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Polysulfone-based materials were fabricated as casted films, porous membranes, and nanofibers by solution casting, phase inversion process, and electrospinning technique, respectively. Photoactive rhodamine B hydrazide molecules were loaded into the fabrics either in preloading or postloading processes. The morphological structure of the fabrics was investigated by scanning electron microscopy and the wettability was determined by contact angle measurements. Detailed spectroscopic characterizations of the closed and open forms of rhodamine B was performed both in solution and in the solid-state composite materials. Theoretical investigations supported the depiction of the absorption and emission features of the two forms. The response of the prepared composite materials to Cu(II) ions has been tested by absorption and emission spectroscopy and confocal fluorescence imaging. The most effective materials for Cu(II) detection were found to be polysulfone films prepared by phase inversion and postloaded with 10% rhodamine B hydrazide. These results open the way to the development of composite sensory membranes. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48408.

Colitis is the term used for chronic inflammatory bowel diseases at substantially increased risk of developing a form of colorectal cancer (CRC) known as colitis-associated cancer. In our study we synthesized core-shell polymeric micelles obtained by self-assembly of block copolymers for high efficiency delivery of anti-inflammatory and anti-cancer compounds to colonocytes and colon mucosa. We achieved an efficient intracellular delivery of these hydrophobic compounds (prednisone, retinoic acid and doxorubicin) to cultured colonocytes without cellular toxicity. The efficacy of retinoic acid and doxorubicin administration was significantly increased using these nanosized carriers. Moreover, these polymeric micelles have been shown to overcome the multidrug resistance efflux mechanism effectively delivering doxorubicin to multidrug-resistant colon cancer cells. These nanocarriers are also suitable for selective in vivo delivery of lipophilic drugs by enema administration to the inflamed colon tissue, specifically targeting the inflamed mucosa. From the Clinical Editor This team of investigators studied polymeric micelles as highly efficient drug delivery systems enabling intracellular delivery of hydrophobic compounds (prednisone, retinoic acid, and doxorubicin) to cultured colonocytes without cellular toxicity, also demonstrating beneficial in vivo effects.

The Reversible Addition-Fragmentation chain-Transfer (RAFT) synthesis of poly(glycidyl methacrylate) (PGMA) copolymers followed by the post-polymerisation treatment with morpholine allows the rational design of amphiphilic block copolymers that are capable of efficiently dispersing single walled carbon nanotubes (SWCNTs) in aqueous media, as shown by comparative photophysical characterisation and AFM analysis.

The radical cation and anion of the title compound were obtained either by treatment with mercury trifluorocatetate in trifluoroacetic acid or by reduction with potassium in tetrahydrofurane. For both species the ESR spectra indicated magnetic non-equivalence of the two phosphorus atoms, as well as of the two methyl groups. Spectra attributed to the corresponding spin adducts were also observed when reacting the title compound with in situ-generated alkoxyl and thiyl radicals. MO calculations carried out for both the ionic radicals and the neutral spin adducts led to questioning the actual nature of some of the latter species.

This paper is aimed at providing an overview of our studies on the title compounds as spin trapping agents, and at emphasising the links between purely cognitive, academic research and industrial applications. Phosphoryl- and thiophosphoryl-dithioformates exhibit a comparable and interesting spin trapping ability, their efficiency being analogous to that of some aromatic thioketones. The spectral hyperfine structure may provide valuable information on the nature of the trapped radical but the phosphorus hfs constant cannot be used as an useful indicator. Thionformates are less efficient spin traps than the corresponding dithioformates, being inert towards stabilised radicals such as benzyl or relatively hindered radicals as tert-butoxyl. In no case could spin adducts to thiolformates be detected, this being an indication that their carbonyl group is significantly deactivated with respect to that of organic and organometallic ketones. Because of their ability in trapping either alkyl or alkoxy radicals both kind of dithioformates were exploited as stabilisers in the processing of such polymers as polypropylene, but their outstanding performance could not compensate for some organoleptic drawbacks that were intrinsic of the thiocarbonyl function. A much more promising application of dithioesters is instead their use as RAFT chain transfer agents in the controlled polymerisation of styrene. Preliminary experiments with benzyl diethoxyphosphoryldithioformate have afforded polystyrene with a polydispersity as low as 1.17, but further studies are needed to fully elucidate the RAFT-polymerisation mechanism and to optimise its outcome.

