Syntheses of well-defined poly(siloxane)-b-poly(styrene) and poly(norbornene)-b-poly(styrene) block copolymers using functional alkoxyamines

Functional alkoxyamines, 1-[4-(4-lithiobutoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (2) and 1-[4-(2-vinyloxyethoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (3) were prepared, and well-defined poly(hexamethylcyclotrisiloxane)-b-poly(styrene)[poly(D₃)-b-poly(St)] and poly(norbornene)-b-poly(St) [poly(NBE)-b-poly(St)] were prepared using the alkoxyamines. The first step was preparation of poly(D₃) and poly(NBE) macroinitiators, which were obtained by the ring-opening anionic polymerization of D₃ using 2 as an initiator and the ring-opening metathesis polymerization of NBE using 3 as a chain transfer. The radical polymerization of St by the poly(D₃) and poly(NBE) macroinitiators proceeded in the ‘living’ fashion to give well-defined poly(D₃)-b-poly(St) and poly(NBE)-b-poly(St) block copolymers.     

Synthesizing and characterization of comb-shaped carbazole containing copolymer via combination of ring opening polymerization and nitroxide-mediated polymerization

The macro-TEMPO agent (poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), PGTEMPO) was synthesized by anion ring-opening polymerization (ROP) of 4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (GTEMPO) using potassium t-butoxide as the initiator. The comb-shaped copolymer, PGTEMPO-g-PVBK, was prepared via nitroxide-mediated free radical polymerization (NMP) using PGTEMPO as macro-TEMPO agent and 9-(4-vinylbenzyl)-9H-carbazole (VBK) as the monomer. The polymerizations showed characteristics of “living”/controlled behavior. The optical properties, thermal analysis and electrochemical properties of the comb-shaped copolymers were investigated. The fluorescence and ultraviolet intensity and cyclic voltammetries of the comb-shaped copolymers with different molecular weight showed a regular order.     

Grafting polymers onto carbon black surface by trapping polymer radicals

Polystyrene, poly(styrene-co-maleic anhydride), poly[styrene-co-(4-vinylpyridine)] and poly(4-vinylpyridine) with well-defined molecular weights and polydispersities were synthesized using 4-hydroxyl-2,2,6,6-tetramethylpiperidin-1-oxyl (HTEMPO)-mediated radical polymerization initiated by azobisisobutyronitrile or benzoyl peroxide. The resultant polymers were grafted onto carbon black surface through a radical trapping reaction at 130 °C in DMF. ¹H NMR, TGA, TEM, AFM, DSC and dynamic light scattering were used to characterize the carbon black grafted with polymers. It was found that the carbon black grafted with polystyrene and poly(styrene-co-maleic anhydride) could be dispersed in THF, chloroform, dichloromethane, DMF, etc., and the carbon black grafted with poly(4-vinylpyridine) and poly[styrene-co-(4-vinylpyridine)] could be well dispersed in ethanol.     

Synthesis of densely grafted copolymers by nitroxide-mediated radical polymerization of styrene using poly(phenylacetylene)s as a macroinitiator

Poly(phenylacetylene)s carrying alkoxyamine moieties in the side chain were prepared by Rh-catalyzed homopolymerization of 1-(4-ethynylphenyl)-1-(2,2,6,6-tetramethyl-1-piperidinyloxyl)ethane (1) and random copolymerization of 1 and 4-methoxy-1-ethynylbenzene (2a) or 4-decyloxy-1-ethynylbenzene (2b). ¹H NMR spectra showed that the poly(phenylacetylene)s adopted a cis-transoid structure. Using the poly(phenylacetylene)s as the macroinitiator the nitroxide-mediated radical polymerization of styrene (St) was carried out at 120 °C to yield densely grafted copolymers as a light yellow powder. The side chain lengths of the graft copolymers were determined by both ¹H NMR and conversion of St, which agreed with each other. The SEC profiles of the graft copolymers were unimodal at low conversions but were not unimodal at high conversion: a shoulder was observed in the high molecular=weight region and a small peak was observed in the low molecular=weight region. ¹H NMR measurements of the graft copolymers indicated that the copolymers adopted a trans-transoid structure, revealing that isomerization from cis-transoid to trans-transoid forms took place during the polymerization of St at 120 °C.     

