Iodine-transfer polymerization and CuAAC “click” chemistry: A versatile approach toward poly(vinylidene fluoride)-based amphiphilic triblock terpolymers

This study presents the synthesis and properties of linear PVDF-based amphiphilic triblock terpolymers with PS and PEO, [PVDF-b-PS-b-PEO], by adopting a procedure that involves: (a) iodine-transfer polymerization (ITP) of VDF with 1-iodoperfluorohexane (C₆F₁₃I) serving as chain-transfer agent (CTA) to afford C₆F₁₃-PVDF-I, (b) ITP of styrene with the C₆F₁₃-PVDF-I macromolecular-CTA to obtain C₆F₁₃-PVDF-b-PS-I diblock copolymer, (c) end-group exchange from iodo- to azido-group by nucleophilic substitution reaction with NaN_3, and (d) copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-terminated PEO to achieve C₆F₁₃-PVDF-b-PS-b-PEO triblock terpolymers. The ¹H and ¹⁹F NMR spectroscopy confirmed the presence of all blocks, while gel permeation chromatography traces showed the living nature of ITP technique. The self-assembly of these terpolymers was investigated in films (atomic force microscopy and DSC), as well as in aqueous and organic solvents (DLS). The analysis of crystalline phases based on the FTIR spectroscopy indicated the conversion of PVDF α-phase into α + β-phases and β + γ-phases upon the incorporation of PS and PEO blocks, respectively. The synthesized amphiphilic copolymers were evaluated (fluorescence spectroscopy) as carriers of small hydrophobic molecules in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 163–171     

Preparation of poly(ε-caprolactone)@attapulgite nanocomposites via a combination of controlled ring-opening polymerization and click chemistry

In this work, by a combination of controlled ring-opening polymerization (CROP) and click chemistry, we report a facile and useful method to synthesize linear poly(ε-caprolactone)@attapulgite nanocomposites with well-defined structures. For this, first, the chlorine-terminated attapulgite was prepared by the self-assembly of 3-chloropropyltrimethoxysilane from the surfaces of attapulgite. And then, the terminal chlorines of modified attapulgite were substituted with azido groups. As the second step, linear propargyl-terminated poly(ε-caprolactone) (PCLs) with different molecular weights were synthesized by the CROP of ε-CL monomer in toluene with stannous octoate as a catalyst and propargyl alcohol as an initiator. The structural characteristics of the obtained linear PCLs have been determined by ¹H NMR and gel permeation chromatography analysis. Finally, the azido-terminated attapulgite was reacted with propargyl-terminated PCLs via the click reaction.     

Functionalization of cellulose via ATRP and “click” chemistry to construct hydrophobic filter paper for oil/water separation

Cellulose - Cellulosic materials show great superiority in oil/water separation owing to abundance, low cost, renewability and biodegradability. Herein, silylated cellulose graft copolymer...     

One-pot tandem ring-opening polymerization of N-sulfonyl aziridines and “click” chemistry to produce well-defined star-shaped polyaziridines

An effective approach for fast synthesis of well-defined star-shaped poly(2-methyl-N-tosylaziridine)s was developed by one-pot tandem ring-opening polymerization (ROP) of N-sulfonyl aziridines with trimethylsilyl azide (TMSN₃) and “click” reaction with alkynes. Azido terminated polyaziridines (α-N₃-PAzs) could be achieved via ROP of N-sulfonyl aziridines with TMSN₃ in the presence of organic superbases. The catalytic efficiency of organobases, including 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), and N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA), was evaluated, and all of them except TBD afforded “living”/controlled ROP of 2-methyl-N-tosylaziridines (TsMAz). Star-shaped polyaziridines were then fastly synthesized by the one-pot tandem strategy. During the reaction process, PMDETA catalyzed ROP first, then was triggered to be a ligand by adding CuBr for “click” reaction. Well-defined 3- and 4-arm star P(TsMAz)s were successfully prepared, and subsequently desulfonylated to give star-shaped polypropylenimines (PPIs). PPI stars exhibited intrinsic photoluminescence properties from the polyamine arms.     

