Lignin Derivative as Visible-Light Photo-Initiating System for the Development of Biocide Materials under Light Irradiation.

The design of a new visible-light methacrylated-based kraft lignin photosensitizer (MAcL) of iodonium salt (Iod) for the free-radical polymerization (FRP) of polyethylene glycol dimethacrylate (PEGDMA) under LEDs@405, 455, 470, 505, and 530 nm is reported. As demonstrated by laser flash photolysis (LFP) and electron paramagnetic resonance spin-trapping (EPR ST) experiments, the combination of MAcL with an electron acceptor (Iod) and trimethylolpropane tris(3-mercaptopropionate) (TT) used as a crosslinker, leads to the formation of highly efficient initiating radicals, i.e.

Thioxanthone-Based Siloxane Photosensitizer for Cationic/Radical Photopolymerization and Photoinduced Sol-Gel Reactions.

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol-gel chemistry, thus avoiding its release. Both liquid H and solid-state Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network.

Tris-benzo[cd]indole Cyanine Enables the NIR-photosensitized Radical and Thiol-ene Polymerizations at 940 nm.

A near-infrared-absorbing heptamethine (HM ) incorporating three bulky benzo[cd]indole heterocycles was designed to efficiently prevent self-aggregation of the dye, which results in a strong enhancement of its photoinitiating reactivity as compared to a parent bis-benzo[cd]indole heptamethine (HMCl ) used as a reference system. In this context, we highlight an efficient free-radical NIR-polymerization up to a 100 % acrylates C=C bonds conversion even under air conditions. Such an important initiating performance was obtained by incorporating our NIR-sensitizer into a three-component system leading to its self-regeneration.

Electrochemically Deposited Zinc (Tetraamino)phthalocyanine as a Light-activated Antimicrobial Coating Effective against .

Light-activated antimicrobial coatings are currently considered to be a promising approach for the prevention of nosocomial infections. In this work, we present a straightforward strategy for the deposition of a photoactive biocidal organic layer of zinc (tetraamino)phthalocyanine (ZnPcNH) in an electrochemical oxidative process. The chemical structure and morphology of the resulting layer are widely characterized by microscopic and spectroscopic techniques, while its ability to photogenerate reactive oxygen species (ROS) is investigated in situ by UV-Vis spectroscopy with α-terpinene or 1,3-diphenylisobenzofuran as a chemical trap.

Contributions of photochemistry to bio-based antibacterial polymer materials.

Surgical site infections constitute a major health concern that may be addressed by conferring antibacterial properties to surgical tools and medical devices functional coatings. Bio-sourced polymers are particularly well-suited to prepare such coatings as they are usually safe and can exhibit intrinsic antibacterial properties or serve as hosts for bactericidal agents. The goal of this Review is to highlight the unique contribution of photochemistry as a green and mild methodology for the development of such bio-based antibacterial materials.

Azacalixphyrins as an innovative alternative for the free-radical photopolymerization under visible and NIR irradiation without the need of co-initiators.

Azacalixphyrins are unique aromatic macrocycles featuring strong absorption from the visible to the near-infrared (NIR) spectral ranges. This work demonstrates through EPR spin-trapping experiments that the -alkyl tetrasubstituted azacalixphyrin (ACP) can lead to the formation of carbon-centered radicals initiating for the free-radical photopolymerization (FRP) of bio-based acrylate monomer upon the irradiation of several light emitting diodes, which emissions range from 455 to 660 nm. Compared to other previously reported systems, the tremendous advantage of the ACP photoinitiating system is its ability to promote photopolymerization on its own, avoiding the introduction of co-initiators.

Lawsone Derivatives as Efficient Photopolymerizable Initiators for Free-Radical, Cationic Photopolymerizations, and Thiol-Ene Reactions.

Two new photopolymerizable vinyl (2-(allyloxy) 1,4-naphthoquinone, ) and epoxy (2-(oxiran-2yl methoxy) 1,4-naphthoquinone, ) photoinitiators derived from lawsone were designed in this paper. These new photoinitiators can be used as one-component photoinitiating systems for the free-radical photopolymerization of acrylate bio-based monomer without the addition of any co-initiators. As highlighted by the electron paramagnetic resonance (EPR) spin-trapping results, the formation of carbon-centered radicals from an intermolecular H abstraction reaction was evidenced and can act as initiating species.

Multi-Directional Mechanofluorochromism of Acetyl Pyrenes and Pyrenyl Ynones.

