Styrene Radical Research Articles

Influence of the synthesis parameters on the efficiency of fluorescent ion-imprinted polymers for lead detection

New fluorescent ion-imprinted polymers (IIPs) specific for Pb(II) detection were synthesized by precipitation polymerization. The fluorescent activity of the IIPs was provided by a fluorescent functional monomer, ANQ-ST, based on the chelating 5-amino-8-hydroxyquinoline moiety coupled to anthracene and a styrenic group. Various synthesis parameters were tested: metal/functional monomer ratio, polymerization solvent and crosslinker (ethyleneglycol dimethacrylate, EGDMA, or divinylbenzene, DVB). The characterization of the different IIPs was carried out by solid-state 13C NMR spectroscopy, to analyse the structure of the polymers and to attest the integration of the ANQ-ST in the polymer matrix, and by scanning electron microscopy and nitrogen adsorption/desorption experiments, to study the morphology of the prepared materials. After characterization, the IIPs and their corresponding non-imprinted polymer (NIPs) were subjected to various fluorescence studies, in order to conclude on the influence of the synthesis parameters onto the polymer properties. The results demonstrated that the IIP synthesized with a metal/functional monomer ratio of 0.42 in DMSO/MeOH (1:1, v/v) and using EGDMA as a crosslinker was very sensitive to the presence of Pb(II) ions and almost not to other tested ions (Ag(I), Na(I), Ca(II), Cd(II), Co(II), Cu(II) and Zn(II)), even introduced in high excess. Calibration curves were performed in various matrices: ultra-pure water, buffered water at pH 7.0 and 8.1, seawater, tap water. They highlighted the low impact of the tested matrices onto the detection and allowed to determine a limit of detection of 2.4 μg/L and a linear range of 8.0–50 μg/L. Finally, the very good recovery obtained in natural samples emphasized the potential for the synthesized IIP to detect Pb(II) in natural waters.

A Dipolar Cyclization/Fragmentation Strategy for the Catalytic Asymmetric Synthesis of Chiral Eight-Membered Lactams

A Dipolar Cyclization/Fragmentation Strategy for the Catalytic Asymmetric Synthesis of Chiral Eight-Membered Lactams

Reductive Electropolymerization and Electrochromism of Iron(II) Complex with Styrene-Based Ligand.

The benzimidazole-based ligand containing polymerizable styrene group has been prepared via condensation of picolinaldehyde derivative containing styrene moiety and benzimidazole-based hydrazine. The ligand reacted with iron(II) tetrafluoroborate and iron(II) trifluoromethanesulfonate giving red-brown complexes of Fe(II) ions of formula [FeL2]X2, where X = CF3SO3− (1) or BF4− (2). Reductive electropolymerization was used to obtain a thin layer of the polymeric complex, poly-1. Further investigation of electrochemical properties of the compound by cyclic voltammetry showed two quasi-reversible redox processes assigned to electrooxidation and electroreduction of the polymer. Spectroelectrochemical measurements confirmed that the polymer undergoes the color changes during oxidation and reduction process. The polymer in its neutral state (Fe(II)) is yellow and it exhibits absorption band at 370 nm, after oxidation to Fe(III) state absorption band shifts to 350 nm and the polymer is almost colorless. While the metal ions are reduced to Fe(I) absorption band at around 410 nm has been observed and the polymer changed its color to intense yellow. The stability of the polymer during multiple oxidation/reduction cycles has also been investigated.

Model development and control of an auto-refrigerated polystyrene polymerization reactor

Dynamic model development and control of an existing operating industrial continuous bulk free radical styrene polymerization process are carried out to evaluate the performance of auto-refrigerated CSTRs (continuous stirred tank reactors). One of the most difficult tasks in polymerization processes is to control the high viscosity reactor contents and heat removal. In this study, temperature control of an auto-refrigerated CSTR is carried out using an alternative control scheme which makes use of a vacuum system connected to the condenser and has not been addressed in the literature (i.e. to the best of our knowledge). The developed model is then verified using some experimental data of the real operating plant. To show the heat removal potential of this control scheme, a common control strategy used in some previous studies is also simulated. Simulation results show a faster dynamics and superior performance of the first control scheme which is already implemented in our operating plant. Besides, a nonlinear model predictive control (NMPC) is developed for the polymerization process under study to provide a better temperature control while satisfying the input/output and the heat exchanger capacity constraints on the heat removal. Then, a comparison has been also made with the conventional proportional-integral (PI) controller utilizing some common tuning rules. Some robustness and stability analyses of the control schemes investigated are also provided through some simulations. Simulation results clearly show the superiority of the NMPC strategy from all aspects.