Unusual temperature-dependent linewidth variations were observed in spin adducts of (dimenthoxy)phosphoryl methyl dithioformate with bulky free radicals, possibly involving a combination of restricted rotation of a methyl group and slow molecular tumbling. Copyright © 2002 John Wiley & Sons, Ltd.

Five new phosphoryldithioformates bearing different substituents on the phosphoryl group have been synthesised and exploited as spin trapping agents in ESR experiments. While the dilauroxy substituted compound led to the observation of ESR spectra indicating photolability of either the compound as such or of its radical adducts, the three diaryloxy-phosphoryl dithioformates exhibited an excellent spin trapping ability, thus proving an attractive alternative to previously described members of this family. This was also the case for the di(2-menthoxy)phosphoryl derivative which led in all cases to very persistent radical adducts. The low melt-flow index values measured in the extrusion of polypropylene with variable additions of some of the dithioformates investigated in this and in previous studies indicated that the tested compounds have a remarkable ability to act as process stabilisers.

The addition of silyl and germyl radicals to a series of substituted cyclopentenones and cyclohexenones has been investigated using EPR spectroscopy. At low temperatures the 3-position is the preferred site for addition unless it is substituted or sterically hindered in which case addition occurs at the carbonyl oxygen. The latter process is also favoured at higher temperatures but no evidence has been obtained for either addition at the 2-position or for an intramolecular migration following initial attack at the 3- or 2-position.

Electron paramagnetic resonance has been used to characterise free radicals formed by the reaction of photochemically generated tert-butoxyl radicals with a range of methyl substituted cyclopentenones and cyclohexenones. The spectra have been interpreted using computer analysis and simulation and assigned to cyclic allylic and alkyl radicals formed by abstraction of a hydrogen atom. The 1-oxocyclohept-2-en-4-yl radical derived by abstraction of bromine from 4-bromocyclohept-2-enone exhibits a temperature dependent EPR spectrum attributed to ring inversion.

The addition of a variety of radicals to triphenylmethyl l, allyl 2, benzyl 3 and but-3-enyl (diethoxyphosphoryl)dithioformate 4 has been investigated by EPR spectroscopy. Reactions with the first substrate always led to displacement of the triphenylmethyl radical; release of the allylic or benzylic moieties from 2 and 3 was observed above 243 K under photolytic conditions, while at lower temperatures or in the dark the adducts resulting from thiophilic addition of the radicals were detected. The weak EPR spectra detected when reacting dithioformates 1–4 and methyl(diethoxyphosphono)dithioformate 5 with Grignard reagents are attributed to the radical anions of the starting compounds and to their ion pairs with magnesium cations.

Single-walled carbon nanotubes (SWCNTs) exhibit excellent mechanical, electrical, thermal, and optical properties. They are considered promising materials for a number of applications for which, however, individual SWCNTs are required instead of the complex mixture of metallic and semiconducting species obtained upon their preparation. The establishment of dispersion and separation protocols for SWCNTs is therefore of capital importance to enable their effective exploitation. There are many different approaches for the dispersion of SWCNTs, which typically entail non-covalent interactions between amphiphilic molecules and the wall of the tubes in aqueous solution. Common surfactants (e.g. SDS, SC, SDBS) are typically used for this purpose. We report an effective strategy for the preparation of single-walled carbon nanotube dispersions, based on the use of an amphiphilic polymer (PHMPMA-b-PSt) and compare it with a standard surfactant (SDBS) and another polymer lacking pendant phenyl groups (PHMPMA-b-PMMA). The polymers used in this work are new and obtained by post-polymerization treatments of RAFT synthesized poly(glycidyl methacrylate) (PGMA). We found that the polymer can form micelles around the SWCNTs through its hydrophobic chain, whilst the hydrophilic part prompts dispersion in water. The excellent dispersion capability of our polymer is demonstrated by electronic absorption spectra, photoluminescence mapping of the SWCNTs (Figure 1) and AFM studies. 1 H. Wang, Curr. Opin. Colloid Interface Sci., 2009, 14, 364-371. 2 M. Benaglia, A. Alberti, L. Giorgini, F. Magnoni and S. Tozzi, Polym. Chem., 2013, 4, 124-132.

