Photoinitiated Polymerization Research Articles

A photocrosslinked hybrid hydrogel based on chitosan/hyaluronic acid/ZnO toward wound sealing

A newly designed photocrosslinked hydrogel, meticulously crafted through the integration of photoinitiated radical polymerization and photo-coupling reaction, exhibits rapid in situ gelation, high modulus and potent antibacterial activity.

Photoinitiated thermoset polymerization through controlled release of metathesis catalysts encapsulated in poly(phthalaldehyde)

Frontal polymerization of dicyclopentadiene initiated by UV-degradable catalyst microparticles with excellent resin stability and tenability.

Solvent polarity-mediated seeded swelling photo-initiated polymerization: Controlled preparation of Janus particles

Solvent polarity-mediated seeded swelling photo-initiated polymerization: Controlled preparation of Janus particles

Photoactive broad-spectrum dressings with antimicrobial and antitumoral properties.

In this work the development of photoactive dressings (PAD) with dual purpose, is presented. These PAD can be used for the topical treatment of persistent infections caused by fungi and bacteria and are also applicable in light antitumor therapy for carcinoma. The synthesized PAD were designed employing conjugated polymer nanoparticles (CPN) doped with platinum porphyrin which serve as polymerization photoinitiators and photosensitizers for the production of reactive oxygen species (ROS). This approach led to the synthesis of N-vinyl-2-pyrrolidone (NVP) hydrogels co-polymerized with [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC). NVP and METAC were selected to impart a good biocompatibility with eukaryotic cell lines and antimicrobial properties, respectively. The combination of METAC with an efficient photogeneration of ROS by doped CPN resulted in a material with outstanding antimicrobial features. These dressings are capable of producing an aseptic environment upon irradiation and demonstrates a bacteriostatic profile in dark conditions. Additionally, the dressings fulfill critical requirements for topical applications, providing protection and acting as a barrier, with appropriate mechanical and swelling properties; as well as adequate water vapor transmission rates. The synthesized PAD have been shown to be biocompatible and non-toxic to erythrocytes and HaCaT cell line. PAD demonstrated efficacy in eliminating microbes such as fungi and bacteria. The underlying light-induced killing mechanism involved protein photooxidation, which amplified the effects of METAC mechanism that disrupt cellular membranes. Furthermore, in vitro studies using carcinoma cell lines displayed a complete cell eradication using a relatively low light dose (36J/cm2 at 395nm). These promising results reveal also the potential of PAD in the treatment of skin cancer.

Phenothiazine Derivative-Based Photoinitiators for Ultrafast Sunlight-Induced Free Radical Polymerization and Rapid Precision 3D Printing.

In this work, we introduce twenty-six phenothiazine derivatives (PTZs) that were designed and synthesized as visible light photoinitiators. These compounds, in combination with an amine [ethyl 4-(dimethylamino)benzoate (EDB)] and an iodonium salt [di-tert-butylphenyl iodonium hexafluorophosphate (Iod)], could furnish high-performance three-component (PTZs/EDB/Iod) photoinitiating systems that were employed for the free radical polymerization of thick films of a low-viscosity model acrylate resin, namely, trimethylolpropane triacrylate (TMPTA) under visible light and sunlight exposure. A commercial thioxanthone, i.e., isopropylthioxanthone (ITX) was selected to design a reference ITX/EDB/Iod photoinitiating system. Double bond conversions of 87% and 76% were measured for the developed and synthesized photoinitiating systems under 405 and 450 nm light-emitting diode irradiation, respectively, and a conversion as high as 70% could be determined under sunlight irradiation─about 23 times higher than the conversion obtained with the comparable system prepared with the commercial photoinitiator. The relevant photoinitiation abilities and photochemical mechanisms are comprehensively investigated by a combination of techniques including real-time Fourier transform infrared spectroscopy, UV-visible absorption spectroscopy, fluorescence spectroscopy, steady-state photolysis, cyclic voltammetry, and electron paramagnetic resonance. Notably, the exceptional performance of the photoinitiators enabled the fabrication of 3D objects with precise morphology and superior resolution through 3D printing and direct laser write techniques. These findings not only provide opportunities for efficient polymerization under artificial and natural light conditions but also pave the way for scalable, cost-effective, environmentally sustainable, and green chemistry-driven curing applications.

