Poly Groups Research Articles

Preparation of highly selective nanofiltration composite membranes based on a novel soluble rigidly contorted monomer

AbstractNanofiltration composite membranes with high selectivity are one of the most critical cores in water treatment, and regulating the surface charge and pore structure of active separation layers in thin film composite membranes is one of the most effective means to improve the selectivity of composite membranes. This article synthesized a novel monomer with positive charge and a rigid twisted Tröger's base structure (named TBDA‐SO3), which was manipulated to improve the microporous structure and surface charge of the composite membrane. By interfacial polymerization, TBDA‐SO3, and piperazine were co‐reacted with trimesoyl chloride to successfully prepare positively charged, highly selective, and strongly microporous polyamide composite nanofiltration membranes. The best‐performing composite nanofiltration membrane in this article has a permeability similar to that of the control group's poly(piperazine amide) (PPA) membrane (pure water flux, 7.8 L m−2 h−1 bar−1), but has excellent divalent cation selectivity (52.57), which is 4.4 times that of the control group's PPA membrane.

Synthesis of a TEMPO-Substituted Polyacrylamide Bearing a Sulfonate Sodium Pendant and Its Properties in an Organic Radical Battery.

A novel nitroxyl radical polymer poly(TEMPO-acrylamide-co-sodium styrene sulfonate) (abbreviated as poly(TAm-co-SSS)) was synthesized using 4-acrylamido-2,2,6,6- tetramethylpiperidine (AATP) copolymerized with styrene sulfonate sodium (SSS). AATP was synthesized through a substitution reaction of acryloyl chloride. Meanwhile, poly(4-acrylamido-2,2,6,6-tetramethylpiperidine-1-nitroxyl radical) (PTAm) was prepared as a control sample. Then, the structures of products were characterized by nuclear magnetic resonance spectroscopy (1H-NMR), Fourier transform infrared spectroscopy (FT-IR), high performance liquid chromatography-mass spectrometry (HPLC-MS), differential scanning calorimetry (DSC), X-Ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR), respectively. Additionally, the electrochemical impedance spectra (EIS) and the charge-discharge cycling properties were studied. The results demonstrated that the poly(TAm-co-SSS) with the side group of sodium sulfonate adjacent to TEMPO group exhibits a better charge-discharge cycling stability than that of the PTAm. Moreover, the charge specific capacity of the poly(TAm-co-SSS) is larger than that of the PTAm. Besides, the first coulombic efficiency of poly(TAm-co-SSS) is higher in comparison with that of PTAm. These superior electrochemical performances were ascribed to the synergistic effect of sulfonate ions group and nitroxyl radical structure, which benefits the improvement of charge carrier transportation of the nitroxyl radical polymers. Consequently, the nitroxyl radical poly(TAm-co-SSS) is promising for use in organic radical battery materials, based on the good electrochemical properties.

