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36. A Methylene Blue/Sodium Sulfinate Photo‐Initiating System for the Red‐Light Emulsion Photopolymerization of Methyl Methacrylate.

Author

Kalout, Hanine, Lansalot, Muriel, Bourgeat‐Lami, Elodie, Morlet‐Savary, Fabrice, Lacôte, Emmanuel, and Lalevée, Jacques

Subjects
METHYL methacrylate, POLYMERIZATION kinetics, METHYLENE blue, MIE scattering, PHOTOPOLYMERIZATION
Abstract

The emulsion photopolymerization of methyl methacrylate (MMA) using red light is reported. The synthesis of poly(methyl methacrylate) (PMMA) latexes is initiated by irradiation of a new, very efficient red‐absorbing methylene blue (MB)/sodium para‐toluenesulfinate (NapTS) system in the red region (660 nm). Visible, and especially red light penetrates the dispersed medium imposed by the emulsion process better than ultra‐violet photons (UVs). However, emulsion photopolymerizations require the development of fully water‐soluble initiating systems activable by red light, which is still hugely challenging because red photons are much less energetic, therefore generally lead to less efficient photochemical processes. The influence of the surfactant concentration and the solids content is examined over particle sizes and polymerization kinetics. The polymerizations work for solids contents between 10 and 25 wt%, with narrowly distributed particles of average sizes ranging from 40 to 65 nm. Calculations of Mie scattering support the observation that at a given wavelength the larger the particles the lower the penetration. All latexes obtained are slightly blue, which are traced to the regeneration of MB when the latexes are exposed to dioxygen. The dye regeneration enables the reactivation of the photopolymerization process. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Towards Photocrosslinkable Lyotropic Blends of Organosolv Lignin and Hydroxypropyl Cellulose for 3D Printing by Direct Ink Writing.

Author

Yapa, Mehmet-Talha, Lalevée, Jacques, and Laborie, Marie-Pierre

Subjects
*PRINTING ink, *THREE-dimensional printing, *HYDROXYL group, *BIOPOLYMERS, *PHOTOCROSSLINKING
Abstract

Polymer blends containing up to 70% organosolv lignin content and lyotropic cellulose derivatives have been established as "lignin inks" for direct ink writing of fully biobased 3D parts. However, a fast-crosslinking mechanism is needed to improve throughput and design space. In this paper, UV-photocrosslinkable organosolv lignin/hydroxypropyl cellulose inks are formulated through doping with common photocrosslinkers. The most potent photocrosslinkers for neat hydroxypropyl cellulose, lignin and their blends are determined through a series of DOEs. Hydroxypropyl cellulose is significantly more amenable to photocrosslinking than organosolv lignin. The optimal photocrosslinkable ink formulations are printable and exhibit up to 70% gel content, although thermal post-curing remains essential. Chemical, thermal, and mechanical investigations of the photocrosslinked 3D parts evidence efficient crosslinking of HPC through its hydroxyl groups, while lignin appears internally plasticized and/or degraded during inefficient photocrosslinking. Despite this, photocrosslinkable inks exhibit improved tensile properties, shape flexibility, and fidelity. The heterogeneous crosslinking and residual creep highlight the need to further activate lignin for homogeneous photocrosslinking in order to fully exploit the potential of lignin inks in DIW. [ABSTRACT FROM AUTHOR]

Published
2024
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38. Acridone Derivatives for Near-UV Radical Polymerization: One-Component Type II vs. Multicomponent Behaviors.

Author

Noon, Adel, Calogero, Francesco, Gualandi, Andrea, Hammoud, Hiba, Hamieh, Tayssir, Toufaily, Joumana, Morlet-Savary, Fabrice, Schmitt, Michael, Cozzi, Pier Giorgio, and Lalevée, Jacques

Subjects
LIGHT emitting diodes, FREE radicals, CYCLIC voltammetry, IODONIUM salts, ACRYLATES, ELECTRON paramagnetic resonance spectroscopy
Abstract

In this work, two novel acridone-based photoinitiators were designed and synthesized for the free radical polymerization of acrylates with a light-emitting diode emitting at 405 nm. These acridone derivatives were employed as mono-component Type II photoinitiators and as multicomponent photoinitiating systems in the presence of an iodonium salt or an amine synergist (EDB) in which they achieved excellent polymerization initiating abilities and high final conversions of the acrylate group. Photoinitiation mechanisms through which reactive species are produced were investigated employing different complementary techniques including steady-state photolysis, steady-state fluorescence, cyclic voltammetry, UV–visible absorption spectroscopy, and electron spin resonance spectroscopy. Finally, these molecules were also used in the direct laser writing process for the fabrication of 3D objects. [ABSTRACT FROM AUTHOR]

Published
2024
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39. NIR‐induced upconversion‐assisted photopolymerization: Key factors, challenges, and future directions.

Author

Kandeloos, Amirhossein Jalali, Bastani, Saeed, Ghahari, Mehdi, Jalili, Mojtaba, and Lalevée, Jacques

Subjects
RADIATION curing, PHOTOPOLYMERIZATION, DOUBLE bonds, RESEARCH personnel, LUMINESCENCE
Abstract

NIR‐induced upconversion‐assisted photopolymerization has gained growing attention in the past two decades because of its numerous advantages over conventional UV/visible photopolymerization and two‐photon polymerization processes. However, research in this area is still in its early stages. To extend the practical application of NIR‐induced radiation curing, it is essential to optimize the factors affecting the photopolymerization reactions. Researchers have been constantly trying to improve these factors to tune the photo‐physical characteristics (luminescence intensity and color) of upconversion particles (UCPs), enhance curing depths and degree of double bond conversion (DC), and investigate the application of UCPs in emerging fields. In this review, first, a brief discussion of the upconversion mechanisms and upconversion efficiency is provided. Then, a detailed discussion of the factors influencing the upconversion‐assisted photopolymerization comprising UCP nature and characteristics, UCP content, presence of fillers/pigments/additives, laser intensity, photoinitiator content, and maximum absorption wavelength of photoinitiator is provided, and recent progress in improving these factors is presented. Finally, the advantages and drawbacks of the UC‐initiated polymerization are discussed, and perspectives for future directions are suggested. Highlights: NIR‐induced upconversion‐assisted photopolymerization garners growing interest.Influential factors in upconversion‐assisted photopolymerization are thoroughly discussed.The recent progress on improving these factors and the future directions are provided. [ABSTRACT FROM AUTHOR]

Published
2024
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