Employing Photosensitizers for Rapid Olefin Metathesis Additive Manufacturing of Poly(dicyclopentadiene)

Leguizamon, Samuel C.; Cook, Adam; Appelhans, Leah

doi:10.1021/acs.chemmater.1c03298

Cited by 26 publications

(30 citation statements)

References 53 publications

(90 reference statements)

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“…Thermal post‐cure is commonly employed for parts produced via DCPD polymerization and generally results in significantly higher glass transition, T g , values and improved mechanical performance. [ 32,46 ] As shown in Figure 3c (and Figures S18 and S19, Supporting Information), the presence of NPPOC‐TMG had no detrimental influence on glass transition temperature, T g , or temperature‐dependent storage modulus. Moreover, dogbones produced with variable NPPOC‐TMG loadings possessed nearly identical tensile strength and Young's modulus values compared with control samples that were cured without PBG.…”

Section: Resultsmentioning

confidence: 88%

“…Our recent work identified HeatMet (HM) (Figure 1) as a photo-active olefin metathesis catalyst to photopolymerize dicyclopentadiene (DCPD) under UV irradiation to yield a highperformance thermoset material. [32,33] To adapt our HM/DCPD system to a dual-wavelength photo-activation/photo-deactivation approach, we explored the use of HM in combination with a photobase generator (PBG). Ru-based metathesis catalysts are susceptible to degradation via metallacyclobutane deprotonation using phosphines or amines [34] ; thus, we envisioned that PBG photolysis could be leveraged to mediate polymerization deactivation.…”

Section: Introductionmentioning

confidence: 99%

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Continuous Additive Manufacturing using Olefin Metathesis

et al. 2022

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The development of chemistry is reported to implement selective dual-wavelength olefin metathesis polymerization for continuous additive manufacturing (AM). A resin formulation based on dicyclopentadiene is produced using a latent olefin metathesis catalyst, various photosensitizers (PSs) and photobase generators (PBGs) to achieve efficient initiation at one wavelength (e.g., blue light) and fast catalyst decomposition and polymerization deactivation at a second (e.g., UV-light). This process enables 2D stereolithographic (SLA) printing, either using photomasks or patterned, collimated light. Importantly, the same process is readily adapted for 3D continuous AM, with printing rates of 36 mm h -1 for patterned light and up to 180 mm h -1 using un-patterned, high intensity light.

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Section: Resultsmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Continuous Additive Manufacturing using Olefin Metathesis

et al. 2022

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“…We recently demonstrated an improved rate of cure for cis− trans isomerization photolatent catalysts by addition of a photosensitizer to the DCPD resin (Figure 1b). 17 This work additionally identified the commercial thermally latent catalyst HeatMet (Ru-1) as a photolatent catalyst despite the absence of a cis−trans isomerization mechanism, suggesting a distinct activation mechanism such as triplet−triplet energy transfer or photoredox catalyst activation. The greatly accelerated rate of photoROMP achieved using Ru-1 and a photosensitizer, 2isopropylthioxanthone (ITX), enabled the AM of complex, three-dimensional pDCPD architectures via DIW.…”

Section: T H Imentioning

confidence: 82%

Photoinitiated Olefin Metathesis and Stereolithographic Printing of Polydicyclopentadiene

et al. 2022

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Recent progress in photoinitiated ring-opening metathesis polymerization (photoROMP) has enabled the lithographic production of patterned films from olefinic resins. Recently, we reported the use of a latent ruthenium catalyst (HeatMet) in combination with a photosensitizer (2-isopropylthioxanthone) to rapidly photopolymerize dicyclopentadiene (DCPD) formulations upon irradiation with UV light. While this prior work was limited in terms of catalyst and photosensitizer scope, a variety of alternative catalysts and photosensitizers are commercially available that could allow for tuning of thermomechanical properties, potlifes, activation rates, and irradiation wavelengths. Herein, 14 catalysts and 8 photosensitizers are surveyed for the photoROMP of DCPD and the structure–activity relationships of the catalysts examined. Properties relevant to stereolithography additive manufacturing (SLA AM)potlife, irradiation dose required to gel, conversionare characterized to develop catalyst and photosensitizer libraries to inform development of SLA AM resin systems. Two optimized catalyst/photosensitizer systems are demonstrated in the rapid SLA printing of complex, multidimensional pDCPD structures with microscale features under ambient conditions.

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“…Like other DIW methods, reinforcing fillers can be incorporated into the ink to produce functional composites. [24][25][26][27] Coordinating deposition speed to the cure kinetics during FP-DIW is a challenging optimization problem. In our initial study, [23] the cure front was thought to be independent of the printing process and the print speed needed to match the front speed at all times, severely limiting the process.…”

Section: Introductionmentioning

confidence: 99%

“…Like other DIW methods, reinforcing fillers can be incorporated into the ink to produce functional composites. [ 24–27 ]…”

Section: Introductionmentioning

confidence: 99%

Self‐Regulative Direct Ink Writing of Frontally Polymerizing Thermoset Polymers

Zhang

Nelson

et al. 2022

Adv Materials Technologies

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significant challenges remain for rapid fabrication of complex structures with high strength, stiffness, and thermal stability. High-speed printing of complex, high-resolution structures has been achieved through photocuring, [13,14] but the thermomechanical properties are often inferior to thermally cured counterparts. DIW is an extrusion-based technique highly suitable for 3D printing thermally cured thermosets with excellent properties. [15] The ability to add reinforcing fibers and particles further enhances the engineering properties of DIW materials. [16,17] However, the inherent viscoelasticity of DIW inks invariably leads to creep and slumping of deposited structures, especially gap-spanning features, often limiting the size and geometrical complexity of the manufactured part. [11,[18][19][20] More recently, Qi and co-workers combined light-and thermal-curing resins to enable rapid initial solidification by photocuring followed by thermal post-curing to achieve desired engineering properties. [21,22] An alternative printing approach for thermoset resins relies on frontal polymerization (FP) during DIW to enable rapid curing of printed structures in tandem with the printing process. [23] FP is initiated by a thermal or photo stimulus, triggering an exothermic cure front that propagates by transport of heat and continued reaction in the monomer. During FP-DIW,The ability to manufacture highly intricate designs is one of the key advantages of 3D printing. Achieving high dimensional accuracy requires precise, often time-consuming calibration of the process parameters. Computerized feedback control systems for 3D printing enable sensing and real-time adaptation and optimization of these parameters at every stage of the print, but multiple challenges remain with sensor embedment and measurement accuracy. In contrast to these active control approaches, here, the authors harness frontal polymerization (FP) to rapidly cure extruded filament in tandem with the printing process. A temperature gradient present along the filament, which is dependent on the printing parameters, can impose control over this exothermic reaction. Experiments and theory reveal a self-regulative mechanism between filament temperature and cure kinetics that allows the frontal cure speed to autonomously match the print speed. This self-regulative printing process rapidly adapts to changes in print speed and environmental conditions to produce complex, high-fidelity structures and freestanding architectures spanning up to 100 mm, greatly expanding the capabilities of direct ink writing (DIW).

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Employing Photosensitizers for Rapid Olefin Metathesis Additive Manufacturing of Poly(dicyclopentadiene)

Cited by 26 publications

References 53 publications

Continuous Additive Manufacturing using Olefin Metathesis

Continuous Additive Manufacturing using Olefin Metathesis

Photoinitiated Olefin Metathesis and Stereolithographic Printing of Polydicyclopentadiene

Self‐Regulative Direct Ink Writing of Frontally Polymerizing Thermoset Polymers

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