Charge transfer complexes as dual thermal/photo initiators for <scp>free‐radical</scp> frontal polymerization

Gary, Daniel P.; Ngo, Douglas T; Bui, Amber

doi:10.1002/pol.20210913

Cited by 14 publications

(16 citation statements)

References 44 publications

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“…Four main ignition categories exist for frontal free-radical polymerizations: thermal, 29,33,44,46,50,67,75,76,78,[88][89][90]92,125,132,165,[198][199][200][201][202]205 photo, [55][56][57]133,165,250,252,254,[257][258][259][260][261][262][263][264] plasma, [265][266][267] and magnetocaloric. 201,234 Thermal triggering typically involves the use of a soldering iron or oil bath to heat a localized region.…”

Section: Ignition Techniquesmentioning

confidence: 99%

“…Photoinitiators follow the same mechanism as that described above for epoxide ring-opening polymerizations (Section 4.2.1), where a mixture of UV-active and thermal radical sources provide more uniform radical concentrations. [55][56][57]133 Recent work from Gary et al 250 demonstrated that the inclusion of iodonium PAG salts enable both photo and thermal initiation modes with acrylate monomers.…”

Section: Ignition Techniquesmentioning

confidence: 99%

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Frontal Polymerizations: From Chemical Perspectives to Macroscopic Properties and Applications

Suslick

Hemmer

Groce

et al. 2022

Preprint

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The synthesis and processing of thermoplastics and thermoset polymeric materials rely on energy-inefficient and environmentally burdensome manufacturing methods. Frontal polymerization has emerged as an attractive, scalable alternative due to its exploitation of the heat of polymerization, which generally is wasted as unutilized heat-loss. The only external energy needed for frontal polymerization is an initial thermal (or photo) stimulus that locally ignites the reaction. The subsequent reaction exothermicity provides local heating; the transport of this thermal energy to neighboring monomers in either a liquid or gel-like state results in a self-perpetuating reaction zone that provides fully-cured polymeric thermosets and thermoplastics. Propagation of this polymerization front continues through the unreacted monomer media until either all reactants are consumed or sufficient heat-loss stalls further reaction. Several different polymerization mechanisms support frontal processes, including free-radical, cat- or anionic, amine-cure epoxides, and ring-opening metathesis polymerization. The choice of monomer, initiator/catalyst, and additives dictates how fast the polymer front traverses the reactant medium, as well as the maximum temperature achievable. Frontal polymerization enables the preparation of moldable thermoplastics derived from linear polymers. When crosslinking is involved, polymeric networks (e.g., rigid thermosets) are obtainable through a related process best described as a frontal curing reaction. Numerous applications of frontally-generated polymers and thermosets exist, ranging from the reinforcement of porous substrates to the design of patterned composite materials. In this review, we examine in detail the physical and chemical phenomena that govern frontal polymerization, as well as outline the existing applications.

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Section: Ignition Techniquesmentioning

confidence: 99%

Section: Ignition Techniquesmentioning

confidence: 99%

Frontal Polymerizations: From Chemical Perspectives to Macroscopic Properties and Applications

Suslick

Hemmer

Groce

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…[19,24,25,33,34] Regarding photopolymerization resins or formulations, in addition to the typical Type I, II photoinitiators which play an important role, [21,35,36] electron donor-acceptor complexes (EDA, also known as charge transfer complexes, CTCs) are also common redox initiators often used in photopolymerization systems. [37,38] Even though the two precursors do not absorb visible light, the resulting EDA complexes often do absorb visible light, therefore the photochemistry of EDA complexes is considered to be a powerful strategy for expanding the chemical potential of visible-lightdriven radical synthesis. [39][40][41][42][43] Back in the 1950s, after 40 years of investigation, spectroscopy showed that benzene and mesitylene form 1:1 complexes of considerable stability with iodine by Benesi and Hildebrand.…”

Section: Introductionmentioning

confidence: 99%

Charge Transfer Complexes (CTCs) with Pyridinium Salts: Toward Efficient Dual Photochemical/Thermal Initiators and 3D Printing Applications

Buchon

Magné

et al. 2022

Macromol. Rapid Commun.

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In both organic and polymer synthesis, photochemistry of charge transfer complexes (CTCs) is considered as a powerful approach to expand visible‐light‐driven radical chemistry reaction. One reports herein on the development of a class of useful CTCs using pyridinium salts as efficient electron acceptors (combined with N, N, 3,5‐tetramethylaniline, TMA) to achieve a multiwavelength (375–560 nm) metal‐free LED photopolymerization process under mild conditions (open to air, without monomer purification and inhibitor removal). The UV–vis absorption spectra and molecular modeling simultaneously verify its potential blue‐green absorbing wavelength range. Also, their good thermal initiation behavior at relatively low temperatures makes it easier to achieve thick samples and/or polymerization in the shadow region in practice. More importantly, with excellent photoinitiating capability, the formulation is successfully applied to direct laser write (DLW) and high‐resolution 3D printing, yielding a series of objects with well‐defined structures, such as letters, ring, solid squares, and chess pieces. These new pyridinium salt acceptors further extend the applicability to visible photopolymerizable resins and additive‐containing formulations for efficient surface and deep curing.

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“…Frontal polymerization (FP) is a fast and self‐sustained polymerization mode, in which only initiation energy is required to form a stable front for the reaction system, and then the propagating front rapidly converts monomers into polymers upon the intrinsic exothermic nature 23–25 …”

Section: Introductionmentioning

confidence: 99%

Rapid synthesis of biocompatible bilayer hydrogels via frontal polymerization

Yang

Liu

et al. 2022

Journal of Polymer Science

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Hydrogels have been attracting much attention as smart soft materials. The exploration of methods allowing hydrogels to have anisotropic composition, structure, and properties would benefit the fabrication of smart materials with versatile multi-functions. Here we report the rapid frontal polymerization (FP) of bilayer hydrogels possessing good water swelling, mechanical strength, self-healing, biocompatibility, and antibacterial capabilities. The bilayer hydrogels, consisting of poly(AM-co-AMPS) (G-1) and poly(AM-co-HPA) (G-2) (AM, acrylamide; AMPS, 2-acrylamide-2-methylpropanesulfonic acid; HPA, hydroxypropyl acrylate), are synthesized in one step within 6 minutes (min) by horizontal FP. These polymer hydrogels have hierarchical porous morphology with pore sizes of several micrometers and several hundreds of micrometers respectively, equilibrium swelling ratio up to 3371% in water, tensile strength up to 0.204 MPa, and self-healing ability. The good cytocompatibility and low toxicity of the hydrogels are demonstrated through cell culture of L929 fibroblasts in vitro experiments. The tests of hydrogels with Escherichia coli and Staphylococcus aureus reveal their antibacterial property. The results demonstrate that biocompatible anisotropic hydrogels with versatile functions could be fabricated via the rapid and energy-saving approach of FP.

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Charge transfer complexes as dual thermal/photo initiators for free‐radical frontal polymerization

Cited by 14 publications

References 44 publications

Frontal Polymerizations: From Chemical Perspectives to Macroscopic Properties and Applications

Frontal Polymerizations: From Chemical Perspectives to Macroscopic Properties and Applications

Charge Transfer Complexes (CTCs) with Pyridinium Salts: Toward Efficient Dual Photochemical/Thermal Initiators and 3D Printing Applications

Rapid synthesis of biocompatible bilayer hydrogels via frontal polymerization

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