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September 16-19, 2025 • Boulder, Colorado

TECHNICAL PROGRAM

Wednesday, September 17

Plenary Sessions, 8:30 – 9:30 AM

Room: SEEC C120

8:30 - 9:00

Irresistible Force vs. Immovable Object: The Challenge of Commercializing New Materials in a Restrictive Regulatory Environment
Michael Gould, Rahn Corp

9:00 - 9:30

Microenvironments as an Explanation for the Mismatch between Photochemical Absorptivity and Reactivity
Christopher Barner-Kowollik, Queensland University of Technology (QUT)

9:30 - 9:45

Break

Parallel Sessions, 9:45 AM – 12:15 PM

TRACK 1 (Rm: SEEC C120)
TRACK 2 (Rm: SEEC S372 A/B)

9:45 - 10:10

Photopolymerisation and controlled depolymerisation of ketone-containing polymers
Andrew Dove, University of Birmingham
Towards high-speed additive manufacturing of nano-resolution polymeric materials - hierarchical structure control via wavelengths and molecular assembly
Kaiwen Hsiao, Texas A&M University

10:10 - 10:30

Mechanistic insights on the photopolymerization of 1,2-dithiolanes utilizing photo NMR
Benjamin Nelson, University of Colorado Boulder
Urethane-Urea Acrylate Resins for 3D printing
Jin Lu, Allnex Inc.

10:30 - 10:55

Green synthesis of photo-clickable polymers for efficient hydrogel crosslinking and programmable degradation
Chien-Chi Lin, Purdue University
Development of 3D Printing Resins with Tunable Properties from Glycerol-Derived Monomers and Waste Plastics
Jason Bara, The University of Alabama

10:50 - 11:10

Break
Break

11:10 - 11:35

4D Grayscale Modulation of Living Systems
Cole DeForest, University of Washington
Speaking in Dp and Ec – Expanding the Working Curve to Standardization, High Resolution, and Mechanical Precision
Jason Killgore, National Institute of Standards and Technology

11:35 - 11:55

Photoresponsive Synthetic ECM to Model Lung Microinjury and Fibrosis-Associated Secretome
Samantha Swedzinski, University of Delaware
Material Development with Focus on Mechanical Performance for Vat Photopolymerization
Ye Wang, TE Connectivity

11:55 - 12:20

UV Curable Dielectric Materials
Don Herr, Arkema
Radical-free 3D printing via photoclick chemistry
Javier Read de Alaniz, UC Santa Barbara

Lunch, 12:20 – 1:45 PM

Parallel Sessions, 1:45 – 3:35 PM

TRACK 1 (Rm: SEEC C120)
TRACK 2 (Rm: SEEC S372 A/B)

1:45 - 2:10

In Situ NMR to Monitor Bulk Photopolymerization Kinetics
Allan Guymon, Brigham Young University
Increase of spatio-temporal resolution of 3D printed objects via controlled polymerization of acrylates or epoxides
Céline Croutxé-Barghorn, Université de Haute Alsace

2:10 - 2:30

UV-Curable Resins and Their Composites for Applications Ranging from the Micrometer to the Meter Scale
Christian Dreyer, Technical University of Applied Sciences Wildau & Fraunhofer IAP Wildau
A Formulator's Guide to Catalytic Chain Transfer in Thermosetting Photopolymers
Brian Donovan, University of Denver

2:30 - 2:50

Design and 3D printing of biobased epoxidized formulations based on vegetable oils with vitrimeric properties
Matilde Porcarello, Politecnico di Torino
Development of Parallax Volumetric Additive Manufacturing for Rapid, Large-Area 3D Fabrication
Chi Chung Li, University of Colorado Boulder

2:50 - 3:10

Photochemistry to the rescue- our 8 year journey to develop a melamine primer
Tommy Haraldsson, Mercene Labs AB
UV Curable Ultra Low Refractive Index Nano-voided Materials
Eric Nelson, 3M