Polymerization-Achieved Cyclodextrin Slide-Ring Supramolecular Hydrogel Self-Generating Flexible Electronic Device.

Supramolecular flexible electronic devices are one of the research hotspots due to their application in the fields of chemistry, biology, and materials. Herein, we reported a slide-ring supramolecular flexible electronic device, which is constructed by acrylamide (AAm), acrylic acid (AA), carboxymethyl-α-cyclodextrin (CM-α-CD), PEG20000 diacrylate (PEG20000DA), and calcium chloride via the photoinitiated polymerization, displaying not only the mechanical force-responded self-generation but also the human-computer information transfer. As compared with the polymer hydrogel, the addition of α-CD polypseudorotaxane to the hydrogel has notably enhanced both the tensile length and the tensile toughness, making it more suitable for flexible electronic device applications. The hydrogel can be stretched to ca. 15 times its original length and quickly recovers after the external force is removed. In addition, it also exhibits a conductivity of 0.21 S/m, demonstrating good electrical conductivity. Significantly, based on the slide-ring supramolecular array for energy harvesting, it can generate an open-circuit voltage of 420 V using the contact separation method for testing, which can be used as a flexible electronic device for human-computer information transfer.

Effects of Electrolyte Salts on Ionic Transport in Solid Polymer Electrolytes Investigated by Operando Raman Spectroscopy

Introduction To achieve carbon-neutral society, battery technologies have been attracting attention in recent years owing to its potential for storing renewable energy and serving as a load leveling power sources. In particular, all-solid-state batteries (ASSBs) utilizing non-volatile and flame-resistant solid electrolytes are actively investigated worldwide for practical implementation, as they are expected to enhance safety. Among solid electrolytes, solid polymer electrolytes (SPEs), which exhibit high flexibility and formability, are expected for their application in electrochemical devices such as ASSBs. In SPEs, cations are solvated by the host polymer and occurs ionic conducte through cooperative transport associated with segmental motion. The ionic transport properties of SPE, affected by molecular structures of electrolyte salt, and are further influenced by processes solvation/desolvation of cation and decomposition reactions under electrochemical conditions, is considered different from static states. Therefore, we focused on applying [Li | SPE | Li] symmetric cells and evaluated the ionic transport processes within SPE under reaction conditions using concentration changes through operando Raman spectroscopy measurements. In this study, we applied the measurement approach for use on SPEs incorporating LiN(SO2F)2 (LiFSA), LiN(SO2CF3)2 (LiTFSA), and LiN(SO2C2F5)2 (LiBETI) as Li salts to investigate the impact of anion structure/molecular weight on ionic transport mechanisms under actual reaction conditions. Experiments Li-based solid polymer electrolytes were prepared by mixing cross-linked polyether-based macromonomer P(EO/PO) (EO: PO = 8:2), Li salts (LiFSA, LiTFSA, LiBETI), and photopolymerization initiator DMPA in acetonitrile under an Ar atmosphere within a glovebox. The resulting solution was vacuum-dried and filled between glass plates using a spacer (thickness: 0.5 mm). Each SPE film was then fabricated by UV irradiation. To investigate the solvation structure and salt dissociation characteristics of SPE (salt concentration: [Li]/[O] = 0.04-0.16) under static conditions, Raman spectroscopy measurements were performed (NRS-4500: Jasco). A 9 mm × 9 mm rectangular-shaped [Li | SPE([Li]/[O]=0.04, 0.16) | Li] symmetric cell was prepared for in situ monitoring of concentration variations into the SPE during electrochemical reactions. The symmetric cell was introduced into a sealed cell with a quartz glass having monitoring window and connected to a potentiostat (HZ-7000, Hokuto Denko). In o perando Raman spectroscopy, Raman spectra were obtained from the vicinity of the working electrode (W.E.) and the counter electrode (C.E.) within the SPE during voltage application. The W.E. and C.E. regions were measured at points approximately 10-30 µm from the electrode/electrolyte interface. Results & Discussion Raman spectrum of the P(EO/PO)-LiTFSA(1) and LiBETI(2) system exhibited the peak at approximately 740 cm-1 derived from SNS vibration of TFSA and BETI anion. This peak, which increases with salt concentration, can be utilized as an indicator to evaluate concentration changes within the SPE induced by electrode reactions. To evaluate the ionic transport properties, operand o Raman spectroscopy measurements were performed using [Li | SPE([Li]/[O]=0.04, 0.16)|Li] symmetry cells. The peak area change (A/A 0) from the initial state was calculated by using the obtained Raman spectra. Fig. 1 and 2 exhibited the relationship between A/A 0 and applied voltage time calculated from measured points near W.E. and C.E. in symmetrical cells using the LiTFSA and LiBETI systems. In both Fig. 1 and 2, the peak area changes (A/A 0) were observed that concentrations near W.E. and C.E. increased or decreased with voltage application. In particular, the peak area changes (A/A 0) of the LiTFSA system exhibited a rapid increase in W.E. and decrease in C.E. within the initial 1 h of measurement, followed by no significant changes over 5 h (Fig. 1). This result suggests that the SPE has reached a steady state within at the end of the experiment. And in Fig. 1, the area changes (A/A 0) of [Li]/[O]=0.04 was significantly higher than that of [Li]/[O]=0.16. This results suggests that the faster ionic transport characteristics of [Li]/[O]=0.04 compared to [Li]/[O]=0.16 can be attributed to the lower concentration of the former. No significant changes were observed both [Li]/[O]=0.04 and 0.16 owing to changes in A/A 0, similar to LiTFSA system (Fig. 2). The lower ionic transport properties of LiBETI can be attributed to the larger molecular weight of BETI anion. These results indicated that the ionic transport mechanisms under reaction conditions differ depending on the anion structure (molecular weight).(1) I. Rey, et al, J. Electrochem. Soc., 145, 3034 (1998).(2) C. Capiglia, et al., J. Electrochem. Soc., 150, A525 (2003). Figure 1

