Radical Initiator Research Articles

Initial surgical performance in robot-assisted radical prostatectomy is associated with clinical outcomes and learning curves.

The association between surgical performance ratings and clinical outcomes in robotic surgery is poorly understood. Additionally, no studies have reported on the relationship between the surgeon's initial case-skill evaluation and the learning curve in robot-assisted surgery. We evaluated whether an objective surgical technique evaluation score for initial robot-assisted radical prostatectomy (RARP) was associated with clinical outcomes and surgeons' learning curves. Six surgeons who were trained in and started to perform RARP at our institution were included. Anonymized, unedited videos of each surgeon's 10th RARP case were evaluated by three reviewers, using modified Objective Structured Assessment of Technical Skill (OSATS) scores. We then divided the surgeons into two groups on the basis of these OSATS scores. We retrospectively compared the clinical outcomes and learning curves of the console time of the two groups for consecutive RARPs, performed from March 2018 to July 2023. We analyzed 258 RARPs (43 cases/surgeon), including 129 cases performed by high-OSATS score surgeons (18.2-19.3 points) and 129 cases performed by low-OSATS score surgeons (11.9-16.0 points). Overall, the high-OSATS score group had significantly shorter operation and console times than the low-OSATS score group did (both P < 0.01) and their patients' rate of continence recovery by 3months post-RARP was significantly higher (P = 0.03). However, complications, blood loss, and positive margins did not differ between the groups (P = 0.08, P = 0.51, and P = 0.90, respectively). The high-OSATS score group had a significantly shorter console time than the low-OSATS score group did after the 11-20 cases. The OSATS score in early RARP cases can predict subsequent surgical outcomes and surgeons' learning curves.

Improved Performance of Polylactic Acid Biocomposites at High Lignin Loadings through Glycidyl Methacrylate Grafting of Melt-Flowable Organosolv Lignin.

Glycidyl methacrylate (GMA) was grafted onto a melt-flowable organosolv lignin, called bioleum (BL), using a melt mixing process. Then, up to 40 wt % of BL-g-GMA was blended with polylactic acid (PLA) in the presence of dicumyl peroxide as a free radical initiator utilizing a melt extrusion method. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and tensile testing were performed to characterize the biocomposites' performance. The FTIR results revealed a successful grafting of GMA onto BL. Overall, BL and PLA compatibility increased significantly with the grafting and resulted in decreased domain size of BL-g-GMA and thus enhanced all the tensile properties (strength, modulus, and elongation at break) at BL loadings as high as 40 wt %. For instance, in the biocomposites containing 30 wt % BL, the GMA grafting increased the tensile strength by 23%. The presence of BL and BL-g-GMA hindered PLA's crystallization even when it was cooled at a rate of 1 °C/min. However, the composites with BL-g-GMA showed a crystallinity value comparable to that of PLA during isothermal crystallization, but with a slower crystallization rate. This work reveals a facile and scalable method that can be adopted to enhance the performance of lignin-based biocomposites.

A Minimalist Method for Fully Oxygen-Tolerant RAFT Polymerization through Sulfur-Centered Trithiocarbonate Radical Initiation.

In recent years, the fully oxygen-tolerant reversible deactivation radical polymerization (RDRP) has become a highly researched area. In this contribution, a new and minimalist method is successfully employed to accomplish fully oxygen-tolerant reversible addition-fragmentation chain transfer (RAFT) polymerization using bis(trithiocarbonate) disulfides (BisTTC) as an iniferter agent, where the released sulfur-centered trithiocarbonate (TTC) radical can initiate monomer. Furthermore, polymerization kinetics revealed the typical "living" features of this polymerization system. More importantly, by high-throughput screening, it is found that dodecyl-substituted TTC is responsible for the fully oxygen-tolerant RAFT polymerization though trithiocarbonate radical initiation and R radical deoxygenation. It is believed that trithiocarbonate radical initiation strategy provides a powerful and minimalist tool for fully oxygen-tolerant RDRPs.

