Iodinated Polystyrene for Polymeric Charge Transfer Complexes: Toward High-Performance Near-UV and Visible Light Macrophotoinitiators

Development of a polystyrene-based microplastic model for bioaccumulation and biodistribution study using radiotracing and nuclear analysis method

The investigation of micro or nano plastics behavior in the environment is essential to minimize the hazards of such pollutants on humans. While the conventional method requires sophisticated procedures and a lot of animal subjects, the nuclear technique confers a sensitive, accurate, and real-time method using radiolabeled micro or nano plastics as a tracer. In this study, polystyrene sulfonate-based microplastic (PSM) was developed with a size of around 3.6 μm, followed by radiolabeling with iodine-131 (131I) or zinc-65 (65Zn) for microplastic radiotracer model. After a stability study in seawater, phosphate buffer saline (PBS), and human serum albumin (HSA) for fifteen days, PSM-131I remained stable (>90 %), except in HSA (50-60 % after day-9), while PSM-65Zn was unstable (<50 %).

Recent Trends in Advanced Photoinitiators for Vat Photopolymerization 3D Printing

3D printing has revolutionized the way of manufacturing with a huge impact on various fields, in particular biomedicine. Vat photopolymerization-based 3D printing techniques such as stereolithography (SLA) and digital light processing (DLP) attracted considerable attention owing to their superior print resolution, relatively high speed, low cost and flexibility in resin material design. As one key element of the SLA/DLP resin, photoinitiators or photoinitiating systems have experienced significant development in recent years, in parallel with the exploration of 3D printing (macro)monomers. The design of new photoinitiating systems can not only offer faster 3D printing speed and enable low-energy visible light fabrication, but also can bring new functions to the 3D printed products and even generate new printing methods in combination with advanced optics. This review evaluates recent trends in the development and application of advanced photoinitiators and photoinitiating systems for vat photopolymerization 3D printing, with a wide range of small molecules, polymers and nanoassemblies involved. Personal perspectives on the current limitations and future directions are eventually provided. This article is protected by copyright. All rights reserved.

Water-Soluble Visible Light Sensitive Photoinitiating System Based on Charge Transfer Complexes for the 3D Printing of Hydrogels

The development of visible-light 3D printing technology by using water-soluble initiating systems has attracted widespread attention due to their potential applications in the manufacture of hydrogels. Besides, at present, the preparation of water-soluble photoinitiators suitable for visible light irradiation (such as LEDs) still remains a challenge. Therefore, this work is devoted to developing water-soluble photoinitiators (PI)/photoinitiating systems (PIS) upon irradiation with a LED @ 405 nm. In detail, a new water-slightly-soluble chalcone derivative dye [(E)-3-(4-(dimethylamino) phenyl)-1-(4-(2-(2-(2-methoxyethoxy) ethoxy) ethoxy) phenyl) prop-2-en-1-one] was synthesized here and used as a PI with a water-soluble coinitiator, i.e., triethanolamine (TEA) which was also used as an electron donor. When combined together, a charge transfer complex (CTC) formed immediately which exhibited excellent initiating ability for the free radical photopolymerization of poly(ethyleneglycol)diacrylate (PEG-DA). In light of the powerful CTC effect, the [dye-TEA] CTC could not only exhibit enhanced water solubility and mechanical properties but could also be effectively applied for 3D printing. This CTC system is environmentally friendly and cost-saving which demonstrates a great potential to prepare hydrogels via photopolymerization.

Macrocyclic Photoinitiator Based on Prism[5]arene Matching LEDs Light with Low Migration

In this work, a naphthalene-based macrocycle prism[5]arene (NP₅ OCH₃ ) is developed as a novel kind of photoinitiator. When NP₅ OCH₃ is irradiated under light, the bond between methylene and naphthalene can be quickly broken owning to the existence of ring tension. The macrocycle is cleaved to linear oligomer biradicals, which can effectively initiate the free radical photopolymerization of acrylate monomers. Compared with conventional photoinitiators, NP₅ OCH₃ has strong light absorption in the wavelength range of 365-405 nm, so it can well match the environment-friendly light-emitting diodes (LEDs) light source to realize highly efficient initiation. In addition, there is no small molecule fragment generated during NP₅ OCH₃ fracture, and the resulted linear oligomer biradicals can be immobilized in the polymer after initiating polymerization, so NP₅ OCH₃ photoinitiators show much lower migration rate and cytotoxicity. Cleavable macrocycle prismarene may provide a new idea for the design of safe and efficient photoinitiators matching long wavelength light.

Recent Advances in bis-Chalcone-Based Photoinitiators of Polymerization: From Mechanistic Investigations to Applications

Over the past several decades, photopolymerization has become an active research field, and the ongoing efforts to develop new photoinitiating systems are supported by the different applications in which this polymerization technique is involved-including dentistry, 3D and 4D printing, adhesives, and laser writing. In the search for new structures, bis-chalcones that combine two chalcones' moieties within a unique structure were determined as being promising photosensitizers to initiate both the free-radical polymerization of acrylates and the cationic polymerization of epoxides. In this review, an overview of the different bis-chalcones reported to date is provided. Parallel to the mechanistic investigations aiming at elucidating the polymerization mechanisms, bis-chalcones-based photoinitiating systems were used for different applications, which are detailed in this review.

3D Printing of Polydiacetylene Photocomposite Materials: Two Wavelengths for Two Orthogonal Chemistries

Polydiacetylene (PDA) materials are appealing and gaining increasing research interest due to their outstanding chromatic transition and fluorescence enhancement effects upon exposure to various environmental stimuli. However, despite the photomask method, there are very few reports about the spatial controllable photopolymerization and subsequent 3D printing of PDA until now. Herein, for the first time, we reported the preparation of PDA photocomposite materials based on polyacrylate through the strategy of dual-wavelength polymerization and orthogonal chemistry. First, diacetylene (DA) monomers were homogeneously dispersed in acrylate resin. Then a violet light emitting diode (LED) (or laser diode) was used for the free radical polymerization of polyacrylate. Finally, UV irradiation was utilized to induce the 1,4-topopolymerization of PDA, which could show a successive blue to purple to red color transition in response to the gradient increment of temperature. Interestingly, instead of photomasks, we applied a 3D printing approach directly to this composite material and fabricated some macroscopic stereo patterns, which also illustrated thermochromic properties. This novel kind of functional photocomposite material would demonstrate a huge application prospect in many potential fields, including colorimetric sensing, information encryption, anticounterfeiting, and so on.

Substituted stilbene-based oxime esters used as highly reactive wavelength-dependent photoinitiators for LED photopolymerization

Different substituents on stilbene-based oxime esters play an important role in the relationship between their structure and properties.

Indole-based charge transfer complexes as versatile dual thermal and photochemical polymerization initiators for 3D printing and composites

Indole-based Charge Transfer Complexes (CTCs) are newly presented dual photo/thermal initiators for safe and robust polymerizations in high tech applications.