Cross-linkable deep-blue small molecular material for solution-processed organic light-emitting diodes

The development of deep-blue electroluminescent fluorescent materials with solution-processability and small molecule has exerted a great influence on the application in organic light-emitting diodes (OLED) field. However, so far there still lack of small molecule deep-blue materials suitable for solution-processed OLEDs and its wide band gap and low carrier mobility are requisite. Notably, the poor solvent resistance of small molecule usually incurs the inter-layer corrosion while using solution process to deposit multiple layers, which would result in poor device performance. In this work, a cross-linkable deep-blue light-emitting material DPCS-DPS containing diphenylsulfone/carbazole units and styrene groups has been designed and synthesized. The hole and electron transport parts composed of diphenylsulfone/carbazole exhibited bipolar charge-transporting properties, and the styrene group exhibited good solvent-resistance after thermal cross-linking, which is beneficial for the preparation of subsequent functional layers by solution process. By using the DPCS-DPS, the non-doped OLED achieved deep-blue emission wavelength of 415 nm, and the doped device approached a maximum current efficiency of 1.19 cd A−1 and maximum power efficiency of 0.75 lm W−1.

INTERACTION OF STYRENE AND METHYL METACRYLAT WITH C60 FULLERENYL RADICALS - TRISADDUTS

INTERACTION OF STYRENE AND METHYL METACRYLAT WITH C60 FULLERENYL RADICALS - TRISADDUTS

Aryl radical initiators accumulated within layered silicates realize polystyrene with directly and regioselectively bonded aryl-terminal groups.

The arbitrary design of a terminal group of polymers exploits the still-veiled functions of polymers with potential for application in fields such as drug delivery systems, photonics, and energy conversions. Here we demonstrate for the first time that polystyrenes with directly and regioselectively bonded aryl-terminal groups can be obtained via styrene radical polymerization initialized by arbitrary aryl radicals accumulated within the interlayer space of smectite clay minerals, which can be prepared by our developed 'Clay Catalysed ab intra Deamination (CCD)' method.

On-substrate postsynthetic metal ion exchange as a tool for tuning electrochromic properties of materials

The hydrazone-based ligand containing polymerizable styrene groups has been designed and prepared. The radical polymerization reaction carried out on ITO substrate leaded to formation of cross-linked thin film of poly-L, which has been converted into polymeric complexes with iron(II) and copper(II) metal ions using dip-coating method. The uniform distribution of metal ions in the obtained thin films has been confirmed by the energy-dispersive X-ray spectroscopy (EDS) and their electrochromic properties were investigated. The metal-ion exchange reaction was monitored in solution by NMR titration and on-substrate by EDS analysis. It was found that Cu(II) ions can be exchanged on-substrate with Fe(II) ions leading to the change of electrochromic properties of materials. Polymeric complexes have been characterized in terms of their electrochromic properties such as long term stability, switching times and coloration efficiencies. It was found that polymers poly-Fe-L obtained by dip-coating method and metal ion exchange exhibit similar electrochromic properties what prove that the transmetalation reaction can be powerful tool for changing observed colors of the films and tuning the electrochromic properties of materials.

Visible-Light-Driven Anti-Markovnikov Hydrocarboxylation of Acrylates and Styrenes with CO 2

Light-driven carbon dioxide (CO2) capture and utilization is one of the most fundamental reactions in Nature. Herein, we report the first visible-light-driven photocatalyst-free hydrocarboxylation ...

Electronically Asynchronous Transition States for C-N Bond Formation by Electrophilic [CoIII(TAML)]-Nitrene Radical Complexes Involving Substrate-to-Ligand Single-Electron Transfer and a Cobalt-Centered Spin Shuttle.