Crosslinkable Nitroxide Radical Polymer for Energy Storage Applications

Due to the amount of waste generated by lithium ion batteries (LIB) disposal, a more environmentally friendly option such as organic batteries, is desired to fulfill the need of this large market. For many years, alternatives to LIBs have been researched, including the use of conductive polymers for completely organic batteries. Redox-active polymers, such as conjugated polyaniline and organic radical poly(2,2,6,6-tetramethylpiperidinyloxy-4-ylmethacrylate) (PTMA), are being studied as electrode materials for organic batteries. As linear PTMA may dissolve in the electrolyte solution and thus degrade battery capacity, crosslinked PTMA is gaining interest as a cathode material. A balance must be struck, however, as diffusion of the electrolyte solution into the polymer may become limited at sufficiently high crosslink density. To balance these competing mechanisms, a random copolymer consisting of PTMA monomer and glycidyl methacrylate (GMA), a UV and thermally crosslinkable monomer, is synthesized (P(TMA-GMA)) and the mechanism of redox activity is studied. This new PTMA copolymer is synthesized using free radical chain-growth polymerization and is then oxidized to produce the characteristic organic radical. Linear P(TMA-GMA) is characterized using UV-VIS, NMR spectroscopy, and gel permeation chromatography. The effect of crosslinking on the thermal properties and the temperature for thermally induced crosslinking is analyzed using differential scanning calorimetry. The crosslink density is calculated for each composition using the linear P(TMA-GMA) molecular weight and solvent uptake of the crosslinked P(TMA-GMA). Determining the most favored crosslink density is necessary for balancing electrolyte diffusion with the dissolution of the polymer. The electrochemical properties of the crosslinked P(TMA-GMA) is studied using cyclic voltammetry (CV) to determine if crosslinking impacts the redox properties. Preliminary results have found that the crosslinked P(TMA-GMA) exhibits a change in the shape of the CV curve and peak heights, associated with some change in the crosslinked polymers electroactivity. In addition, the crosslink density of the P(TMA-GMA) with 5 mol% GMA is quantified and is similar to previous studies of poly(ethylene glycol). Finally, the thermal properties are represented by a glass transition temperature that did not significantly change with varying GMA content. This new P(TMA-GMA) shows promise for application in organic batteries by providing a processable yet crosslinkable alternative to PTMA.

Photoinduced oxidation reactions of the pendent macrocyclic complexes: Al(III) phthalocyanine and Ni(II) annulene mechanistic considerations

The goal of the work was to expand the understanding of the photoinduced redox reactions of the Al(III) sulfonated phthalocyanine, HOAlIIItspc, and Ni(II) tertramethyldibenzotetraazaannnulene, [NiII(tmdbTAA)], as components of polymeric structures in which poly(ethyleneimino) and poly(isobutyl-alt-maleate) are the respective backbones of poly(HOAlIIItspc) and poly([NiII(tmdbTAA)]). Saccharide and flavonoid glycosides form adducts that quench the photo-generated oxidizing radicals in the case of poly(HOAlIIItspc) with rate constants≈1×104s−1, largely independent of reductant structure. The charge-separated intermediate, CS, in the case of poly([NiII(tmdbTAA)]) shows greater reactivity with the saccharides and flavonoid glycosides, particularly with the flavonoid glycoside rutin where the rate constant is 2.7×106s−1. While phthalocyanine-centered radicals in poly(HOAlIIItspc) were reduced by dAMP (adenosine-5-monophosphate) and CT-DNA, energy transfer with these reagents competed with the formation of the CS intermediate in poly([NiII(tmdbTAA)]). A study of the intensity of the upper conversion luminescence (λem<500nm), modulated by the concentration of dAMP suggests that this is attributed to the formation of adducts of poly([NiII(tmdbTAA)]) with dAMP that affect the deactivation of the electronically excited Ni(II) tetraazaannnulene pendants before the formation of the CS intermediate.

Configuration and conformation of poly(3-carbazolylacetylene) including cis and trans radicals revealed by ESR spectroscopy

π-Conjugated cis and trans radicals of poly(N-isobutyl-3-carbazolylacetylene) were stereospecifically prepared using the [Rh(norbornadiene)Cl]2-NEt3 catalyst, and their geometric structures were determined using the electron spin resonance (ESR) method.

Brush-like poly(ethylene glycol) grafting on SiO2nanoparticles within-situpolymerization

This work presents the grafting of poly(ethylene glycol) (PEG) on the SiO2 nanoparticles by the use of the azo-groups bonded SiO2 as a radical initiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as a macromonomer, respectively. Then a kind of organic–inorganic composite particles with brush-like PEG fixed covalently on the SiO2 nanoparticles, SiO2–PEG, is synthesized. The successful synthesis of SiO2–PEG is confirmed by FT-IR, XPS, and TEM techniques. Results show that the conversion degree of PEGMA can reach nearly 30% while the PEG graft amount accounts for ca. 43% of the total weight of the composite particles. After the PEG is grafted on the SiO2 nanoparticles, the mobility of PEG chains is hindered by the proximity of oxide phase of SiO2. As a result, PEG phase is strongly disturbed. Consequently, the grafted PEG melts at a low temperature with small quantity of heat enthalpy. Copyright © 2014 John Wiley & Sons, Ltd.