3:10 - 4:00

Break
Break

Poster Session A and Vendor Exhibit, 4:00 – 6:00 PM

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Irresistible Force vs. Immovable Object: The Challenge of Commercializing New Materials in a Restrictive Regulatory Environment

Michael Gould, Rahn Corp

With a 40 year history of creating new molecules, the author will reflect on the ever-more restrictive global regulatory landscape (immovable object) at a time when new technologies demand new, better, safer and more sustainable chemical building blocks (irresistible force).Photopolymer 3D printing, as an example, is a demanding application that begs greater performance from materials historically created for other industrial applications. During the past 10 years, the need for new high performance photopolymer materials has grown dramatically as printer and process capabilities evolve in rapid generational leaps. At the very same time, global legislators have ‘seized the moment’ and created a historically challenging gauntlet of rules and regulations that obstruct innovation and ‘tax’ commercial endeavors to a point where innovation is prohibitively expensive. Feedback to elected officials is the only sure way to move the needle back to a more common sense perspective. Until we reach that place, patience and determination are necessary to maintain creative momentum in a positive direction.

Microenvironments as an Explanation for the Mismatch between Photochemical Absorptivity and Reactivity

Christopher Barner-Kowollik, Queensland University of Technology (QUT)

When selecting a light source for a photochemical process — including for photopolymerizations — we often consider the likelihood of a photon to be absorbed by a chromophore at a given wavelength as an accurate predictor of how well a photo-chemical process will proceed when irradiated with different colors of light. Over the last decade this paradigm has been repeatedly challenged for many photochemical systems, as a distinct mismatch between the absorption spectrum and the wavelength resolved photochemical reactivity has been observed. Herein, we unravel underlying mechanisms behind the mismatched reactivity and absorbance in photocycloadditions. Initially, we probe the impact that an equilibrium established between reversible photochemical processes has on the mismatch for a pyrene-chalcone molecule. Subsequently, we establish a critical link between photophysics and photochemistry with a theory based on the selective excitation of specific microenvironments leading to molecular transitions that allow for favourable wavelength-dependent reactivity. Time-resolved and steady-state fluorescence spectroscopy measurements confirm the presence of this selectivity, with both displaying significant red-edge effects that are observed in fluorescence spectroscopy literature, further supporting our theory. By synthetically tethering chromophores together, we further evidence the importance of microenvironments and their wavelength-dependent excited-state lifetimes, presenting the missing link that explains the mismatch for many photochemical systems. The implications of the theory presented herein stretch from additive manufacturing to photo-dynamic therapy, meaning that we can potentially leverage photochemical mismatches by changing the properties of the environment surrounding the chromophore. Carrol, J. A.; Pashley-Johnson, F.; Klein, M.; Stephan, T.; Pandey, A. K.; Walter, M.; Unterreiner, A. N.; Barner-Kowollik, C. J. Am. Chem. Soc. 2025, in press.

Photopolymerisation and controlled depolymerisation of ketone-containing polymers

Andrew Dove, University of Birmingham

While many routes exist to mediate photopolymerisation of a range of monomers, the reverse process, depolymerisation is much less studied. While photodegradation of polyketones, typically accessed by copolymerisation of CO with alkenes, is well established to occur by Norrish photodegradation pathways, it results in an uncontrolled photodegradation to a mixture of products. Herein, we will present the photomediated synthesis of poly(enone sulfide)s and discuss their selective photo-depolymerisation.

Towards high-speed additive manufacturing of nano-resolution polymeric materials – hierarchical structure control via wavelengths and molecular assembly

