Diphenyliodonium Salt Research Articles

Synthesis and characterization of epoxy-chain end(s) functional macromonomer of polystyrene and its use in photoinitiated cationic polymerization

A novel epoxy chain-end(s) functional polystyrene macromonomer (PSt-CHO) was prepared via free radical polymerization (FRP) of styrene (St) initiated by 4,4′-azobis(3-cyclohexenylmethyl-4-cyanopentanoate) (ACCP) azo initiator and epoxidation on workup with 3-chloroperoxybenzoic acid under inert atmosphere in methylene chloride at 0 °C. 4,4′-Azobis(4-cyanopentanoyl chloride) (ACPC) was obtained by the reaction of 4,4′-azobis(4-cyanopentanoic acid) (ACPA) with phosphorus pentachloride in methylene chloride. The ACCP was synthesized by the condensation reaction of 3-cyclohexene-1-methanol with ACPC. The FRP of styrene with ACCP has yielded polystyrene with cyclohexene end(s) group (PSt-CH). Epoxidation of the PSt-CH was performed using 3-chloroperoxybenzoic acid to obtain epoxy chain-end(s) functional polystyrene macromonomer (PSt-CHO). This macromonomer was used as precursor in photoinitiated cationic polymerization for obtaining brush-type and graft copolymers. Photoinitiated cationic homopolymerization of the macromonomer in the presence of diphenyliodonium salt at λ = 300 nm yielded brush-type polymers. Photoinitiated cationic copolymerization of the macromonomer with cyclohexene oxide (CHO) monomer and diphenyliodonium salt at λ = 350 nm produced graft copolymers. The polymers synthesized were characterized by means of FTIR, 1HNMR and gel permeation chromatography measurements. All the spectroscopic studies revealed that a macromonomer of polystyrene with cyclohexene oxide (CHO) functionality at the chain end(s) (PSt-CHO) and their brush-type and graft copolymers were obtained.

ChemInform Abstract: Synthesis of Mono‐Fluorinated Functionalized Cyclopropanes and Aziridines Using the α‐Fluorovinyl Diphenyl Sulfonium Salt.

The α-fluorovinyl diphenyl sulfonium salt 1 is attractive due to its high potential for the synthesis of mono-fluorinated cyclopropanes and aziridines as useful three-membered rings. The synthetically useful salt 1 is readily prepared from α-fluorovinyl phenyl sulfide and diphenyl iodonium salt in one step.

Synthesis and Properties of Hybrid Curing Siloxane Modified Epoxy Resin/Polyurethane Acrylate Coating

In order increasing properties of polyurethane acrylate coating, the epoxy resin/ polyurethane acrylate coating was prepared by UV and thermal dual curing with diphenyliodonium salt. The curing reaction and kinetics was investigated by UV-radiation and DSC, and the influence of the siloxane of methylacryloylpropyl-trimethoxysilane (MAPTMS) content on the properties of coating was determined by DMA and other physical methods. The results showed the hardness and glass transition temperature Tg of the coating film increased with the increasing MAPTMS content and the coating has good adhesion. When the content of MAPTMS reach 12 wt%, the Tg is the highest, which is 8.2°C higher than the before; When the triethylene glycol divinyl ether (DVE-3) can change the reaction from UV free radical/cationic reaction into thermal radical/cationic reaction, and can be described by autocatalytic Šesták-Berggre model (S-B) and the average activation energy Ea is 70.55 kJ/mol.

Effects of diphenyliodonium salt addition on the adhesive and mechanical properties of an experimental adhesive