ChemInform Abstract: Ti(III)‐Catalyzed Cyclizations of Ketoepoxypolyprenes: Control over the Number of Rings and Unexpected Stereoselectivities.

AbstractSeveral synthetic applications of the primary reaction products are described.

Controlled radical emulsion polymerization of polystyrene

In this paper, a new water-soluble initiator system, 2-bromopropane/CuSO4/sodium ascorbate, was used as the initiator for emulsion polymerization. Radical emulsion poly- merization of styrene was successfully carried out at 80 °C by using sodium dodecylbenzenesulfonate as the emulsifier. The 2-bromopropane/CuSO4/sodium ascorbate-initiated emulsion polymerization shows the controlled free-radical polymeriza- tion features with linear growth of molecular weight. Polysty- rene with a relatively high molecular weight and a narrow molecular weight distribution can be synthesized by this method. On the other hand, stable polystyrene latex can be obtained, and the size of the polystyrene latex increased with the increase in monomer conversion.

The preparation and characterization of carboxylic acid‐coated silica nanoparticles

AbstractThe preparation of carboxylic acid‐coated silica nanoparticles was investigated. A monolayer of carboxylic acid residues with controllable graft density was anchored to the nanoparticle by a ring‐opening reaction with succinic anhydride. Poly(methacrylic acid) [poly(MAA)] grafted nanoparticles were prepared via a polymerization–deprotection strategy. Tert‐butyl methacrylate was polymerized from the surface of silica nanoparticles in a predictable manner and with excellent control over the molecular weight distribution. Subsequent removal of the tert‐butyl group resulted in poly (MAA) grafted nanoparticles. The polymer nanoparticles were also functionalized with dyes, which may be useful in tracking the particles in biological systems. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Stereospecific Free Radical and RAFT Polymerization of Bulky Silyl Methacrylates for Tacticity and Molecular Weight Controlled Poly(methacrylic acid)

A series of silyl methacrylates [CH2═C(CH3)CO2SiR3] with varying silyl group bulkiness [R3Si: Me3Si, Et3Si, Me2tBuSi, iPr3Si, Ph2tBuSi, Ph3Si, and (Me3Si)3Si] were synthesized and radically polymerized to efficiently give soluble polymers with the exception of the highly bulky tris(trimethylsilyl)silyl methacrylate (TTMSSMA), which resulted in insoluble polymers. All the polymers can easily be converted into poly(methacrylic acid) (PMAA) via acid- or fluoride-induced deprotection of the silyl groups and further into poly(methyl methacrylate) (PMMA) via methylation with trimethylsilyldiazomethane for the analysis of molecular weight and tacticity. The tacticity was dependent on the bulkiness of the silyl substituents; the isotacticity increased with increasing bulkiness. Thus, a series of PMAAs and PMMAs with various tacticities ranging from syndiotactic-rich (rr = 74%; Me2tBuSi) to atactic (mr = 50%; iPr3Si) and highly isotactic [mm = 93%; (Me3Si)3Si] enchainment were obtained by conventional radical poly...

Enhancement of mechanical properties of poly(vinyl chloride) with polymethyl methacrylate-grafted halloysite nanotube

Halloysite nanotubes(HNTs) grafted with Polymethyl methacrylate(PMMA) were synthesized via radical poly- merization. The properties of PMMA-grafted HNTs were characterized by transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The results showed that PMMA grafted to the surfaces of HNTs successfully. Then, PVC/PMMA-grafted HNTs nanocomposites were prepared by melt compounding. The morphology, mechanical properties and thermal properties of the nanocomposites were investigated. PMMA-grafted HNTs can effectively improve the toughness, strength and modulus of PVC. The glass transition and thermal decomposition temperatures of PVC phase in PVC/PMMA-grafted HNTs nanocomposites are shifted toward slightly higher temperatures. The grafted HNTs were uniformly dispersed in PVC matrix as revealed by TEM photos. The fracture surfaces of the nanocomposites exhibited plastic deformation feature indi- cating ductile fracture behaviors. The improvement of toughness of PVC by PMMA-grafted HNTs was attributed to the improved interfacial bonding by grafting and the toughening mechanism was explained according to the cavitation mecha- nism.