Effect of graphite oxide on the mechanical, thermal, structural and hydrophilicity proprieties of Polypropylene / Poly(Propylene-Glycol) Acrylate / Glycidyl Methacrylate PP/PPGA/GMA composite

This research aims to investigate the synergistic effects of grafting flexible fractions and incorporating reinforcing fillers in polypropylene (PP) matrix. The primary objective is to establish an experimental methodology for preparing and characterizing Polypropylene / Poly(Propylene-Glycol) Acrylate / Glycidyl Methacrylate (PP/PPGA/GMA) composites loaded with graphite oxide (GtO).The process of oxidizing natural graphite powder using a mixture of sulfuric acid and nitric acid was validated through various analytical techniques including IRTF, AFM, DRX, XRF and ATG. The grafting reaction of PPGA and GMA on polypropylene and the incorporation of graphite oxide with varying levels were carried out in the melt state in a Brabender internal mixer; Dicumyl peroxide (DCP) was used as a radical initiator. A comprehensive assessment of the obtained materials was conducted through conventional analyses encompassing mechanical properties (tensile and impact), thermal behaviors (ATG and DSC), morphological characteristics (SEM) and the chemical state of film surfaces (Contact angle).The investigation revealed two key outcomes. Firstly, it showcased the grafting effect of PP on the polymer's morphology and properties. Secondly, it underscored the consequential impact of incorporating graphite oxide on the overall behavior of produced materials.

Radical-Mediated Trifunctionalization Reactions.

Synthetic radicals have intrinsic power for cascading and multifunctional reactions to construct diverse molecular scaffolds. In the previous review series, we covered 1,2-difunctionalizations, remote 1,3-, 1,4-, 1,5-, 1,6-, and 1,7-difunctionalizations, addition followed by cyclization reactions, and cycloaddition-initiated difunctionalizations. Presented in this paper are radical addition-initiated trifunctionalization reactions of alkenes, alkynes, and their derivatives. After the initial radical addition, there are different pathways, such as group or hydrogen atom transfer, cyclization, and radical coupling, to complete the second and third functionalizations.

Strain-Releasing Ring-Opening Diphosphinations for the Synthesis of Diphosphine Ligands with Cyclic Backbones.

Diphosphine ligands based on cyclobutane, bicyclo[3.1.1]heptane, and bicyclo[4.1.1]octane were synthesized from the corresponding highly strained, small, cyclic organic molecules, i.e., bicyclo[1.1.0]butane, [3.1.1]propellane, and [4.1.1]propellane, employing a ring-opening diphosphination. Under photocatalytic conditions, the three-component reaction of a diarylphosphine oxide, one of the aforementioned strained molecules, and a diarylchlorophosphine results in the smooth formation of the corresponding diphosphines in high yield. The obtained diphosphines can be expected to find applications in functional molecules due to their unique structural characteristics, which likely impart specific properties on their associated metal complexes and coordination polymers (e.g., a zigzag-type structure). The feasibility of the initial radical addition can be estimated using density-functional-theory calculations using the artificial force induced reaction (AFIR) method. This study focuses on the importance of integrating experimental and computational methods for the design and synthesis of new diphosphination reactions that involve strained, small, cyclic organic molecules.

K2S2O8-Mediated or Azobisisobutyronitrile-Catalyzed Regioselective Aerobic Oxidative Cleavage of 1-Arylbutadienes to Cinnamaldehydes.

This work reveals the regioselective oxidative cleavage of 1-arylbutadienes to cinnamaldehydes mediated by K2S2O8 or catalyzed by azobisisobutyronitrile, a very common free radical initiator, in an easy to handle, simple procedure and free of transition metals. This approach demonstrates excellent regioselectivity, mild reaction conditions, and compatibility with a broad range of functional groups (45 examples).

