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September 16-19, 2025 • Boulder, Colorado

TECHNICAL PROGRAM

Thursday, September 18

Plenary Sessions, 8:30 – 10:00 AM

Room: SEEC C120

8:30 - 9:00

Regulating polymer properties through combined covalent and physical network structure
Jeff Stansbury, University of Colorado

9:00 - 9:30

Photomediated Synthesis of Ultra-High Molecular Weight Polymers for Advanced and Programmable Circular Materials
Brent Sumerlin, University of Florida

9:30 - 10:00

Photopolymer Challenges for Volumetric Additive Manufacturing
Robert McLeod, University of Colorado Boulder

10:00 - 10:15

Break

Parallel Sessions, 10:15 – 12:15 PM

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

10:15 - 10:40

Spatial Control of Thiol-Ene Curing Kinetics by Antagonistic Photoreactions
Thomas Griesser, University of Leoben
Switching between Cationic and Radical Polymerizations
Brett Fors, Cornell University

10:40 - 11:00

Thiol-based coatings enhance the optical properties of elastomers fabricated with VAT photopolymerization for medical applications
Alan Aguirre-Soto, Tecnologico de Monterrey
Digital Light Processing of Bio-Derived Conductive Composites with Joule-Heating Capabilities
Alberto Cellai, Politecnico di Torino

11:00 - 11:15

Break
Break

11:15 - 11:40

Sub-optical stress field analysis in heterogeneous polymer films
Lewis Cox, Montana State University
Sustainable UV-Cured polymer: from coatings to composites and additive manufacturing
Marco Sangermano, Politecnico di Torino

11:40 - 12:00

Kinetic modeling of diffusion-limited thiol-ene photopolymerization
Yunfeng Hu, University of Colorado Boulder
Understanding reactive conversion of polymers for additive manufacturing of functional materials
Max Saccone, University of Colorado Boulder

12:00 - 12:45

Constructing and Deconstructing Thermosets with Light and Thiols: Polarity Reversal Catalysis and Dual-Trigger Strategies
Derek Patton, University of Southern Mississippi
Kinetics-Driven Design of Next-Generation 3D Printing Materials
Sijia Huang, University of Utah
 

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

Shape-morphing particles from photocrosslinkable copolymer films
Ryan Hayward, University of Colorado
Aqueous PhotoATRP of Responsive Polymers from Structured Peptide Assemblies
Christopher Kloxin, University of Delaware

2:10 - 2:30

3D printable, mechanically robust, nanostructured block copolymer hydrogels
Arkodip Mandal, University of Colorado Boulder
Dual Cure Approaches to Polymer Networks Involving Dynamic Chemistry
Alexander Osterbaan, University of Colorado Boulder

2:30 - 2:50

3D Printing of PolyHIPE Scaffolds with Bioactive Glasses: a Bio-Based Platform for Bone Tissue Regeneration
Matteo Bergoglio, Politecnico di Torino
Production of Rare Earth Elements Using 3D Printed Ion Exchange Resins
Sophie Morton, University of Utah

2:50 - 3:10

High-Performance 3D-Printing Resins Based on Triazine Cores and Isocyanate-Free Urethane–Acid Networks
Sean Keyser, University of Colorado
Surface-Initiated Photopolymerization: Exploring the Power of Germanium Photoinitiators
Christine Bandl, Technical University of Leoben

3:10 - 3:35

Hierarchically structured, functional coatings from photo-based processes
Caroline Szczepanski, Michigan State University
Photo + ROMP: Using light in unique ways to control ring-opening metathesis polymerizations
Leah Appelhans, Sandia National Laboratories

3:35 - 4:00

Break
Break

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

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Regulating polymer properties through combined covalent and physical network structure

