Article
Chemistry, Applied
Zhaoxian Tang, Yanjing Gao, Shengling Jiang, Jun Nie, Fang Sun
Summary: In this study, four ethyl cinnamoylformate derivatives photoinitiators (ECFs) were designed and synthesized with good photobleaching ability and cytocompatibility. The research on the initiating and photobleaching mechanisms of ECFs under visible LED revealed their higher initiating rate compared to the commercial photoinitiator ITX. Furthermore, ECFs exhibited good photobleaching performance, migration stability, and cytocompatibility, and could initiate deep-layer photopolymerization under 455 nm LED.
PROGRESS IN ORGANIC COATINGS
(2022)
Article
Chemistry, Applied
Can Xu, Shang Gong, Xiang Wu, Yuwei Wu, Qiuyan Liao, Ying Xiong, Zhen Li, Hongding Tang
Summary: The development of carbazole-based photo-bleachable dyes as free radical initiators for visible light polymerization showed promising results in effectively initiating the photopolymerization of thick materials. Carbazole-based dyes like CM-2 and CI-2 demonstrated better free radical initiating efficiencies and successful polymerization of thick films under visible light irradiation. These findings suggest great potential for deep photocuring of thick materials using these dyes.
Article
Chemistry, Physical
Liqiang Li, Di Zhu, Xiaotong Peng, Pu Xiao
Summary: Photopolymerization is popular for its mild reaction conditions and controllability, but concerns about the leachability of photoinitiators have risen. A novel polymerizable photoinitiator was designed in this study, showing excellent migration stability and potential applications in biomedical and food packaging industries.
Review
Polymer Science
Frederic Dumur
Summary: Visible light photopolymerization has gained renewed interest due to its application in 3D printing. New structures disconnected from traditional photoinitiators are being widely examined for developing visible light photoinitiating systems. The parameters such as excited state lifetimes, redox properties, and molar extinction coefficients of newly prepared photoinitiators need to be considered for efficient interaction with additives in photocurable resins. Thiophene, widely used in Organic Electronics, is a potential candidate for visible light photoinitiators due to its low oxidation potential and easy chemical modification. Different types of thiophene-based photoinitiators have been developed over the years. This review provides an overview of recent advances in thiophene-based photoinitiators and compares them with reference photoinitiating systems to highlight their significance.
EUROPEAN POLYMER JOURNAL
(2022)
Article
Polymer Science
Frederic Dumur
Summary: Photopolymerization is currently a focused area of research due to the need for visible light-activated photoinitiating systems. Pyrrole has been identified as an interesting scaffold for designing various dyes and developing new formulations with fast polymerization kinetics, high monomer conversions, low energy consumption, and activation in the visible range.
EUROPEAN POLYMER JOURNAL
(2022)
Article
Polymer Science
Frederic Dumur
Summary: This review provides an overview of the recent developments concerning phenothiazine-based photoinitiators of polymerization, highlighting the evolution and structural changes of these molecules within photoinitiators. By comparing with reference photoinitiating systems, the pertinence of this approach is demonstrated.
EUROPEAN POLYMER JOURNAL
(2022)
Article
Engineering, Manufacturing
D. Zhu, X. Peng, P. Xiao
Summary: A photoinitiating system based on a blue food colorant, indigo carmine, was developed for 3D printing of biomedical materials, addressing safety and water solubility challenges.
ADDITIVE MANUFACTURING
(2022)
Article
Polymer Science
Frederic Dumur
Summary: This article provides a detailed review of the recent advances in benzylidene cyclopentanones, demonstrating a significant improvement in photoinitiating ability compared to their acyclic analogues.
EUROPEAN POLYMER JOURNAL
(2022)
Article
Polymer Science
Frederic Dumur
Summary: Photopolymerization under visible light has made significant progress in recent years, thanks to the development of new irradiation setups based on LEDs. Efficient photoinitiating systems that match the light sources used in 3D printers have become increasingly important. However, visible light photoinitiators, although they increase the thickness of the polymerized films, are often strongly colored compounds that hinder the use of photopolymers for everyday applications. To tackle this issue, the development of photobleachable photoinitiating systems has emerged as a promising research field. This review provides an overview of recent advances in photobleachable photoinitiators and discusses the exploration of various structures to address the challenge of achieving colorless coatings.
