Letteratura scientifica selezionata sul tema "Photothermal polymerization"

Because of the increasing scarcity of water resources, the desalination of seawater by photothermal evaporation with harvested solar energy has gradually become a popular research topic. The interconnected macroporous cryogel prepared from polymerization and crosslinking below the freezing temperature of the reactant solution has an excellent performance in photothermal water evaporation after loading photothermal materials. In this study, polyacrylamide (PAM) cryogels were prepared by cryo-polymerization and sulfonated in an alkaline solution containing formaldehyde and Na2SO3. Importantly, the evaporation enthalpy of water in sulfonated PAM cryogel was reduced to 1187 J·g−1 due to the introduction of sulfonate groups into PAM, which was beneficial to increase the photothermal evaporation rate and efficiency. The sulfonated PAM cryogels loaded with polypyrrole and the umbrella-shaped melamine foam substrate were combined to form a photothermal evaporation device, and the evaporation rate was as high as 2.50 kg·m−2·h−1 under one-sun radiation. Meanwhile, the evaporation rate reached 2.09 kg·m−2·h−1 in the 14 wt% high-concentration saline solution, and no salt crystals appeared on the surface of the cryogel after 5 h of photothermal evaporation. Therefore, it was evidenced that the presence of sulfonate groups not only reduced the evaporation enthalpy of water but also prevented salting-out from blocking the water delivery channel during photothermal evaporation, with a sufficiently high evaporation rate, providing a reliable idea of matrix modification for the design of high-efficiency photothermal evaporation materials.

SiO2@AuAg/Polydopamine core/shell nanospheres, which possessed synergistic “Ag+-release–photothermal” antibacterial and catalytic behaviors, have been successfully prepared via a simple in situ redox polymerization method.

A new smart supramolecular polypeptide copolymer P(Glu-co-Lys) was synthesized by the polymerization of α-amino acids using the N-thiocarboxylic acid anhydride (NTA) method, using the pH dynamic response peptide of L-glutamic acid and L-lysine as a carrier for tumor cells. The drug delivery system activated by external acid can self-assemble (pH 7.4) and disassemble (pH 5.5) under the adjustment of pH to load the drug and control its release. Doxycycline (DOX) and the photothermal reagent hydrophilic quanternary stereo-cyanine (HQS-Cy) were loaded into the peptide copolymer to obtain HQS-Cy/DOX nanoparticles (NPs) for chemo-photothermal therapy. Gentle photothermal heating can enhance the absorption of drugs by cells and enhance the efficacy of chemotherapy. In addition, chemo-photothermal therapy can solve the defect of easy recurrence after single photothermal therapy. The ingenious nanodrug delivery system of HQS-Cy/DOX NPs provides great potential for the improvement of chemo-photothermal therapy and will achieve excellent therapeutic effects in cancer treatment.

Three synthesized photothermal initiators (2959-HDHP, 184-HDHP, 1173-HDHP) exhibited better photoinduced thermal frontal polymerization effect than mixture system due to higher heat transfer efficiency from photopolymerization to thermal initiator.

In this work, polythiophene nanoparticles (PTh–NPs) were synthesized by a surfactant-free oxidative chemical polymerization method at 60 °C, using ammonium persulphate as an oxidant. Various physicochemical properties were studied in terms of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy, and differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA). Photothermal performance of the as-synthesized PTh–NPs was studied by irradiating near infra-red of 808 nm under different concentration of the substrate and power supply. The photothermal stability of PTh–NPs was also studied. Photothermal effects of the as-synthesized PTh–NPs on colorectal cancer cells (CT-26) were studied at 100 µg/mL concentration and 808 nm NIR irradiation of 2.0 W/cm2 power. Our in vitro results showed remarkable NIR laser-triggered photothermal apoptotic cell death by PTh–NPs. Based on the experimental findings, it is revealed that PTh–NPs can act as a heat mediator and can be an alternative material for photothermal therapy in cancer treatment.