Jeff Stansbury, University of Colorado

The goal of this study is to develop a better understanding of how an integrated monomer design and comonomer selection strategy in photocurable formulations can be employed to achieve favorable properties in both the monomeric and polymeric states. To approach this, we use urethane-based monomers and oligomers with systematically varied urethane group number and placement. These will be combined with mono- or di-vinyl monourethane monomers that contribute to significant reductions in viscosity while also providing control of overall urethane content, reactive group concentration and covalent network density. Reduced covalent crosslink densities tend to limit polymer modulus and strength potential but here, we incorporate comonomers with specific affinities for urethane group hydrogen bonding that promote further reductions in pre-cure viscosity. This also provides a pathway for noncovalent reinforcement in the photopolymers that allows lower covalent network density while maintaining or enhancing polymeric mechanical properties. Taken together, this work demonstrates a method to achieve high-performance formulations that allow polymer strength and stiffness to be raised in parallel with increased toughness. Results with conventional and novel materials will be displayed in addition to highlighting analytical characterization techniques that purposely target critical material properties.

Photomediated Synthesis of Ultra‚ÄëHigh Molecular Weight Polymers for Advanced and Programmable Circular Materials

Brent Sumerlin, University of Florida

We report a photomediated polymerization strategy that uses only mild UV or visible light irradiation of thiocarbonylthio compounds to access ultra-high molecular weight (UHMW) block polymers, semi telechelic polymers, and polymer–protein conjugates. This method achieves number average molecular weights exceeding 10^7 g/mol and degrees of polymerization over 100,000 Рrepresenting the highest molecular weights attained via living polymerization to date. These UHMW polymers are effective in applications such as pressure-sensitive adhesives, thermally conductive materials, and mucin mimetics. Remarkably, the same photochemistry also enables controlled depolymerization back to monomers, paving the way for recyclable, low-energy polymer life-cycle management and subtractive manufacturing processes. This illustrates a powerful concept of “programmable” polymer design for sustainable, circular materials.

Photopolymer Challenges for Volumetric Additive Manufacturing

Robert McLeod, University of Colorado Boulder

Vat photopolymerization techniques such as stereolithography and digital light projection have driven optimization of photopolymers to meet processing (e.g. low viscosity, fast curing, large dark conversion) and final property (e.g. modulus, toughness, biocompatibility) requirements. The rapidly developing field of volumetric additive manufacturing (VAM) presents new material opportunities and challenges for the photopolymer field. Challenges include shrinkage and the subsequent densification because this leads to sinking of unsupported parts. Since VAM fabricates entire parts dramatically faster than layer-by-layer methods, the exotherm of reaction is proportionally more important to manage. Haze and refractive index changes induced by conversion can interfere with the light delivery into the resin volume. Conversely, some requirements like viscosity are relaxed since no resin need move, allowing printing even into solids. I will review recent advances in VAM architectures including one created by my research group, Parallax Manufacturing. I will contrast the fabrication results of these systems with traditional layer-by-layer methods. These examples will illustrate opportunities for photopolymer chemistry and processing for this new paradigm of additive manufacturing.

Spatial Control of Thiol-Ene Curing Kinetics by Antagonistic Photoreactions

Thomas Griesser, University of Leoben

The use of two wavelengths to activate different photoreactions in a resin system has recently attracted much attention in the scientific community.[1] In this contribution, antagonistic photochemistry is employed to enable spatial control over the curing kinetics of a thiol-ene photopolymerization. Thiol-ene networks are known for their excellent biocompatibility and toughness, making them attractive alternatives to conventional (meth)acrylate systems.[2] However, the application of previously reported antagonistic concepts—such as the selective termination of radical polymerizations through radical recombination—remains questionable in thiol-based systems due to radical transfer reactions.[3] Prior studies by Bowman et al. have shown that amines can exert a retarding effect on the thiol-ene reaction. Based on these findings, a photo latent base was utilized to inhibit thiol-ene photopolymerization triggered with UV light of 365 nm. This antagonistic mechanism allows for spatial modulation of curing kinetics through selective light exposure. Using two wavelength laser writing experiments, a sub-micron resolution with feature sizes below 0.5 µm was achieved, while gray-scale patterning enabled continuous tuning of polymerization kinetics. Importantly, several ene monomers were shown to undergo successful photobase-induced inhibition, indicating the broader applicability of this concept. In summary, a dual-wavelength, antagonistic photoreactive system was developed, enabling spatially resolved inhibition and modulation of thiol-ene polymerization with potential for advanced photofabrication techniques such as interference lithography.