The oxidation state of the redox noninnocent tetra-amido macrocyclic ligand (TAML) scaffold was recently shown to affect the formation of nitrene radical species on cobalt(III) upon reaction with PhI=NNs [van LeestN. P.; J. Am. Chem. Soc.2020, 142, 552−56331846578]. For the neutral [CoIII(TAMLsq)] complex, this leads to the doublet (S = 1/2) mono-nitrene radical species [CoIII(TAMLq)(N•Ns)(Y)] (bearing an unidentified sixth ligand Y in at least the frozen state), while a triplet (S = 1) bis-nitrene radical species [CoIII(TAMLq)(N•Ns)2]– is generated from the anionic [CoIII(TAMLred)]– complex. The one-electron-reduced Fischer-type nitrene radicals (N•Ns–) are formed through single (mono-nitrene) or double (bis-nitrene) ligand-to-substrate single-electron transfer (SET). In this work, we describe the reactivity and mechanisms of these nitrene radical complexes in catalytic aziridination. We report that [CoIII(TAMLsq)] and [CoIII(TAMLred)]– are both effective catalysts for chemoselective (C=C versus C–H bonds) and diastereoselective aziridination of styrene derivatives, cyclohexane, and 1-hexene under mild and even aerobic (for [CoIII(TAMLred)]–) conditions. Experimental (Hammett plots; [CoIII(TAML)]-nitrene radical formation and quantification under catalytic conditions; single-turnover experiments; and tests regarding catalyst decomposition, radical inhibition, and radical trapping) in combination with computational (density functional theory (DFT), N-electron valence state perturbation theory corrected complete active space self-consistent field (NEVPT2-CASSCF)) studies reveal that [CoIII(TAMLq)(N•Ns)(Y)], [CoIII(TAMLq)(N•Ns)2]–, and [CoIII(TAMLsq)(N•Ns)]– are key electrophilic intermediates in aziridination reactions. Surprisingly, the electrophilic one-electron-reduced Fischer-type nitrene radicals do not react as would be expected for nitrene radicals (i.e., via radical addition and radical rebound). Instead, nitrene transfer proceeds through unusual electronically asynchronous transition states, in which the (partial) styrene substrate to TAML ligand (single-) electron transfer precedes C–N coupling. The actual C–N bond formation processes are best described as involving a nucleophilic attack of the nitrene (radical) lone pair at the thus (partially) formed styrene radical cation. These processes are coupled to TAML-to-cobalt and cobalt-to-nitrene single-electron transfer, effectively leading to the formation of an amido-γ-benzyl radical (NsN––CH2–•CH–Ph) bound to an intermediate spin (S = 1) cobalt(III) center. Hence, the TAML moiety can be regarded to act as a transient electron acceptor, the cobalt center behaves as a spin shuttle, and the nitrene radical acts as a nucleophile. Such a mechanism was hitherto unknown for cobalt-catalyzed hypovalent group transfer and the more general transition-metal-catalyzed nitrene transfer to alkenes but is now shown to complement the known concerted and stepwise mechanisms for N-group transfer.

Structure and Dielectric Properties of Electroactive Tetraaniline Grafted Non-Polar Elastomers

Intrinsic modification of polybutadiene and block copolymer styrene–butadiene–styrene with the electrically conducting emeraldine salt of tetraaniline (TANI) via a three-step grafting method, is reported in this work. Whilst the TANI oligomer grafted at a similar rate to both polybutadiene and styrene–butadiene–styrene under the same conditions, the resulting elastomers exhibited vastly different properties. 1 mol% TANI-PB exhibited an increased relative permittivity of 5.9, and a high strain at break of 156%, whilst 25 mol% TANI-SBS demonstrated a relative permittivity of 6.2 and a strain at break of 186%. The difference in the behaviour of the two polymers was due to the compatibilisation of TANI by styrene in SBS through π-π stacking, which prevented the formation of a conducting TANI network in SBS at. Without the styrene group, TANI-PB formed a phase separated structure with high levels of TANI grafting. Overall, it was concluded that the polymer chain structure, the morphology of the modified elastomers, and the degree of grafting of TANI, had the greatest effect on the mechanical and dielectric properties of the resultant elastomers. This work paves the way for an alternative approach to the extrinsic incorporation of conducting groups into unsaturated elastomers, and demonstrates dielectric elastomers with enhanced electrical properties for use in actuation devices and energy harvesting applications.