Stable free radical polymerization of styrene with 4-sulphonate-2,2,6,6-tetramethylpiperidine-N-oxyl as mediators

The stable free radical polymerizations of styrene were investigated with five 4-sulphonate-2,2,6,6-tetramethylpiperidine-N-oxyl stable radicals as mediators and benzoyl peroxide (BPO) as initiators at 125 °C. The results indicated that the polymerizations proceeded in a “living”/controlled manner, i.e., the polymerization rates were first-order with respect to the monomer concentrations, molecular weights increased linearly with conversions and the molecular weight distributions were relatively low (M _w/M _n = 1.2–1.4), ¹H NMR analysis of the polymer chain-ends and successful chain extensions. The polymerization rates were faster than that of 4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl (OH-TEMPO) mediated ones. The effects of steric interference of different substitute groups at four-position of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), the molar ratios of stable radical to BPO and the temperature on the polymerizations were investigated.     

Synthesis and characterization of novel type poly (4-chloromethyl styrene-grft-4-vinylpyridine)/TiO2 nanocomposite via nitroxide-mediated radical polymerization

This paper describes the synthesis and characterization of novel type poly (4-chloromethyl styrene-graft-4-vinylpyridine)/TiO₂ nanocomposite. Firstly, poly (4-chloromethyl styrene)/TiO₂ nanocomposite was synthesized by in situ free radical polymerizing of 4-chloromethyl styrene monomers in the presence of 3-(trimethoxysilyl) propylmethacrylate (MPS) modified nano-TiO₂. Thereafter, 1-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-OH) was synthesized by the reduction of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). This functional nitroxyl compound was covalently attached to the poly (4-chloromethyl styrene)/TiO₂ with replacement of chlorine atoms in the poly (4-chloromethyl styrene) chains. The controlled graft copolymerization of 4-vinylpyridine was initiated by poly (4-chloromethyl styrene)/TiO₂ nanocomposite carrying TEMPO groups as a macroinitiators. The coupling of TEMPO with poly (4-chloromethyl styrene)/TiO₂ was verified using ¹H nuclear magnetic resonance (NMR) spectroscopy. The obtained nanocomposites were studied using transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and the optical properties of the nanocomposites were studied using ultraviolet-visible (UV-Vis) spectroscopy.     

Polyallene with pendant nitroxyl radicals

A new polyradical containing polyallene backbone and stable pendant nitroxyl radicals was synthesized using 4-hydroxyl-2,2,6,6-tetramethylpiperidine as starting material. Firstly, a new allenyl ether monomer, 4-allenyloxyl-2,2,6,6-tetramethyl piperidine was prepared by 2 steps. Next, BPO initiated the traditional free radical polymerization of 4-allenyloxyl-2,2,6,6-tetramethyl piperidine at 100 °C to obtain the homopolymer, poly(4-allenyloxyl-2,2,6,6-tetramethyl piperidine). Finally, the homopolymer was quantitatively oxidized by H₂O₂/Na₂WO₄·2H₂O/EDTA at room temperature to yield the final product, poly(4-allenyloxyl-2,2,6,6-tetramethyl piperidine-1-oxyl). Studies on the electrochemical properties of polyradical showed excellent charging/discharging reversibility and stability with a high columbic efficiency of 98%, which suggested that the synthesized polyradical is a promising cathode material for lithium secondary battery.     