Switching between Cationic and Radical Polymerizations

Brett Fors, Cornell University

Synthetic polymers are of significant importance in all aspects of modern life, and during the last few decades, these materials have facilitated major societal advances. Innovative polymeric materials have the potential to address humankind’s next grand scientific and technological challenges; however, taking advantage of the opportunities presented by these materials requires new methods for gaining precise control of polymer structure and function. To address this challenge, our research group focuses on the development of new synthetic methods and catalyst systems to control polymer architecture, composition, and function to yield next-generation materials. This presentation will detail the development of methods that enable switching of polymerization mechanism and monomer selectivity using external stimuli to control polymer structure and function. Additionally, recent discoveries in our group on controlled cationic polymerizations that can be run open to the air without monomer purification will be discussed. These new methods enable the streamlined synthesis of polymeric materials with precisely controlled structures.

Thiol-based coatings enhance the optical properties of elastomers fabricated with VAT photopolymerization for medical applications

Alan Aguirre-Soto, Tecnologico de Monterrey

An ideal vascular phantom should be anatomically accurate, have mechanical properties as close as possible to the tissue, and be sufficiently transparent for ease of visualization. However, materials that enable the convergence of these characteristics have remained elusive. The fabrication of patient-specific vascular phantoms with high anatomical fidelity, optical transparency, and mechanical properties close to those of vascular tissue is reported. These final properties are achieved with patient-specific vascular replicas fabricated through vat photopolymerization with commercial elastomeric acrylic-based resins before coating them with thiol-based photopolymerizable resins. A PETMP/allyl glycerol ether (AGE)/polyethylene glycol diacrylate (PEGDA) coating with a 30/70% AGE/PEGDA ratio applied on a flexible resin yielded elastic modulus, UTS, and elongation of 3.41 MPa, 1.76 MPa, and 63.2%, respectively, in range with the human aortic wall. The PETMP/AGE/PEGDA coating doubled the optical transmission from 40% to 80%, approaching 88% of the benchmark silicone-based elastomer. Higher transparency correlates with a decrease in surface roughness from 2000 to 90 nm after coating. Coated 3D-printed anatomical replicas are showcased for pre-procedural planning and medical training with good radio-opacity and echogenicity. Thiol-click chemistry coatings, as a surface treatment for elastomeric stereolithographic 3D-printed objects, address inherent limitations of photopolymer-based additive manufacturing.

Digital Light Processing of Bio-Derived Conductive Composites with Joule-Heating Capabilities

Alberto Cellai, Politecnico di Torino

This study explores the development of sustainable, smart materials for 3D printing by combining bio-based chemistry with functional performances. A photocurable acrylate polyglycerol monomer, derived from renewable sources such as saponified vegetable oils or microbial fermentation, was used to create photopolymerizable resins, suitable for Digital Light Processing (DLP). To introduce functionality, various conductive fillers,including silver, copper, nickel powders, and recycled carbon fibers (RCF), were incorporated into the resin. These additions enable electrical conductivity and the potential for heat generation through the Joule effect, opening up opportunities for smart, responsive devices. A comprehensive set of characterization techniques, including FT-IR, photo-DSC, rheology, DMTA, electrical conductivity tests, and thermal imaging, revealed that while higher filler contents increase viscosity and slightly reduce polymerization rates, they significantly boost electrical performance. In particular, Ag and RCF fillers allowed for efficient, homogeneous heating of the printed parts under low voltages. To demonstrate the potential for real-world applications, a wearable smart ring was 3D-printed using a formulation with 50 wt% silver. The device reached surface temperatures of around 60 °C with an applied voltage as low as 1–3 V, showcasing the feasibility of using these materials in custom-designed electronic or medical devices. Overall, this work highlights a promising route toward functional, sustainable 3D-printed components using bio-based photopolymers and conductive fillers.