Polymerization and Preparation of High Functional Ophthalmic Lens Material Containing 2-Fluoro Styrene with Si and Ag Nanoparticles

This research was conducted to produce the high functional silicone hydrogel ophthalmic lens containing styrene group and nanoparticles. 2F (2-fluorostyrene) was added to enhance polymerization stability during lens formation, Si and Ag nanoparticles were used as additives for the basic combination including Sil-H (Silicone monomer), TSMA (Trimethylsilyl methacrylate), DMA (N,N-Dimethylacetamide) and MMA (methyl methacrylate). And also, the materials were copolymerized with EGDMA (ethylene glycol dimethacrylate) as the crosslinking agent and AIBN (azobisisobutyronitrile) as the initiator. Measurement of the physical, optical, surface and antimicrobial characteristics of the produced material showed the possibility of utilization as an opthalmic contact lens. As a result of the polymerization stability measurement, no significant difference was observed in all the samples, so it can be judged that the stabilization of nanoparticles in the polymer was maintained. Therefore, these materials are expected to satisfy the basic requirements of ophthalmic lenses and used usefully as an antimicrobial material for silicone hydrogel ophthalmic lens.

One‐pot exchange reaction of acyl hydrazone combined with radical polymerization of styrene derivatives bearing acyl hydrazone moieties

ABSTRACTWe developed a one‐pot reaction combining an exchange reaction of the benzylidene moiety in an acyl hydrazone with styrene radical polymerization. The one‐pot reaction of a styrene derivative bearing a 4‐(dimethylamino)benzylidene acyl hydrazone moiety was conducted in the presence of 4‐cyanobenzaldehyde and pyridinium p‐toluene sulfonate/H2O for the exchange reaction and AIBN as the radical polymerization initiator in N,N‐dimethylformamide at 70 °C for 20 h. The exchange reaction proceeded quantitatively, with the 4‐(dimethylamino)benzylidene acyl hydrazone moiety being exchanged with 4‐(methoxy)benzylidene acyl hydrazone, and polymerization proceeded smoothly to provide the corresponding polymer in 70% yield. Compared to traditional stepwise methods and polymer post‐polymerization modifications, this one‐pot system exhibits distinct advantages for the facile and efficient preparation of various functional polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2505–2510

Analysis of Physical Properties of Hydrogel Lenses Polymer Containing Styrene and PVP

This research is carried out to analyze the effects of Styrene and PVP on the properties of silicone hydrogel lenses. Styrene group and PVP(Polyvinylpyrrolidone) are used as additives for a basic combination containing silicone monomer, TSMA(trimethylsilyl methacrylate) and DMA(n,n-dimethylacrylamide) added to the mix at ratios of 1~10 %. Silicone hydrogel lens is produced by cast-mold method. The polymerized lens sample is hydrated in a 0.9 % saline solution for 24 hours before its optical and physical characteristics are measured. Measurement of the physical characteristics of the produced material shows that the refractive index is 1.3682~1.4321, water content 77.11~45.73 %, visible light transmittance 95.14~88.20 %, and tensile strength 0.0652~0.3113 kgf. The results show a decrease of refractive index as the ratio of additives and water content decreases. The result of the stabilization test of polymerization show an increase of extractables along with increase of the ratio of additives, but the difference is not significant for all samples, so it can be judged that the stabilization of the polymer is maintained. Therefore, the additions of styrene and PVP should be taken into consideration for their effects on the physical properties of silicone hydrogel lens.

Synthesis, self-assembly, and photomechanical actuator performance of a sequence-defined polyviologen crosslinker

ABSTRACT Although it is well known that viologen radical cations can self-assemble into stacks or complexes on account of radical-radical pairing interactions, it has only recently been demonstrated that reduction of main-chain polyviologens integrated into hydrogel networks can trigger actuation. In these earlier examples, hydrogels comprising oligoethylene glycol-based polyviologens and poly(ethylene glycol) were functionalized with terminal azide groups to prepare ‘click’-based gels. Here, we report a new structural design for the functional polyviologen that consists of main-chain viologen subunits separated by hexamethylene groups instead of glycols and is capped at each end with styrene groups. Activation of this viologen-based macrocrosslinker was achieved using chemical- and photoreduction methods and its ability to undergo intramolecular chain-folding was monitored by absorption spectroscopy. Acrylate-based organogels and hydrogels were also prepared and a comparison was carried out to assess the actuator performance in each gel in terms of the rate of contraction and changes in stiffness.