EUROPEAN POLYMER JOURNAL
(2023)
Article
Polymer Science
Frederic Dumur
Summary: This review presents an overview of different photoinitiators containing a triphenylamine unit, and demonstrates their significance through comparisons with benchmark photoinitiators.
EUROPEAN POLYMER JOURNAL
(2022)
Article
Chemistry, Applied
Lin Deng, Liuyan Tang, Jinqing Qu
Summary: Two novel visible light photoinitiators, PBO and BMPPO, were successfully designed and synthesized. The photoinitiating system of BMPPO/iodonium/amine demonstrated rapid polymerization and high vinyl group conversions under UV-LED, blue LED, and solar light irradiation. In addition, BMPPO showed rapid photobleaching and good biocompatibility, making it suitable for light-color coatings and food packaging.
PROGRESS IN ORGANIC COATINGS
(2022)
Review
Polymer Science
Frederic Dumur
Summary: In recent years, research efforts have focused on multicomponent photoinitiating systems, especially for the design of visible light photoinitiating systems. Monocomponent Type II photoinitiators have been designed to simplify the elaboration of photocurable resins. Sulfonium salts, as remarkable photoinitiators, lack absorption in the visible range, leading to various structural modifications for redshifting their absorptions. This work provides an overview of different sulfonium salts activable under visible light.
Article
Chemistry, Multidisciplinary
Florian Lind, Kirill Markelov, Armido Studer
Summary: This article introduces a photocleavable alcohol protecting group based on acyl silanes, which can be easily synthesized in three concise steps with high overall yield. The protection of alcohols occurs under mild conditions and can be removed through exposure to visible light. This approach demonstrates remarkable tolerance to diverse functional groups and showcases its robustness against various transformations.
Article
Chemistry, Physical
Binghui Bao, Jian You, Dongxiao Li, Haitao Zhan, Luhang Zhang, Mingyang Li, Tao Wang
Summary: In this study, four novel double benzylidene ketone dyes were synthesized and demonstrated to have good charge transfer characteristics and high absorption capability. These dyes can be used as photoinitiators or charge transfer sensitizers to initiate photopolymerization under specific light sources. The experiments showed that the dyes with polyarylamine groups exhibited high sensitization and initiation activities under specific light sources.
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
(2022)
Article
Polymer Science
Zheng Liu, Frederic Dumur
Summary: Simplification of photocurable resin is a major research challenge, and the complexity of formulations has hindered its industrial application. Coumarins are identified as a promising scaffold for designing photoinitiators, particularly oxime esters.
EUROPEAN POLYMER JOURNAL
(2022)
Article
Polymer Science
Markus Kury, Katharina Ehrmann, Christian Gorsche, Peter Dorfinger, Thomas Koch, Jurgen Stampfl, Robert Liska
Summary: By adjusting the radical curing mechanism using difunctional vinyl sulfonate esters, the final material properties of acrylate networks can be modified to obtain toughened 3D structured materials. The resulting materials show improved thermomechanical behavior compared to those regulated by state-of-the-art reagents such as thiols, with reduced shrinkage stress, warpage, higher conversion, and glass transition temperature.
POLYMER INTERNATIONAL
(2022)
Article
Polymer Science
Roland Taschner, Robert Liska, Patrick Knaack
Summary: This passage discusses the use of epoxides in coatings and their reactivity with onium salt initiators. The synthesized salts were characterized and some showed good reactivity and high conversion rates. Some new photochemically interesting cationic initiators were identified with potential applications in sensitization.
POLYMER INTERNATIONAL
(2022)
Article
Polymer Science
Yazgan Mete, Patrick Knaack, Robert Liska
Summary: This study focuses on the use of photoacid generators in the formation of polyesters, demonstrating the ability to quickly produce highly crystalline products in a short amount of time without solvents at elevated temperatures. Additionally, the influence of temperature on the crystallinity, molecular weights, and dispersities of the polymers is investigated and presented.