Sub-optical stress field analysis in heterogeneous polymer films

Lewis Cox, Montana State University

Orthogonal actinic resins provide a spatial control over network topology that has revitalized long-standing engineering interests in stress transfer across dissimilar material interfaces, the critical concept underpinning structural failure and fracture. Mapping a stress field in heterogeneous media requires spatial correlation of displacement gradients and mechanical properties. Characterizing this information becomes complicated when relevant stress fields occur across sub-optical length scales. Digital image correlation (DIC) of atomic force microscopy (AFM) topography scans has traditionally been used to obtain sub-optical displacement gradients, although it has been limited by challenges associated with feature contrast and noise, and fast acquisition of force displacement measurements can now be used to provide high resolution maps of mechanical properties. This talk navigates the challenges associated with stress field mapping and establishes simple protocols for others to follow. Specifically, we demonstrate that DIC of tapping mode error (amplitude) channels enable displacements of sub-nanometer surface textures to be tracked, circumventing traditional challenges with feature contrast and noise filtering. We articulate a simple methodology for quantifying suitable DIC subset and step sizes for AFM images using free power spectral density analysis tools. Finally, a process for overlaying mechanical properties onto DIC-generated strain fields is presented and the complications associated with application of the technique to viscoelastic materials is discussed.

Sustainable UV-Cured polymer: from coatings to composites and additive manufacturing

Marco Sangermano, Politecnico di Torino

Biobased monomers are becoming increasingly important to develop green products to substitute petroleum-based materials [1]. In this study different biobased monomers have been synthesized and exploited both in cationic and radical UV-Curing [2]. Reactivity of curing process was investigated, and the crosslinked materials fully characterized. An easy tailoring of the properties of the final UV-cured coatings is demonstrated by varying the ratio of the monofunctional-difunctional epoxy monomer or by in-situ generation of hybrid organic-inorganic networks. The same formulations were processed in 3D-printing using the hot-lithography technique when processing epoxy monomers [3]. Curing and printability conditions have been defined and the printed object fully characterized. Finally, UV-Cured composites were achieved by exploiting the frontal induced photopolymerization process [4]. This technique allowed to exploit UV-Curing also to achieve thick composites.

Kinetic modeling of diffusion-limited thiol-ene photopolymerization

Yunfeng Hu, University of Colorado Boulder

Thiol-ene photopolymerizations are widely used, yet their behavior under diffusion-limited conditions remains poorly understood and underexplored in kinetic modeling. A reaction kinetic model integrating free volume theory was developed to elucidate diffusion-controlled kinetics and quantitatively predict the ultimate functional group conversion in radical-mediated thiol-ene step-growth photopolymerizations. The glass transition temperature (Tg) of the reaction mixture was experimentally correlated with monomer conversion using a combination of photo-DSC and temperature-sweep DSC. The Tg values at 0% and 100% conversion were incorporated into the kinetic framework to model free volume evolution during polymerization, resulting in highly accurate predictions of both the reaction rate and final conversion—within 5% of experimental measurements. Using this model, we systematically evaluated the influence of crosslinking density, reaction temperature, and plasticizer loading on polymerization behavior. This model was further applied to simulate the spatial and temporal kinetics in holographic recording of photopolymers, providing critical insights for the design of high-performance holographic photopolymer systems.