Combined Photopolymerization and Localized Photochromism by Aza-Diarylethene and Hemiindigo Synergy.

Molecular photoswitches produce light-controlled changes at the nanometer scale and can therefore be used to alter the states and behavior of materials in a truly bottom-up fashion. Here an escalating photonic complexity of material property control with light is shown using a recently developed aza-diarylethene in combination with hemiindigo (HI) photoswitches. First, aza-diarylethene can be used as a photoswitch in polystyrene (PS) to reversibly inscribe relief-type 3D structures into PS. Second, aza-diarylethene can further be used as a photoinitiator for light-induced polymerization of methyl acrylate (MA), demonstrating for the first time light-controlled chemical reactivity control with its zwitterionic switching state. Third, aza-diarylethene and HIs are implemented into aza-diarylethene polymerized MA, generating photochromic polymers. At the fourth level, a binary mixture allows to synergize aza-diarylethene-induced photopolymerization with localized photochromism changes of the simultaneously entrapped functional HI. With such multilevel light response, the utility of this particular photoswitch combination for applications in advanced photonic materials is demonstrated.

Multimaterial Thermoset Synthesis: Switching Polymerization Mechanism with Light Dosage.

The synthesis of polymeric thermoset materials with spatially controlled physical properties using readily available resins is a grand challenge. To address this challenge, we developed a photoinitiated polymerization method that enables the spatial switching of radical and cationic polymerizations by controlling the dosage of monochromatic light. This method, which we call Switching Polymerizations by Light Titration (SPLiT), leverages the use of substoichiometric amounts of a photobuffer in combination with traditional photoacid generators. Upon exposure to a low dose of light, the photobuffer inhibits the cationic polymerization, while radical polymerization is initiated. With an increased light dosage, the buffer system saturates, leading to the formation of a strong acid that initiates a cationic polymerization of the dormant monomer. Applying this strategy, patterning is achieved by spatially varying light dosage via irradiation time or intensity allowing for simple construction of multimaterial thermosets. Importantly, by the addition of an inexpensive photobuffer, such as tetrabutylammonium chloride, commercially available resins can be implemented in grayscale vat photopolymerization 3D printing to prepare sophisticated multimodulus constructs.