Kaiwen Hsiao, Texas A&M University

Polymeric materials containing hierarchical structures ranging from micrometer to nanometer feature sizes play a significant role in accelerating transport properties, critical for energy-water and biomedical applications. Major advances in high-speed, high-resolution additive manufacturing (AM) have demonstrated the capability of creating architected materials at the micrometer resolution. However, challenges existed in achieving sub < 500nm nanostructure control due to the limitation in projection optics and writing speed, as well as limited understanding of preservation and evolution of nano-morphologies during photo-patterning. In this research, we aim to address this challenge with two approaches. In the first part of the talk, we will focus on the introduction of dual-wavelength 3D printing platform coupled with controlled living radical polymerization to tackle the diffraction-limited patterning. The critical timescales of reaction-diffusion mechanism are elucidated with experiment and simulation. It was found that at the diffusion-limited printing time, the patterning resolution is dictated by the diffusivity and lifetime of the macroradicals. To achieve sub-500nm resolution, macroradical reactivity and projection optics exposure time needs to be simultaneously controlled to enter reaction-limited regime. In the second part of the talk, we will focus on a bottom-up approach using macromolecular-amphiphilic templates for controlling self-assembly nano-morphologies formation during rapid photo-crosslinking in AM platforms. The nano-morphologies preservation before and after printing are elucidated with SAXS, SEM, and DSC. It was found that without effective functionalized amphiphilic templates, the onset of polymerization driven microphase separation occur due to the thermodynamic depletion effect, leading to nano-morphologies coarsening of the bi-continuous micellar domains. Functionalized amphiphilic macromolecules are introduced to control the evolution of nanostructure formation. Taken together, the research builds on fundamental reaction-diffusion control with two different approaches to achieve sub-500 nm resolution within scalable AM platform, and provides a fundamental understanding towards the enhancement of patterning resolution with low-energy laser systems.

Mechanistic insights on the photopolymerization of 1,2-dithiolanes utilizing photo NMR

Benjamin Nelson, University of Colorado Boulder

The rapid development of 1,2-dithiolanes for material applications continues to be reported by several groups. A key feature of dithiolanes useful in materials science is their ability to undergo polymerization via a variety of mechanisms, including thermal, anionic, cationic, radical, and initiator-free photopolymerization. This inherent capability of photopolymerization has been a central driving force in the materials development utilizing dithiolanes. However, the long-standing hypothesis of a radical mediated polymerization mechanism has fallen under scrutiny given both recent and older developments reported in the literature. Namely, the requirement for exogenous photoinitiator in the copolymerizations of dithiolanes and various alkenes, as well as the pronounced solvent effect on the polymer structure and distribution casts doubt on a radical mechanism. In this study, the unconventional technique of photo NMR was used to track the kinetics of the initiator free dithiolane photopolymerization, using lipoic acid as a model dithiolane, revealing mechanistic insights about the polymerization. Through time resolved spectroscopy during light irradiation, a reactive intermediate was tracked and identified. This mechanistic understanding of the polymerization mechanism furthermore enabled the use of lipoic acid as a cationic photoiniator to polymerize vinyl ethers.

Urethane-Urea Acrylate Resins for 3D printing

Jin Lu, Allnex Inc.

3D printing by photo-polymerization has been successful in the dental market due to the efficiency of printing custom products in complex shapes in great detail. This printing process is also becoming increasingly accepted in the medical and industrial markets. Digital light processing (DLP) applies LED light to the whole surface of the resins in a single pass, offering faster printing speed than Stereolithography (SLA), thus gaining more popularity in the market. Many 3D printing applications require high thermoplastic-like performance but in a thermoset system. A lower viscosity is also needed to enable fast printing. To tackle these challenges, we designed and created a new type of urethane-urea acrylate oligomers, which can be formulated by high levels of monofunctional monomers without losing their strong mechanical performance. This photocurable resin system can be printed at a fast speed by a DLP printer and offers strong layer-to-layer adhesion and toughness.