The treatment of poly( glycidyl methacrylate) with nucleophilic agents yielded new linear homo/co-polymers. The materials obtained have different physicochemical properties depending upon the nucleophiles utilized and thus, by this way, water soluble polymers are easily accessible. This approach is also very convenient for the synthesis of amphiphilic block copolymers. Additional chemical modifications can further transform the obtained polymers after the post-polymerization treatment. Starting from RAFT pre-synthesized/pre-functionalized polymers, the described procedures allow us to obtain a wide variety of chemically diverse materials characterized by controlled structure and specific functions.

PS-b-PMA block copolymers carrying terminal anionic groups have been studied. Their synthesis is achieved by mean of 3-(benzylsulfanyl thiocarbonylsulfanyl) propionic acid and 3-(1-phenylethylsulfanyl thiocarbonylsulfanyl) propanesulfonic acid sodium salt as RAFT agents. These block copolymers, when dispersed in methanol, display a pseudo-amphiphilic behaviour and provide micelles that can be suspended in water by osmosis. During the self-assembling process, the anionic terminations lead to the formation of nanosized monodispersed particles and confer stability to the micelles in aqueous media. The core of the micelles is loaded with Nile Red to achieve the intracellular delivery of a lipophilic substance; this has been demonstrated by Confocal Laser Scanning Microscopy. The particles, when loaded with Doxorubicin, are able to overcome the intrinsic resistance of LoVo-MDR cancer cells. A further stabilization is given to the micelles by covalent shell crosslinking provided by triethylene glycol diacrylate. The increased intracellular stability of the crosslinked micelles makes them stain, when loaded with Nile Red, the aqueous cytosol instead of the lipophilic cellular compartments. The unimers constituting the micelles have been covalently labelled with fluorescein to follow their fate once incorporated into the cells.

The use of "switchable" RAFT agents in expanding the use of RAFT polymerization in block copolymer synthesis is decsribed. N-(4-pyridinyl)-N-methyldithiocarbamates provide excellent control over polymerization of less activated monomers (LAMs) (e.g., vinyl acetate, N-vinylcarbazole), and, after addition of one equivalent of a protic or Lewis acid, become effective in controlling polymerization of more activated monomers (MAMs) (e.g., styrene, methyl methacrylate). They thus allow a convenient synthesis of polyMAM-block-polyLAM with narrow molecular weight distributions. Advantages, limitations and factors effecting the scope of the process are discussed.

3,5-Di-tert-butylthiobenzoyltriphenylsilane (DBTBTPS) has been synthesized and tested as a spin trapping agent for electron spin resonance studies. Upon reaction with a variety of radicals of different nature inside the cavity of the ESR spectrometer, DBTBTPS leads to the observation of rather persistent spectra which in nearly all cases allow the unambiguous identification of the trapped species. DBTBTPS is somewhat less stable than thiobenzoyltriphenylsilane (TBTPS), the unsubstituted thiobenzoyltriphenylsilane; yet, as it affords spin adducts whose spectra are characterized by a smaller number of lines, it may prove more useful than TBTPS itself when dealing with radicals leading to species with a large number of magnetically active nuclei interacting with the unpaired electron.

The kinetics of decomposition of oxynitroxides Me 3 CN(O . )OMR 3 , with R 3 M=Me 3 C, Bu 3 Sn, Ph 3 Ge, and Ph 3 Si, has been studied by EPR at different temperatures, and the activation parameters have been determined

The radical anions from thiobenzophenone, thiobenzoyltriphenylsilane, and 3,5-di-tert-butylthiobenzoyltriphenylsilane were detected by EPR spectroscopy when these compounds were reacted with a number of Grignard reagents, RMgBr. The radical adducts resulting from addition of R• radicals to the thiones were also detected. The formation of the radical anions indicates unambiguously the occurrence of a SET process which might be the initial stage of these reactions. In the case of tris(trimethylsilyl)ethanethial only the radical adducts were detected. The first reduction potentials of these thiones have also been measured in order to verify the feasibility of the SET process. In agreement with the EPR experiments, the calculated standard free energy changes suggest that electron transfer is possible in the first three cases and disfavored with the thioaldehyde.