Reversible Hydrogel Photopatterning: Spatial and Temporal Control over Gel Mechanical Properties Using Visible Light Photoredox Catalysis.

There is a growing interest in being able to control the mechanical properties of hydrogels for applications in materials, medicine, and biology. Primarily, changes in the hydrogel's physical properties, i.e., stiffness, toughness, etc., are achieved by modulating the network cross-linking chemistry. Common cross-linking strategies rely on (i) irreversible network bond degradation and reformation in response to an external stimulus, (ii) using dynamic covalent chemistry, or (iii) isomerization of integrated functional groups (e.g., azobenzene or spiropyran). Many of these strategies are executed using ultraviolet or visible light since the incident photons serve as an external stimulus that affords spatial and temporal control over the mechanical adaptation process. Here, we describe a different type of hydrogel cross-linking strategy that uses a redox-responsive cross-linker, incorporated in poly(hydroxyethyl acrylate)-based hydrogels at three different weight percent loadings, which consists of two viologen subunits tethered by hexaethylene glycol and capped with styrene groups at each terminus. These dicationic viologen subunits (V2+) can be reduced to their monoradical cations (V•+) through a photoinduced electron transfer (PET) process using a visible light-absorbing photocatalyst (tris(bipyridine)ruthenium(II) dichloride) embedded in the hydrogel, resulting in the intramolecular stacking of viologen radical cations, through radical-radical pairing interactions, while losing two positive charges and the corresponding counteranions from the hydrogel. It is shown how this concerted process ultimately leads to collapse of the hydrogel network and significantly (p < 0.05) increases (by nearly a factor of 2) the soft material's stiffness, tensile strength, and percent elongation at break, all of which is easily reversed via oxidation of the viologen subunits and swelling in water. Application of this reversible PET process was demonstrated by photopatterning the same hydrogel multiple times, where the pattern was "erased" each time by turning off the blue light (∼450 nm) source and allowing for oxidation and reswelling in between patterning steps. The areas of the hydrogel that were masked exhibited lower (by 1-2 kPa) shear storage moduli (G') than the areas that were irradiated for 1.5 h. Moreover, because the viologen subunits in the functional cross-linker are electrochromic, it is possible to visualize the regions of the hydrogel that undergo changes in mechanical properties. This visualization process was illustrated by photopatterning a larger hydrogel (∼9.5 cm on its longest side) with a photomask in the design of an array of stars.

On the β relaxations in poly(butadiene) and poly(styrene-butadiene) rubbers

The influence of the chemical microstructure on the secondary mechanical relaxations of PB and SBR has been studied by varying the content of vinyl, cis, trans butadiene and styrene groups. Two relaxational mechanisms are involved in their β mechanical relaxations with two distinct activation energies. The fitting by the summation of two Havriliak Negami functions of the experimental isochronal and isothermal curves prove that the vinyl groups are responsible for the contribution of the High Temperature part of the β-relaxation, whereas the butadiene 1,4 groups, cis and trans are at the origin of the low temperature part of this relaxation. Moreover, the intensity of the relaxation associated to each monomer appears to be proportional to their volume (and molar) fraction. Given the random characteristics of the studied copolymer, this suggests that the involved mechanisms are localized at the level of only one monomer unit.

Assessment of acid strength in sodium-exchanged resin catalysts: Consequences on glycerol etherification with isobutene in batch and flow reactors

Consequences of a decrease in the number of acid sites by the cation exchange on the acid strength of the resin catalysts were assessed using ammonia as a probe molecule. IR spectra illustrated that ν(NH) bands on NH3-saturated Amberlyst 15™ shift linearly to higher frequencies with an increase in the degree of sodium exchange associated with an increase in the Brønsted acid strength. These results were further confirmed by density functional theory calculations illustrating that the deprotonation energy of a sulfonated styrene group decreases upon Na+-exchange on its neighboring counterparts. Consequences of these changes in acid strength were investigated on glycerol etherification with isobutene. Batch reactor measurements at high conversions illustrated that selectivity to desired glycerol ethers increases as that of isobutene dimerization is suppressed with an increase in acid strength. The effects of acid strength on the complex reaction network were further investigated using a once-through flow reactor specifically focusing on low conversions. These measurements showed that mono-tert-butyl glycerol ether and di-isobutene were the primary products on pristine Amberlyst 15™, while di- and tri-tert-butyl glycerol ethers also become a primary product on sodium-exchanged counterpart catalysts.

