and to diminish the radical‐radical coupling. The final products and intermediates were characterized by means of size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) and Fourier transform‐infrared (FTIR) spectroscopy. The length of PMMA arms was determined by SEC after cleavage of ester bond linked to PGOH core. Glass transition temperature (T_g), thermal stability and rheological properties of the multiarm star copolymers were also studied. Finally, tapping mode atomic force microscopy (TMAFM) allowed the clear visualization of nano‐sized particles (80–200 nm) corresponding to individual star molecules. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Star-shaped alkylated poly(glycerol methacrylate) reverse micelles: Synthesis and evaluation of their solubilizing properties in dichloromethane

Amphiphilic star-shaped polymers were synthesized by atom transfer radical polymerization (ATRP). Four-, 5-, and 6-arm ATRP initiators were prepared and used to polymerize glycidylmethacrylate. The resulting polymers were hydrolyzed to yield poly(glycerolmethacrylate)s (PG_OHMAs), and then partially esterified with lauroyl or stearoyl chloride (40–60 mol % vs. hydroxyl groups). Alkylated PG_OHMAs were found to assemble into 20–60 nm aggregates in dichloromethane (DCM) above a critical concentration. Particle size essentially depended on the branching degree of the polymer. The micelles were extremely efficient in extracting Congo red from water into DCM, with the highest incorporations (97 mg/g) obtained for the 6-arm polymer modified with stearoyl chloride (60 mol %). The entrapment efficiency for the latter was further improved in alkaline solution. The high level of incorporation achieved for these amphiphilic multiarm polymers suggests that such reverse micelles could be potentially useful as drug delivery systems and nanoreactors in catalytic organic reactions or for water purification. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2425–2435, 2007     

Synthesis of poly(methyl methacrylate) in a pyridine solution by atom transfer radical polymerization

Pyridine was used as a solvent for the atom transfer radical polymerization (ATRP) of methyl methacrylate. The homopolymerizations were carried out with methyl 2‐halopropionate (MeXPr, where X was Cl or Br) as an initiator, copper halide (CuX) as a catalyst, and 2,2′‐bipyridine as a ligand from 80 to 120 °C. The mixed halogen system methyl 2‐bromopropionate/copper chloride was also used. For all the initiator systems used, the polymerization reaction showed linear first‐order rate plots, a linear increase in the number‐average molecular weight with conversion, and relatively low polydispersities. In addition, the dependence of the polymerization rate on the temperature is presented. These data are compared with those obtained in bulk, demonstrating the effectiveness of this solvent for this monomer in ATRP. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3443–3450, 2001     

Star macromolecules with hyperbranched poly(arylene oxindole) cores and polyacid arms: Synthesis and solution behavior

The synthesis of pH‐sensitive star polymers with 100% hyperbranched cores and polyacrylic or polymethacrylic acid arms is reported. A series of stars obtained via atom transfer polymerization of tert‐butyl acrylate and methacrylate onto poly(arylene oxindole)s were subjected to acidic hydrolysis to obtain structures with polyacid arms. The obtained polyacid stars were characterized by NMR and FTIR spectroscopy. Dynamic and static light scattering experiments were performed to provide information regarding the shape of these macromolecules in solution. In an aqueous solution, the stars formed aggregates with a radius of gyration reaching 130 nm and aggregation numbers of up to 280 stars per particle. Similar to other polyacid‐based copolymers with different branched topologies, the dimensions and aggregation numbers were found to decrease with increasing pH. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of branching on the thermal properties of novel branched poly(4‐ethyleneoxy benzoate)

Poly(4‐ethyleneoxy benzoate) (PEOB) was synthesized by the self‐condensation of ethyl 4‐(2‐hydroxyethoxy) benzoate (E4HEB) under transesterification conditions. Branched PEOB was prepared by the condensation of E4HEB with an AB₂ monomer, ethyl 3,5‐bis(2‐hydroxyethoxy) benzoate (EBHEB), under similar conditions. Varying amounts of branching (0–50%) were introduced into the linear polymer by changes in the composition of the comonomers in the feed. The solution viscosity of the polymers indicated that they had reasonable molecular weights; the extent of branching in these copolymers was established from their ¹H NMR spectra. Differential scanning calorimetry studies indicated that, as expected, the introduction of branching drastically affected the percent crystallinity of the copolymers (as seen from their ΔH_m, the enthalpy of melting), and when the extent of the incorporation of the AB₂ monomer exceeded 10 mol %, the copolymers were completely amorphous. The melting temperatures of the copolymers decreased with an increase in the branching content, whereas the peak crystallization temperature in quenched (amorphous) samples followed the exactly opposite trend. The glass‐transition temperatures (T_g) of the branched copolymers first decreased at low extents of branching, passed through a minimum, and then increased to attain the T_g of the pure hyperbranched polymer of EBHEB. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 261–268, 2000     