POLYMER INTERNATIONAL
(2022)
Article
Chemistry, Physical
Markus Lunzer, Joseph S. Beckwith, Franziska Chalupa-Gantner, Arnulf Rosspeintner, Giuseppe Licari, Wolfgang Steiger, Christian Hametner, Robert Liska, Johannes Froehlich, Eric Vauthey, Aleksandr Ovsianikov, Brigitte Holzer
Summary: A series of soluble and symmetric chalcogenophenes have been designed and synthesized as potential two-photon absorption initiators. The photophysical analysis reveals their good 2PA properties, especially the strong influence of selenium on 2PA cross sections, making them promising new 2PA photoinitiators. The efficiency and spectral versatility of two selenium-containing lead compounds have been confirmed through structuring and threshold tests, showing superior reactivity and dose compared to commercial initiators.
CHEMISTRY OF MATERIALS
(2022)
Article
Polymer Science
Yazgan Mete, Konstanze Seidler, Christian Gorsche, Thomas Koch, Patrick Knaack, Robert Liska
Summary: This study presents a novel approach to 3D print polyesters directly from ε-caprolactone via stereolithography at elevated temperatures. The introduction of low amounts of crosslinkers improves the stability of the structure while maintaining its degradability and semicrystallinity. The study also highlights the significant influence of the amount and type of crosslinker on the material properties.
POLYMER INTERNATIONAL
(2022)
Article
Polymer Science
Barbara Dellago, Altan Alpay Altun, Robert Liska, Stefan Baudis
Summary: Vinyl esters (VEs) have been extensively studied as monomers for additive manufacturing in tissue engineering due to their low cytotoxicity, good biocompatibility, and favorable degradation behavior. However, crosslinked VEs have poor mechanical properties, especially brittleness. A previous study found that covalently incorporating high molecular weight additives into the vinyl ester-thiol network can overcome this issue. In this work, poly(epsilon-caprolactone)-based additives modified with photopolymerizable end groups were used to improve the mechanical properties, specifically toughness, and to enable application in digital light processing stereolithography. Different toughness-enhancing additives and their effects on photochemical and (thermo)mechanical characteristics were investigated, as well as the impact of commercial flexible and synthesized rigid thiols on these properties. The results showed that the covalently incorporated toughness enhancers significantly improved the mechanical properties, particularly tensile toughness, without sacrificing photoreactivity.
JOURNAL OF POLYMER SCIENCE
(2023)
Correction
Polymer Science
Benjamin Grob, Benedikt Frieser, Robert Liska, Yohann Catel
EUROPEAN POLYMER JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Katharina Gallas, Dominik Wohlmuth, Zhiquan Li, Aliasghar Ajami, Aleksandr Ovsianikov, Robert Liska, Christian Slugovc
Summary: This study reports the synthesis of two dye-labeled azides through de-symmetrization using a copper (I)-catalyzed alkyne-azide cycloaddition (CuAAC) method. Dansyl derivative and perylene diimide derivative with alkyne functional groups were employed as the fluorescent dyes. The photo-physical properties of these dye dyads were described, and their performance in multi-photon grafting onto polyethylene glycol-based hydrogels was investigated. It was found that the dansyl-conjugated BAC derivative was suitable for multi-photon grafting with lasers operating at 800 nm, while the perylene diimide-bearing dye did not yield the desired result.
MONATSHEFTE FUR CHEMIE
(2023)
Article
Chemistry, Applied
Stephan Schandl, Thomas Koch, Juergen Stampfl, Katharina Ehrmann, Robert Liska
Summary: Aliphatic polycarbonates are highly regarded for being sustainable, biodegradable, and biocompatible. Recently, photobase generators have made cyclic carbonates available for light-induced anionic ring-opening polymerization, leading to the formation of pure aliphatic polycarbonate networks. The polymerization mechanism was investigated using photo-DSC and photorheology on synthesized cyclic carbonates. Different ratios of reactive diluent to crosslinker were tested to obtain materials with tunable mechanical properties.