Synthesis and properties of polyacetylenes having pendent phenylethynylcarbazolyl groups

Novel acetylene monomers substituted with phenylethynylcarbazolyl groups, 3-[(4-octylphenyl)ethynyl]-9-propargylcarbazole (1), 3,6-bis[(4-octylphenyl)ethynyl]-9-propargylcarbazole (2), 9-(4-ethynylphenyl)-3-[(4-octylphenyl)ethynyl]carbazole (3), and 9-(4-ethynylphenyl)-3,6-bis[(4-octylphenyl)ethynyl]carbazole (4) were synthesized, and polymerized with Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃] and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 9200 to 94?000 were obtained in 20-98% yields. The IR spectra of the polymers revealed that acetylene polymerization took place at the terminal ethynyl group, while the ethynylene group remained intact. The UV-vis absorption band edge wavelengths of W-based poly(3) and poly(4) were longer than those of the other polymers. W-Based poly(4) emitted fluorescence with the highest quantum yield (41%). Poly(1) exhibited excimer-based fluorescence in dilute solution.     

Characterization of surface-modified polyurethane blends,poly(vinyl alcohol), and poly(4-hydroxybutyl acrylate) for biomedical application by electron spin resonance spectroscopy

Two polyurethane blends—poly(carbonate urethane)/poly(vinyl alcohol) [PCU/PVA] and the aliphatic poly(ether urethane) (Tecoflex?)/poly(pentanedioic acid mono-4-(acryloyloxy)butyl ester) [Tecoflex?/COOH]—were surface-modified. Poly(vinyl alcohol) [PVA] and poly(4-hydroxybutyl acrylate) [PHBA] were used as model surfaces. 4-Isocyanato butanoic acid methyl ester was coupled as a spacer molecule to PVA and the PVA-containing polyurethane blend. Saponification of the generated ester group was verified by means of Electron Spin Resonance (ESR) spectroscopy using the nitroxyl radical 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) as a reporter group. In the case of Tecoflex? and PHBA, glutaric anhydride served as a spacer molecule. 4-Amino-TEMPO was coupled to this spacer as well. ESR spectroscopy as a bulk method was used together with the surface-sensitive method X-Ray Photoelectron Spectroscopy (XPS) verifying the modification steps by elemental composition, ESR line shapes, and determination of the rotational correlation time τ_c. © 1995 John Wiley & Sons, Inc.     

Fluorescent polyolefins by free radical post-reactor modification with functional nitroxides

The 4-(1-naphthoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (NfO-TEMPO) has been synthesized and successfully grafted in the melt onto a random poly(ethylene-co-1-ottene) copolymer. Functionalized polyolefins have been prepared by coupling reaction between NfO-TEMPO free radicals and macroradicals which have been formed by H-abstraction induced by the presence of a peroxide. In order to deepen insight into the functionalization mechanism, the reaction has been investigated by Electron Paramagnetic Resonance (EPR). EPR spectra collected during the reaction run, have evidenced the decrease of TEMPO signal as a consequence of temperature increasing. This decrease has been attributed to the formation of a covalent bond between macroradicals and nitroxide free radical. The resulting functionalized polyolefins, PO-g-(NfO-TEMPO), have been characterized by FT-IR and ¹H NMR which has allowed to evaluate their functionalization degree, whereas UV–Vis and fluorescence spectroscopy have been used to investigate their optical properties. The comparison with low molecular weight model compounds, has allowed to state that our methodology can be conveniently adopted to prepare fluorescent polyolefins where the optical properties of the chromophore has been completely transferred to polymer backbone both in solution and in the condensed phase.     