ObjectivesThe aim of this study was to assess the microtensile bond strength (μTBS), nanoleakage (NL), nano-hardness (NH) and Young's modulus (YM) of resin–dentine bonding components formed by an experimental adhesive system with or without inclusion of diphenyliodonium salt (DPIH) in the camphorquinone–amine (CQ) system. MethodsOn 12 human molars, a flat superficial dentine surface was exposed by wet abrasion. A model simplified adhesive system was formulated (40wt.% UDMA/MDP, 30wt.% HEMA and 30wt.% ethanol). Two initiator systems were investigated: 0.5mol% CQ+1.0mol% EDMAB and 0.5mol% CQ+1.0mol% EDMAB+0.2mol% DPIH. Each adhesive was applied and light-cured (10s; 600mW/cm2). Composite build-ups were constructed incrementally and resin–dentine specimens (0.8mm2) were prepared. For NL, 3 bonded sticks from each tooth were coated with nail varnish, placed in the silver nitrate, polished down with SiC papers and analysed by EDX-SEM. NH and YM were performed on the hybrid layer in 2 bonded sticks from each teeth. The remaining bonded sticks were tested on μTBS (0.5mm/min). The data from each test were submitted to a Student t-test (α=0.05). ResultsNo significant difference was found for μTBS between groups (p>0.05). Significant lower NL and higher NH and YM were found in the hybrid layer and adhesive layer produced with the iodinium salt-containing adhesive (p<0.05). ConclusionsThe inclusion of the DPIH to the traditional CQ is a good strategy to improve the adhesive and mechanical properties of a simplified etch-and-rinse adhesive system.

Green‐Light‐Induced Cationic Ring Opening Polymerization Reactions: Perylene‐3,4:9,10‐bis(Dicarboximide) as Efficient Photosensitizers

AbstractNew perylene‐3,4:9,10‐bis(dicarboximide) (PBI) photoinitiators/photosensitizers derived from perylene‐3,4:9,10‐tetracarboxylic dianhydride are synthesized and investigated for the formation of free radicals under air and under very soft irradiation (i.e., halogen lamp) or laser diode exposure at 532 nm. Such a PBI in combination with a diphenyl iodonium salt and N‐vinylcarbazole or a silane very efficiently promotes the ring‐opening polymerization of epoxides and can also generate acrylate/epoxide interpenetrated polymer networks. It partly behaves as a metal‐free organic photocatalyst operating in an oxidative catalytic cycle. The different chemical intermediates are characterized by ESR and laser flash photolysis experiments. The mechanisms involved in the initiation step are discussed.magnified image

Synthesis of mono-fluorinated functionalized cyclopropanes and aziridines using the α-fluorovinyl diphenyl sulfonium salt

The α-fluorovinyl diphenyl sulfonium salt 1 is attractive due to its high potential for the synthesis of mono-fluorinated cyclopropanes and aziridines as useful three-membered rings. The synthetically useful salt 1 is readily prepared from α-fluorovinyl phenyl sulfide and diphenyl iodonium salt in one step.

Phototriggered In‐Situ Generation of Triethylborane for Polymer Synthesis Under Air

AbstractUpon demand, 1,3‐diamino‐propane‐triethylborane (DAPTB) is photolyzed in the presence of an acid generator such as a diphenyliodonium salt. Interestingly, triethylborane is released. In the presence of oxygen, ethyl radicals are generated and initiate an acrylate polymerization. This is the first example of a phototriggered production of a triethylborane usable in the photoinitiation of acrylate polymerizations. This approach is also worthwhile to overcome the oxygen inhibition for free‐radical polymerization processes.

Long Wavelength Photosensitizers for Diaryliodonium Salts Based on the 2-Benzyl-2H-benzo[d][1,2,3]triazole Skeleton

Two benzotriazole derivatives, 2-benzyl-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3]triazole (BBTS) and 2-benzyl-4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2H-benzo[d] [1,2,3]triazole (BBTES) were employed as photosensitizers for diaryliodonium salt photoinitiators in photoinitiated cationic polymerization of various epoxide and vinyl ether monomers. Diphenyliodonium hexafluorophosphate (Ph2I+PF6 –) salt was used as the photoinitiator in this study. Extended conjugation and electron-rich moieties of the photosensitizers enabled the use of long wavelength UV and visible light emitting light sources in cationic photopolymerizations. Having low oxidation potentials and good solubility in cationically polymerizable monomers make them efficient photosensitizers for the diphenyliodonium salt in the photoinitiated cationic polymerization. Polymerizations were achieved at room temperature and monitored by optical pyrometry. Moreover, photopolymerization of a diepoxide monomer with ambient solar irradiation in the presence of BBTES and BBTS were examined.