Controlling Polymer Topology by Atom Transfer Radical Self-Condensing Vinyl Polymerization of p-(2-Bromoisobutyloylmethyl)styrene

A new unsymmetrical AB* inimer, p-(2-bromoisobutyloylmethyl)styrene (BiBMS), was applied to the atom transfer radical polymerization (ATRP) to prepare a family of polymers with the topologies ranging from linear to branched. The catalyst system was Cu/CuBr2 coupled with 2,2′-bipyridine (Bipy) or N,N-bis(2-pyridylmethyl)octylamine (BPMOA) as a ligand in toluene or anisole at different temperatures, which ensured a very low catalyst (CuBr) concentration throughout the polymerization by a slow reduction process. First, BiBMS was polymerized in anisole at 0 °C using Cu/CuBr2/BPMOA as a catalyst system; at this temperature, the initiating activity of the formed A* was frozen and the polymerization was a step-growth polymerization, resulting in the formation of a linear polymer (LP1) whose main chain was linked by ester bonds. Second, BiBMS was polymerized in toluene at 20 °C using Cu/CuBr2/Bipy as a catalyst system. Under this condition, initiation from the B* of BiBMS was slow, followed by a fast radical poly...

The Effect of Vinylene Carbonate Additive on Surface Film Formation on Both Electrodes in Li-Ion Batteries

The effect of vinylene carbonate (VC) as electrolyte additive on the formation mechanisms of passivation films covering both electrodes in lithium-ion batteries was investigated by X-ray photoelectron spectroscopy (XPS). /graphite coin cells using a /ethylene carbonate:diethyl carbonate:dimethyl carbonate liquid electrolyte with or without VC were charged at 20 and . The identification of VC-derived products formed at the surface of the electrodes was carried out by a dual experimental/theoretical approach. From a classical XPS core peak analysis completed by a detailed interpretation and simulation of valence spectra supported by ab initio calculations, and through direct synthesis of the VC polymer, we could evidence the formation of the radical poly(VC) at the electrode/electrolyte interfaces. We showed that the radical polymerization is the main reaction mechanism of VC contributing to the formation of the passivation layers at the surface of both electrodes.

Synthesis of Block Copolymers by Transformation of Free Radical Promoted Cationic Polymerization to Atom Transfer Radical Polymerization

The transformations of free radical promoted cationic polymerization to atom transfer radical poly- merization (ATRP) to form the block copolymers of cyclohexene oxide (CHO) with styrene (St) were performed. In the first step, bromine terminated poly(CHO)s (PCHO-Br) were prepared by free radical promoted cationic polymerization of CHO monomer in the presence of 2-oxo-1,2-diphenylethyl-2-bromopropanoate, shortly bromo benzoin, (B-Br) and an onium salt namely 1-ethoxy-2-methylpyridinium hexafluorophosphate (EMP þ SbF6 � ) as the initiating system. The bromine functionalized polymers thus prepared were used as initiators in ATRP of St, in bulk, in conjunction with CuBr/2,2 0 -bipyridine as catalyst gave well-defined block copolymer of CHO and St. Block copolymer formations were evidenced by 1 H NMR and gel permeation chromatography (GPC) measurements. (DOI 10.1295/polymj.37.700)

Middle Macroradicals and Their Influence on the Strength of Oriented Polymers

The macroradicals formed through the detachment of hydrogen atoms in amorphous-crystalline polymers are studied using electron-nuclear double resonance (ENDOR) spectroscopy. The 1H ENDOR spectra are analyzed, and the hyperfine interaction constants of the nearest neighbor and remote protons are measured. The conformational structure of radicals in poly(ethylene) (PE), poly(propylene) (PP), and poly(caproamide) (PCA) is determined. The ENDOR and EPR spectra of fibers subjected to tensile loading are recorded. It is revealed that torsional strain arises in the radicals with a nonplanar structure. The results of mechanical testing of irradiated oriented polymers demonstrate that the weakening of β bonds in the radicals has an effect on the macroscopic strength.

