Photo‐Iniferter RAFT Polymerization

Hartlieb, Matthias

doi:10.1002/marc.202100514

Cited by 110 publications

(103 citation statements)

References 203 publications

(307 reference statements)

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“…There are in principle two strategies to accomplish such an activation of the CTA: photo-electron/energy-transfer (PET)–RAFT polymerization 16,18,19 and photo-iniferter (PI)–RAFT polymerization. 20…”

Section: Introductionmentioning

confidence: 99%

The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers

2022

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Section: Introductionmentioning

confidence: 99%

The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers

2022

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“…The residue of the photoinitiator or photocatalyst in fabricated materials remains toxic and may cause negative effects on their properties and usage. − In the meantime, these catalysts make the process more complex and increase the cost. Photoiniferter RAFT polymerization, originating from Otsu’s work, , provides an alternative way to inherently avoid these drawbacks. In this method, the initiating species comes from the direct photolysis of the RAFT agents (Scheme ); thus, no exogenous radical source, such as photocatalyst or photoinitiator, is necessary.…”

Section: Introductionmentioning

confidence: 99%

Xanthate-Based Photoiniferter RAFT Polymerization toward Oxygen-Tolerant and Rapid Living 3D Printing

Zhao

Yuan

et al. 2022

Macromolecules

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Three-dimensional (3D) printing based on photoinduced reversible addition–fragmentation chain transfer (RAFT) polymerization is emerging as a versatile and powerful method to prepare “living” 3D objects, which can be postmodified with various functionalities. However, an additional photoinitiator or photocatalyst is necessary in these systems, which is toxic and will cause negative effects on the properties of the prepared materials. Here, we report oxygen-tolerant and rapid living 3D printing based on photoiniferter RAFT polymerization, which does not need additional photoinitiators or photocatalysts. A xanthate, O-ethyl-S-2-ethyl propionate, was chosen as both the photoinitiator and RAFT agent in this process. Various monomers and RAFT agents were screened in this system. Materials with different properties were prepared utilizing the postfunctionalization of the printed living objects. Furthermore, a polymer welding method was proposed by painting fresh monomers between two living objects for post-photocuring. This photoiniferter RAFT polymerization-based living 3D printing method was also successfully applied to a commercial digital light processing technique-based 3D printer, offering a facile method to fabricate living 3D materials with different shapes.

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“…This approach has been shown to yield a narrower molecular weight distribution and glass transition region while also improving monomer conversion [66,67]. The RAFT approach shows promise for a wide variety of applications in photocuring [68] including visible-light curing in 3D printing applications [69] and in NIR irradiation [70]. Commercial formulations are becoming available in dentistry that demonstrably achieve a 4-mm depth of cure with only 3 s of irradiation [67].…”

Section: Introductionmentioning

confidence: 99%

Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

et al. 2022

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Photopolymers are an attractive option for large-format additive manufacturing (LFAM), because they can be formulated from structural thermosets and cure rapidly in ambient conditions under low-energy ultraviolet light-emitting diode (UV LED) lamps. Photopolymer cure is strongly influenced by the depth penetration of UV light, which can be limited in the 2–4 mm layer thicknesses typical of LFAM. Photoinitiator (PI) systems that exhibit photobleaching have proven useful in thick-section cure applications, because they generate a photoinitiation wavefront, but this effect is time-dependent. This study investigates the light transmission and through-thickness cure behavior in (meth)acrylate photopolymer formulations with the photobleaching initiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO). Utilizing an optical model developed by Kenning et al., lower concentrations (0.1 wt% to 0.5 wt%) of BAPO were predicted to yield rapid onset of photoinitiation. In situ cure measurements under continuous UV LED irradiation of 380 mW/cm2 showed that a 0.1 wt% concentration of BAPO achieved peak polymerization rate within 2.5 s at a 3-mm depth. With only 1 s of irradiation at 1.7 W/cm2 intensity, the 0.1 wt% BAPO formulation also achieved the highest level of cure of the formulas tested. For an irradiation dose of 5.5 J/cm2 at a duration of 3.7 s, cured polymer specimens achieved a flexural strength of 108 MPa and a flexural modulus of 3.1 GPa. This study demonstrates the utility of optical modeling as a potential screening tool for new photopolymer formulations, primarily in identifying an upper limit to PI concentration for the desired cure depth. The results also show that photobleaching provides only a limited benefit for LFAM applications with short (1.0 s to 3.7 s) UV irradiation times and indicate that excess PI concentration can inhibit light transmission even under extended irradiation times up to 60 s.

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Photo‐Iniferter RAFT Polymerization

Cited by 110 publications

References 203 publications

The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers

The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers

Xanthate-Based Photoiniferter RAFT Polymerization toward Oxygen-Tolerant and Rapid Living 3D Printing

Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

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