Dual layer-coating of PDMS to prevent calcification and bacterial infection for the potential use of urinary tract biomaterials

Polydimethylsiloxane (PDMS) is widely used in medical devices because of its exceptional properties. However, challenges, such as biofouling and bacterial infections, arise from their hydrophobic nature, especially in devices intended for the urinary tract. To address these issues, this study pioneered a surface modification strategy aimed at enriching PDMS with both hydrophilicity and antifouling attributes, making it ideal for urinary tract device applications. We introduced a novel dual-layer coating process, initially grafting a hydrogel-like poly(acrylic acid) (PAA) layer onto PDMS through benzophenone-mediated photoinitiated polymerization to enhance surface hydrophilicity. Subsequently, polyethyleneimine (PEI) was covalently bonded to the PAA layer, ensuring the formation of a stable antifouling surface that prevented bacterial adhesion and calcium deposition. This method guarantees a robust coating that performs consistently across various environmental conditions, including the fluctuating pH levels typical of the urinary tract. Comprehensive surface characterization validated the substantial improvements in hydrophilicity along with significant reductions in bacterial adhesion and calcium deposition. The innovative PAA/PEI dual-layer coating demonstrated marked superiority over conventional uncoated and single-layer-coated PDMS samples, offering a promising solution for enhancing the safety and efficacy of PDMS-based urinary tract devices. The implications of this study extend beyond immediate applications and provide valuable insights into the domains of biomaterials and medical device engineering.

Synthesis and properties of a new photoinitiator of polymerization by visible irradiation based on 3,5-di-tert-butyl-o-benzoquinone

Synthesis and properties of a new photoinitiator of polymerization by visible irradiation based on 3,5-di-tert-butyl-o-benzoquinone

Methacrylate-Containing <i>n</i>-Derivatives of <i>N</i>,<i>N</i>-Diethyl-4-(Phenyldiazenyl)Aniline as Initiators in Two-Photon Polymerization

The possibility of using a number of methacrylate-containing N,N-diethyl-4-(phenyldiazenyl)anilines with various para-substituents with respect to the azo group (-H, -Br, -NO2) as photoinitiators of radical polymerization is considered. The electrochemical and photoluminescent properties of these compounds have been studied. In the presence of azo dyes, two-photon photopolymerization of pentaerythritol triacrylate was carried out by focused radiation from a femtosecond laser with a wavelength of 780 nm. Structures with minimum linear element sizes of 94 ± 5 nm were obtained by DLW nanolithography, as well as 3D microstructures of complex architecture.

Impact of UV Light Exposure During Printing on Thermomechanical Properties of 3D-Printed Polyurethane-Based Orthodontic Aligners

Aim: Polyurethane-based aligners, created through photoinitiated free-radical polymerization, have been the subject of numerous studies focusing solely on their mechanical properties. In contrast, we investigate their thermomechanical properties, which are crucial for their efficacy. This paper aims to investigate the effects of different UV light exposure durations on the complex modulus of elasticity, tan delta, glass transition temperature, and the degree of conversion (DC). Methods: Aligners were printed using Tera Harz TC-85 and NextDent Ortho Flex resin with specific exposure times (2, 2.4, 3, 4, and 4.5 s for Tera Harz; 5, 6, 7, and 8 s for NextDent) and processed per manufacturer guidelines. The degree of conversion was analyzed using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, while Dynamic Mechanical Analysis (DMA) characterized the mechanical properties (complex modulus and tan delta) and the glass transition. Results: Tera Harz TC-85 showed a higher degree of conversion (90.29–94.54%), suggesting fewer residual monomers, which is potentially healthier for patients. However, its lower glass transition temperature (35.60–38.74 °C) might cause it to become rubbery in the mouth. NextDent Orto Flex, with a higher storage modulus (641.85–794.55 MPa) and Tg (49.36–50.98 °C), offers greater rigidity and stability at higher temperatures (greater than temperature in the oral cavity), ideal for orthodontic forces, though its lower degree of conversion raises health concerns. Conclusions: Tera Harz TC 85 generally achieves higher DC and more stable polymerization across different UV exposure times than NextDent Orto Flex. Optimal polymerization times significantly impact both the mechanical and thermal properties of these dental resins, with NextDent showing optimal properties at 7 s and Tera Harz benefiting from both very short and extended exposure times.

