Recombination of Lophyl Radicals in Pyrrolidinium‐Based Ionic Liquids

Berdzinski, Stefan; Horst, Joachim; Straßburg, P.; Strehmel, Veronika

doi:10.1002/cphc.201300098

Cited by 29 publications

(22 citation statements)

References 65 publications

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“…3a and 3b, inset) indicate an absence of radicals in the as-formulated HABI solutions but confirm significant radical formation upon irradiation, establishing the indigo color generation as attributable to HABI-derived lophyl radical formation (see Fig. 1b) [38, 45]. As shown in Fig.…”

Section: Resultsmentioning

confidence: 72%

“…Upon irradiation, HABIs undergo homolytic cleavage to yield two lophyl radicals (Fig. 1b) that are unreactive with oxygen and show slow recombination rates [38], attributable to steric hindrance and electron delocalization [39]; indeed, HABI photoinitiators show no initiation activity in (meth)acrylate formulations without the presence of a hydrogen-donating coinitiator [40]. Thiols are commonly used as coinitiators in conjunction with HABIs [40], where hydrogen abstraction by the HABI-derived lophyl radicals yields initiating thiyl radicals (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Hexaarylbiimidazoles as visible light thiol–ene photoinitiators

et al. 2015

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Objectives The aim of this study is to determine if hexaarylbiimidazoles (HABIs) are efficient, visible light-active photoinitiators for thiol–ene systems. We hypothesize that, owing to the reactivity of lophyl radicals with thiols and the necessarily high concentration of thiol in thiol–ene formulations, HABIs will effectively initiate thiol–ene polymerization upon visible light irradiation. Methods UV-vis absorption spectra of photoinitiator solutions were obtained using UV-vis spectroscopy, while EPR spectroscopy was used to confirm radical species generation upon HABI photolysis. Functional group conversions during photopolymerization were monitored using FTIR spectroscopy, and thermomechanical properties were determined using dynamic mechanical analysis. Results The HABI derivatives investigated exhibit less absorptivity than camphorquinone at 469 nm; however, they afford increased sensitivity at this wavelength when compared with bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide. Photolysis of the investigated HABIs affords lophyl radicals. Affixing hydroxyhexyl functional groups to the HABI core significantly improved solubility. Thiol–ene resins formulated with HABI photoinitiators polymerized rapidly upon irradiation with 469 nm. The glass transition temperatures of the thiol–ene resin formulated with a bis(hydroxyhexyl)-functionalized HABI and photopolymerized at room and body temperature were 49.5±0.5°C and 52.2±0.1°C, respectively. Significance Although thiol–enes show promise as continuous phases for composite dental restorative materials, they show poor reactivity with the conventional camphorquinone/tertiary amine photoinitiation system. Conversely, despite their relatively low visible light absorptivity, HABI photoinitiators afford rapid thiol–ene photopolymerization rates. Moreover, minor structural modifications suggest pathways for improved HABI solubility and visible light absorption.

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Section: Resultsmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Hexaarylbiimidazoles as visible light thiol–ene photoinitiators

et al. 2015

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“…[43] N-Methylpyrrolidine (20 mL, 0.19 mol) was dissolved in isopropanol (20 mL), then 1-chlorobutane (22 mL, 0.20 mol) was added slowly at room temperature. [43] N-Methylpyrrolidine (20 mL, 0.19 mol) was dissolved in isopropanol (20 mL), then 1-chlorobutane (22 mL, 0.20 mol) was added slowly at room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…Because of low viscosity and good solubility in most laboratory solvents, P 14 Cl was selected as the cation and synthesized by am odified reported method. [43] N-Methylpyrrolidine (20 mL, 0.19 mol) was dissolved in isopropanol (20 mL), then 1-chlorobutane (22 mL, 0.20 mol) was added slowly at room temperature. The reaction mixture was stirred at 85 8Cf or 24 h. After cooling to room temperature, the solvent was decanted, and the obtained pale-yellow powder was purified by reprecipitation from ethyl acetate and acetonitrile several times, followed by washing with ethyl acetate ( % 300 mL) until the pale-yellow color disappeared, and was dried under heat and vacuum.…”

Section: Synthesis Of 1-butyl-1-methylpyrrolidinium Chloride(p 14 Cl)mentioning

confidence: 99%

Electrochemical Thermoelectric Conversion with Polysulfide as Redox Species

et al. 2019

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Thermocells convert waste heat to electricity without any pollution; however, the high cost and corrosivity of redox species hinder their commercialization. In this work, a thermocell that utilizes abundant polysulfide as redox species was demonstrated for the first time. 1‐Butyl‐1‐methylpyrrolidinium polysulfide [(P14)2S3] was synthesized, and the redox species were prepared by the addition of sulfur to the (P14)2S3 solution in DMSO. In thermoelectric measurements, the Seebeck coefficient changed from −0.68 to +0.5 mV K−1 through addition of sulfur to the cell. Operando UV/Vis spectroscopy and open‐circuit voltage analysis revealed that this effect was attributed to the change in the dominating redox reactions by the addition of sulfur. This result also provides a thermodynamic view on polysulfides electrochemistry, which is of high importance for lithium–sulfur batteries.

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“…Furthermore, the alkyl substituent bound at the cation of the ionic liquid monomer 5 and 7 affects the polymerization process as well because of viscosity and mobility differences between the ionic liquid monomers bearing a variation of the alkyl substituent [16,17,27,28].…”

Section: Synthesis Of Cationic Homopolymers By Polymer Analogous Reacmentioning

confidence: 99%