Le groupe Mäder s’est lancé depuis quelques années dans une nouvelle thématique, la polymérisation « dual-cure ». Il s’agit d’un processus photo-thermique couplant réactivité photochimique et thermique. Cette thématique vise des applications pour lesquelles le produit est épais et/ou fortement chargé. La photopolymérisation étant limitée en profondeur, le processus thermique permet de compléter la polymérisation au coeur de l’échantillon ou encore dans les zones non accessibles par la technologie UV/LED. Cette thématique a fait l’œuvre d’une première thèse (2007-2010) menée par le doctorant Adrien Criqui au sein du Département de Photochimie Général (DPG). Au cours de cette thèse, la polymérisation radicalaire photo-thermique à partir d’aldéhydes a été étudiée. Des résultats concluant ont été obtenus donnant naissance à une technologie innovante notamment avec des applications sous air. Dès lors, il s’est posé la question de savoir si les aldéhydes pouvaient être utilisés dans la polymérisation cationique photo-thermique. La première année de thèse a donc commencé par l’étude du potentiel des aldéhydes dans la polymérisation cationique photo-thermique de résine époxydes. Les aldéhydes ont montrés qu’ils sont de bons photosensibilisateurs de la photopolymérisation cationique amorcée par un sel d’iodonium. Certaines structures aldéhydes couplées à un sel d’iodonium ont conduit à une polymérisation thermique. Les vitesses de polymérisation sont néanmoins trop lentes pour pouvoir être exploitées. La voie des aldéhydes a donc été abandonnée suite à ces résultats. Malgré ceci, ce sujet a fait l’œuvre d’une étude mécanistique qui a permit de conclure que le couple sel d’iodonium/aldéhyde réagit selon un mécanisme redox au courant duquel l’auto-oxydation de l’aldéhyde est indispensable. La réduction du photoamorceur par le radical issu de l’auto-oxydation de l’aldéhyde permet d’amorcer la polymérisation cationique. Par la suite, une importante bibliographie sur la polymérisation cationique des époxydes a été réalisée, le but étant de rechercher de nouveaux systèmes amorceurs. Plusieurs systèmes ont alors été retenus à savoir, les acides de Lewis et de Brönsted ainsi que les espèces cationiques. Les acides de Lewis étudiés n’ont pas apportés de résultats satisfaisants et ont donc été abandonnés. Parmi les acides de Brönsted, les acides sulfoniques ont été sélectionné. Des résultats mitigés ont été obtenus. En effet, soit la polymérisation s’est montrée trop rapide et non contrôlable soit trop lente. Le mécanisme de polymérisation amorcé par ces espèces ne semble pas adapté aux résines époxydes. La synthèse d’une structure appropriée a été envisagée mais pour des raisons stratégiques a été par la suite abandonnée. Plusieurs structures d’espèces cationiques ont été étudiées, à la fois des espèces commerciales (ex : triphénylcarbénium, …) ainsi que des espèces synthétisées au laboratoire (ex : xanthénium, …). Les travaux effectués sur ces systèmes amorceurs ont montrés qu’un amorçage indirect avec formation de l’amorceur in situ était une voie à privilégier.A partir de ce constat, deux technologies ont été étudiées. La première, à caractère purement académique, concerne une voie redox. Un système déjà publié basé sur le système sel d’iodonium/sel de cuivre/acétoïne a été ré-évalué. Les résultats obtenus ne correspondant pas au mécanisme publié, une étude mécanistique a été réalisée afin de proposer un nouveau mécanisme réactionnel. Le mécanisme de réaction est basé sur une réaction de décomposition, probablement par complexation, du sel d’iodonium par un sel de cuivre. Le produit de décomposition formé étant sensible à l’hydrolyse, il est possible d’accélérer la vitesse de polymérisation par la présence d’un composé hydroxylé type acétoïne. [...]
In the past few years, The Mäder Group has launched a new theme, " dual- cure " polymerization and process. This process is a coupling between photochemical and thermal reactivity. This theme is designed for applications where the product is thick and/or loaded with fillers. The photopolymerization is limited in depth and then the thermal process is used to complete the polymerization of the sample or in the non-irradiated areas. This theme has been the work of a first PhD (2007-2010) conducted by the student Adrien Criqui in the “Département de Photochimie Générale (DPG)”. In this PhD, the photo- and thermal radical polymerization with aldehydes was studied. Results have given birth to an innovative technology, particularly with applications under air. Therefore, it wonder if aldehydes could be used in the photo- and thermal cationic polymerization.The first year of PhD has begun with the study of the potential of aldehydes in the photo- and thermal cationic polymerization of epoxy resin. Aldehydes have shown that they are good photosensitizers of the cationic photopolymerization initiated by an iodonium salt. Some aldehydes coupled with an iodonium salt led to thermal polymerization. However rates of polymerization are too slow to be exploited. The way of aldehydes has been aborted due to these results. Despite this, this topic has been the work of a mechanistic study that led to the conclusion that the iodonium/aldehyde salt couple reacts according to a redox mechanism in which the auto-oxidation of the aldehyde is essential. The reduction of the photoinitiator by the radical derived from the auto- oxidation of the aldehyde aollow to initiate cationic polymerization.Subsequently, an extensive bibliography on the cationic polymerization of epoxides was carried out with the aim to find new initiator systems. Therefore, several systems have been selected i.e., Lewis and Brösted acids, and cationic species. Lewis acids studied gave no satisfactory results and were therefore given up. Among the Bronsted acids, sulfonic acids were selected. Mixed results were obtained. Sometimes the polymerization has been too fast and sometimes too slow. The polymerization mechanism initiated by these species does not seem suitable for epoxy resins. The synthesis of a suitable sulfonic acid was considered but for strategic reasons was later dropped. Several structures of cationic species have been also studied, both commercial species (eg: triphenylcarbenium , ... ) as well as synthesized species (eg: xanthénium ...). Work on these initiator systems convinced to use an indirect method to initiate polymerization.From this, two technologies have been studied. The first, relates to a redox pathway. A published system based on iodonium salt/copper salt/acetoïne combination has been re-evaluated. Results do not match the published mechanism. A new mechanistic has been proposed. The reaction mechanism is based on a decomposition reaction, presumably by complexation, of the iodonium salt with a copper salt. The decomposition product formed is susceptible to hydrolysis. Rates of polymerization have been accelerated the by the presence of a hydroxy compound like acetoïne. From the knowledges, ways of controlling the rate of polymerization (eg: complexing metal salt) and a new initiator system have been proposed. The second technology relates to a bi-component consisting of a photoinitiator/thermal initiator and a co- initiator. The reaction between the initiator and co-initiator allows initiating the polymerization. The polymerization rate can be controlled from the structure of initiator and co-initiator. The initiator is also a photoinitiator, the photo- and thermal nature is ensured. Two classes of co-initiators have been studied from a fundamental point of view (hydroperoxides and vinyl ether). It has been shown that hydroperoxides reduce initiator by an electron transfer. [...]