A series of acetyl pyrenes and pyrenyl ynones with and without tert-butyl groups showed distinct mechanofluorochromism (MFC). Four pairs of polymorphic solids were found out of six compounds and interestingly, each of them showed hypsochromic, bathochromic or off-to-on MFC. The MFC properties were rationalized by categorizing the packing schemes into herringbone, sandwich, beta and gamma motifs depending on the relative contributions of C⋅⋅⋅C (or π-π) against C⋅⋅⋅H contacts.

Light and Hydrogels: A New Generation of Antimicrobial Materials.

Nosocomial diseases are becoming a scourge in hospitals worldwide, and new multidrug-resistant microorganisms are appearing at the forefront, significantly increasing the number of deaths. Innovative solutions must emerge to prevent the imminent health crisis risk, and antibacterial hydrogels are one of them. In addition to this, for the past ten years, photochemistry has become an appealing green process attracting continuous attention from scientists in the scope of sustainable development, as it exhibits many advantages over other methods used in polymer chemistry.

Two-Photon Initiating Efficiency of a Ditopic Alkoxynitrostilbene Reacting through a Self-Regenerative Mechanism.

The photophysical properties and the photoinitiating reactivity of a ditopic alkoxynitrostilbene were compared to those of its single branch chromophore used as a reference. Whereas a trivial additive effect is observed when considering the one- and two-photon absorption properties, a clear and very significant amplification has been highlighted for the photoreactivity of this free radical photoinitiator which was used as a hydrogen abstractor in presence of an aliphatic amine co-reactant. We indeed demonstrate that the proximity of two nitroaromatics moieties within the same molecular architecture gives rise to an original cycling mechanism based on a stepwise photo triggering of each photoredox center followed by a subsequent regenerative process.

Co-Networks Poly(hydroxyalkanoates)-Terpenes to Enhance Antibacterial Properties.

Biocompatible and biodegradable bacterial polyesters, poly(hydroxyalkanoates) (PHAs), were combined with linalool, a well-known monoterpene, extracted from spice plants to design novel antibacterial materials. Their chemical association by a photo-induced thiol-ene reaction provided materials having both high mechanical resistance and flexibility. The influence of the nature of the crosslinking agent and the weight ratio of linalool on the thermo-mechanical performances were carefully evaluated.

Photoactive Polyoxometalate/DASA Covalent Hybrids for Photopolymerization in the Visible Range.

The synthesis of TBA-DASA-POM-DASA, the first photoactive covalent hybrid polyoxometalate (POM) incorporating a donor-acceptor Stenhouse adduct (DASA) reverse photochrome, is presented. It has been evidenced that in solution the equilibrium between the colorless cyclopentenone and the highly colored triene conformers is strongly dependent not only on the nature of the solvent but also the countercations, allowing to tune its optical properties. This complex has been further associated to photochromic spironaphtoxazine cations, resulting in a material which can be activated by two distinct optical stimuli.

Photoinitiating Systems Based on Anthraquinone Derivatives: Synthesis of Antifouling and Biocide Coatings.

Photoinitiating systems combining 2,6-diaminoanthraquinone (AQD), iodonium salt (Iod), and benzyl alcohol derivatives have been developed to efficiently initiate the cationic polymerization of epoxy monomers upon light exposure. Electron spin resonance spin-trapping (ESR ST) experiments, fluorescence investigations, and steady-state photolysis have demonstrated that a dye-sensitized reaction occurs between AQD and the benzyl alcohol derivatives through a hydrogen abstraction mechanism upon light illumination, followed by reduction of Iod. The in situ liberation of protic acids promotes the cationic photopolymerization of epoxy monomers concomitantly with hydrolysis and condensation of the reactive methoxysilanes of an organic-inorganic precursor, for example, 3-glycidyloxypropyltrimethoxysilane (GPTMS).

Antibacterial properties of nanostructured Cu-TiO surfaces for dental implants.

The influence of copper derived TiO surfaces (nCu-nT-TiO) on the death of nosocomial Staphylococcus aureus (Sa) and Escherichia coli (Ec), was investigated. TiO nanotube (nT-TiO) arrays were fabricated by anodic oxidation of pure titanium sheets in fluorhydric solutions, leading to surface nanostructuration and creation of specific reactive sites. Copper nanocubes with a mean size of 20 nm have been synthesized and deposited on the nT-TiO surface by pulsed electrodeposition from a copper sulphate solution.

Pamidronic acid-grafted nHA/PLGA hybrid nanofiber scaffolds suppress osteoclastic cell viability and enhance osteoblastic cell activity.

