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September 16-19, 2025 • Boulder, Colorado

TECHNICAL PROGRAM

Tuesday, September 16

Short Course, 9:00 – 2:15 PM

Room: SEEC S228

9:00 – 10:00
Amelia Davenport (Arkema) – Intro to Fundamentals of UV Curing
10:10 – 11:25
Chris Bowman (University of Colorado) – Photopolymerization Kinetics
12:00 – 1:00
Mike Idacavage (Radical Curing) – Applications of UV Curing
1:10 – 2:10
Allan Guymon (University of Iowa) – Design of Experiments

Plenary Sessions, 2:30 – 5:30 PM

Room: SEEC C120

2:30 – 3:00

Photoresponsive and adaptable hydrogels for biological applications

Kristi Anseth, University of Colorado Boulder

3:00 – 3:30

Novel Photopolymerization of Lipoic Acid Derivatives

Craig Hawker, UC Santa Barbara

3:30 – 4:00

Singlet-singlet resonance energy transfer: a valuable mechanism to speed up the photoreactivity in photopolymerization processes

Xavier Allonas, Universite de Haute Alsace

4:00 – 4:15

Break

4:15 – 4:45

Better Together: Photoredox & Copper Dual Catalysis ATRP

Krzysztof Matyjaszewski, Carnegie Mellon University

4:45 – 5:15

Crystallinity in polymer networks for differentiation of mechanical and optical properties in multi-material printing

Katharina Ehrmann, Technische Universität Wien

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Photoresponsive and adaptable hydrogels for biological applications

Kristi Anseth, University of Colorado Boulder

This talk will illustrate several examples of the development and application of poly(ethylene glycol) (PEG) hydrogels with photo-adaptable and/or responsive crosslinkers, especially those that impart unique material properties for biological applications. One example will illustrate the formation of hydrogels from bottlebrush polymers and how strain-stiffening mechanics facilitates the formation of protrusion-rich osteogenic cell populations, similar to osteocyte networks found in bone. In another vignette, dithiolanes are investigated as PEG crosslinkers, producing biomaterials capable of multiple light-driven mechanical transformations including stiffening, softening, and photo-induced stress relaxation. This same chemistry is further exploited to provide controllable elasticity in highly dynamic dual-crosslinked hydrogels that also contain boronate ester bonds. These matrices are compatible with light-based biofabrication techniques, allowing for spatiotemporally templated encapsulation of cells that rapidly self-organize and colonize the synthetic microenvironment as a function of viscoelasticity. Finally, photoadaptable, allyl sulfide functionalized PEG hydrogels allow for the growth of intestinal organoids, and the subsequent application of photopatterned light to locally alter epithelial curvature, initiating symmetry breaking events, and ultimately directing cell fate.

Novel Photopolymerization of Lipoic Acid Derivatives

Craig Hawker, UC Santa Barbara

The radical ring-opening polymerization (rROP) of α-lipoic acid (LA) and its derivatives represents a synthetically accessible, efficient, and scalable strategy to impart degradability into functional copolymers. By combining with traditional photopolymerization techniques, the design of sustainable materials containing LA through rROP driven by light can be achieved. This allows for a wide variety of new approaches to be contemplated. For example, the development of renewable vinyl-based photopolymer resins offers a promising solution to reducing the environmental impact associated with 3D printed materials. Lipoate monomers and cross-linkers containing dynamic disulfide bonds can be combined with acrylic monomers (n-butyl acrylate) and conventional photoinitiators to develop photopolymer resins that are compatible with commercial stereolithography 3D printing. The incorporation of disulfide bonds within the polymer network’s backbone imparts the 3D printed objects with self-healing capabilities and complete degradability. In addition, this facile synthetic approach provides access to dithiols which creates opportunities for upcycling of degraded materials and the ability to prepare multiblock copolymers using a synthetically simple and versatile photopolymerization platform.

Singlet-singlet resonance energy transfer: a valuable mechanism to speed up the photoreactivity in photopolymerization processes

Xavier Allonas, Université de Haute Alsace

Photopolymerization reactions have been continuously evolving for over 60 years. Today, new horizons have emerged, particularly in vat photopolymerization-based 3D printing. This highly specialized field has led to numerous publications in recent years and is considered one as of the most promising for the future. However, it must be acknowledged that radical photopolymerization, despite its widespread use, is currently reaching a plateau: increasing the efficiency of photoinitiators in the UV or visible range remains a significant challenge. In this paper, we will describe an original way to improve the reactivity of Type I photoinitiators. Recently, we have found an intriguing photosensitization process based on singlet-singlet resonance energy transfer from a fluorescent dye to phosphine oxide photoinitiators [1-2]. This effect allows a remarkable increase in reactivity, with sensitization ratio higher than 4. The underlying photochemistry is deeply described, taking into account the spectral overlap between the emission spectrum og the photosensitizer and the absorption spectrum of the photoinitiator.

Better Together: Photoredox & Copper Dual Catalysis ATRP

Krzysztof Matyjaszewski, Carnegie Mellon University

Photomediated Atom Transfer Radical Polymerization (photoATRP) is an activator regeneration method that enables the controlled synthesis of well-defined polymers through light irradiation. Traditional photoATRP is often limited by the need for high-energy ultraviolet or violet light. These could negatively affect the control and selectivity of the polymerization, promote side reactions, and may not be applicable to biologically relevant systems. This drawback can be circumvented by introducing a catalytic amount of photocatalysts, which absorb visible and/or NIR light. Therefore, controlled, regenerative ATRP can be performed with the dual-catalytic cycle. Recent developments in the field of dual-catalysis concerning Cu-catalyzed ATRP at ppm level and photocatalysts down to ppb level will be discussed. Well-defined polymers are prepared at rates dependent on the amount and quantum efficiency of PC, and their controlled polymer architecture is defined by the Cu-catalysts. Thus, Cu catalysts and photocatalysts can act much better together, providing robustness, oxygen tolerance, and access to new materials.

Crystallinity in polymer networks for differentiation of mechanical and optical properties in multi-material printing

Katharina Ehrmann, Technische Universität Wien

Long-range order, i.e. crystallinity, in polymer networks is difficult to achieve, in particular for fast polymerization mechanisms suitable for stereolithography or DLP printing. While post-polymerization crystallization is suitable for elastic networks, the issue becomes even more pronounced for rigid polymer networks with a rather high crosslinking density, lowering achievable degrees of crystallinity. We demonstrate the “trapping” of crystallinity via photopolymerization from the liquid crystalline state of a thiol-ene formulation at temperatures of 80-110 °C, enabling us to produce bulk and DLP printed crystalline specimens with melting enthalpies up to 25 J g-1 (estimated to be about 37% crystalline), in combination with high initial strain responses of 10-20 MPa (before yielding). In a second step, we tuned the curing conditions via printing temperature and irradiation intensity such that 3D printing at 80 °C yielded opaque, stiff semi-crystalline materials and printing at 110 °C yielded transparent, elastic amorphous materials from the same formulation. We further demonstrate data storage and shape memory applications for these multi-material structures.