Preparation and properties of biomass castor oil polyurethane films

In order to investigate the optimal conditions for the formation of castor oil-based polyurethane (CO-PU) films and their comprehensive performance, a series of experiments were carried out utilising biomass castor oil (CO) as the main reactant, 4,4-diphenylmethane diisocyanate (MDI) as the other main reactant, benzoyl peroxide (BPO) as the radical initiator, and dibutyltin dilaurate (DBTDL) as the catalyst. The CO-PUs with different R-values (the number ratio of –NCO/–OH substances) were prepared by pre-polymerisation under single-variable control. The effects of different R-values, DBTDL contents and curing temperatures on the mechanical properties and film-forming state of the CO-PUs were then investigated. Finally, the liquid-resistant medium properties and thermo-gravimetric analyses of CO-PU films were investigated. The experimental results demonstrate that when the R value is 2.5, the DBTDL content is 0.1 ‰, and the curing temperature of the film-forming process is 80 °C, the tensile strength and elongation at break of the CO-PU film are 36.4 MPa and 49.05 % respectively, and the hardness of the pencil at this time is 6H. The water absorption rate is 0.01 %, and the contact angle of water is up to 83.5°. CO-PU displays a commendable resistance to sulfuric acid, sodium hydroxide, and ethyl acetate. Additionally, CO-PU exhibits a high thermal decomposition temperature. The comprehensive performance of CO-PU can be enhanced by modifying the film-forming conditions of CO-PU, which paves the way for further expansion of the applications of CO-PU in the future.

Conjugation of Lysozyme and Epigallocatechin Gallate for Improving Antibacterial and Antioxidant Properties.

One of the main interests in the food industry is the preservation of food from spoilage by microorganisms or lipid oxidation. A novel alternative is the development of additives of natural origin with dual activity. In the present study, a chemically modified lysozyme (Lys) with epigallocatechin gallate (EGCG) was developed to obtain a conjugate (Lys-EGCG) with antibacterial/antioxidant activity to improve its properties and increase its application potential. The modification reaction was carried out using a free radical grafting method for the Lys modification reaction, using ascorbic acid and hydrogen peroxide as radical initiators in an aqueous medium. The synthesis of Lys-EGCG conjugate was confirmed by spectroscopic (FT-IR, 1H-RMN, and XPS) and calorimetry differential scanning (DSC) analyses. The EGCG binding to the Lys biomolecule was quantified by the Folin-Ciocalteu method; the antibacterial activity was evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MCB) against Staphylococcus aureus and Pseudomonas fluorescens; the antioxidant activity was evaluated by ABTS, DPPH, and FRAP. The spectroscopic results showed that the Lys-EGCG conjugate was successfully obtained, and the DSC analysis revealed a 20°C increase (P < 0.05) in the denaturation temperature of Lys due to EGCG modification. The EGCG concentration in Lys-EGCG was 97.97 ± 4.7µmol of EGCG/g of sample. The antibacterial and antioxidant activity of the Lys-EGCG conjugate was higher (P < 0.05) than pure EGCG and Lys. The chemical modification of Lys with EGCG allows for the bioconjugate with a dual function (antibacterial/antioxidant), broadening the range of Lys and EGCG applications to different areas such as food, cosmetic, and pharmaceutical industries.

Step-growth irreversible deactivation radical polymerization: synergistic developments with chain-growth reversible deactivation radical polymerization

Abstract Recent advances in chain-growth reversible deactivation radical polymerization (CG-RDRP), i.e. the so-called “living radical polymerization”, have synergistically developed step-growth radical polymerizations via controlled formation of radical species from covalent bonds followed by irreversible deactivation of the resulting radical species. The monomers for radical polyaddition are thus designed to possess carbon–halogen or thioester bonds, which can generate radical species in the presence of transition metal catalysts and radical initiators, as well as carbon‒carbon double bonds, which will irreversibly form carbon–halogen or thioester bonds. Radical polycondensations are achievable via radical coupling reactions of carbon-centered radicals generated from carbon–halogen bonds or radical quenching reactions with nitroxides. Furthermore, radical addition-condensation polymerizations are achieved by a sequence of reactions, i.e. the formation of radical species from carbon–halogen bonds, radical addition to nitroso or thiocarbonylthio compounds, and coupling or quenching reactions with the resulting stable radical. These step-growth irreversible deactivation radical polymerizations (SG-IDRP) enable the synthesis of a variety of polymers, such as polyethers, polyesters, polyamides, and polyimides, which have aliphatic, aromatic, polar, and degradable groups in their main chains. Sequence-regulated vinyl polymer structures can also be constructed by designing monomers. Combinations with CG-RDRPs further lead to unique hybrid block, multiblock, graft, hyperbranched, and network polymers.