Osteoclasts have the capability to resorb bone. When osteoclastic activity is excessively high, bones generally become weakened and more prone to fracture. In order to treat excessive osteoclastic cell activity, maintain the balance between bone formation and resorption, and enhance osseointegration, pamidronic acid-grafted nanorod hydroxyapatite/poly(lactide-co-glycolide) (P-g-nHA/PLGA) scaffolds were fabricated via an electrospinning technique.

Design of functionalized biodegradable PHA-based electrospun scaffolds meant for tissue engineering applications.

Modification of electrospun nanofibrous poly(3-hydroxyalkanoate) (PHA)-based mats was implemented through two routes to obtain biomimetic scaffolds meant for tissue engineering applications. The first strategy relied on a physical functionalization of scaffolds thanks to an original route which combined both electrospinning and electrospraying, while the second approach implied the chemical modification of fiber surface via the introduction of reactive functional groups to further conjugate bioactive molecules. The degree of glycidyl methacrylate grafting on PHA reached 20% after 300s under photoactivation.

Design of cytocompatible bacteria-repellent bio-based polyester films via an aqueous photoactivated process.

Nosocomial infections are often induced by the presence of pathogenic organisms on the surface of medical devices or hospital equipment. Chemical or topographical modifications of the surface are recognized as efficient strategies to prevent bacteria adhesion but they may have negative impact on the material interaction with living tissues. Here we have developed a photoactivated method for the modification of a biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) under aqueous conditions.

Rotamerism-driven large magnitude host-guest binding change in a crown ether derivatized pyridinium-phenolate series.

Two TICTOID-based pyridinium-phenolates bearing a crown ether macrocycle have been designed for the complexation of a potassium cation. The nucleophilicity of the intraannular phenolate -O(-) function can be strongly modulated by biaryl twisting. Such a structure/electronic transduction effect gives rise to a host-guest binding change by more than two orders of magnitude.

Photoinduced development of antibacterial materials derived from isosorbide moiety.

A straightforward method for immobilizing in situ generated silver nanoparticles on the surface of a photoactivable isosorbide-derived monomer is developed with the objective to design a functional material having antibacterial properties. The photoinduced thiol-ene mechanism involved in these syntheses is described by the electron spin resonance/spin trapping technique. The resulting materials with or without silver nanoparticles (Ag NPs) were used as films or as coatings on glass substrate.

The first photochemical in situ production of Ti-based nanoparticles: a SH2 strategy using bis(cyclopentadienyl)titanium dichloride (Cp2TiCl2).

Bis(cyclopentadienyl)titanium dichloride (Cp2TiCl2) is a high performance additive under UV light activation for both i) radical photopolymerization reactions (when added to a Type I photo-initiator such as 2,2-dimethoxy-2-phenylacetophenone, the oxygen inhibition is reduced) and ii) a concomitant in situ photoinduced and oxygen mediated formation of Ti-based nanoparticles (diameters ranging from 45 to 220 nm). The photochemical properties of Cp2TiCl2 are investigated by steady state photolysis and electron spin resonance, and its photoinitiation ability checked. The nanoparticles (NPs) are well characterized by transmission electron microscopy.

Photoinduced modification of the natural biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) microfibrous surface with anthraquinone-derived dextran for biological applications.

A straightforward and versatile method for immobilizing polysaccharides on the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) electrospun fibers is developed with the objective of designing a new functional biomaterial having a significant effect on cell proliferation. The approach relies on a one-step procedure: UV grafting of a photosensitive dextran (AQ-Dext) on the surface of PHBHV fibers according to a "grafting onto" method, with the use of an anthraquinone derivative. The photografting is conducted through a photoinduced free radical process employing an anthraquinone-based photosensitizer in aqueous medium.

Zirconocene Dichloride: An Efficient Cleavable Photoinitiator Allowing the in Situ Production of Zr-Based Nanoparticles Under Air.

CpZrCl is presented as both an effective photoinitiator and additive for radical photopolymerization reactions in aerated conditions. This compound is characterized by remarkable properties: (i) an efficiency higher than that of a reference Type I photoinitiator (2,2-dimethoxy-2-phenylacetophenone, DMPA), (ii) an excellent ability, when added to DMPA, to overcome the oxygen inhibition of the polymerization, and (iii) a never reported in situ photoinduced and oxygen-mediated formation of zirconium-based nanoparticles (diameter ranging from 50 to 70 nm). The photochemical properties of CpZrCl are investigated by steady state photolysis and electron spin resonance (ESR) experiments.