Synthesis of structurally well-controlled ω-vinylidene functionalized poly(alkyl methacrylate)s and polymethacrylonitrile by organotellurium,organostibine, and organobismuthine-mediated living radical polymerizations

The reaction of poly(methyl methacrylate) (PMMA), poly(i-butyl methacrylate), poly(2-hydroxyethyl methacrylate), and polymethacrylonitrile bearing organotellurium, organostibine, and organobismuthine ω-living polymer end groups with 2,2,6,6-tetramethylpiperidine 1-oxy (TEMPO) under thermal or photochemical conditions gave the corresponding ω-vinylidene functionalized polymethacrylates and polymethacrylonitrile with high end group fidelity. Treatment of the PMMA with ethyl 2-[(tributylstannyl)methyl]acrylate also gave a PMMA bearing the same ω-vinylidene end functionality. ¹H NMR, GPC, MALDI TOF MS, and thermogravimetric analyses revealed the highly controlled and defined structure of poly(alkyl methacrylate)s and polymethacrylonitrile in terms of molecular weight, molecular weight distribution, and the ω-polymer end structure.     

An approach to the preparation of conjugated polyradicals

Summary A new conjugated polymer, (poly(4-ethynylphenyl)diphenylmethyl) was prepared and characterized. The preparation involved the synthesis of a new acetylenic monomer, (4-ethynylphenyl)diphenylmethanol, which was polymerized by the well-defined catalysts (t-BuO)₂Mo(=CH-t-Bu)(NAr) and [Rh(COD)Cl]₂. The resulting conjugated polymer was reacted with thionyl chloride and then reduced with silver to yield a material with pendant triphenylmethyl radicals attached to the conjugated polymer chain.     

Targeting an EGFR Water Network with 4-Anilinoquin(az)oline Inhibitors for Chordoma

Quinoline- and quinazoline-based kinase inhibitors of the epidermal growth factor receptor (EGFR) have been used to target non-small cell lung cancer (NSCLC) and chordomas with varying amounts of success. We designed and prepared compounds to probe several key structural features including an interaction with Asp855 within the EGFR DGF motif and interactions with the active site water network. EGFR target engagement was then evaluated in a cellular assay, with the inhibitors then profiled in representative cellular models of NSCLC and chordomas. In addition, structure–activity relationship insight into EGFR inhibitor design with potent dimethoxyquin(az)olines identified compounds 1 [N-(3-ethynylphenyl)-6,7-dimethoxyquinolin-4-amine], 4 [N-(3-ethynylphenyl)-6,7-dimethoxyquinazolin-4-amine], and 7 [4-((3-ethynylphenyl)amino)-6,7-dimethoxyquinoline-3-carbonitrile]. We also identified 6,7-dimethoxy-N-(4-((4-methylbenzyl)oxy)phenyl)quinolin-4-amine (compound 18 ), which is the most potent inhibitor (IC₅₀=310 nm ) of the UCH-2 chordoma cell line to date.     

Plasticizer diffusion into PVC particles as studied by ESR spin probe method

Summary The spin probe technique of electron spin resonance (ESR) spectroscopy has been applied for studying the plasticizer diffusion, migration, and redistribution processes in suspension polymerized PVC particles. In the first series of experiments six PVC powder samples with different K values (58, 61, 64, 67, 70, and 72) were mixed with diisooctyl phthalate (DOP) containing 10^–4 M 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) as stable free radical spin probe. In the second run TEMPO-doped dry PVC powders were mixed with DOP plasticizer. Finally we studied the plasticizer transport phenomena between plasticized and non-plasticized polymer particles in powder mixtures. The observed diffusion properties of different samples were interpreted in terms of the different porosities of powders.     

Synthesis of 3-alkylated triacetonamine derivatives

Reaction of a lithiated imine derivative of 2,2,6,6-tetramethyl-4-piperidone (triacetonamine, 1 ) with activated or less reactive alkyl halides or styrene oxide and subsequent hydrolysis afforded 3-alkylated triacetonamine derivatives. Thus, 3-benzyl-2,2,6,6-tetramethyl-4-piperidone ( 3 ), 3-(n-butyl)-2,2,6,6-tetramethyl-4-piperidone ( 4 ), 3-(3-chloropropyl)-2,2,6,6-tetramethyl-4-piperidone ( 5 ), 2,2,3,6,6-pentamethyl-4-piperidone ( 6 ) and two diastereomers of 3-(2-hydroxy-2-phenylethyl)-2,2,6,6-tetramethyl-4-piperidone ( 7 ) were prepared in 26–53% yield. Reaction of the imine anion derived from 1 with benzyl bromide to give 3 has to be performed at low temperatures in order to avoid a competing proton transfer. No reaction at the unprotected piperidine nitrogen was observed.     