The kinetics of decomposition of oxynitroxides Me 3 CN(O . )OMR 3 , with R 3 M=Me 3 C, Bu 3 Sn, Ph 3 Ge, and Ph 3 Si, has been studied by EPR at different temperatures, and the activation parameters have been determined

The polymerization of most monomers that are polymerizable by radical polymerization can be controlled by the reversible addition-fragmentation chain transfer (RAFT) process. However, it is usually required that the RAFT agent be selected according to the types of monomer being polymerized. Thus, RAFT agents (dithioesters, trithiocarbonates) suitable for controlling polymerization of "more activated" monomers (MAMs; e.g., styrene, acrylates, methacrylates, etc.) tend to inhibit polymerization of "less activated" monomers (LAMs; e.g., vinyl acetate, N-vinylpyrrolidone, etc.). Similarly RAFT agents suitable for polymerizations of LAMs (xanthates, certain dithiocarbamates) tend to give little or poor control over polymerizations of MAMs. We now report a new class of "switchable" RAFT agents, N-(4-pyridinyl)-N-methyldithiocarbamates, that provide excellent control over polymerization of LAMs and, after addition of 1 equiv of a protic or Lewis acid, become effective in controlling polymerization of MAMs, allowing the synthesis of poly(MAM)-block-poly(LAM) with narrow molecular weight distributions.

Silyl, germyl, stannyl radicals have been reacted with a variety of ring substituted benzo[2,1,3]thiadiazoles, and the paramagnetic adducts resulting from addtion to one of the heterocyclic nitrogens have been characterized by means of ESR spectroscopy. Reactions with unsymmetrically substituted substrates lead to the formation of two distinct isomeric adducts, whose relative amounts depend on the steric and electronic effects exerted by the substituents. With compounds bearing a substituent in position 5, the amount of each individual isomeric adduct appears to be directly related to the extent of its resonance stabilization. Substituents in position 4 can be divided into two classes: those exerting only steric effects (Me, Cl) direct the additional to the less hindered nitrogen, while substituents like MeO and, a lesser extent, CN favour radical attack on the closer. although more hindered nitrogen. Upon increase in the temperature a reversal of the relative stability of the two species is sometimes observed.

The direct EPR detection of thioacyl radicals has been reported only once, while thioacyl nitroxides remain an elusive species. We failed to detect the thioacyl radicals from two thioaldehydes and from phosphoryldithioformates but have obtained EPR evidence that thioacyl radicals react with 2-methyl-2-nitrosopropane to give thiocarbonyloxyaminyls rather than thioacyl nitroxides. The results of DFT calculations support this unexpected reactivity of thioacyls, while making questionable their previous EPR identification.

A series of tertiary dithiobenzoates differently substituted on the phenyl group (Z) were synthesized in order to investigate the RAFT-mediated polymerization of MMA. The chain-transfer agent 2-eyanoprop-2-yl dithiobenzoate, although an excellent RAFT agent for polymerization of MMA, does not yield a very narrow polydispersed polymer at low conversion. The introduction of electron-withdrawing substituents on the dithiobenzoate aromatic ring improves the activity of the chain-transfer agent narrowing the molecular weight distribution, especially in the first 2 h of the process; conversely, electron-donating substituents deteriorate the performance of the process in the early stages. Substituents on the dithiobenzoate that, for reasons of steric hindrance reduce the conjugation of the phenyl with the C=S double bond of the dithiogroup, diminish the effectiveness of the chain-transfer agent. The nature of the leaving group (R) also has a strong influence on the process: the substitution of 2-cyanoprop-2-yl with the bulkier 2-cyano-4-methylpent-2-yl as leaving group improves remarkably the MMA polymerization, especially in the early stages. The solvent effect on MMA RAFT polymerization using benzene, acetonitrile, and DMF was also investigated. The lower propagation rate constant of MMA in benzene gives rise to reduced rates of polymerization but narrower polydispersities of the polymer, especially at low conversions. The RAFT polymerizations of MMA were carried out at 60 and 90 degrees C to assess the temperature dependence of the process. The higher temperature increases both the rate of polymerization and the transfer constant of the RAFT agent, resulting in lower polydispersities at a given conversion. Ab initio calculations confirmed the observed experimental results.