Oxidation of 1-amino-4,5-bis(dimethylamino)naphthalene as a route to the double ��proton sponges�� based on dibenzo[a,h]phenazine and 1,1��-azonaphthalene

Behavior of 4-amino-1-dimethylamino- and 1-amino-4,5-bis(dimethylamino)naphthalenes sharply differs on their treatment with tosyl chloride and oxidation with the Bu^tOK/O₂ system. While the former upon the action of tosyl chloride in protic media is transformed to sulfonamide, the latter unexpectedly forms 4,5,11,12-tetrakis(dimethylamino)dibenzo[a,h]phenazine in ??20% yield as a product of the competitive reaction, which represents the earlier unknown type of double ??proton sponges??. In contrast to this, the oxidative dimerization of the indicated amines with Bu^tOK/O₂ leads to 5,12-bis(dimethylamino)dibenzo[a,h]phenazine and 4,5,4??,5??-tetrakis(dimethylamino)-1,1??-azonaphthalene, respectively. Possible mechanisms of these reactions were considered, as well as problems of coloring, solvatochromism, and protonation of the compounds obtained.     

Synthesis and characterisation of a calix[4]pyrrole functional polystyrene via ‘click chemistry’ and its use in the extraction of halide anion salts

A polystyrene with pendant calix[4]pyrroles was prepared via ‘click reaction’ strategy. First, a poly(styrene-co-chloromethylstyrene) with approximately 12% of chloro groups was prepared by conventional free radical polymerisation. The chloro groups were then converted to azido groups using NaN₃ in N,N-dimethylformamide. An alkyne-functionalised calix[4]pyrrole was then coupled to the azido-functionalised polystyrene by click chemistry with high efficiency. The resulting polystyrene with pendant calix[4]pyrroles was used to extract fluoride and chloride anions (as their tetrabutylammonium salts) from their aqueous solutions to organic media.     

Dibromomethane as one-carbon source in organic synthesis: a versatile methodology to prepare the cyclic and acyclic α-methylene or α-keto acid derivatives from the corresponding terminal alkenes

Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH₂Br₂-Et₂NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes.     

Synthesis,functionalization and properties of incompletely condensed “half cube” silsesquioxanes as a potential route to nanoscale Janus particles

Multiple literature reports describe the synthesis of [RSiO(OH)]₄ or [RSiO(ONa)]₄ compounds. Surprisingly, in the majority of cases the OH or ONa groups all lie on the same face of the cyclomers or half cubes. Consequently, it appears possible to couple R containing half cubes with R’ containing half cubes to form bi-functional (Janus) silsesquioxane cages or cubes. We report here synthesis of [PhSiO(ONa)]₄ and [p-IPhSiO(ONa)]₄ half cubes. We thereafter discuss efforts to react the [PhSiO(ONa)]₄ salt with (R = Me, vinyl, and cyclohexyl) RSiCl3 in MeOH to produce the compounds {PhSiO[OSi(OMe)2R]}₄ species which were characterized using traditional spectroscopic procedures. These compounds were then subjected to acid catalyzed hydrolysis tohydrolytically remove the OMe groups to generate Janus cubes. While it is possible to isolate the target compounds, which were also characterized in detail, the yields were lower than expected perhaps because of competitive hydrolytic cleavage of the Si-O-SiR(OMe)₂ linkage.     

Molybdosphoric Acid Mixed with Titania Used as a Catalyst to Synthesize Diphenyl Carbonate via Transesterification of Dimethyl Carbonate and Phenol

The 12-molybdosphoric acid mixed with titania (MPA-TiO2) was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) via transesterification of dimethyl carbonate (DMC) and phenol. The X-ray diffraction (XRD) and infrared (IR) techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate (MPC) were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5:1.     