Ces dernières années, la photopolymérisation a fait l'objet d'intenses efforts de recherche en raison de la croissance constante des applications industrielles. C’est un processus rapide pouvant être réalisée à température ambiante, sans solvant et permettant d'obtenir un contrôle spatial et temporel de la polymérisation. Ces dernières années, l'utilisation de conditions d'irradiation douce qui constitue une alternative aux procédés de photopolymérisation UV à l'origine de nombreux soucis de sécurité est activement recherchée. Par conséquent, le développement de nouveaux systèmes photoamorceurs absorbant fortement dans la région visible ou du proche infra-rouge sont activement recherchés par les communautés académiques et industrielles. Néanmoins, même si certains résultats sont prometteurs, les systèmes reportés sont souvent caractérisés par des réactivités modérées et rivalisent difficilement avec les systèmes UV actuels. Dans ce contexte, nous avons synthétisé une large librairie de molécules photosensibles capables d’absorber la lumière dans le domaine du visible ou du proche infrarouge et capables d’amorcer une réaction de polymérisation avec un système photoamorceur basée sur la catalyse photoredox. Dans ce manuscrit, nous présentons aussi bien la synthèse et les capacités de polymérisation de différentes familles de colorants. Leurs propriétés photochimiques ont également été étudiées par spectrométrie UV-visible, luminescence, photolyse, surveillance de la température et expériences de résonance paramagnétique électronique. Des applications telles que l'impression 3D et les expériences d'écriture laser sont également présentées
In recent years, photopolymerization has been the subject of intense research efforts due to the constant growth of industrial applications. It is a quick process that can be performed at room temperature, solvent-free conditions and enables to get a spatial and a temporal control of the polymerization process. In recent years, the use of irradiation conditions that constitutes an alternative to the UV photopolymerization processes at the origin of numerous safety concerns are actively researched. Therefore, the development of new photoinitiating systems which absorb strongly in the visible or near infrared region are actively researched by both the academic and industrial communities. Nevertheless, even if some results are promising, the reported systems are often characterized by moderate reactivities and hardly compete with current UV systems. In this context, we have synthesized a large library of photosensitive molecules capable of absorbing light in the visible or near infrared range and capable of initiating a polymerization reaction with a photoinitiating system based on photoredox catalysis. In this manuscript, we present both the synthesis and the polymerization abilities of different families of dyes. Their photochemical properties were also studied by UV-Visible spectrometry, luminescence, photolysis, temperature monitoring and electronic paramagnetic resonance experiments. Applications such as 3D printing and laser write experiments are also presented

State-of-the-art technologies for manufacture of fiber-reinforced polymer composites (FRPCs) rely on bulk polymerization of matrix thermoset resins at elevated temperatures for several hours (up to 24 h) in an autoclave or oven. This process is energy- and time-intensive, generates a significant carbon footprint, and requires expensive equipment. In recent years, frontal polymerization (FP) has emerged as an alternative approach for rapid and energy-efficient curing of FRPCs. However, widespread and practical adoption of this curing technique at industrial scale is limited by the low front velocities (<10 cm min-1), the need for using highly thermally insulating tooling materials (e.g., polymer foams), and low degree of cure of resin in produced composites. In addition, frontal curing of thin composite laminates is quite challenging even on highly thermally insulating tooling materials due to the high rate of heat loss through boundaries compared to the generated heat, resulting in quenching of reaction and incomplete cure. Here, we present a new approach for rapid curing (~50 cm min-1) of FRPC panels via FP by supporting the underlying thermal curing reaction using a moving infrared heating source. In our approach, following the infusion of a carbon fiber composite layup by an FP resin system, an infrared heating source is linearly moved along the length of the layup to not only initiate the FP reaction via photothermal energy conversion effect but also locally pre-heat the resin and increase its frontal reactivity and front velocity. We successfully cure a 5 Å~ 15 cm2 composite panel on a glass tool plate within 24 s with a total energy consumption of 8.3 kJ as a proof of concept. Differential scanning calorimetry measurements are also conducted on produced laminates to determine the degree of cure of produced FRPCs. Finally, a thin laminate, consisting of a single ply of carbon fabric is fabricated as a proof-of-concept to further demonstrate the capability of our technique for rapid manufacturing of thin composites, which is promising for use in space and aerospace applications.