Tunable Organophotocatalysts for Polymerization Reactions Under Visible Lights.

New organic photocatalysts derived from pyrene, anthracene, naphthacene, and pentacene are presented here for the formation of free radicals through a photoredox catalysis. These OPCs can work according to an oxidative cycle in a three component system in combination with diphenyl iodonium salt and a silane or in a reductive cycle in combination with amine and alkyl halide. This OPC behavior is highlighted through an investigation of the associated excited state and redox properties. The free radicals generated are characterized by ESR or photolysis experiments. Upon household LED bulb or Xe lamp exposure, the oxidative three-component system is able to promote the ring-opening polymerization ROP of an epoxide whereas the reductive three-component system is very efficient to initiate the free radical photopolymerization FRP of an acrylate. This ability of OPCs to initiate different polymerization reactions (ROP and FRP) is clearly an outstanding property.

Direct UV-written highly fluorinated aromatic-aliphatic copolyethers for optical waveguides

A bisphenol monomer (4-methoxy) phenylhydroquinone (Me-HQ) was prepared and further polymerized with 2,2,3,3,4,4,5,5,6,6,7,7-dodeca-fluoro-1,8-octanediol (12F-diol) and decafluorobiphenyl (DFBP) to obtain highly fluorinated aromatic-aliphatic copolyethers containing methoxy groups. After demethylation and the reaction with epoxy chloropropane, a series of novel highly fluorinated aromatic-aliphatic copolyethers bearing epoxy groups (FA-APE EP) at different feed ratios of (Me-HQ)/(12F-diol) were obtained. The chemical structures of all the copolymers were analyzed by 1H NMR, 13C NMR and 19F NMR spectra. A series of highly fluorinated photoresists were prepared by composing of fluorinated copolyethers, diphenyliodonium salt as a photoacid generator (PAG) and solvent. After UV-curing, the cross-linked films exhibited excellent chemical resistance and high thermal stability (Td ranged from 230 to 278 °C). The refractive indices of the films could be controlled between 1.5127 and 1.4749 at 1550 nm by varying the feed ratio of comonomers. A clear negative pattern was obtained through direct UV exposure and chemical development. For waveguides without upper cladding, the propagation loss of the channel waveguides was measured to be 0.18 dB/cm at 1550 nm.

Free Radical Shadow Cure Initiated Using Two-Component and Three-Component Initiator Systems

In photopolymerization systems, “shadow cure” may be defined as polymerization which extends into regions which are not illuminated by the incident initiating light source. The objective of this study is to evaluate the use of fluorescent additives for polymerization in masked regions that are unilluminated by the incident initiating light. Two different fluorescent dyes are investigated: fluorescein (FL) and eosin Y spirit soluble (EYss). A systematic series of studies was performed to characterize the effects of fluorescence intensity, the incident light intensity, and the presence of a diphenyl iodonium salt on the observed degree of shadow cure. It was concluded that shadow cure may be enhanced if one or more fluorescent compounds emit fluorescent light at wavelengths absorbed by the dye in a two- or three-component photoinitiator system. The addition of DPI to the two-component systems containing MDEA and FL or EYss led to a significant enhancement in the observed shadow cure. This result was attributed to the fact that DPI will increase both the number of active centers and the mobility of the active centers as a result of the electron transfer reactions in which it participates.

Organic Photocatalyst for Polymerization Reactions: 9,10-Bis[(triisopropylsilyl)ethynyl]anthracene

A new organic photocatalyst (9,10-bis[(triisopropylsilyl)ethynyl]anthracene, An-Si) is proposed here for the formation of free radicals under very soft irradiation conditions under air through a photoredox catalysis. It works according to an oxidative cycle that uses the combination of An-Si, a diphenyl iodonium salt along with a silane. This behavior is highlighted through an investigation of its excited state and redox properties. The different chemical intermediates are characterized by ESR experiments. In addition, the reversibility of the oxidation reaction of An-Si was investigated by cyclic voltammetry. This three-component system is able to promote the ring-opening photopolymerization of an epoxide as well as the free radical photopolymerization of an acrylate upon household LED bulb and Xe lamp exposure. Excellent polymerization profiles (mainly in ROP) are obtained. The specific properties of this catalyst are outlined.