Understanding reactive conversion of polymers for additive manufacturing of functional materials

Max Saccone, CU Boulder

Photopolymers can be used as scaffolds, reactors, or reactants in subsequent materials transformations that yield architected materials such as hard carbons, ceramics, and metals. To break paradigms of accessible material class and resolution, these processes typically rely on heating additively manufactured parts in a reactive environment to drive polymer decomposition and precursor conversion to target materials. However, there remain gaps in our understanding of the fundamentals of how these reactions occur, as well as gaps in our ability to fabricate certain classes of materials. This talk will explore recent progress towards understanding how polymer chemistry, reaction conditions, and reactor design influence polymer conversion processes to form inorganic materials. One example of using reactive conversions is hydrogel infusion additive manufacturing (HIAM), a technique which enables fabrication of many metals such as copper, nickel, tungsten, and multicomponent alloys from a single photoresin system using an infusion-reaction paradigm. In this process, 3D printed hydrogels are swelled with aqueous metal precursors, then calcined and reduced to create miniaturized metal replicas, enabling quick iteration, compositional tuning, and multimaterial fabrication. This infusion-reaction approach has recently been extended to create composites containing polyacrylonitrile, a conventionally hard-to-print polymer that can be pyrolyzed to form architected carbon materials with carbon yields above 40%. Synthesis of polymer-derived inorganic materials is also synergistic with novel 3D printing processes including roll-to-roll printing and microfluidic printing with continuous resin injection. Analysis of these processes has led to an extension of the canonical Jacobs working curve for situations in which photopolymer is continuously introduced through microfluidic channels. Altogether, this work provides a path for photopolymer additive manufacturing to fabricate a wide range of inorganic materials at the microscale, with applications from the biomedical to aerospace to energy fields.

Constructing and Deconstructing Thermosets with Light and Thiols: Polarity Reversal Catalysis and Dual-Trigger Strategies

Derek Patton, University of Southern Mississippi

This work demonstrates photoinduced thiol-catalyzed hydrogen abstraction and β-scission of acyclic benzylidene acetals as an innovative strategy to “command-destruct” polymer thermosets. Poly(thioether acetal) networks, synthesized via thiol-ene photopolymerization, degrade rapidly into alkyl benzoate byproducts upon light exposure, transitioning from solid to liquid within seconds. This dual-mode photochemistry enables rapid photopolymerization and photodegradation with a single light source, leveraging the distinct kinetics of radical-mediated polymerization and thiol-catalyzed β-scission. The process relies on stoichiometrically imbalanced thiol-ene formulations, where residual free thiols in the network are essential for efficient degradation. Substituent effects were investigated to modulate photodegradation rates. Spatial control was achieved using photolithography to pattern thermoset degradation, while wavelength-selective degradation was demonstrated with a violet light-sensitive photoinitiator. Furthermore, thermal protecting groups were introduced to excess thiols, creating a dual-trigger “AND” gate requiring both heat and light for activation. This approach to photoinduced command-construct and command-destruct processes shows potential for a range of applications, including degradable adhesives, additive/subtractive manufacturing, and more broadly as environment friendly materials with well-defined end-of-use management strategies.

Kinetics-Driven Design of Next-Generation 3D Printing Materials

Sijia Huang, University of Utah

Vat photopolymerization (VP) techniques have enabled the fabrication of complex geometries by balancing high precision with fast processing speeds. However, current VP techniques still face several challenges, including limited design freedom for unsupported features, restricted material selections, and the absence of in-situ monitoring techniques to better understand the printing process. To address these limitations, I will discuss our recent efforts in engineering chemical reactions to close these gaps. Specifically, I will introduce a newly designed orthogonal chemistry framework for printing a base-degradable thermoset, allowing support structures to be patterned in a one-pot formulation alongside the primary structural material. This approach enables dual-wavelength patterning of sacrificial thermoset supports, expanding the range of accessible 3D-printable materials and geometries. In addition, I will present a new digital twin platform for 2D and 3D visualization of reaction kinetics in additive manufacturing, which opens new possibilities in precision fabrication and functional material design.