Green synthesis of photo-clickable polymers for efficient hydrogel crosslinking and programmable degradation

Chien-Chi Lin, Purdue University

Orthogonally crosslinked thiol-norbornene hydrogels are a versatile biomaterial platform for tissue engineering applications. Multi-arm poly(ethylene glycol)-norbornene (PEGNB) is a popular synthetic macromer choice for thiol-norbornene hydrogel crosslinking, owing to its rapid reaction kinetics and high cytocompatibility. However, the synthesis of this photo-reactive polymer has been troublesome due to its tedious reaction conditions and the use of nauseous 5-norbornene-2-carboxylic acid. Furthermore, hydrogels crosslinked by conventional PEGNB do not provide highly tunable degradation, limiting their use in the tissue regeneration space. This talk will present carbic anhydride-based synthesis of PEGNB variants. The synthesis is greener, faster, and highly efficient, producing three new PEGNB variants: PEG-ester-norbornene-carboxylate (PEGeNBCA), PEGeNB-tyramide (PEGNB-T), and PEG-amide-NBCA (PEGaNBCA). These three PEGNB variants all have rapid thiol-norbornene photocrosslinking kinetics. Additionally, hydrogels photocrosslinked by these PEGNB variants afford highly tunable degradation, including slow hydrolytic degradation, fast dissolution, and user-controlled photodegradation. Autonomous hydrolytic degradation can be engineered over hours to months, whereas user-defined on-demand photodegradation can be achieved in minutes. The new family of photocrosslinkable PEGNBCA hydrogels is cytocompatible for in situ cell encapsulation and can be adapted for various biofabrication application workflows, including microgel fabrication, digital light processing (DLP) printing, and sacrificial bioprinting.

Development of 3D Printing Resins with Tunable Properties from Glycerol-Derived Monomers and Waste Plastics

Jason Bara, The University of Alabama

Development of sustainable and environmentally friendly stereolithography (SLA) 3D printing resins has gained considerable attention in recent years. Towards this goal, we have successfully employed glycerol-based 1,3-diether-2-methacrylate monomers that offer tunable mechanical and thermal properties based on selection of functional groups. These monomers also act as solvents for thermoplastics such as polystyrene (PS), poly(methyl-methacrylate) (PMMA), and poly(vinyl chloride) (PVC). This dual functionality enables the direct fabrication of polymer blends using a consumer-grade SLA 3D printer. This presentation will provide an overview of our synthetic methods, resin preparation, and the resulting structure-property relationships of the 3D printed materials.

4D Grayscale Modulation of Living Systems

Cole DeForest, University of Washington

Hydrogel biomaterials have proven indispensable for three-dimensional (3D) cell culture but have fallen short in replicating the innate physiochemical complexity of real tissue. Though traditional photolithography affords localized material manipulation, robust methods that govern when, where, and to what extent such phototailoring occurs throughout materials would be profoundly enabling towards fabricating more-realistic 3D tissue constructs. Here, we introduce “grayscale image z-stack-guided multiphoton optical-lithography” (GIZMO) as a generalizable and intuitive strategy to rapidly photomodulate materials in full 3D non-binary patterns at submicron resolutions spanning large volumes (>mm3). Highlighting its versatility, we employ GIZMO to variably photopattern stiffening/softening and biochemical (de)functionalization of cell-laden hydrogel biomaterials based on biologically derived or synthetic grayscale image stacks with unprecedented complexity. Additionally, combining GIZMO with next-generation optogenetic strategies, we demonstrate 4D grayscale activation bioactive proteins in functional materials and in living cells. We anticipate that GIZMO will enable new opportunities to probe and manipulate cell fates, as well as to engineer complex functional tissue.

Speaking in Dp and Ec – Expanding the Working Curve to Standardization, High Resolution, and Mechanical Precision

