Intramolecular Coumarin-Dimer Containing Polyurethanes: Optical Tuning via Single- and Two-Photon Absorption Processes

Mechanically tunable porous gels constructed via the dual coordination/covalent polymerization of coumarin-functionalized rhodium-organic cuboctahedra

Polymer-based soft materials constructed from defined molecular pores, such as metal-organic polyhedra (MOPs), promise to merge the outstanding and diverse mechanical properties of conventional nonporous polymers with atomically-precise molecular recognition capabilities. Thus far, soft MOP networks have been constructed primarily using rigid, labile coordination bonds or dynamic covalent bonds, providing static networks without intrinsic mechanisms to optimize their response to mechanical stimuli. Here, we report the construction of flexible, doubly crosslinked MOP gels via mutually compatible coordination and covalent polymerization techniques. Our method employs dirhodium paddlewheel-based MOPs bearing both open metal sites, which enable their coordination-driven assembly, and photodimerizable coumarin side chains for covalent polymerization (Coumarin-RhMOPs). Incubation of Coumarin-RhMOPs with ditopic linkers enabled their coordination-driven polymerization into porous colloidal gels. Site-selective irradiation of coordination-linked Coumarin-RhMOP gels afforded doubly crosslinked gels with improved strain tolerance and higher stiffness. Selective dissociation of coordination-crosslinkers provided highly deformable covalent Coumarin-RhMOP gels. The postsynthetic addition of ditopic ligands to covalent gels enabled the reversible modulation of their mechanical properties. These findings highlight the possibility of incorporating multiple responsive crosslinks in porous MOP networks to rationally tune their responses to mechanical stress, paving the way to their practical implementation as next-generation chemical separators, catalysts, and drug delivery vehicles.

Photoinduced polyelectrolyte complexation for the formation of stable films with reversible crosslinking

Thin films formed by complexation of oppositely charged polyelectrolytes have significant potential in applications such as separation membranes, biocompatible or anticorrosion coatings, and drug delivery systems. While layer-by-layer deposition is a reliable method for producing conformal films, this multi-step process limits scalability. In this study, we functionalize polymers with photoactive protecting and crosslinking groups, allowing a one-step approach for preparing polyelectrolyte complex (PEC) films. To achieve this goal, we introduced o-nitrobenzyl and coumarin groups into a polyanion. The o-nitrobenzyl protecting groups can be selectively deprotected upon exposure to 365 nm light, revealing charged pendent groups that initiate polyelectrolyte complexation. Simultaneously, the coumarin units in the copolymers undergo dimerization, enhancing the solvochemical stability of the PEC films. Notably, short-wave UV irradiation (254 nm) enables retrocyclization of the coumarin dimers, returning the PEC film to its uncrosslinked state. These UV-driven deprotection, crosslinking, and de-crosslinking processes provide a versatile and tunable platform for fabricating reversibly crosslinked films. By integrating photoresponsive polymers and reversible covalent linkages, this approach offers new opportunities for designing PEC materials with tunable dynamic properties for advanced applications.

Custom-Design of Multi-Stimuli-Responsive Degradable Silica Nanoparticles for Advanced Cancer-Specific Chemotherapy

Chemotherapy is crucial in oncology for combating malignant tumors but often encounters obatacles such as severe adverse effects, drug resistance, and biocompatibility issues. The advantages of degradable silica nanoparticles in tumor diagnosis and treatment lie in their ability to target drug delivery, minimizing toxicity to normal tissues while enhancing therapeutic efficacy. Moreover, their responsiveness to both endogenous and exogenous stimuli opens up new possibilities for integrating multiple treatment modalities. This review scrutinizes the burgeoning utility of degradable silica nanoparticles in combination with chemotherapy and other treatment modalities. Commencing the elucidation of degradable silica synthesis and degradation mechanisms, emphasis is placed on the responsiveness of these materials to endogenous (e.g., pH, redox reactions, hypoxia, and enzymes) and exogenous stimuli (e.g., light and high-intensity focused ultrasound). Moreover, this exploration delves into strategies harnessing degradable silica nanoparticles in chemotherapy alone, coupled with radiotherapy, photothermal therapy, photodynamic therapy, gas therapy, immunotherapy, starvation therapy, and chemodynamic therapy, elucidating multimodal synergies. Concluding with an assessment of advances, challenges, and constraints in oncology, despite hurdles, future investigations are anticipated to augment the role of degradable silica in cancer therapy. These insights can serve as a compass for devising more efficacious combined tumor treatment strategies.

Upgrading the Toolbox: Two-Photon Absorption Induced Cleavage of Coumarin Dimers for Light-Based 4D Printing

The use of light for shaping and changing matter is of high relevance in polymer and material science. Herein, a photopolymer method is presented, which comprises the combination of 3D photo-printing at 405 nm light and subsequent modification under two-photon absorption (TPA) conditions at 532 nm light, adding the fourth dimension. The TPA-triggered cycloreversion reaction of an intramolecular coumarin dimer (ICD) structure occurs within the absorbing material. The 3D-printable matrix does not show any degradation under the TPA conditions. With the presented photochemical tool of TPA processes inside absorbing 3D photo-printable matrices, new possibilities for post-printing modification, e. g. for smart materials, are added.

Enhancing the photochemical reversibility of coumarin-containing polymers by molecular orientation control

With the use of an intramolecular approach and restrictions in the mobility, the reversibility of photoresponsive coumarin dimer-containing polymers was enhanced.