A Breakthrough toward Long Wavelength Cationic Photopolymerization: Initiating Systems Based on Violanthrone Derivatives and Silyl Radicals

The silyl radical chemistry is used here for the free radical promoted cationic polymerization (FRPCP) of epoxy monomers ((3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate EPOX and limonene dioxide LDO) and the free radical photopolymerization FRP of an acrylate monomer (trimethylolpropane triacrylate TMPTA). The new three-component photoinitiating systems are based on violanthrone derivatives, diphenyl iodonium salt and a silane. The use of very soft irradiations (household fluorescent and LED bulbs, sunlight and xenon lamp as visible light sources) is described. Excellent polymerization profiles are obtained. Addition of ruthenium tris(bipyridine) still enhances the performance. A sunlight irradiation of 2 min leads to a conversion ∼70% of EPOX. The specific role of the silyl radicals generated in this system is investigated and discussed. Comparative assessments with existing initiating systems are also provided evidencing the very high efficiency of the new proposed approach.

Efficient dual radical/cationic photoinitiator under visible light: a new concept

A new concept based on the photoredox catalysis is proposed for the design of a photoinitiating system able to efficiently generate, in a single catalytic cycle, both a radical and a cation as initiating species. This is exemplified here by the tris(1,10-phenanthroline)ruthenium(II) (Ru(phen)32+) complex in combination with a diphenyl iodonium salt and a silane. Interesting and promising photopolymerization profiles in free radical photopolymerization (FRP) and free radical promoted cationic photopolymerization (FRPCP) are obtained under air and upon xenon lamp exposure and even soft irradiation conditions (fluorescence bulb, sunlight). An acrylate/epoxide blend is also easily polymerized under air using a fluorescent bulb. The mechanisms are investigated by ESR and Laser Flash Photolysis experiments.

Benzotriazole derivatives as long wavelength photosensitizers for diaryliodonium salt initiators

AbstractTwo benzotriazole derivative dyes 4,7‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)‐2‐dodecyl‐2H‐benzo[1,2,3]triazole, and 2‐dodecyl‐4,7‐bis(4‐hexylthiophen‐2‐yl)‐2H‐benzo[d][1,2,3]triazole are shown to work as efficient photosensitizers for a diphenyliodonium salt initiator in cationic photopolymerization of epoxide and vinyl monomers. Substituted thienyl groups are attached to benzotriazole backbone to extend conjugation and enhance electron density of the molecules. Thereby, it was possible to initiate polymerizations at room temperature using long wavelength UV and visible light. The progress of photopolymerizations was monitored using optical pyrometry. The photopolymerization of an epoxide monomer using solar irradiation was also demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Acid formation in polymer solids by radiation-induced chain reactions of diphenyliodonium salts

In order to develop chemically amplified radiation resist having ability of acid multiplication, acid formation in γ-irradiated polymer films and solutions of acetal compounds containing diphenyliodonium salt has been studied. Acids were generated in the films and solutions by chain reactions of large G-value. The G-value depends on the chemical structure of the polymers and acetal compounds. Compounds containing cyclic acetal structure give large G-values. This dependence can be explained by difference in the possibility of electron transfer from radicals of the polymers and acetal compounds to diphenyliodonium salt. Polyvinyl acetals will be a candidate for the dually amplified resist.

Preparation and Reactions of (β-Trifluoromethyl)vinyl Sulfonium Salt

(Beta-trifluoromethyl)vinyl sulfonium salt as a novel three-carbon fluorinated building block was conveniently prepared from easily available (beta-trifluoromethyl)vinyl sulfide and diphenyl iodonium salt in excellent yield. This easily handled crystalline reagent displayed two types of useful transformation involving aziridination and vinylation to afford the corresponding trifluoromethylated compounds in excellent yields.