Jason Killgore, National Institute of Standards and Technology

The working curve describes the fundamental relationship between cure depth and radiant exposure in a photopolymer resin. Jacobs showed that a semi-log fit of the working curve yielded 2 parameters, the depth of light penetration Dp and the critical exposure energy Ec. Despite their implicit nature as material properties and ubiquity in vat photopolymerization literature, the precise measurement and demonstrated utility of Dp and Ec remain unresolved. For Dp and Ec to represent material properties, it is essential that the community adopt standards on how the measurement should be performed. Our results show that adoption of a common measurement method dramatically reduced the measurement variation from up to 7000 % for Ec and 700 % for Dp, down to ≈5 % or less for both quantities. Despite standardization providing a common basis for comparing resin properties, the values of Dp and Ec are still known to depend on numerous other factors such as irradiance of the light source and size of the printed features. To elucidate the impact of such process variables on Dp and Ec in bioprint relevant inks, we developed a novel instrument combining a high-resolution, high-power digital light processing projector and a high-speed optical coherence tomography imaging system. This instrument allows real time measurement of working curves on patterned features down to 10 µm in width, at irradiances up to 450 mW cm-2, through varying window materials. Working curves are seen to exhibit extreme size dependence, particularly at lower irradiances where the duration of cure allows considerable time for diffusion. Notably, by correcting for the size dependency of Dp and Ec ,one can determine exposure conditions that yield uniform cure depth across multiple pattern length scales. Finally, we consider how Dp and Ec affect the intralayer mechanical property gradients in printed parts. We introduce a new measurement of intralayer modulus coined the “wedge method” that employs a sloped removable backplate to measure the modulus at a given intralayer depth. By printing wedges at different irradiance and exposure, we observe a broad range of intralayer gradients. However, when the exposure is scaled by the irradiance-dependent Ec, the gradients collapse onto a master curve. Overall, consideration of Dp and Ec on a voxel-scale (with lateral and thickness dimensions) basis allows for parts to be manufactured with improved geometric and mechanical precision.

Photoresponsive Synthetic ECM to Model Lung Microinjury and Fibrosis-Associated Secretome

Samantha Swedzinski, University of Delaware

Microinjuries to the lung epithelial layer are hypothesized to trigger fibrotic cascades associated with lung diseases and cancer recurrence. A primary trait of these cascades are changes in the mechanical properties of the cellular microenvironment, including large increases in stiffness that correspond to decreases in lung function due to inhibited gas exchange. The early stages of these diseases are particularly not well understood due to the extended amount of time between disease initiation and onset of symptoms that lead to diagnosis. Therefore, we aim to create a synthetic hydrogel platform that mimics microinjuries and the subsequent increasing modulus of the ECM for probing cellular responses caused by these dynamic changes. Here, a bioinert poly(ethylene glycol) (PEG)-based hydrogel was formed using a coumarin-containing crosslinker to enable injury mimetic properties via selective photodegradation. The stiffening mimetic properties were then enabled by triggering thiol-yne reactions via visible light photoinitiation of Eosin Y. The biomechanical properties of this hydrogel-based synthetic ECM were modulated to mimic injury via selective photolithographic degradation and subsequent bulk photostiffening to mimic the injury-fibrosis cascade. Assessment of these mechanical properties was done by rheometry and confocal microscopy. Epithelial cells were cultured on these hydrogels at the air-liquid interface (ALI) and then subjected to injury, stiffening, or injury followed by stiffening and cellular responses assessed (cellular, proteomic, transcriptomic assays). The use of this photoresponsive hydrogel-based synthetic ECM platform enables insights into cellular responses to dynamic biomechanical changes associated with injury and fibrosis toward improved mechanistic understanding and therapeutic approaches.

Material Development with Focus on Mechanical Performance for Vat Photopolymerization

Ye Wang, TE Connectivity

Vat photopolymerization (VP), a major additive manufacturing process, has been widely adopted as manufacturing method for prototyping, tooling, and end-use parts. In the connector industry, development of VP machines, materials, and processes enables shorter design cycle and product time-to-market. However, the full potential of VP still needs to be explored, especially better understanding of VP material mechanical, physical, and other properties. In this work, a series of VP materials was prepared using base acrylate photopolymers with different additives to demonstrate recent development of materials with focus on mechanical properties. The addition of different liquid or solid additives to the base photopolymers can hugely impact material reaction under UV exposure, which further affects material response to external forces, material printability, part dimension accuracy, and product level performance. Through multiple case studies, we demonstrate the progress of VP materials development being explored for the connector industry.