Exploring the role of SAP chemical composition in the internal curing of high-performance cementitious materials

This study investigates the impact of the chemical composition of superabsorbent polymers (SAPs) on their effectiveness in internal curing within high-performance cementitious materials. Although the use of commercial SAPs in cementitious systems has been widely researched, there is still no consensus on how different SAP structures influence material properties. For the first time, this research employs photoinitiated free radical polymerization technology to synthesize three structurally distinct SAPs: SAP with sulfonic acid groups (PAMPS), SAP with amide groups (PAM), and SAP with carboxyl groups (PAAs). The effects of these SAPs on the cement hydration process and microstructure were examined by analyzing their water absorption behavior in cement filtrate. The residual cation content on the SAP surface was evaluated using EDS, while XRD and TGA were used to study how SAP structure affects cement hydration products. Furthermore, the impact of these SAPs on the strength and autogenous shrinkage of the material was investigated. The results indicate that PAMPS, with its sulfonic acid groups, exhibited stable water absorption performance in the alkaline cement environment, promoting hydration reactions and increasing the formation of needle-shaped C-S-H. This stability contributed to mitigating the negative effects on mechanical properties. While the inclusion of SAPs generally reduced the strength of the cement matrix, PAMPS was the most effective in mitigating autogenous shrinkage, achieving a shrinkage mitigation efficiency of 86 %. These findings highlight the importance of SAP chemical structure in influencing cement hydration and material performance, offering insights for the development of effective internal curing agents to enhance high-performance concrete.

Novel Ketone Derivatives Involving Triphenylamine Electron‐Donating Group as Low Migration Photoinitiators for Visible Light Radical Polymerization and 3D Printing

AbstractGiven the ongoing advancements in photopolymerization technology, there is an imperative need to develop novel free radical photoinitiators (PIs) with long‐wavelength absorbance and low migration. To meet the demand for visible light photopolymerization, four novel ketone derivatives photoinitiators (PHMOs) were synthesized in this study via a one‐step reaction. By constructing the push‐pull structure, the maximum absorption wavelength of the new PIs was red‐shifted to the vicinity of 400 nm, satisfying the requirement of visible excitation. The one‐component photoinitiation effect of PHMOs under visible light was comparable to that of Irgacure 1173, among which the photopolymerisation performance of PHMO‐2 was significantly superior to that of 1173. The photopolymerization effect of the two‐component photoinitiaton system composed by the addition of hydrogen donor was significantly improved. PHMO‐1 was successfully used in 3D printing to produce well‐defined printed products. The photolysis mechanism of PHMOs was investigated by steady‐state photolysis and electron spin resonance test. In addition, PHMOs had good solubility, thermal stability and good biosafety. Attributed to the presence of double bonds, PHMOs had low migration. These excellent properties indicated that PHMOs had desirable potential applications in the field of visible light polymerization.

Highly Stretchable, Transparent, Solvent-Resistant Multifunctional Ionogel with Underwater Self-Healing and Adhesion for Wearable Strain Sensors and Barrier-Free Information Transfer.

Ionogels with excellent deformability, high ionic conductivity, and a sensitive stimulus response have been widely used and rapidly developed in flexible wearable systems. However, previously reported ionogels are mainly limited to atmospheric environments applications and have difficulty meeting the requirements of solvent-resistant, self-healing, and adhesion properties in underwater environments. Herein, a multifunctional ionogel capable of underwater applications is prepared by one-step photoinitiated polymerization of a fluorine-containing monomer (2,2,3,4,4,4-hexafluorobutyl acrylate, HFBA) and acrylic acid (AA) in a hydrophobic ionic liquid ([EMIM][TFSI]). The dynamic physical interactions of hydrogen bonds and ionic dipoles endow the ionogel with remarkable transparency, tunable mechanical properties, and underwater self-healing properties. Moreover, the fluoropolymer matrix offers high resistance to water and various solvents and exhibits strong underwater adhesion on different substrates. Thus, the sensor based on the ionogel exhibits excellent sensing properties, including high sensitivity, fast response, and superior durability. In particular, the ionogel can be used as a wearable underwater sensor to perform barrier-free information transfer. This study provides a design idea for the development of underwater flexible strain sensors.