Shape-morphing particles from photocrosslinkable copolymer films

Ryan Hayward, University of Colorado

Photocrosslinkable polymer films based on copolymers containing pendent benzophenone moieties have proven to be a versatile system for defining stimuli-responsive shape-morphing materials. In particular, this system allows for spatial definition of crosslink density within swellable hydrogel materials, and/or of multiple materials with varying properties. While our past studies have relied on these methods to fabricate millimeter-scale objects in a one-by-one fashion, we have recently focused on preparing micrometer-scale particles in a more scalable fashion using a commercial maskless lithography system. This enables production of particles with a wide variety of geometries, including cylindrical shells, spherical caps, saddles, and helical ribbons, that can be varied via changes in temperature. We are working to characterize how assembly and collective behavior of these particles are driven by changes in shape in a variety of contexts.

Aqueous PhotoATRP of Responsive Polymers from Structured Peptide Assemblies

Christopher Kloxin, University of Delaware

Photoinduced atom transfer radical polymerization (photoATRP) enables precise polymer growth under mild, aqueous conditions by generating radicals on demand with light. In this work, we used aqueous photoATRP to grow polymers directly from bundlemers, coiled-coil peptide assemblies that serve as structurally defined nanoscale scaffolds. Site-specific installation of bromoisobutyramide initiators allowed light-controlled polymerization without disrupting the native coiled-coil structure. This approach produced uniform, low-dispersity conjugates with tunable polymer lengths and responsive lower critical solution temperature (LCST) behavior. We further demonstrated sequential photoATRP and modular initiator placement to create bottlebrush-like architectures and explored their assembly using microscopy and simulations. Overall, this strategy showcases how aqueous photoATRP can combine the stability of protein nanostructures with the dynamic functionality of light-activated polymers, offering a versatile platform for designing adaptive hybrid materials.

3D printable, mechanically robust, nanostructured block copolymer hydrogels

Arkodip Mandal, University of Colorado Boulder

Tremendous advances over the past two decades in macromolecular design and network architecture and topology have led to the development of mechanically robust hydrogels, significantly expanding their applications to load-bearing implants, wearable sensors and patches, drug delivery systems, and soft-robotic actuators. Nevertheless, many of these hydrogel systems continue to suffer from key limitations, such as mechanical deterioration in physiological environments, poor fatigue resistance due to irreversible network damage, limited self-recovery at ambient conditions following deformation, lack of dissipation mechanisms, or incompatibility with advanced manufacturing techniques. Here, we overcome these limitations by designing nanostructured block copolymer (BCP) based hydrogels in a highly modular fashion from macromolecular building blocks that crosslink via thiol-ene based photoclick reactions. The hierarchical architecture of the BCP hydrogels at the nano- and meso-scales, comprising self-assembled domains and ordered grains, underpin their robust and complex mechanical response. This results in hydrogels exhibiting high modulus, high stretchability, high fracture toughness, high energy dissipation, high fatigue-resistance, and rapid, complete self-recovery under ambient conditions. Importantly, the precursors can be formulated as resins compatible with lithography-based additive manufacturing, enabling the rapid fabrication of complex 3D hydrogel architectures with high spatial resolution. This unique combination of mechanical performance, bottom-up tunability, and processibility make these BCP hydrogels attractive for diverse biomedical applications.

3D Printing of PolyHIPE Scaffolds with Bioactive Glasses: a Bio-Based Platform for Bone Tissue Regeneration