UV Curable Dielectric Materials

Don Herr, Arkema

The need for high performance polymeric dielectric materials has been an area of commercial importance and R&D focus for several decades given the advancement of fields such as miniaturized and ruggedized electronics, flat panel and flexible displays, and battery component coatings. Unique and high throughput manufacturing processes for contemporary devices, including 3D printing, have created opportunities for reactive materials that extend beyond traditional insulator options such as epoxies, polyimides, silicones, and fluorocarbons. This talk will review 100% solids liquid light curable material options to create fairy high performance and cost effective dielectric devices, coatings and adhesives. Testing techniques and comparative data will be presented in relation to critical performance parameters such as such as bulk resistivity, breakdown strength, dissipation factor, and dielectric constant. The use of fillers in achieving targeted dielectric and other performance targets introduces resin/filler interface and light penetration challenges as with other filled UV curable materials. Key principles of structure/property design will be presented as guidance to the selection of base materials and the formulation of high performance light-cured products.

Radical-free 3D printing via photoclick chemistry

Javier Read de Alaniz, UC Santa Barbara

Photons have multiple enabling advantages to control chemical reactions, processes and 3D printed materials. In this seminar, I will discuss our groups effort to design and develop a radical- and additive free photo-resin system based on Diels–Alder click chemistry. Inspired by the high reactivity of cyclopentadiene (Cp), we employ photo-caged Cp derivatives that undergo efficient, light-triggered cycloaddition with maleimide groups. This design enables rapid gelation under mild conditions without metal catalysts or highly reactive radical initiators. The resulting hydrogels exhibit excellent photo-curability, as confirmed by photo-rheology studies, and support spatially controlled post-functionalization. Our system demonstrates full compatibility with DLP 3D printing, enabling the fabrication of complex hydrogel architectures with high resolution and minimal material waste. Furthermore, the modularity of our design offers pathways toward recyclability and degradability, essential for advancing circular material systems.

In Situ NMR to Monitor Bulk Photopolymerization Kinetics

Allan Guymon, Brigham Young University

Precisely measuring photopolymerization kinetics is critical in controlling curing characteristics and material properties in photocurable systems. Traditional methods used to measure kinetics, such as real-time Fourier-transform infrared spectroscopy (RT-IR), are often limited by broadening mechanisms intrinsic to the system, overlapping signals, and poor spectral resolution. This presentation will discuss an in situ NMR spectroscopy technique to monitor bulk photopolymerization reactions wherein the polymer system is separated from the locking solvent via a capillary insert and photoexcited using an LED-coupled fiber optic. This technique allows the isolated observation of the bulk reaction system while also benefiting from the high spectral resolution and rich chemical information offered by NMR. To optimize acquisition parameters, the relationship between nuclear relaxation and resin viscosity is investigated as a function of monomer conversion. The utility of this technique is shown by monitoring monomer conversion in photocurable hexyl acrylate and demonstrates exceptional reproducibility, minimal dark cure, and remarkable sensitivity to changes in reaction parameters such as light intensity and photoinitiator concentration. This technique is also applied to two challenges relevant to applications in photopolymerization, i.e. monitoring hydrogel polymerization kinetics and independent monitoring of acrylate/methacrylate monomer in a copolymerization reaction. By observing kinetic data of simple photopolymer systems, this work demonstrates the utility of in situ NMR photopolymerization as a complementary technique to conventional RT-IR and other methods for kinetic monitoring of bulk photopolymerization reactions.

Increase of spatio-temporal resolution of 3D printed objects via controlled polymerization of acrylates or epoxides

Céline Croutxé-Barghorn, Université de Haute Alsace

3D DLP printing of acrylate-based thermoplastics or epoxy-based thermosets was investigated by addition of RAFT-agents or pyridine derivatives, respectively. The impact of these compounds on the radical or cationic polymerization kinetics and the resolution of the 3D printed objects was explored. RAFT agents have an impact on the photopolymerization of acrylates, through the formation of more homogeneous 3D polymer network. Consequently, a significant improvement of the mechanical properties was noticed, with increased elongation at break values for samples exhibiting the same conversion. The toughness was also improved by about 20–25%. For epoxy-based resins, an increase of the inhibition time and a decrease of the heat flow were observed in the presence of pyridine derivatives and attributed to the trapping of the initiating species and the stabilization of the growing chains. This allows for the confinement of the polymerization process and limits the presence of lateral defects around the printed objects.