Polyaniline/poly(methyl methacrylate) coaxial fibers: The fabrication and effects of the solution properties on the morphology of electrospun core fibers

Electrically conductive polyaniline (PANi)/poly(methyl methacrylate) (PMMA) coaxial fibers were prepared through the chemical deposition of PANi onto preformed PMMA fibers via in situ polymerization. PMMA fibers were prepared as core materials via electrospinning. Spectral studies and scanning electron microscopy observations indicated the formation of PANi/PMMA coaxial fibers with a diameter of approximately 290 nm and a PANi layer thickness of approximately 30 nm. The conductivity of the PANi/PMMA coaxial fibers was significantly higher than that of electrospun fibers of PANi/poly(ethylene oxide) blends and blend cast films of the same PANi composition. To reproducibly generate uniform‐core polymer fibers, the organic solution properties that affected the morphology and diameter of the electrospun fibers were investigated. The polymer molecular weight, solution concentration, solvent dielectric constant, and addition of soluble organic salts were strongly correlated to the morphology of the electrospun fiber mat. In particular, the dielectric constants of the solvents substantially influenced both the fiber diameter and bead formation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3934–3942, 2004     

Synthesis and solution properties of poly(methacrylate)s with semipolar structures on the side chains

Poly{2‐(N,N‐dimethylamino)ethyl methacrylate [poly(DMMA)]}, which was prepared by radical polymerization initiated with dimethyl 2,2‐azobis(2‐methylpropionate), was reacted with hydrogen peroxide, diethyl sulfate, and chloroacetic acid to yield poly[N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)amine N‐oxide] [poly(DMANO)], poly[N‐ethyl‐N,N‐dimethyl‐N‐(2‐methacryloyloxyethyl)ammonium ethyl sulfate] [poly(EDMES)], and poly[N,N‐dimethyl‐N‐(2‐methacryloyloxy)ethylammonioacetate] [poly(DMEAA)] as ion‐containing water‐soluble polymers, respectively. The solution properties of these charged polymers were compared via the reduced viscosities of these three charged polymers in aqueous solutions as a function of the concentration. Poly(EDMES) showed typical polyelectrolyte behavior, and the other two polymers [poly(DMANO) and poly(DMEAA)] exhibited antipolyelectrolyte behavior. Furthermore, the antipolyelectrolyte behavior was different for poly(DMANO) and poly(DMEAA); that is, poly(DMANO) was less dependent on small electrolytes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 129–141, 2005     

Architectural control of polystyrene physical properties using branched anionic polymerization initiated at ambient temperature

Ambient temperature-initiated anionic polymerization has generated branched polystyrenes of varying molecular weights and architectures by inclusion of a distyryl branching comonomer into a conventional sec-Butylithium-initiated polymerization of styrene. Primary chain length control within the branched polymers, and restriction of the branching points to varying segments of the primary chains, led to variations of glass transition temperature with no direct correlation to the branched polymer molecular weight but a strong relationship to the length of individual chains comprising the branched macromolecules.     

Synthesis of linear and starlike polymers from poly(propylene glycol) methacrylate using controlled radical polymerization

The copper‐catalyzed atom transfer radical polymerization (ATRP) of poly(propylene glycol) methacrylate (PPGM) in solution to produce linear and starlike polymers is reported, using methylethyl ketone as the solvent and a temperature of 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer without protecting hydroxyl end groups of monomer. The polymerizations were consistent with “living” or controlled processes, as revealed by the linear evolution of molecular weight with conversion. Increasing the [M]₀:[I]₀ ratio resulted in increasing molecular weights, whereas the polydispersity indices remained low (M_w/M_n < 1.4) even at high conversion. Decreasing the [CuBr]₀:[I]₀ ratio resulted in lower conversions, slightly larger polydispersities, and decreased molecular weights, likely resulting from a lower initiation efficiency. Polymers were characterized by ¹H and ¹³C NMR; molecular weights of polymers with low degrees of polymerization were estimated by end‐group analysis from ¹³C NMR spectra obtained using distortionless enhancement by polarization transfer and the gated decoupling techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 334–343, 2002     

Spectroscopic and photopolymerization studies of benzyl methacrylate/poly(benzyl methacrylate) two‐component system