Highly efficient electrocatalytic oxidation of sterol by synergistic effect of aminoxyl radicals and Se?Ni5P4

The exploration of efficient and environmentally friendly oxidation method is highly desirable to overcome the critical problems of poor selectivity and heavy metal contamination for the fine chemicals industry. Herein, a self-supported three-dimensional (3D) Se Ni₅P₄ nanosheet electrocatalyst was rationally designed and fabricated. Benefiting from the synergistic effect of aminoxyl radical and mesoporous Se Ni₅P₄/graphite felt (GF), an excellent performance of ≥98% selectivity and 33.12 kg (m⁻³ h⁻¹) space–time yield was obtained for sterol intermediate oxidation with the enhanced mass transfer effect of the continuous flow system. The doping of anionic selenium and phosphorus modulated the electronic structure of Se Ni₅P₄, and the oxyhydroxides generated by surface reconstruction accelerated the turnover of 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO), thereby enhancing the intrinsic electrocatalytic activity. A scale-up experiment was conducted with stacked-flow electrolyzer demonstrated the application potential. This work provided an efficient synergistic electrocatalytic strategy to facilitate rapid electron and mass transfer for electrochemical alcohol oxidation and highlighted the potential for practical electrosynthesis applications.     

Synthesis of new polymeric hindered amine light stabilizers: Performance evaluation in styrenic polymers

Polymeric hindered amine light stabilizers (HALSs), in which the HALS functionality was attached to the terminal isocyanate chain end of poly(styryl‐co‐styryl isocyanate), were synthesized by a two‐step process. First, cinnamoyl azide was prepared and copolymerized with styrene by a free‐radical copolymerization method. Polymeric low‐molecular‐weight and high‐molecular‐weight 2,2,6,6‐tetramethyl‐4‐pipridinol‐graft‐poly(styryl‐co‐styryl isocyanate) and 4‐amino‐2,2,6,6‐tetramethyl piperidine‐graft‐poly(styryl‐co‐styryl isocyanate) were synthesized by a grafting method. The photodegradation and stabilization of different grades of high‐impact polystyrene (HIPS) were studied at 55°C in air at different time intervals, and the photostabilizing efficiency of polymeric HALSs was compared with conventional light stabilizers, such as 2,2,6,6‐tetramethyl‐4‐pipridinol and bis(2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate. Polymeric HALSs showed significant improvements in the photostabilization of HIPS. The solubility and diffusion coefficient of polymeric HALSs were studied. The morphological changes in HIPS caused by photooxidation were also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1126–1138, 2003     

Synthesis and characterization of light‐absorbing cyclopentadithiophene‐based donor–acceptor copolymers

