Additive manufacture of lightly crosslinked semicrystalline thiol–enes for enhanced mechanical performance

Childress, Kimberly K.; Alim, Marvin D.; Hernandez, Juan J.; Stansbury, Jeffrey W.; Bowman, Christopher N.

doi:10.1039/c9py01452g

Cited by 31 publications

(37 citation statements)

References 31 publications

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“…[ 5–9 ] Introducing alternative crosslinking chemistries to the VAM realm, as well as AM more broadly, is highly desirable as an alternative method to gain access to a wider range of mechanical, thermal, and optical performance. [ 10–14 ] Thiol‐ene‐based polymers are one class of materials that have drawn significant attention owing to their controllable, tunable mechanical properties. [ 15–17 ] This is generally attributed to more uniform molecular networks in thiol‐ene materials, resulting from the step‐growth mechanism of the polymerization reaction.…”

Section: Figurementioning

confidence: 99%

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

et al. 2020

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Volumetric additive manufacturing (VAM) is an emerging approach to photo polymerbased 3D printing that produces complex 3D structures in a single step, rather than from layer-by-layer assembly. [1] This paradigm holds promise because it overcomes many of the drawbacks of layerbased fabrication, such as long build times and rough surfaces. VAM also augurs a broadening of the materials available for photopolymer 3D printing, having fewer constraints on viscosity and reactivity compared to layerwise printing. Indeed, though VAM has been demonstrated with extremely soft hydrogels, [2,3] it has relied until now almost exclusively on acrylate-based chemistry. [4] This is natural, because the oxygen inhibition of acrylate polymerization provides the threshold behavior required for VAM. However, acrylate chemistry is in general limiting due to the brittle and glassy properties of the resulting materials. Accordingly, extensive efforts have been made to identify and target specific soft, elastic acrylate formulations. [5-9] Introducing alternative crosslinking chemistries to the VAM realm, as well as AM more broadly, is highly desirable as an alternative method to gain access to a wider range of mechanical, thermal, and optical performance. [10-14] Thiol-ene-based polymers are one class of materials that have drawn significant attention owing to their controllable, tunable mechanical properties. [15-17] This is generally attributed to more uniform molecular networks in thiol-ene materials, resulting from the step-growth mechanism of the polymerization reaction. [18,19] Thiol-ene materials have already shown promise for applications including use in adhesives, electronics, and as biomaterials. [20,21] This work expands the versatility of volumetric AM by introducing a new class of VAM-compatible thiol-ene resins. We demonstrate the formulation of thiol-ene resins with the nonlinear threshold-type kinetics required for VAM and show bulk-equivalent performance in the resulting 3D printed parts, confirming the advantage of the layerless whole-part process. In our volumetric AM system, a 3D distribution of light energy is delivered to the resin vat by superimposing exposures from multiple angles, a method termed computed axial litho graphy (CAL) (Figure 1a). [2] The exposures are a sequence of projections calculated from 3D CAD models using algorithms from computed Volumetric additive manufacturing (VAM) forms complete 3D objects in a single photocuring operation without layering defects, enabling 3D printed polymer parts with mechanical properties similar to their bulk material counterparts. This study presents the first report of VAM-printed thiol-ene resins. With well-ordered molecular networks, thiol-ene chemistry accesses polymer materials with a wide range of mechanical properties, moving VAM beyond the limitations of commonly used acrylate formulations. Since free-radical thiol-ene polymerization is not inhibited by oxygen, the nonlinear threshold response required in VAM is introduced by incorporating 2,2,6,6-tetrameth...

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Section: Figurementioning

confidence: 99%

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

et al. 2020

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“…[74][75][76][77] For example, Childress et al used commercially available thiol and alkene monomers with DLP printing to fabricate crosslinked semicrystalline materials with Young's moduli between 40 and 90 MPa while having an elongation at break between 300% and 800%. 78 At the other end of the mechanical properties spectrum, Warner et al demonstrated the use of diallyl diurethane monomers with multifunctional thiols to synthesize materials with Young's moduli between 400 and 2500 MPa, all with elongation at break exceeding 80%. 75 Residual surface thiols and alkenes/alkynes can be used for surface functionalization.…”

Section: Materials Compatible With Vp Polymersmentioning

confidence: 99%

Three‐dimensional chemical reactors: in situ materials synthesis to advance vat photopolymerization

Yee

Greer

2021

Polymer International

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Vat photopolymerization (VP) is one of the most remarkable additive manufacturing techniques today and has been used for a variety of applications, from materials research to product manufacturing. The main challenge with VP is the limited choice of compatible materials, which motivates significant interest in VP materials development. We provide a brief overview of the materials that are currently accessible via VP and highlight recent advances in the field. We also provide perspective on expanding the library of materials compatible with VP using in situ materials synthesis.

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“…This is characteristic of stress-oscillation behaviour observed in numerous polymer systems, however origins of this phenomenon are often disputed. 26,27 A possible explanation is the formation of "voids" in the amorphous regions during elongation which leads to a stress drop and the reorientation of polymer crystallites leading to a stress increase. 28 Remarkably, this behaviour was considerably reduced in samples containing cyclopropane.…”

Section: Polymer Chemistry Papermentioning

confidence: 99%

Understanding structure–property relationships of main chain cyclopropane in linear polyesters

Stubbs

Dove

2020

Polym. Chem.

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Additive manufacture of lightly crosslinked semicrystalline thiol–enes for enhanced mechanical performance

Abstract: Semicrystalline crosslinked thiol–ene networks achieved rapid polymerization kinetics, and mechanical properties substantially improved from the linear thiol–ene thermoplastic.

Cited by 31 publications

References 31 publications

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

Three‐dimensional chemical reactors: in situ materials synthesis to advance vat photopolymerization

Understanding structure–property relationships of main chain cyclopropane in linear polyesters

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