The influence of the viscosity of a two‐component system on its molecular dynamics (on the basis of hypersonic wave velocity and attenuation coefficient) and photopolymerization kinetics was studied. The system investigated represented the solution of poly(benzyl methacrylate), PBzMA (MW = 70000) in its monomer, benzyl methacrylate (BzMA). The viscosity of the system was varied by adding various amounts of the polymer to the monomer (10–50 wt %). The molecular dynamics in the neat BzMA was studied by the proton Nuclear Magnetic Resonance (NMR) spin‐lattice relaxation time measurements and the wide‐line ¹H NMR spectroscopy in a wide range of temperature. Information on the local dynamics in liquid BzMA above its melting temperature was gained from the high‐resolution ¹H and ¹³C NMR spectra. The hypersonic wave velocity and the attenuation coefficient were investigated in the appropriate temperature range related to a viscoelastic relaxation process by the Brillouin light scattering method. The kinetic measurements have demonstrated that the photopolymerization rate rapidly increases and the monomer conversion decreases with increasing polymer‐to‐monomer ratio; this effect has been noted in the whole range of polymer concentration and reaction temperature studied. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1336–1348, 2010     

Synthesis and characterization of graft copolymers containing poly(p-phenylene) main chains and mesogen-jacketed liquid-crystalline polystyrene side chains

A series of novel comblike mesogen-jacketed liquid-crystalline graft copolymers, poly(p-phenylene)-g-poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PPP-g-PMPCS) copolymers, have been designed and successfully synthesized by a Yamamoto coupling reaction and subsequent atom transfer radical polymerization (ATRP). ¹H NMR spectroscopy, ultraviolet–visible spectra, and gel permeation chromatography (GPC) have been used to confirm the molecular structure of the macroinitiator and the copolymers. A study of the polymerization kinetics of ATRP has shown that the molecular weight of the copolymer increases linearly with the conversion of the monomer, whereas the polydispersity remains narrow (≤1.28), indicating that the ATRP of 2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene is well controlled. Thermogravimetric analysis and differential scanning calorimetry (DSC) measurements have indicated that the PPP-g-PMPCS copolymers have better thermal stabilities than the macroinitiator, and their thermal stabilities increase with increasing molecular weight. The liquid-crystalline behavior has been examined with polarized optical microscopy, DSC, one-dimensional wide-angle X-ray diffraction (1D WAXD), and two-dimensional wide-angle X-ray diffraction (2D WAXD). The results show that all the comblike copolymers exhibit obvious liquid-crystalline behaviors, even though the GPC molecular weight of the segments of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) have been determined to be far less than the critical value of linear PMPCS. Moreover, 1D WAXD measurements show that the temperature at which the comblike mesogen-jacketed liquid-crystalline copolymers can transform into a liquid-crystalline phase is low; about 20 °C in comparison with the linear ones. 2D WAXD analysis has revealed that these comblike copolymers should be assigned to a hexatic columnar nematic (Φ_HN) phase. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2543–2555, 2007     

Synthesis and properties of novel conjugated poly(silylacetylene silazane)s

A series of novel conjugated polymers, poly(silylacetylene silazane)s having different substituents, were prepared by ammonolysis of the corresponding α,ω‐dichlorosilyleneacetylene oligomers. The structures and properties of the poly(silylacetylene silazane)s were characterized by Fourier transform infrared, ¹H, ¹³C, ²⁹Si NMR, and elemental analyses, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and spectrofluorophotometry. The resulting polymers had good thermal properties and were moderately fluorescent. Their thermal stability was improved, and obvious red shift was observed when a phenyl substituent was attached on a silicon atom of polymers in the emission spectra. These polymers have the potential to be used as light‐emitting materials with good thermal stability. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2897–2903, 2004     

Synthesis and properties of poly(dipropargyl sulfoxide)

The preparation and cyclopolymerization of dipropargyl sulfoxide were studied. The polymerization of dipropargyl sulfoxide was carried out by various transition metal catalysts. WCl₆–EtAlCl₂, MoCl₅, and PdCl₂ catalyst systems were very effective. The resulting poly(dipropargyl sulfoxide) structures were characterized by NMR (¹H and ¹³C), IR, and elemental analysis to have conjugated polyene units. Poly(dipropargyl sulfoxide) prepared by PdCl₂ was mostly soluble in organic solvents such as DMF and DMSO. Thermal and oxidative properties of poly(dipropargyl sulfoxide) were also studied. The electrical conductivity of iodine-doped poly(dipropargyl sulfoxide) was 5.2 × 10^?2 Ω^?1 cm^?1. Comparisons of poly(dipropargyl sulfoxide) properties with other similar polymers from dipropargyl sulfur derivatives such as dipropargyl sulfide and dipropargyl sulfone were also carried out. © 1993 John Wiley & Sons, Inc.     