Eutectogel adhesives with underwater-enhanced adhesion to hydrophilic surfaces and strong adhesion in harsh environments

It has been a challenge to achieve strong adhesion strength for gel adhesives in water. In this study, a novel eutectogel adhesive is synthesized via one-step photoinitiated polymerization of N-vinylpyrrolidone (NVP) in deep eutectic solvent (DES). The abundant hydrogen bonding interactions and the hydrophilic polyvinylpyrrolidone network structure endow the eutectogel with excellent adhesion to both hydrophilic and hydrophobic surfaces in air and underwater. Moreover, for hydrophilic substrates, the underwater adhesion strength of the eutectogel adhesives is 1.3 times larger than that in air, demonstrating an underwater-enhanced adhesion effect. In contrast, for hydrophobic substrates, the underwater adhesion strength is lower than in air. Furthermore, strong adhesion performance is maintained even in boiling water, strong acidic medium, strong basic medium, and organic solvents. The experimental and simulation results have unveiled the underwater adhesion enhancement mechanism of the eutectogel. It is believed that the designed eutectogel will show great promise in the development of the next-generation of gel adhesives with underwater adhesion capabilities and high environmental adaptability.

Rapid synthesis of solid polycarboxylate superplasticizers via photoinitiated radical polymerization

The synthesis and performance optimization of solid polycarboxylate superplasticizers (PCEs) present significant challenges. In our study, a rapid synthesis of a solid polycarboxylate superplasticizer (IPCE10) was achieved using photoinitiated free radical polymerization. IPCE10 exhibited good dispersibility and improved compressive strength in concrete. Dynamic light scattering tests and molecular dynamics simulations demonstrated that the adsorption conformation of IPCE10 on the calcium silicate hydrate surface was relatively dispersed, with a thicker adsorption layer. This indicates that IPCE10 has stronger steric hindrance, resulting in superior dispersibility. Additionally, density functional theory calculations of the reaction energy barriers for radical generation by photoinitiated and azo-initiated monomers revealed that the energy barrier in the photoinitiated system was significantly lower than that in the azo-initiated system, indicating that photoinitiated polymerization is more feasible. This study proposes a simple and rapid method for the preparation of solid polycarboxylate superplasticizers, providing valuable insights for the development of high-value-added construction materials.

Digital Light Processing of Thermoresponsive Hydrogels from Polyproline-Based Star Polypeptides.

The first report of star poly(L-proline) crosslinkers is disclosed for digital light processing 3D printing of thermoresponsive hydrogels. Through chain end functionalization of star poly(L-proline)s with methacryloyl groups, access to high-resolution defined 3D hydrogel structures via digital light processing is achieved through photoinitiated free radical polymerization. Changing the poly(L-proline) molecular weight has a direct influence on both thermoresponsiveness and printability, while shape-morphing behavior can be induced thermally.

POSS based poly (zwitterionic liquids) electrolytes with 3D crosslinked networks for lithium metal batteries

Polymer electrolyte is a potential candidate for the next-generation lithium metal batteries. However, its low room temperature ionic conductivity limited its practical application. Here, a novel POSS-based poly (zwitterionic liquids) organic–inorganic hybrid electrolyte with 3D crosslinked networks was proposed for enabling lithium-ion fast transport by photoinitiated radical polymerization of vinyl zwitterionic monomers and acrylate monomers containing rich EO units and POSS. The synergistic effect of unique structures of 3D organic–inorganic hybrids gel electrolytes such as zwitterionic, rich EO segments and POSS cages facilitate Li+ conduction, resulting in high room temperature ionic conductivity (1.03 × 10-3 S cm-1) and a satisfactory Li+ transference number (0.45). The lithium-symmetric batteries assembled with the novel POSS-based poly (zwitterionic liquids) gel hybrid electrolytes can operate continuously at 0.1 mA cm-2 for 2300 h without any obvious short circuit, indicating good interfacial compatibility between the electrolytes and lithium electrodes. The Li/LiFePO4 batteries assembled with the novel POSS-based poly (zwitterionic liquids) gel hybrid electrolytes exhibit long-term stability.