Cyclopentadithiophene and benzothiadiazole based donor–acceptor polymers are fast emerging as the most promising class of materials for organic solar cells. Here we report on a series of Cyclopentadithiophene and benzothiadiazole based conjugated polymers, namely poly[4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole] (P1), poly[4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole‐alt‐9‐(heptadecan‐9‐yl)‐2,7‐bis(4,4,5,5‐tetramethyl)‐1,3,2‐dioxaborolan‐2‐yl)‐9H‐carbazole] (P2) and poly[4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole‐alt‐5,11‐bis(2‐hexyldecyl)‐3,9‐bis(4,4,5,5‐tetramethyl)‐1,3,2‐dioxaborolan‐2‐yl)‐5,11‐dihydroindolo[3,2‐b]carbazole] (P3), with alternating donor and acceptor units and discuss their photophysical and electrochemical properties. Stille coupling of 2‐tributylstannyl‐4,4‐dioctylcyclopenta[2,1‐b:3,4‐b′]dithiophene with 4,7‐dibromobenzo[1,2,5]thiadiazole generated the alternating donor–acceptor monomer 4,7‐bis(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene‐2‐yl)benzo[1,2,5]thiadiazole (CPDT‐BT‐CPDT). Homopolymer P1 of CPDT‐BT‐CPDT was synthesized by oxidative polymerization using FeCl₃. Copolymers P2 and P3 were synthesized by palladium‐catalysed Suzuki polycondensation. The synthesized polymers showed good solubility in common organic solvents, and UV‐visible measurements showed that the absorption maxima of the polymers lie in the range 624 to 670 nm. The energy gaps of these polymers were found to lie in the range 1.29 to 1.50 eV. Gel permeation chromatography measurements against polystyrene standards showed the number‐average molecular weight to be in the range (2.2–6.0) × 10⁴ g mol^?1. Thermogravimetric analysis showed the polymers to possess high thermal stability. A preliminary study of photodiode devices prepared using polymers P1, P2 and P3 when blended with the PC₇₁BM electron acceptor found that P2 is the optimum chemical structure for pursuing further device optimization.© 2015 Society of Chemical Industry     

Synthesis and characterization of AB2-type star polymers via combination of ATRP and click chemistry

Homo/miktoarm star polymers were successfully synthesized via combination of the “arm-first” and “coupling-onto” strategies. Firstly, the multifunctional coupling agent (core), 2, 4, 6-tris(3-ethynylphenyl)-1,3,5-triazine-2,4,6-triamine (TPTTA), was synthesized. Secondly, the linear polystyrene-Cl (PS-Cl) and poly(2-(dimethylamino)ethyl methacrylate)-Br (PDMAEMA-Br) were prepared by atom transfer radical polymerization (ATRP) method. Then, the linear PS-Cl and PDMAEMA-Br chains were modified by a nucleophilic substitution reaction with sodium azide. Finally, homo/miktoarm star polymers PS₃ and PS(PDMAEMA)₂ were designed by click reaction between the core (TPTTA) and the arm precursor (PS-N₃ or PDMAEMA-N₃). The structures of the PS₃, PS(PDMAEMA)₂ and the precursors were all characterized by NMR, FT-IR, UV and GPC analysis. Moreover, the self-assembly behaviors of the miktoarm amphiphilic copolymer PS(PDMAEMA)₂ was also investigated by transmission electron microscopy (TEM).     

Antioxidant action of a lipophilic nitroxyl radical,cyclohexane-1-spiro-2′-(4′-oxyimidazolidine-1′-oxyl)-5′-spiro-1″-cyclohexane,against lipid peroxidation under hypoxic conditions

Nitroxyl radicals are known to act as radical scavenging antioxidants. In the present study, a lipophilic nitroxyl radical, cyclohexane-1-spiro-2′-(4′-oxyimidazolidine-1′-oxyl)-5′-spiro-1″-cyclohexane (nitroxyl radical I) was synthesized and its antioxidant capacity was assessed in comparison with a hydrophilic nitroxyl radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (Tempol). Both nitroxyl radical I and Tempol inhibited methyl linoleate oxidation induced by free radicals, and the efficacy increased with decreasing partial pressure of oxygen, the effect being more pronounced for nitroxyl radical I than Tempol. Their hydroxylamines inhibited lipid peroxidation more effectively than their corresponding parent nitroxyl radicals. In liposomal membranes, a synergistic effect was observed in the combination of nitroxyl radical I with ascorbic acid, whereas only an additive effect was observed between Tempol and ascorbic acid. The present study suggests that nitroxyl radical I and its hydroxylamine may act as potent antioxidants, especially in combination with ascorbic acid under hypoxic conditions.