Indolinonic aromatic nitroxides have been shown to efficiently inhibit free radical mediated oxidation reactions in biological systems. Since all antioxidants also possess pro-oxidant activity, possibly through a hydrogen abstraction process from suitable substrates, the relative hydrogen abstraction abilities of these compounds were evaluated. Different hydrogen donors were reacted with an indolinic and two indolinonic nitroxides and the rates of hydrogen abstraction were determined using UV-Vis spectroscopy. From the data obtained, a structure-activity relationship was found. In addition, the hydrogen abstraction ability of these compounds was found to be much greater than that of the aliphatic nitroxide TEMPO, despite existing reports indicating that these two classes of compounds show similar antioxidant activities in biological systems.

ESR studies carried out during the reaction of ferrocenoylsilanes with Grignard reagents at low temperature led to the detection of the radical anions of the former compounds. Cyclic voltammetric experiments indicate that the observed radical anions are likely to originate through an inner-sphere electron transfer process. Different radical species were observed upon annealing, originating from destruction of the ferrocenyl moiety. Paramagnetic species were also detected on reacting ferrocenoylsilanes with LiAlH4. Copyright © 2004 John Wiley & Sons, Ltd.

Thermal decomposition of tertiary azo compounds in the presence of a triphenylmethyl dithioester results in the formation of the corresponding tertiary dithioesters. This procedure is especially useful for the synthesis of tertiary phosphoryldithioformates, but also represents an easy synthetic methodology of general applicability.

Benzyl (diethoxyphosphoryl)dithioformate (1) has been used to control the AIBN initiated radical polymerization of Styrene. In a comparative study with the more popular RAFT transfer agent benzyl dithiobenzoate (2), compound 1 led to higher molecular weight polymers, although with a slightly worse polydispersity. During the polymerization process mediated by 1 a few radicals have been intercepted and characterized by means of ESR spectroscopy. The nature and relative amount of the various radical species varied as the polymerization proceeded, matching expectations based on the generally accepted RAFT mechanism. The present ESR results induce to a reassessment of the identity of a radical species observed in a previous preliminary study.

The identification of the species observed by EPR spectroscopy in the SmI(2)-promoted coupling of N-(N', N'-dialkylaminoalkyl)benzotriazoles as substituted benzyl radicals is disputed on the basis of results obtained studying the model radical derived from tribenzylamine.

The reduction of a number of phosphoryl- and thiophosphoryl formates, monothioformates and dithioformates has been studied by means of cyclic voltammetry and EPR spectroscopy. The reduction potentials of all dithioformates are close to −1 V vs. SCE, and increase for S-alkyl monothioformates and even more for O-alkyl monothioformates. The radical anions of the compounds bearing the thiocarbonyl function have been characterised by means of EPR spectroscopy, whereas those of the compounds having the carbonyl function underwent decomposition before detection. Reduction at higher potentials led in most cases to the detection of paramagnetic dianions derived from fragmentation of the initially formed radical anions.

A PS-b-PMA block copolymer bearing a terminal carboxylic group has been synthesized using 3-(benzylsulfanyl thiocarbonylsulfanyl) propionic acid as RAFT agent. When dispersed in methanol, this block copolymer displays pseudo-amphiphilic behaviour providing micelles which can be suspended in water by osmosis. The carboxylic terminations are fundamental during the self-assembling process contributing to the formation of nanosized monodispersed particles. Furthermore, the anionic corona confers the to micelles stability in aqueous media. The core of the micelles was loaded with Nile Red to achieve the intracellular delivery of a lipophilic substance; this was demonstrated by Confocal Laser Scanning Microscopy. The particles, when loaded with doxorubicin, are able to overcome the intrinsic resistance of LoVo-MDR cancer cells. Further stabilization is given to the micelles by covalent shell crosslinking using triethylene glycol diacrylate. Because of the increased intracellular stability of the crosslinked micelles, they stain, when loaded with Nile Red, the aqueous cytosol instead of the lipophilic compartments. The unimers constituting the micelles were covalently labeled with fluorescein to follow their fate once incorporated into the cells.