Visible-light photolysis of [FeCp(η6-toluene)][PF6] as a clean,convenient and general route to iron-vinylidene and iron-acetylide complexes

Visible-light photolysis of the cheap starting material [FeCp(η⁶-toluene)][PF₆] (Cpη⁵-C₅H₅) using a simple 100-W globe in the presence of diphenyldiphosphinoethane (dppe) and terminal alkynes cleanly yields the vinylidene complexes [FeCp(dppe)(CCHR)][PF₆] and, upon further deprotonation, the iron-alkynyl complexes; the reaction is extended to ferrocenylacetylene to yield a bimetallic complex.     

Addition of alkyl radicals, generated from carboxylic acids via photochemical decarboxylation, to glyoxylic oxime ether: a mild and efficient route to α-substituted α-aminoesters

Radical addition to a glyoxylic oxime ether was accomplished under mild conditions using an alkyl radical generated from a free carboxylic acid via photochemical decarboxylation. The photoreaction provided an efficient route to α-substituted α-aminoesters from carboxylic acids and oxime ether.     

Combination of electrochemical hydrogenation and Mössbauer spectroscopy as a tool to show the radiation effect of energetic heavy ions in Fe–Zr amorphous alloys

Radiation effects of energetic heavy ion irradiation in Fe–Zr amorphous alloys were investigated by the help of Mössbauer spectroscopy, X-ray diffraction and electrolytical hydrogenation. The electrolytical hydrogenation of non-irradiated and irradiated samples was carried out by a unique cathodic potential (−1000 mV versus SHE). The combination of electrolytical hydrogenation and Mössbauer analysis gives a very sensitive method for detecting structural changes of these amorphous alloys. It was found that the structural changes in the amorphous state, which are undetectable without hydrogenation by Mössbauer spectroscopy, modify the localization and the concentration of introduced hydrogen, and are reflected in a significant change of magnetic hyperfine interaction. The results can be associated with structural changes due to the effect of energetic heavy ion irradiation.     

Preparation of magnetic indole-3-acetic acid imprinted polymer beads with 4-vinylpyridine and β-cyclodextrin as binary monomer via microwave heating initiated polymerization and their application to trace analysis of auxins in plant tissues

Auxin is a crucial phytohormone for precise control of growth and development of plants. Due to its low concentration in plant tissues which are rich in interfering substances, the accurate determination of auxins remains a challenge. In this paper, a new strategy for isolation and enrichment of auxins from plant tissues was obtained by the magnetic molecularly imprinted polymer (mag-MIP) beads, which were prepared by microwave heating initiated suspension polymerization using indole-3-acetic acid (IAA) as template. In order to obtain higher selective recognition cavities, an enhanced imprinting method based on binary functional monomers, 4-vinylpyridine (4-VP) and β-cyclodextrin (β-CD), was adopted for IAA imprinting. The morphological and magnetic characteristics of the mag-MIP beads were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and vibrating sample magnetometry. A majority of resultant beads were within the size range of 80-150μm. Porous surface morphology and good magnetic property were observed. Furthermore, the mag-MIP beads fabricated with 4-VP and β-CD as binary functional monomers exhibited improved recognition ability to IAA, as compared with the mag-MIP beads prepared with the individual monomer separately. Competitive rebinding experiment results revealed that the mag-MIP beads exhibited a higher specific recognition for the template than the non-imprinted polymer (mag-NIP) beads. An extraction method by mag-MIP beads coupled with high performance liquid chromatography (HPLC) was developed for determination of IAA and indole-3-butyric acid (IBA) in plant tissues. Linear ranges for IAA and IBA were in the range of 7.00-100.0μgL(-1) and 10.0-100.0μgL(-1), and the detection limits were 3.9 and 7.4μgL(-1), respectively. The analytical performance was also estimated by seedlings or immature embryos samples from three different plant tissues, pea, rice and wheat. Recoveries were in the range of 70.1-93.5%. The results show that the present imprinting method is a promising approach for preparation of selective adsorbents for sample preparation of auxin analysis in plant tissues.