Threonine Aldolase-Catalyzed Enantioselective α-Alkylation of Amino Acids through Unconventional Photoinduced Radical Initiation.

Visible light-driven pyridoxal radical biocatalysis has emerged as a promising strategy for the stereoselective synthesis of valuable noncanonical amino acids (ncAAs). Previously, the use of well-tailored photoredox catalysts represented the key to enable efficient pyridoxal phosphate (PLP) enzyme-catalyzed radical reactions. Here, we report a PLP-dependent threonine aldolase-catalyzed asymmetric α-C-H alkylation of abundant amino acids using Katritzky pyridinium salts as alkylating agents. The use of engineered threonine aldolases allowed for this redox-neutral radical alkylation to proceed efficiently, giving rise to challenging α-trisubstituted and -tetrasubstituted ncAA products in a protecting-group-free fashion with excellent enantiocontrol. Mechanistically, this enantioselective α-alkylation capitalizes on the unique reactivity of the persistent enzymatic quinonoid intermediate derived from the PLP cofactor and the amino acid substrate to allow for novel radical C-C coupling. Surprisingly, this photobiocatalytic process does not require the use of well-established photoredox catalysts and operates through an unconventional photoinduced radical generation involving a PLP-derived aldimine. The ability to develop photobiocatalytic reactions without relying on classic photocatalysts or photoenzymes opens up new avenues for advancing stereoselective intermolecular radical reactions that are not known in either organic chemistry or enzymology.

Aggregation of positively charged poly(methyl methacrylate) latex particles in the presence of trifluoromethanesulfonate anion

Abstract We investigated the unique aggregation behavior of 3 types of positively charged poly(methyl methacrylate) (PMMA) latex particles in the presence of a trifluoromethanesulfonate (triflate) anion. The particles were prepared based on surfactant-free emulsion polymerization using azo radical initiators. The triflate anion was strongly adsorbed to surfaces of positively charged PMMA latex particles, as confirmed by electrophoresis. Additionally, its presence significantly reduced the critical coagulation concentration of the cationic PMMA latex particles compared with other anions.

Boosting gas-phase radical reactions for efficient oxidative dehydrogenation of propane over boron-based macropore catalyst

Efficiently boosting gas-phase radical reactions in the oxidative dehydrogenation of propane (ODHP) over boron-based catalysts requires the initiation, release, and propagation of radicals to work in a concerted manner within the catalytic system. To address this challenge, we developed a three-dimensional ordered macropore (3DOM) Al2O3 supported B2O3 catalyst. This unique design allows for the initiation, release, and propagation of radical reactions to take place within the macropore. By effectively balancing these processes, the designed catalyst demonstrated improved efficiency. The propane conversion over the B2O3/3DOM-Al2O3 catalyst with a pore size of 0.8 μm increased from 10 % to 25 % compared to that over the catalyst without the macropore. We attribute this enhancement to the ability of the 3DOM structure to facilitate the quick release of radicals from the B2O3 on the macropore surface into the same or nearby macropore within the 3DOM support. This efficient release of radicals minimizes the quenching losses that typically occur during the release process and ensures their efficient utilization in subsequent gas-phase radical reactions. This discovery offers a promising way for the development and optimization of boron-based catalysts for ODH of alkane.

Visible Light-Induced Copper-Catalyzed Regio- and Stereoselective Difluoroalkylthiocyanation of Alkynes.

The first regio- and stereoselective difluoroalkylthiocyanation of alkynes with BrCF2R and KSCN has been disclosed under visible light-induced copper catalysis. The copper complex photosensitizer formed in situ not only promotes the generation of CF2-alkyl radicals but also facilitates the construction of C-SCN bonds, allowing the reaction to proceed smoothly without any additional photocatalysts or radical initiators. Moreover, the challenging internal alkynes can also be transformed to deliver CF2-derived tetrasubstituted olefins with potential applications in agricultural and medicinal chemistry.