Synthesis and dilute solution properties of divinylbenzene-linked polystyrene stars with mixed arm lengths: Evidence for coupled stars

Sequential anionic polymerization of styrene and divinylbenzene (DVB) is known to lead to the formation of star-shaped polymers. This ‘arms-first’ method has been widely used and studied. It is known that this polymerization forms stars with anionically active cores. This article is concerned with the attempt to make asymmetric-star polymers utilizing these living carbanionic sites present in the core to form a second set of shorter arms growing out from the star core. The presence of remaining unreacted DVB within the core was found to cause the stars to couple to form linked double stars and other larger structures. Results from detailed dilute solution studies of the resulting polymers are reported. It was found that the results obtained from size exclusion chromatography for the double stars were flow rate dependent; only at low flow rates was a true size separation obtained. © 1997 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(methyl methacrylate)‐block‐poly(methylphenylsilane)‐ block‐poly(methyl methacrylate) by atom transfer radical polymerization

ABA block copolymers of methyl methacrylate and methylphenylsilane were synthesized with a methodology based on atom transfer radical polymerization (ATRP). The reaction of samples of α,ω‐dihalopoly(methylphenylsilane) with 2‐hydroxyethyl‐2‐methyl‐2‐bromoproprionate gave suitable macroinitiators for the ATRP of methyl methacrylate. The latter procedure was carried out at 95 °C in a xylene solution with CuBr and 2,2‐bipyridine as the initiating system. The rate of the polymerization was first‐order with respect to monomer conversion. The block copolymers were characterized with ¹H NMR and ¹³C NMR spectroscopy and size exclusion chromatography, and differential scanning calorimetry was used to obtain preliminary evidence of phase separation in the copolymer products. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 30–40, 2003     

Star polymer with crosslinked core and water‐soluble poly(N‐hydroxyethylacrylamide)‐arms: Synthesis by arm‐first method using ATRP and characterizations by SEC‐MALS and SAXS measurement in water

Core crosslinked star (CCS)‐polymers with water‐soluble arms composed of poly(N‐hydroxyethylacrylamide) (PHEAA) are described. N‐Hydroxyethylacrylamide was polymerized by the atom transfer radical polymerization consisting of ethyl 2‐chloropropionate, copper(I) chloride (CuCl), and tris[2‐(dimethylamino)ethyl]amine in an ethanol/water mixed solvent at 20 °C. The obtained PHEAA‐arms were subsequently coupled using N,N′‐methylenebisacrylamide as the crosslinking agent and sodium L ‐ascorbic acid (AscNa) as the reaction activator. A total of 17 representative coupling reactions with diverse conditions are discussed together with the characterizations of the products mainly by size exclusion chromatograph equipped with the multiangle laser light scattering detector (SEC‐MALS). Consequently, the coupling reactions provided CCS‐polymers with PHEAA‐arms (CCS‐PHEAAs) having weight averaged‐molecular weights determined by SEC‐MALS (M_w,MALS) ranging from 63.8 kg mol^?1 to 832 kg mol^?1, which corresponded to the average arm‐number (N_arm) ranging from 4.1 to 42, respectively. CCS‐PHEAA with the M_w,MALS of 250 kg mol^?1 was isolated and characterized by small angle X‐ray scattering measurements in 0.05 M NaNO₃ aq. at 25 °C, which was shown to possess a star‐shaped structure and exist as single molecules with a radius of gyration at the infinite dilution condition (<R_g²>_z,0^1/2) of 74 ± 4 Å. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Polymerization of branched thiophene monomers and optoelectronic properties of materials

Bithiophene monomers ( 5HBTh and 5HBThO ) were prepared by the Suzuki coupling reaction of 3‐thienylboronic acid with 2‐bromo‐5‐hexylthiophene and 2‐bromo‐5‐hexylthiophene‐1,1‐dioxide. The oxidation polymerization mediated by vanadium catalyst gave poly(5HBTh) and oligo(5HBThO) . 5HBThO bearing thiophene‐1,1‐dioxide had an absorption maximum at longer wavelength region than 5HBTh due to the intramolecular charge transfer interaction, while peak maxima blue shifted and their difference became small after the polymerization. Terthiophene monomers ( 5″HTTh , 3,5″DHTTh , and 4,5″DHTTh ) were subsequently prepared by the mono‐bromination of 5HBTh followed by the Suzuki coupling reaction with boronic acid derivatives. The vanadium‐catalyzed oxidation polymerization of 5″HTTh and 4,5″DHTTh afforded soluble polymers and the absorption maximum wavelengths red shifted after the polymerization in contrast to bithiophene monomers and 3,5″DHTTh . The absorption and emission spectra of poly(5″DHTTh) red shifted when compared with those of poly(4,5″DHTTh) . Thus the presence and position of n‐hexyl chain influenced the monomer polymerizability and optoelectronic properties of branched polythiophenes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3034–3044, 2009