Use of latent metathesis polymerization systems for photopolymerization-based additive manufacturing
View Patent ↗Photolatent olefin metathesis catalysts can be used in combination with metathesis-active monomers or resins for photopolymerization-based additive manufacturing via ring-opening metathesis polymerization (ROMP). A variety of alternative catalysts and photosensitizers are commercially available that allows for tuning of thermomechanical properties, potlifes, activation rates, and irradiation wavelengths. As an example, two optimized catalyst/photosensitizer systems were demonstrated in the rapid stereolithographic printing of complex, multidimensional poly-dicyclopentadiene structures with microscale features under ambient conditions.
1. A method for photopolymerization-based additive manufacturing, comprising
providing a bath of liquid resin, wherein the resin comprises
a metathesis-active monomer,
a photosensitizer, and
a photolatent metathesis catalyst that can be activated by a light to initiate a ring-opening metathesis polymerization (ROMP) of the metathesis-active monomer;
irradiating the bath of liquid resin with a directed light exposure, thereby activating the photolatent metathesis catalyst to initiate ROMP of the metathesis-active monomer and forming a layer of photopolymer; and
repeating the irradiating step to build a printed object layer-by-layer.
2. The method of claim 1 , wherein the metathesis-active monomer comprises a cyclic olefin.
3. The method of claim 2 , wherein the cyclic olefin comprises a norbornadiene, norbornene, oxonorbornene, azanorbornene, cyclobutene, cyclooctene, cyclooctadiene, cyclooctatetraene, dicyclopentadiene, or derivatives thereof.
4. The method of claim 1 , wherein the photolatent metathesis catalyst comprises a photolatent ROMP catalyst.
5. The method of claim 4 , wherein the photolatent ROMP catalyst comprises a ruthenium, tungsten, molybdenum, rhenium, or titanium catalyst.
6. The method of claim 5 , wherein the photolatent ROMP catalyst comprises a ruthenium-based Grubbs or Hoveyda-Grubbs catalyst.
7. The method of claim 5 , wherein the photolatent ROMP catalyst comprises
8. The method of claim 1 , wherein the resin comprises 0.01 to 1 mol % photolatent metathesis catalyst.
9. The method of claim 1 , wherein the resin comprises 0.01 to 0.08 mol % photolatent metathesis catalyst.
10. The method of claim 1 , wherein the photosensitizer comprises isopropylthioxanthone, camphorquinone, benzophenone, phenothiazine, benzil, Rose Bengal, rhodamine, anthracene, perylene, or coumarin.
11. The method of claim 1 , wherein the resin comprises less than 3 wt % photosensitizer.
12. The method of claim 1 , wherein the resin comprises 1:1 to 16:1 wt/wt photolatent metathesis catalyst to photosensitizer.
13. The method of claim 1 , wherein the resin further comprises a co-initiator that accelerates the rate of initiation of the photosensitizer.
14. The method of claim 13 , wherein the co-initiator comprises ethyl 4-(dimethylamino)benzoate.
15. The method of claim 1 , wherein the resin further comprises ethylidene norbornene.
16. The method of claim 1 , wherein the resin further comprises at least one filler.
17. The method of claim 1 , further comprising post-print thermal curing of the printed object.
18. The method of claim 1 , wherein the light comprises ultraviolet or visible light.
19. The method of claim 1 , wherein the resin has a dose required to gel of less than 10 J cm −2 .
20. The method of claim 1 , wherein the photopolymerization-based additive manufacturing comprises stereolithography or digital light processing.