Exploiting Photoinduced Atom Transfer Radical Polymerizations with Boron-Dopant and Nitrogen-Defect Synergy in Carbon Nitride Nanosheets.

Graphitic carbon nitrides (g-C3N4) possess various benefits as heterogeneous photocatalysts, including tunable bandgaps, scalability, and chemical robustness. However, their efficacy and ongoing advancement are hindered by challenges like limited charge-carrier separation rates, insufficient driving force for photocatalysis, small specific surface area, and inadequate absorption of visible light. In this study, boron dopants and nitrogen defects synergy are introduced into bulk g-C3N4 through the calcination of a blend of nitrogen-defective g-C3N4 and NaBH4 under inert conditions, resulting in the formation of BCN nanosheets characterized by abundant porosity and increased specific surface area. These BCN nanosheets promote intermolecular single electron transfer to the radical initiator, maintaining radical intermediates at a low concentration for better control of photoinduced atom transfer radical polymerization (photo-ATRP). Consequently, this method yields polymers with low dispersity and tailorable molecular weights under mild blue light illumination, outperforming previous reports on bulk g-C3N4. The heterogeneity of BCN enables easy separation and efficient reuse in subsequent polymerization processes. This study effectively showcases a simple method to alter the electronic and band structures of g-C3N4 with simultaneously introducing dopants and defects, leading to high-performance photo-ATRP and providing valuable insights for designing efficient photocatalytic systems for solar energy harvesting.

Cleavable azobenzene linkers for the design of stimuli-responsive materials.

The azo linkage (NN) is one of the very few functional groups in organic chemistry that exhibits sensitivity towards thermal, chemical, photochemical, and biological stimuli. Consequently, this property has given rise to a distinct class of responsive materials. For example, thermal sensitivity has led to generation of free radical initiators useful in curing and polymerization applications. Chemically-induced cleavage has aided the development of self-immolative polymers and reactive scaffolds for proteomics applications. Photo-isomerization capability has given rise to photo-responsive systems. Azobenzene cleavage in biologically reducing environments, such as that of the colon, and under tumor hypoxia conditions has led to diagnostic, therapeutic, and delivery materials. Such conditions have also allowed for control over formation (assembly) and disruption (disassembly) of micellar nanoparticles. The aim of this review article is to look beyond the prevalent photosensitivity aspect of the aromatic azo compounds and draw attention to the azo scission reaction as a trigger of the change in the structure and properties of organic materials. Thus, the main discussion begins with the mechanism of the reductive cleavage. Then, its application in the design of molecules that can be activated as drugs and fluorescent sensors, (nano)materials with potential to release active substances, and polymers with side-chain and main-chain self-immolative capacity is discussed. Finally, the status and future challenges in this field are discussed.

Thermodynamic and kinetic models for the photolytic and hydrolytic degradation of picaridin: A computational and theoretical study

The popularity of insect repellents presents the opportunity for continuous human and environmental exposure to such chemical mixtures. Consequently, the effects of their chemical components on human health and environmental safety is significantly reliant on their stability and hence, residence times under typical environmental conditions. Hence, for the first time, a thorough density functional theoretical (DFT) study on some possible hydrolytic and photolytic degradation pathways is presented and applied in the derivation of a comprehensive kinetic model, allowing evaluation of the residence time of picaridin; a very popular insect repellent. These results show that picaridin undergoes very slow hydrolysis via two pathways which present activation free energy barriers (ΔG‡) of ca. 225 and ca. 247 kJ mol−1 due to the asynchronous formation of four-membered cyclic activated complexes in both cases. Similarly, their photolytic transformations occur via two pathways, both of which are limited by the formation of the initial radical cation.

Comparative Effect of Antioxidant and Antibacterial Potential of Zinc Oxide Nanoparticles from Aqueous Extract of Nepeta nepetella through Different Precursor Concentrations.