Ring-Opening Metathesis Polymerization Using Alkenyl Sulfides as Chain-Transfer Agents: Efficient Routes to Unsymmetrical Poly(norbornene)-Based Macroinitiators Bearing a Terminal Hydroxy Group

Convenient routes to hydroxy-terminated poly(norbornene)s (PNBEs) have been developed. Hydroboration of PNBEs bearing a terminal vinyl group with 9-BBN followed by oxidation with H2O2/NaOH forms hydroxy-terminated PNBEs in high yields. The parent PNBEs are prepared by ring-opening metathesis polymerization (ROMP) of norbornene using vinylic sulfides as chain-transfer agents (CTAs). On the other hand, ROMP of norbornene using (Z)-1-phenylthio-1-propen-3-ol as a CTA causes one-step synthesis of ω-hydroxy-terminated PNBE, where the molecular weight of polymer depends linearly on the initial feed ratio of CTA to monomer. Similarly, ROMP reactions using (Z)-1-phenylthio-1-propen-3-ols having bromo, amino, and 4-(chloromethyl)benzamido substituents at the para position of the phenyl group as CTAs afford the corresponding α,ω-heterodifunctionalized (heterotelechelic) PNBEs. The resulting PNBEs serve as macroinitiators for anionic ring-opening polymerization (AROP) of e-caprolactone and atom-transfer radical poly...

Influence of C60 Fullerene on the Oxidative Degradation of a Free Radical Poly(Methyl Methacrylate)

The results of studies of thermal and oxidative degradation of a free-radical poly(methyl methacrylate) (PMMA) and the influence of a fullerene C60 on these processes are considered. The best characteristic of the change of the thermal stability is the temperature shift of the entire thermal gravimetric (TG) curve (or the middle part of it), but not the shift of onset or the starting temperature of the mass loss. During oxidative degradation in air of PMMA, three processes occur practically simultaneously: thermal degradation, or scission of chains; oxidation, or insertion of oxygen atoms in the polymer chains and in products of the degradation; and a sublimation of degradation products. The competition between exothermic and endothermic processes results in sharp changes in the balance of heat energy in the system and the sign of the total heat effect. In accord with these changes all of the process of PMMA oxidative degradation can conditionally be divided into three stages. The introducing of small quantities of C60 in a system results in replacement of oxygen by a fullerene or to a partial avoidance of oxidation, as a result of which, at the first stage, a smaller quantity of degradation products is formed and oxidized. There is a “transfer” of degradation products and heat generation from the first, lowest temperature stage, to the third, highest one. Simultaneous application of DSC and TG techniques has shown that during oxidative degradation of PMMA, especially in the presence of a fullerene, there is a latent degradation manifested in exothermal effects on DSC curves without mass losses on the TG curves. The introducing of C60 results in narrowing of the peaks (by ∼1.5 times) on DTG and MTA curves that may be explained by the narrowing of a set of possible degradation reactions. The C60 molecules are divided during oxidative degradation of PMMA into two groups: linked (∼20%) and nonlinked with macroradicals of PMMA. The nonlinked molecules of C60, in turn, are subdivided into oxidized and volatilizing without oxidation and degradation. The inhibiting effect of C60 on the thermal oxidative degradation reduces basically to two processes: to formation of fullerene-containing chains of PMMA and to nonchain inhibition. The matrix of PMMA also has a significant influence on the thermal behavior of C60.