Matteo Bergoglio, Politecnico di Torino

PolyHIPEs are porous polymers fabricated using a technique known as high internal phase emulsion (HIPE) templating. This process involves polymerising monomers within an emulsion where the dispersed (internal) phase makes up at least 74% of the total volume. Polymerisation locks the emulsion structure in place, yielding a highly porous polymer with an interconnected network of voids, ideal for nutrient transport and cell infiltration in biomedical applications. This study presents the development, characterisation, and biological assessment of biobased thiol-ene polyHIPE scaffolds reinforced with bioactive glass (BG) particles for bone tissue engineering applications. The scaffolds were formulated using renewable monomers and processed via HIPE templating to achieve highly porous, interconnected structures. To enhance patient-specific adaptability, the materials were also successfully 3D printed, maintaining their porosity while introducing macroporosity into the architecture. Morphological analysis confirmed the formation of open-cell foams with interconnected pores, favourable for in situ nutrient transport and cell infiltration. Contact angle measurements showed a progressive increase in surface hydrophilicity with higher BG content, attributed to hydroxyl groups on the glass surface, an advantageous property for biological interactions. Gel content analysis indicated a highly crosslinked network, while thermogravimetric analysis (TGA) confirmed both the high thermal stability of the polymer matrix and the successful incorporation of BG. Dynamic Mechanical Thermal Analysis (DMTA) revealed a BG-dependent increase in glass transition temperature (Tg), suggesting reduced polymer chain mobility and improved stiffness. Compression testing demonstrated a substantial increase in elastic modulus with BG addition, without compromising shape-memory behaviour. Biological evaluations using MG-63 osteoblast-like cells confirmed excellent cytocompatibility for all formulations. Resazurin assays showed sustained metabolic activity and cell proliferation over 7 days. Phalloidin/DAPI staining revealed progressive cell spreading and adhesion, while OsteoImage assays conducted after 28 days indicated hydroxyapatite deposition that increased with BG content, demonstrating the osteoinductive potential of the scaffolds. Overall, the combination of 3D printability, high porosity, mechanical performance, and bioactivity makes these biobased thiol-ene polyHIPE scaffolds strong candidates for sustainable and effective bone regeneration strategies.

Production of Rare Earth Elements Using 3D Printed Ion Exchange Resins

Sophie Morton, University of Utah

Rare earth elements (REEs) are essential in a wide range of technologies from consumer electronics to medical and industrial-grade applications. Conventional solvent extraction techniques for REE recovery involve intense hydrometallurgical processing and leaching, require high solvent consumption, and generate significant chemical waste. Ion exchange resins have emerged as an alternative method in the extraction of REEs due to their durability, cost-effectiveness, and tunable selectivity. This work investigates methacrylate- and methacrylamide-based photopolymer resins synthesized with varying secondary monomers and crosslinkers to optimize ion selectivity and binding capacity. Formulations were designed to be compatible with stereolithography (SLA) 3D printing, which offers greater control over polymer architecture and lattice geometry as well as reduces curation time to seconds. Once the printed lattice structures were optimized, the samples underwent multi-cycle adsorption/desorption testing to evaluate reusability and long-term stability. The integration of customizable SLA-printed ion exchange resins demonstrates a more sustainable and efficient method for REE recovery systems.

High-Performance 3D-Printing Resins Based on Triazine Cores and Isocyanate-Free Urethane–Acid Networks

Sean Keyser, University of Colorado

Achieving both high stiffness and toughness in a single photopolymer remains a central challenge in additive manufacturing. Conventional urethane-linked networks have been used to address this, introducing hydrogen bonds that enhance toughness while retaining high modulus. However, their synthesis typically relies on toxic, petroleum-derived isocyanates. While scalable and widely used, isocyanates pose significant health and handling risks due to their reactivity and sensitization potential. Incorporating carboxylic acids alongside urethanes has been shown to further increase hydrogen bond density and improve mechanical performance, but still does not eliminate the reliance on isocyanates, limiting progress toward safer, more sustainable material platforms. This work introduces a new class of triazine-based resins that enable urethane–acid chemistry through an isocyanate-free carbonate–amine route. Rigid, multifunctional triazine cores support a modular, isocyanate-free synthetic route to urethane formation, enabling the synthesis of both homo- and hetero-functional monomers and oligomers with precise control over branching, molecular weight, and functionality. All reactions proceed under mild conditions using low-cost, scalable reagents in yields exceeding 90%, providing a flexible and tunable foundation for high-performance resin formulations. When combined with hydrogen-bonding carboxylic acid comonomers, these resins cure into photopolymer networks with dry-state moduli above 5 GPa, flexural strengths over 180 MPa, and toughness exceeding 10 MJ/m³, matching and surpassing the performance of leading commercial systems, without the use of isocyanates. This safer, tunable system advances resin design for vat and multimaterial printing, offering a viable path to high-performance additive manufacturing without isocyanates.