Photopolymerization of vinyl ether networks using an iodonium initiator—The role of photosensitizers

AbstractPhoto‐differential scanning calorimetry (photo‐DSC) and UV‐visible spectrometry were used to investigate the photocuring kinetics of visible light initiated cationic photopolymerization of triethyleneglycol divinyl ether with a diphenyl iodonium salt and three photosensitizers, 1‐chloro‐4‐propoxy‐9H‐thioxanthen‐9‐one (CPTXO), acridine orange (AO), and camphorquinone (CQ). Although all photosensitizers were effective in causing photopolymerization, CPTXO and AO photo‐reacted during the irradiation; whereas CQ was not significantly consumed during the timescale of the photo‐DSC experiment. This difference in photo‐reactivity has not been reported previously, and indicates that the reaction of the iodonium ion with CPTXO and AO results in the formation of the photosensitizer radical cation, whereas the CQ mechanism involves the reduction of the CQ excited state to a ketyl radical by a H‐donor (monomer) followed by the oxidation of the ketyl radical by the iodonium salt and thus regeneration of the CQ. For the CPTXO and AO systems, the photopolymerization rate was retarded by a radical inhibitor but the CQ system was unaffected, which confirms that different mechanisms are involved. The cure rate was found to be proportional to the concentrations of CPTXO and CQ but appeared to follow an approximately square root dependence on the AO concentration. Mechanisms to explain these differences were presented. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5474–5487, 2009

Photopolymerization of Vinyl Ether Networks Using an Iodonium Initiator: Effect of Radiation Intensity and Iodonium Concentration

Photo-differential scanning calorimetry (photo-DSC) was used to investigate the photocuring kinetics of visible light initiated cationic photopolymerization of triethylene glycol divinyl ether (TEGDVE) with a diphenyl iodonium salt initiator and the three photosensitizers: 1-chloro-4-propoxy-9H-thioxanthen-9-one (CPTXO), camphorquinone (CQ), and acridine orange (AO). The effects of water, a tertiary amine, and a radical scavenger were used to probe the photocuring mechanism. The rate of photopolymerization was approximately proportional to the incident light intensity, and in each system, the final conversions, as measured by photo-DSC, also increased with raised incident light intensity. The power-law dependence of the reaction rate on the concentration of iodonium salt with CPTXO and AO was ∼1.5, while the order is nearly unity with CQ as the photosensitizer, suggesting that these photosensitizers do not follow the same sensitization mechanism. For the three photosensitizers, the final conversions all increased with higher iodonium salt concentrations. After cessation of irradiation, a dark reaction was observed—although the rate of this process decreased rapidly with time (as shown by photo-DSC), the polymerization continued very slowly over a long period of time.

Effect of the electron donor structure on the shelf‐lifetime of visible‐light activated three‐component initiator systems

AbstractIn this study, we investigated the effect of electron donor structures on the shelf life of three‐component initiator systems which also included methylene blue (MB) as a photosensitizer and diphenyl iodonium salt (DPI) as an electron acceptor. For this research, N‐phenylglycine (NPG), N‐methyldiethanolamine (MDEA), N,N‐diisopropyl‐3‐pentylamine (DIPA), and 1,4‐diazabicyclo[2.2.2]octane (DABCO) were used as electron donors, with different of proton transfer efficiencies and radical/cation persistence. To aid characterization of the shelf‐life or dark storage stability of three‐component initiator systems, the relative polymerization kinetic profile of each freshly prepared initiator system was first obtained using photo‐DSC. The standardized photopolymerization reactions were repeated after various dark storage intervals. Thermal stability of each initiator system was compared by applying a ramped temperature program to monomer samples in the DSC in the dark. To analyze the kinetic changes as a function of storage time more quantitatively, we suggested an equation and characterized the shelf‐lifetime constant (k) of three‐component initiator systems. From the experiments and analysis, we conclude that the order of shelf‐life is consistent with the of radical cation (DH·+) persistence; DABCO &gt; DIPA &gt; MDEA &gt; NPG, and inversely related to the proton transfer efficiency of the electron donor; NPG &gt; MDEA &gt; DIPA &gt; DABCO. The effects of electron donor structures on thermal stability were consistent with the results of kinetic shelf‐life experiments. This investigation provides an effective means to characterize as well as predict shelf lifetimes of initiator systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009