Antibiotic resistance is a global health crisis caused by the overuse and misuse of antibiotics. Accordingly, bacteria have developed mechanisms to resist antibiotics. This crisis endangers public health systems and medical procedures, underscoring the urgent need for novel antimicrobial agents. This study focuses on the green synthesis of ZnO nanoparticles (NPs) using aqueous extracts from Nepeta nepetella subps. amethystine leaves and stems, employing different zinc sulfate concentrations (0.5, 1, and 2 M). NP characterization included transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), along with Fourier transform infrared spectroscopy (FTIR) analysis. This study aimed to assess the efficacy of ZnO NPs, prepared at varying concentrations of zinc sulfate, for their capacity to inhibit both Gram-positive and Gram-negative bacteria, as well as their antioxidant potential using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. SEM and TEM results showed predominantly spherical NPs. The smallest size (18.5 ± 1.3 nm for leaves and 18.1 ± 1.3 nm for stems) occurred with the 0.5 M precursor concentration. These NPs also exhibited remarkable antibacterial activity against both Gram-positive and Gram-negative bacteria at 10 µg/mL, as well as the highest antioxidant activity, with an IC50 (the concentration of NPs that scavenge 50% of the initial DPPH radicals) of 62 ± 0.8 (µg/mL) for the leaves and 35 ± 0.6 (µg/mL) for the stems. NPs and precursor concentrations were modeled to assess their impact on bacteria using a 2D polynomial equation. Response surface plots identified optimal concentration conditions for antibacterial effectiveness against each species, promising in combating antibiotic resistance.

Nucleoside Cation Radicals: Generation, Radical-Induced Hydrogen Atom Migrations, and Ribose Ring Cleavage in the Gas Phase.

Nucleoside ions that were furnished on ribose with a 2'-O-acetyl radical group were generated in the gas phase by multistep collision-induced dissociation of precursor ions tagged with radical initiator groups, and their chemistry was investigated in the gas phase. 2'-O-Acetyladenosine cation radicals were found to undergo hydrogen transfer to the acetoxyl radical from the ribose ring positions that were elucidated using specific deuterium labeling of 1'-H, 2'-H, and 4'-H and in the N-H and O-H exchangeable positions, favoring 4'-H transfer. Ion structures and transition-state energies were calculated by a combination of Born-Oppenheimer molecular dynamics and density functional theory and used to obtain unimolecular rate constants for competitive hydrogen transfer and loss of the acetoxyl radical. Migrations to the acetoxyl radical of ribose hydrogens 1'-H, 2'-H, 3'-H, and 4'-H were all exothermic, but product formation was kinetically controlled. Both Rice-Ramsperger-Kassel-Marcus (RRKM) and transition-state theory (TST) calculations indicated preferential migration of 4'-H in a qualitative agreement with the deuterium labeling results. The hydrogen migrations displayed substantial isotope effects that along with quantum tunneling affected the relative rate constants and reaction branching ratios. UV-vis action spectroscopy indicated that the cation radicals from 2'-O-acetyladenosine consisted of a mixture of isomers. Radical-driven dissociations were also observed for protonated guanosine, cytosine, and thymidine conjugates. However, for those nucleoside ions and cation radicals, the dissociations were dominated by the loss of the nucleobase or formation of protonated nucleobase ions.

PTFE-g-GMA graft copolymer synthesis promoted by oxidative gamma-rays method and characterization

The functionalization of polymeric matrices through graft polymerization offers various advantages by providing new properties, allowing for additional chemical reactions that the matrix alone could not undergo or that would require drastic chemical conditions to occur. In this work, epoxy groups were incorporated through a graft polymer of poly(glycidyl methacrylate), using a prefunctionalization with peroxide groups in the polytetrafluoroethylene matrix through gamma radiation. These peroxide groups were subsequently used as radical chemical initiators in the graft polymerization reaction of glycidyl methacrylate. The graft polymerization reaction was studied based on the absorbed dose, monomer concentration, reaction time, and temperature.Graphical abstract