REACTIVE & FUNCTIONAL POLYMERS
(2023)
Article
Chemistry, Inorganic & Nuclear
Christa Grogger, Michaela Flock, Madeleine Heurix, Ana Torvisco, Andreas W. W. Kyri, Harald Stueger
Summary: This study reports the synthesis of a series of backbone silylated 1,3-dialkylimidazol-2-thiones. The developed synthesis protocol involves the silylation of N,N-dimethylimidazol-2-thione 1 followed by the addition of organochlorosilanes RnSiCl4-n (R=Me, Ph; n=0-4), enabling the synthesis of the C-silylated derivatives with monocyclic, silyl-bridged, or fused tricyclic structures. Reactivity studies have shown stable silicon-vinyl bonds and reactivity patterns similar to the unsilylated species. Combined UV-spectroscopic and computational studies indicate minimal impact of the silyl substituents on the electronic structure of the imidazol-2-thione ring.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Applied
Lisa Staubmann, Agnes Mistlberger-Reiner, El Mehdi Raoui, Gertrude Brunner, Lisa Sinawehl, Marion Winter, Robert Liska, Marc Pignitter
Summary: This study investigates the stabilizing effects of pectin, guar gum, locust bean gum, and their combinations on ready-to-drink beverages containing 7% orange juice. Results show that in beverages with larger juice particles (0.6-200 μm), using 2.5 g pectin and 2.5 g guar gum per kg base is most suitable for stabilizing turbidity, while in beverages with smaller juice particles (0.5-120 μm), using 2 g pectin or 2.5 g pectin and 2.5 g locust bean gum per kg base can maintain stability. The combination of hydrocolloids has greater effects on long-term storage stability of the beverages compared to individual stabilizers.
FOOD HYDROCOLLOIDS
(2023)
Article
Engineering, Manufacturing
Viola Hobiger, Anna-Lea Kutsch, Juergen Stampfl, Robert Liska, Stefan Baudis, Peter Krajnc
Summary: A highly reactive thiol-ene high internal phase emulsion was developed for light-driven additive manufacturing, resulting in highly porous customizable poly(high internal phase emulsion) materials. The formulation facilitates short irradiation times and low amounts of photoinitiator, while avoiding the need for harmful solvents. The addition of a selected thiol as a chain-transfer agent improves the brittleness of the acrylate-based system and potential oxygen inhibition, producing printed layers with a thickness<50 μm and an average pore size<5 μm.
3D PRINTING AND ADDITIVE MANUFACTURING
(2023)
Article
Materials Science, Multidisciplinary
Roland Taschner, Thomas Koch, Raffael Wolff, Juergen Stampfl, Robert Liska, Patrick Knaack
Summary: Sulfonium hexafluorophosphates and perfluorinated tetraphenylborates are established initiators in cationic photopolymerization. The cyanide-ligated borane-based photoinitiator B2 outperforms commercial initiators in terms of molecular weight, cost, and reactivity. In addition, B2 shows excellent thermal and storage stability, and can be sensitized by anthracene derivatives. When used in hot lithography at 90°C, B2 exhibits superior layer quality and coloration compared to existing sulfonium initiators.
ACS APPLIED POLYMER MATERIALS
(2023)
Article
Polymer Science
Larissa Alena Ruppitsch, Jakob Ecker, Thomas Koch, Katharina Ehrmann, Juergen Stampfl, Robert Liska
Summary: Supramolecular polymers play a significant role in influencing dynamic mechanical properties in slightly crosslinked polymer networks. The introduction of 2-ureido-4[1H]-pyrimidinones (UPy) as supramolecular building blocks in photopolymerizable systems brings about dynamic behavior. This study investigates the impact of UPy-motif on reactivity and (thermo)mechanical properties through various testing methods. Furthermore, the UPy-based photopolymerizable system is successfully applied in Hot Lithography printing to create complex 3D-printed parts with high precision.
JOURNAL OF POLYMER SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Roland Taschner, Thomas Koch, Raffael Wolff, Jurgen Stampfl, Robert Liska, Patrick Knaack
Summary: Sulfonium hexafluorophosphates and perfluorinated tetraphenylborates are commonly used initiators in cationic photopolymerization and have been applied in 3D-printing at high temperatures. The cyanide-ligated borane-based photoinitiator B2 shows higher reactivity and lower cost compared to other borates. B2 exhibits excellent performance in epoxy monomer conversions at a wide range of temperatures. In addition, B2-based formulations are stable and can be sensitized by anthracene derivatives. B2 also outperforms existing sulfonium initiators in terms of layer quality and coloration in hot lithography.
ACS APPLIED POLYMER MATERIALS
(2023)
