Photopolymerization Approach to Advanced Polymer Composites: Integration of Surface-Modified Nanofillers for Enhanced Properties

The incorporation of functionalized nanofillers into polymers via photopolymerization approach has gained significant attention in recent years due to the unique properties of the resulting composite materials. Surface modification of nanofillers plays a crucial role in their compatibility and polymerization behavior within the polymer matrix during photopolymerization. This review focuses on the recent developments in surface modification of various nanofillers, enabling their integration into polymer systems through photopolymerization. The review discusses the key aspects of surface modification of nanofillers, including the selection of suitable surface modifiers, such as photoinitiators and polymerizable groups, as well as the optimization of modification conditions to achieve desired surface properties. The influence of surface modification on the interfacial interactions between nanofillers and the polymer matrix is also explored, as it directly impacts the final properties of the nanocomposites. Furthermore, the review highlights the applications of nanocomposites prepared by photopolymerization, such as sensors, gas separation membranes, purification systems, optical devices, and biomedical materials. By providing a comprehensive overview of the surface modification strategies and their impact on the photopolymerization process and the resulting nanocomposite properties, this review aims to inspire new research directions and innovative ideas in the development of high-performance polymer nanocomposites for diverse applications.

5,12-Dihydroindolo[3,2-a]Carbazole Derivatives-Based Water Soluble Photoinitiators for 3D Antibacterial Hydrogels Preparation

Indolo[3,2-a]carbazole alkaloids have drawn a growing interest in recent years owing to their potential electrical and optical properties. With 5,12-dihydroindolo[3,2-a]carbazole serving as the scaffold, two novel carbazole derivatives are synthesized in this study. Both compounds are extremely soluble in water, with solubility surpassing 7% in weight. Intriguingly, the introduction of aromatic substituents contributed to drastically reduce the π-stacking ability of carbazole derivatives, while the presence of the sulfonic acid groups enables the resulting carbazoles remarkably soluble in water, allowing them to be used as especially efficient water-soluble PIs in conjunction with co-initiators, i.e., triethanolamine and the iodonium salt, respectively, employed as electron donor and acceptor. Surprisingly, multi-component photoinitiating systems based on these synthesized carbazole derivatives could be used for the in situ preparation of hydrogels containing silver nanoparticles via laser write procedure with a light emitting diode (LED)@405 nm as light source, and the produced hydrogels display antibacterial activity against Escherichia coli.

High-Performance Photoinitiating Systems for LED-Induced Photopolymerization

Currently, increasing attention has been focused on light-emitting diodes (LEDs)-induced photopolymerization. The common LEDs (e.g., LED at 365 nm and LED at 405 nm) possess narrow emission bands. Due to their light absorption properties, most commercial photoinitiators are sensitive to UV light and cannot be optimally activated under visible LED irradiation. Although many photoinitiators have been designed for LED-induced free radical polymerization and cationic polymerization, there is still the issue of the mating between photoinitiators and LEDs. Therefore, the development of novel photoinitiators, which could be applied under LED irradiation, is significant. Many photoinitiating systems have been reported in the past decade. In this review, some recently developed photoinitiators used in LED-induced photopolymerization, mainly in the past 5 years, are summarized and categorized as Type Ⅰ photoinitiators, Type Ⅱ photoinitiators, and dye-based photoinitiating systems. In addition, their light absorption properties and photoinitiation efficiencies are discussed.

Effect of intramolecular charge transfer on nonlinear optical properties of chalcone derivatives: a visual description of the charge transfer process

Intramolecular charge transfer (ICT) is an important factor in the nonlinear optical (NLO) properties of organic molecules. In order to study the effect of ICT on two-photon absorption (TPA) and excited-state absorption (ESA), three chalcone derivatives (1, 2 and 3) with different electron push-pull systems were designed and synthesized. The ICT performance of these chalcone derivatives depends on the electron push-pull systems and mainly includes ultrafast ICT in the femtosecond time domain and long-lived charge transfer state (CTS) in the picosecond time domain, which dominate the performance of molecular TPA and ESA respectively. Hole-electron analysis and femtosecond Z-scan experiment indicate that the TPA cross section of these chalcone derivatives can be effectively enhanced by introducing stronger ultra-fast ICT in the case of little difference in ground-state absorption and expanding the molecular π-conjugated structure. Transient absorption spectrum (TAS) experiments of these compounds in solvents of varying polarities were conducted to visualize the establishment of CTS. The local excited state (LES) and charge transfer state (CTS)-based ESA of these chalcone derivatives are extremely dependent on the strength of ICT. Our experimental results show that the superposition of LES and CTS by enhancing ICT performance can effectively improve the ESA, which offers us a practical method to improve the long-impulse response of organic materials.

Effects of the number and position of methoxy substituents on triphenylamine-based chalcone visible-light-absorbing photoinitiators

Five visible-light-absorbing triphenylamine-based chalcone photoinitiators (CY1–CY5) have been synthesized for application in free radical photopolymerization.

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.

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.