📄 chemistry

Extrusion-induced topological evolution mediated polymer-based flexible full-color circularly polarized luminescent materials towards 3D printing

This study presents a strategy combining chiral micro-crosslinked double-networks and extrusion-induced topological evolution to fabricate flexible, full-color circularly polarized luminescent materials with tunable mechanics and 3D printability, enabling the automated manufacturing of complex chiroptical devices.

Original authors: Wei Zhang, Gong Zhang, Zhichuang Liao, Nianwei Wang, Jiaxing Zhang, Ruizhe Xing, Zixiang He, Zhiwei Zhao

Published 2026-09-24

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CC BY 4.0

Original authors: Wei Zhang, Gong Zhang, Zhichuang Liao, Nianwei Wang, Jiaxing Zhang, Ruizhe Xing, Zixiang He, Zhiwei Zhao

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine a world where the screens on your smartwatch or the displays in your car could bend, stretch, and wrap around your wrist without breaking, yet still project images with a special kind of depth that makes 3D movies look real. This is the promise of flexible electronics, but a major hurdle has always been the materials themselves. Most materials that can create these special 3D images are either too brittle to bend or too fluid to hold a shape. They often require rigid containers or complex chemical setups that make them impossible to print into custom shapes. Scientists have long sought a material that is soft enough to move with the human body but strong enough to be molded into intricate designs, all while maintaining the ability to emit light that spins in a specific direction, a property known as circularly polarized luminescence.

In a new study, researchers have developed a way to create such a material using a clever combination of chemistry and physics. They created a gel-like substance that behaves like a thick paste when sitting still but flows smoothly when squeezed through a tube. Once squeezed, this paste instantly transforms into a solid, stretchy structure that glows with vibrant colors. The key to this transformation lies in how the molecules inside the gel rearrange themselves when forced through a narrow opening. By pushing the gel through a syringe, the researchers triggered a change in the internal structure of the material, causing the long molecular chains to line up and lock together. This process not only made the gel much stronger and more stretchable but also amplified its ability to emit light with a specific spin, making the colors brighter and more distinct.

The team started by designing a specific type of plastic molecule that had tiny hooks on its sides. They mixed these molecules with a second type of plastic and a chiral substance, which is a material that has a "handedness" like a left or right glove. This mixture formed a precursor gel that was soft and fluid enough to be pushed through a syringe. When the researchers extruded this gel, the physical force of the squeezing acted as a catalyst. It caused the molecular chains to orient themselves in a specific direction and form new, strong connections. This phenomenon, which the authors call extrusion-induced topological evolution, turned the weak, squishy gel into a robust, self-supporting material. The result was a gel that could be stretched to more than three times its original length without breaking, yet it retained its ability to glow with intense, circularly polarized light.

What makes this discovery particularly exciting is that the researchers were able to tune the material to produce a full spectrum of colors. By slightly altering the chemical structure of the main plastic molecules, they created versions that glowed blue, green, and red. They even mixed these different colored gels together to create a material that emitted a bright, pure white light. This versatility means that the same basic method can be used to create a wide variety of visual effects. The team demonstrated that these gels could be used as ink in a 3D printer. Without needing any extra binding agents or support structures, the gel could be printed layer by layer to build complex, multi-colored objects. The printed shapes held their form, could be bent and twisted, and continued to glow with their specific colors and light-spinning properties.

The study also showed that the properties of these gels could be fine-tuned after they were printed. By exposing the printed objects to light and a secondary chemical agent, the researchers could make the material stiffer or more flexible, depending on the needs of the final product. This level of control suggests that these materials could be used to create wearable devices that conform to the skin, flexible displays that can be rolled up, or even advanced security labels that are impossible to copy. The ability to print these materials directly into complex shapes opens the door to manufacturing soft, chiral optical devices on a large scale, moving us closer to a future where our electronic devices are as flexible and adaptable as the human body itself.

Technical Summary: Extrusion-Induced Topological Evolution Mediated Polymer-Based Flexible Full-Color Circularly Polarized Luminescent Materials

Problem Statement
Circularly polarized luminescence (CPL) materials are critical for next-generation photonic applications, including 3D displays, optical communications, and information encryption. While existing CPL-active materials such as liquid crystals, supramolecular assemblies, and polymers offer unique optical properties, they face significant limitations in practical application. Cholesteric liquid crystals often require encapsulation due to fluidity, and supramolecular assemblies suffer from processing constraints imposed by their spontaneous formation in solution. A primary challenge remains the construction of flexible, processable CPL materials that possess large luminescence dissymmetry factors ( $g_{lum}$ ) and can seamlessly integrate with dynamically moving biological tissues or wearable devices. Specifically, creating extrudable gels that balance flowability during extrusion, shape retention post-extrusion, and chirality preservation is a formidable task.