Surface-Initiated Photopolymerization: Exploring the Power of Germanium Photoinitiators

Christine Bandl, Technical University of Leoben

Applications and perspectives of Ge-based PI in surface initiated photopolymerization will be presented with a special focus on surface initiated free radical promoted cationic photopolymerization pathways. Ge-based photoinitiators (PI) offer several advantages over their P-based counterparts including low toxicity, high reactivity towards monomers and an extended absorption up to 480 nm enabling excitation of the PI in the visible range. Irradiation of these compounds initiates Norrish type I cleavage resulting in highly reactive germanium centered radicals (germyl radicals), which readily add to monomeric double bonds. Beyond this free radical polymerization, our latest results also show that free radical promoted cationic polymerization of monomers such as epoxides and vinylethers proceeds in the presence of iodonium salts. The respective photochemical reaction pathway was proved by chemically induced dynamic nuclear polarization spectroscopy. Both approaches are utilized for surface initiated grafting-from polymerizations, which are characterized by various techniques including FTIR, solid-state NMR, XPS, SEM, ToF-SIMS and TGA, proving the growth of polymer chains from the modified surfaces and assessing the structure of these polymers as well as the grafting densities. Due to their low toxicity, strong absorption in the visible range, and versatile reaction mechanisms, the investigated Ge-based photoinitiators (PIs) represent highly promising photoreactive systems. These properties make them well-suited for advanced applications such as dental nanocomposite resins, controlled drug release systems, cancer therapy, dye-doping, silica-coated quantum dots, and many more.

Hierarchically structured, functional coatings from photo-based processes

Caroline Szczepanski, Michigan State University

Hierarchical topography, meaning a surface with features of multiple length scales, can enhance coating performance. Specifically, hierarchical topography impacts optical properties (matte appearance, structural color), adhesion, and even allows for unique wettability regimes such as guided fluid transport or fog collection. While complex, multi-scale topography can be engineered via machining, lithography and additive manufacturing, these strategies can be limiting in terms of time, energy, and excess material waste. In this talk, I will highlight recent efforts from our team using straight-forward photopolymerizations to engineer surface topography and chemical patterning. This includes introducing heterogeneous polymerizations so multiple scales of topography form during a single UV-curing step: (1) traditional wrinkling patterns resulting from depth-wise gradients in cross-link density due to oxygen inhibition and (2) macro-scale features due to phase domains of differing stiffness. Taking this one step further, I will highlight our recent efforts at achieving transient and on-demand topographies, mainly via the use of coumarin functionalities within a coating network. We take advantage of the photo-responsive nature of coumarin (dimerization upon exposure to long wave UV (365 nm) and cleavage when exposed to short wave UV (254 nm)) to manipulate coating cross-link density, and thus the scale of surface instabilities (e.g. wrinkles) that form. I will discuss how these hierarchical, and potentially dynamic structures are of interest for smart coatings and devices.

Photo + ROMP: Using light in unique ways to control ring-opening metathesis polymerizations

Leah Appelhans, Sandia National Laboratories

Photoactivated catalysts have been extensively investigated for the initiation of ring-opening metathesis polymerization. However, much less work has been done on using light to enable active control of ROMP. Our group is investigating multiple approaches to use light to control both reaction rates and polymer composition. With catalyst-based photocontrol we demonstrate control over the front velocity and direction of propagation of a frontal ring-opening metathesis polymerization (FROMP). Frontal reactions continue propagation after initiation through a self-sustaining thermal front, and the speed and direction of a propagating front cannot be easily controlled. Using the photobase generator NPPOC-TMG and different photosensitizers we have demonstrated both acceleration and deceleration of FROMP. In addition, we can control the direction and shape of FROMP propagation in a sheet of resin. We will also share initial results on monomer-based photocontrol approaches which utilize photoisomerizable monomers to control the composition and thermomechanical properties of a FROMP copolymer, and show applications in photolithography and DIW 3D printing. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525