UV-Curable Resins and Their Composites for Applications Ranging from the Micrometer to the Meter Scale

Christian Dreyer, Technical University of Applied Sciences Wildau & Fraunhofer IAP Wildau

The presentation provides a comprehensive overview of the authors’ latest developments in the field of UV-crosslinking polymers, including a wide range of applications: Heat-resistant coatings which are cross-linked using modern energy-efficient UV LED modules for high-performance glass-fibers for the transmission of high (optical laser) power for use in laser surgery and material processing are described. Further applications in the micrometer range deal with photoresists, optical polymers and nanocomposites for optical waveguides for integrated optical components. The use of inorganic nanoparticles functionalized with organic groups leads to optically transparent waveguides with reduced thermo-optical coefficients (TOC). Furthermore, the development of adaptable materials for lenses and other applications in photonics is explained. Another project deals with the development of polymeric materials as well as process and tool development for UV-reactive injection molding. The use of UV-reactive resins for injection molded products promises higher fibre-volume contents (for example of short glass fiber reinforced components due to the significantly lower initial viscosity of reactive resins compared to thermoplastic melts) and thus higher achievable mechanical strengths as well as higher heat deflection temperatures – the last due to the network structure of the final components. Compared to the established purely thermal reactive injection molding, significantly shorter cycle times can be achieved with UV LED curing. One project that has already been successfully implemented in industrial practice involves the development of material and process for the hybrid (UV and heat) production of glass fiber-reinforced pultrudates as a continuous process. In addition to significant energy savings, an increase in speed of + 400 % was achieved.

A Formulator’s Guide to Catalytic Chain Transfer in Thermosetting Photopolymers

Brian Donovan, University of Denver

Methacrylate photopolymers are widely used in industries such as 3D printing and microelectronics due to their rapid curing under UV or visible light and ultimate performance characteristics. However, the chain-growth nature of their polymerizations often leads to brittleness, significant shrinkage stress, and limited mechanical properties. Conventional solutions involve custom-synthesized materials or complex multi-component formulations, as well as chain transfer agents (CTAs) that can be costly and require high loadings of specialized monomers (>20 wt. %). Herein, we present a sulfur-free catalytic CTA that can be added in ppm quantities to commercial monomer feedstocks, achieving similar results to traditional CTAs but at 10,000-fold lower loadings. Based on macrocyclic cobaloximes, these catalysts enable exceptional tunability in the (thermo)mechanical properties of methacrylate photopolymers while maintaining a complete cure. Significantly, modulus can be tuned as a function of light intensity and temperature, enabling the selective curing of a single composition into rigid, tough, or elastomeric forms, or the creation of high-fidelity, multi-modulus materials prepared via grayscaling techniques. Further, this technique is broadly applicable to high modulus (>1 GPa) and low modulus (<1 kPa) formulations.

Design and 3D printing of biobased epoxidized formulations based on vegetable oils with vitrimeric properties

Matilde Porcarello, Politecnico di Torino

In this work, we developed and characterized bio-based formulations derived from functionalized vegetable oils, aiming to create sustainable vitrimeric resins suitable for 3D printing. Epoxidized castor oil (ECO), known for its inherent vitrimeric behaviour due to the presence of hydroxyl groups enabling transesterification, was used as the primary component. However, its high viscosity at room temperature limits its printability. To address this, epoxidized soybean oil (ESO), a less viscous and equally bio-based alternative, was blended with ECO in varying weight ratios: 100% ECO, 100% ESO, ECO:ESO 70:30, and ECO:ESO 50:50. UV-curing characterizations of the prepared formulations were performed through FTIR and photo-DSC. Their thermal and mechanical properties were investigated through DMTA and tensile tests, while rheological analyses assessed their printability. Vitrimeric behaviour was evaluated via stress relaxation tests in the presence of a biobased transesterification catalyst eugenol-based phosphate ester (EUGP). Among the blends, the ECO:ESO 70:30 formulation retained a good vitrimeric dynamics, while in the 50:50 blend this feature decreased due to the lack of hydroxyl groups in ESO. The vitrimeric systems demonstrated successful 3D printability and were proven to be reprocessable both thermally and chemically. This work highlights the potential of renewable, plant-oil-based materials in advancing circular, sustainable additive manufacturing technologies.