Methodology
The authors propose a synergistic strategy combining chemical design and physical processing to address these challenges. The methodology involves three core components:

Synthesis of Functional Polymers: Novel polyfluorene derivatives were synthesized via Yamamoto coupling. These polymers feature side-chain vinyl groups (crosslinkable sites) and were designed with varying electron-withdrawing groups (BT and DTBT units) to tune emission colors.
Construction of Chiral Micro-Crosslinked Double-Network (CMCDN) Precursor Gels:
- Micro-Crosslinking: A thiol-ene click reaction was performed between the polymer side-chain double bonds and a dithiol crosslinker (DODT) under UV irradiation. This created a micro-crosslinked network (MCN) with approximately 30% double bond conversion, leaving residual double bonds for secondary regulation.
- Chiral Assembly: The MCN polymer was mixed with poly(methyl methacrylate) (PMMA) and a chiral inducer (S- or R-limonene). PMMA formed a second network via non-covalent interactions and physical entanglement, creating a double-network structure.
- Precursor Formation: The mixture was frozen to form an extrudable precursor gel (Pre-Gel) exhibiting shear-thinning behavior.
Extrusion-Induced Topological Evolution (EITE): The precursor gel was extruded through a syringe. This mechanical shear process triggered a topological evolution where the polymer chains underwent orientational rearrangement, partial crystallization, and strengthened non-covalent interactions (van der Waals, C-H/O=C, and $\pi$ - $\pi$ stacking).
Secondary Crosslinking and 3D Printing: Residual double bonds allowed for secondary crosslinking using a tetrathiol crosslinker (PETMP) to tune mechanical stiffness. The extrudable gels were subsequently used as inks for Direct Ink Writing (DIW) 3D printing without auxiliary resins.

Key Results

Enhanced Mechanical and Optical Properties: The EITE process significantly transformed the material properties. The storage modulus ( $G'$ ) and loss modulus ( $G''$ ) of the extruded gel (S-P1-Gel) increased by approximately 100-fold compared to the precursor gel. The luminescence dissymmetry factor ( $g_{lum}$ ) improved from $8.9 \times 10^{-4}$ in the precursor to $7.8 \times 10^{-3}$ in the extruded gel (an 8.8-fold increase) at 551 nm.
Structural Mechanism: Structural characterization via 2D GIWAXS and Polarized Optical Microscopy (POM) revealed that the extrusion induced a transition from a disordered structure to an oriented one. The extruded gel exhibited a higher proportion of "face-on" packing and distinct $\pi$ - $\pi$ stacking (d-spacing of 5.57 Å), which facilitated chiral amplification and mechanical reinforcement. Theoretical calculations (mIGM) confirmed that shear forces enhanced attractive interactions between the P1 and PMMA chains.
Full-Color Emission: By synthesizing two additional polyfluorene derivatives (P2 and P3) with different bandgaps, the authors achieved full-color CPL gels emitting blue (P2), green (P1), and red (P3). The $g_{lum}$ values for the red and blue gels reached $5.9 \times 10^{-3}$ and $5.4 \times 10^{-3}$ , respectively. A white CPL gel was also fabricated by mixing the three polymers in a specific ratio (1:3:0.5), achieving CIE coordinates of (0.32, 0.33).
Tunability and 3D Printing: Secondary crosslinking allowed for the rational regulation of mechanical properties; increasing crosslinking time increased the Young's modulus while decreasing tensile strain. The gels demonstrated excellent 3D printability, enabling the fabrication of self-supporting, multi-layered, and flexible structures (e.g., "2025" patterns) that retained their chiroptical performance and flexibility after printing.

Significance and Claims
The paper claims to present a versatile chemical-physical synergistic strategy that overcomes the traditional trade-offs between processability, mechanical robustness, and optical performance in CPL materials. By leveraging extrusion-induced topological evolution, the authors successfully constructed flexible, full-color CPL gels that are directly printable via DIW without auxiliary materials. The work demonstrates that mechanical processing (extrusion) can be used not just for shaping, but as a critical step to amplify chirality and mechanical strength through chain orientation and crystallization. The authors position this approach as a pathway toward the automated, large-scale manufacturing of soft chiroptical devices, with potential applications in flexible 3D displays, wearable anti-counterfeiting labels, and chiral sensing.

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