An ESR study on γ-irradiated poly(vinyl alcohol)

The formation of radicals in poly(vinyl alcohol), PVA, powder irradiated at 77 K by γ-rays and the transformations of these radicals during photolysis with visible wavelengths and on thermal annealing have been studied. After irradiation a four-line ESR spectrum was observed. It was assigned to a triplet of the C α -radical (38%), with a splitting of 3.27 mT, superimposed on a doublet (62%) with a splitting of 2.7 mT. The doublet appears to be composed of two radicals, one of which is photo-bleachable (58%) and the other which is not photo-bleachable (42%). This suggests that the latter radical is a neutral radical. The photo-bleachable component of the doublet has been assigned to a carbonyl anion radical, but the second doublet due to a neutral radical is unassigned. The total G-value for formation of radicals at 77 K was found to be 2.41±0.03. Upon illumination with visible light, the anion radicals were removed and the doublet components of the spectrum diminished in intensity, while the three-line spectrum of the C α -radical became more clearly visible. This transition was due to the photo-detachment of electrons from traps which were proposed to be located on carbonyl groups in the polymer resulting from incomplete hydrolysis of the vinyl acetate. The photo-decay of the anion radicals could be satisfactorily described by a two-stage process. The first stage comprised the decay of approximately 80% of the anion radicals present, while the second stage was associated with the decay of the remaining 20%. Subsequent thermal annealing of a photolysed sample to 290 K led to a change in the shape of the spectrum to form a more clearly defined triplet. As the doublet of the neutral radical decays on thermal annealing between 150 and 250 K, the C α -radical is formed.

ESR Study of Stable N,N,N",N"-Tetramethyl-4,4"-diaminodiphenylmethane Radicals in Solid Solutions

The ESR spectra of γ-irradiated N,N,N",N"-tetramethyl-4,4"-diaminodiphenylmethane (Am) in solid solutions of poly(vinyl chloride), poly(methyl methacrylate), and benzene were studied. The formation mechanism of the free radical Am·in these solutions was discussed. Along with Am·, the formation of radicals with the cyclohexadienyl structure was shown to be possible in Am irradiation. The influence of the matrix structure on the radiation-chemical yield of Am·radicals and their thermal stability was established. The radiation-induced chemical transformations of free radicals and transient ionic species resulting in the formation of terminal alkyl radicals in poly(methyl methacrylate) were investigated. Data on the mechanism of the protective action of the Am additive during PMMA radiolysis were obtained.

Thermal polymerization and photopolymerization of ethyl methacrylate with bis(cyclopentadienyl)titanium dichloride in a water-methanol mixture: Formation of a polymer with novel solubility characters

Methacrylate monomers such as methyl methacrylate, ethyl methacrylate (EMA), phenyl methacrylate, and benzyl methacrylate were found to be heterogeneously polymerized in high yields with bis(cyclopentadienyl)titanium dichloride (Cp2TiCl2) at 40°C in a 1:1 (v/v) water–methanol mixture under irradiation of a 15-W fluorescent room lamp. The polymerization of EMA with Cp2TiCl2 in a 1:1 (v/v) water–methanol mixture also proceeded at a moderate rate in the dark. The polymerization behavior of EMA with Cp2TiCl2 in a water–methanol mixture was examined under various conditions, both in the dark and under irradiation. The resulting poly(EMA) was observed to contain a considerable part that was acetone insoluble. In contrast to the usual radical poly(EMA), the fractionated acetone-insoluble part was insoluble in tetrahydrofuran, chloroform, ethyl acetate, methyl ethyl ketone, acetonitrile, dimethyl sulfoxide, and dimethylformamide, though it was soluble in aromatic solvents such as benzene and toluene. We prepared a bilayer film (48.7 μm) consisting of one acetone insoluble layer and one acetone-soluble layer. The film was observed to bend toward side of the acetone-insoluble layer in a 1:1 (v/v) water–acetone mixture. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 166–175, 2001