Development of Parallax Volumetric Additive Manufacturing for Rapid, Large-Area 3D Fabrication

Chi Chung Li, University of Colorado Boulder

Volumetric additive manufacturing (VAM) is an emerging technology that enables the rapid creation of complex 3D freeform structures directly within photoresin by simultaneously exposing all points of the target geometry in parallel. VAM offers numerous advantages, including state-of-the-art fabrication speed, a mechanically stable and self-supporting printing environment, and the ability to create structures on top of prebuilt objects. However, current VAM methods require light to be delivered tomographically from the sides of the object, which imposes a strong limitation on achievable lateral size and hinders scalability for large-area applications. To address this constraint, we introduce a new approach—Parallax VAM—that circumvents horizontal scalability issues by delivering all exposure light in a top-down or bottom-up manner. This novel configuration eliminates the need to rotate the material container and enables the fabrication of extremely wide, aperiodic structures. As a result, this approach to volumetric 3D printing unlocks many new applications in both industrial and research settings. In this presentation, we discuss our development progress in Parallax VAM, showcase its current capabilities, and highlight several practical challenges for widespread adoption.

Photochemistry to the rescue- our 8 year journey to develop a melamine primer

Tommy Haraldsson, Mercene Labs AB

Melamine formaldehyde laminate surfaces are everywhere in our homes and offices. The products made possible with this material range from very inexpensive bookshelves and cupboards to exclusive dinner tables made from high pressure laminate (HPL). The vast majority of melamine laminates are sold without surface treatment where the pattern and the texture are determined by a press plate. However, there is an increasing trend to lacquer melamine with industrial UV-coatings to improve haptics and scratch resistance. Coating melamine is easy, but making the coating stick to the chemically inert melamine surface is a challenge that until recently was not met to the full satisfaction of furniture producers. Traditional primers rely on surface energy matching, which fails if the melamine surface has been over or under cured in the press, while 2 component isocyanate primer solutions suffer from short pot life and an extended period before full adhesion is obtained, which complicates manufacturer’s logistics. We have developed a surface activator which relies on photochemical bonding to melamine via electron deficient carbon carbon double bonds. These create a charge transfer complex with a nitrogen electron lone pair and illumination with high energy UVC photons lead to a cascade of reactions ending in the creation of covalent bonds. In this presentation, I will describe the 8 year long tortuous journey to reach this solution, complete with a spectacular failure, patent opposition and, ultimately, a good commercial product in use at 5 different companies with a combined production of 100 M sq ft UV-lacquered melamine faced boards per year.

UV Curable Ultra Low Refractive Index Nano-voided Materials

Eric Nelson, 3M

This submission will describe the process of producing nano-voided materials for use as ultralow index materials. UV curable materials can be combined with non-curable materials to produce nanometer size phase separated materials. Subsequent removal of the non-curable material produces air-filled foam materials with a composite ultralow refractive index. Materials with refractive index as low as 1.15 to 1.20 have been produced by this method. The development of these materials has been mostly focused on optical applications where air gaps between optical components are required. The reaction rate and miscibility of the different materials are used to develop the pore size and foam structure. Materials with low haze (less than 1% in the visible) and very high haze (100% in the visible) can be produced by controlling the compositions and kinetics. The high haze materials have been shown to have excellent diffusing and hiding properties in many applications. However, one drawback of these nanovoided materials is their ability to absorb materials and therefore increase their refractive index. Development of a method to seal the top surface of the coating during the manufacturing process will be demonstrated. Sealing the surface allows conventional pressure sensitive adhesive to be used to join the ultralow index materials to other films producing laminated structures with air gap properties.