Five of the title N-oxides 1 when reduced either chemically (phenylhydrazine, hydrazobenzene) or electrochemically (DMF–TEAP–protonating agent) were found to afford the corresponding, 5-hydroxyindoles 6. The reduction process takes place in two steps leading initially to 1,5-dihydroxyindoles 4 which undergo loss of water and are eventually converted into the products. EPR spectroscopic studies of the chemical and electrochemical reduction led to the characterization of the intermediate radical anions and neutral radicals, and a mechanism based on these results as well as on polarographic and cyclic voltammetric studies is proposed for the process.

The paramagnetic species detected by EPR spectroscopy upon electrochemical reduction of bis(2,4,7-tri-tert-butyl-phenyl)-1,3-diphosphaallene in THF solution has been unambiguously identified as the title radical, the identi-fication being supported by DFT calculations

The radical ions from 5-nitrospiro[indoline-2,3′-naphthopyran]1, 8′-nitrospiro[indoline-2,3′-naphthopyran]2, and 5,8′-dinitrospiro[indoline-2,3′-naphthopyran]3 have been investigated electrochemically and by means of electron paramagnetic resonance spectroscopy.The first reduction potentials of these compounds reflect the position of the nitro groups and vary between –1.532 V for 1 and –1.273 V for 2vs. SCE, while 3 exhibits two reduction waves at, potentials similar to those of 1 and 2, suggesting no or very little interaction between the two moieties of the molecules. The oxidation potentials are dominated by the indolinic moiety increasing in the order 2 < 1 < 3.The reduction with butoxide in DMF leads to the EPR observation of the expected radical anions of 1 and 2, while the spectrum observed with 3 shows, against expectations, reduction of the indolinic moiety. Photoreduction with Bu4NBH4 in THF affords the radical anions of 2 and 3 but not of 1, the measured hfs constants being similar to those measured in DMF without light. Addition of in situ generated triphenylgermyl radicals to 1–3 affords rather persistent germyloxy-aminoxyls which give identical spectra both under UV irradiation and in the dark.

Some mechanistic considerations based on the results of an ESR spectroscopic study of the IBDA (iodosobenzene diacetate) induced iododecarboxylation of several aliphatic carboxylic acids are reported. Both acetoxy units in IBDA are replaced by carboxylate groups in the first step of the reaction, forming a hypervalent iodine complex which then undergoes homolytic photodegradation. The R. radicals deriving from decarboxylation of the starting acids have been trapped by means of thiobenzoyl triphenylsilane and identified using ESR spectroscopy.

The paramagnetic adducts between a variety of phosphinyl, phosphonyl or thiophosphonyl radicals and thiobenzophenone, 9,H-xanthen-9-thione, 9, H-thiaxanthen-9-thione, 9, H-selenaxanthen-9-thione and di-tert-butyl thioketone have been generated and studied by means of ESR spectroscopy. Attention has been focused on the variations of a (31P) with the nature of the ligands L in the attacking PLn radicals and with the nature of the thiocarbonylic substrates. In all cases the reactions with the precursors of phosphinyl radicals afforded, beside the expected adducts, additional paramagnetic species, identified as the corresponding phosphonyl and thiophosphonyl adducts: while the formation of the former reflects the high sensitivity of tervalent phosphorus compounds to oxidizing agents, the latter adducts are believed to originate from desulfuration of the thioketones by the starting phosphines.

A wide variety of radicals has been added to three relatively stable thiocarbonyl compounds, namely thiobenzoyltriphenylsilane (TBTPS), 2,4,6-tri-t-butylthiobenzaldehyde (TBTBA), and tris(trimethylsilyl)ethan-ethial or trisylthioaldehyde (TSTA), in order to test their ability to act as radical scavengers and the possibility of using them as spin-trapping agents. Reactions with radicals centred at elements from Groups IV to VI afforded in all cases persistent spin adducts which were studied by e.s.r. spectroscopy. In particular the adducts with TBTPS showed well resolved e.s.r. spectra for which the hyperfine pattern allowed in most cases an unambiguous identification of the trapped radical. The decay of some of the TBTA and TSTA adducts has been monitored, and the rate constants for the process determined. The rate of addition of the t-butoxyl and pivaloyl radicals to TSTA were also measured as (1.2 ± 0.5)× 107 and (1.9 ± 0.5)× 106 dm3 mol–1 s–1, respectively.