Radical Polymers Alter the Carrier Properties of Semiconducting Carbon Nanotubes

Radical polymers are composed of nonconjugated macromolecular backbones and pendant groups that bear stable open-shell sites; these functional macromolecules have been utilized in myriad electrochemical, optoelectronic, and thermoelectric devices to date. Here, we combine radical polymers with semiconducting single-walled carbon nanotubes (SWCNTs) to form composite materials using a scalable fabrication process. Importantly, we are able to tune the charge carrier characteristics of the SWCNTs by controlling the macromolecular architecture of the radical polymer used to form the composite. This is a critical handle as creating stable, electron-transporting (i.e., n-type) SWCNT thin films using scalable processes is a long-sought goal in the field. Specifically, hole-transporting (i.e., p-type) SWCNT thin films were deposited using a simple drop-casting methodology. Then, a radical polymer thin film was coated on top of the SWCNT thin film in order to create a composite system. Three different radical polymer chemistries were evaluated in terms of their ability to manipulate the optoelectronic properties of the composite systems relative to the pristine SWCNT thin films. Two of the three radical polymer chemistries, poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA) and poly(2,3-bis(2′,2′,6′,6′-tetramethylpiperidinyl-N-oxyl-4′-oxycarbonyl)-5-norbornene) (PTNB), contained different macromolecular backbones but shared the same nitroxide radical open-shell chemistry. Instead, the third radical polymer, poly(2,6-ditert-butyl-4-((3,5-ditert-butyl-4-phenoxyl)(4-vinylphenyl)methylene)cyclohexa-2,5-dienone) (PGSt), was based upon the galvinoxyl styrene radical. Neither of the nitroxide-based radical polymers demonstrated any significant electrochemical interaction with the SWCNT thin films. Conversely, the addition of the galvinoxyl styrene-based radical polymer converted the SWCNT thin films from ones that were unipolar p-type materials to a system that allowed for both hole and electron transport (i.e., ambipolar behavior was observed) when the thin films were incorporated into organic field-effect transistor (OFET) test bed devices. In these ambipolar systems, the hole mobility and electron mobility values were determined to be 0.07 and 0.24 cm2 V–1 s–1, respectively. A combination of ultraviolet–visible–near-infrared (UV–vis–NIR) light absorption and Raman spectroscopy revealed the means by which this doping occurred. This provides for a foundational underpinning for the observed behavior, and this work also demonstrates a straightforward and scalable means by which to apply these functional open-shell macromolecules in flexible and printed electronic devices.

Initiator‐Free Natural Light‐Driven Vapor Phase Synthesis of a Porous Network of 3D Polystyrene Branched Carbon Nanofiber Grafted Polyurethane for Hexane /Water Separation

AbstractA unique approach of vapor phase polymerization is introduced to synthesize a 3D porous network of polystyrene branched carbon nanofiber on polyurethane (CNF/PS) using natural light (NL) initiation. The introduced natural light vapor phase polymerization of the styrene in the confined reactor containing CNF grafted PU offers a porous network with substantial stability. The natural light in a confined reactor performed two major functions. Its first role was to vaporize the styrene by increasing the reactor temperature and, in the second step, it generated styrene radicals. The radical styrene in vapor phase reacted with CNF to produce polystyrene branches by generating active sites on CNF. Without CNF, the polymerization on polyurethane (PU) provided a very delicate and fragile surface; however, CNF reinforced the 3D porous structure and provided active sites for radical polymerization. After polymerization, the surface area of the PU was substantially increased from 9 to 184 m2/g and the pore size was decreased from 2567 to 10 Å. The 3D porous network of natural light assisted polystyrene branched carbon nanofiber supported PU (3D‐NL‐PS/CNF/PU) provided a highly hydrophobic surface with a high water contact angle of ≈148±3°. The prepared 3D network was found to be highly oleophilic and provided rapid gravity driven separation of hexane and water without using any external force.