Stimuli-responsive polymers, with properties changing upon different environmental factor variations such as pH, light, mechanical stress or temperature, and polymeric nanoparticles have found many ...important applications in fields such as drug delivery, biosensing and environmental research.
In this work, thermoresponsive nanoparticles that are able to react by Diels-Alder reaction (a diene-dienophile cycloaddition) were studied. Thermoresponsive polymers were synthesized from a biocompatible polymer (poly(lactic-co-glycolic) acid, PLGA) and diene (furan) or dienophile (maleimide) derivatives. Emulsification-evaporation method was then used as a fast and reproducible method to obtain highly monodispersed polymeric nanosuspensions able to react by Diels-Alder (DA) reaction.
The nanoparticles’ size decreased down to 25 nm by increasing the emulsification’s time. The possible direct and retro-Diels-Alder (rDA) reactions between furan- and maleimide-functionalized nanoparticles were studied by dynamic light scattering and electron microscopy. For the first time, the reactivity of the interfacial DA and rDA reactions between functionalized-nanoparticles was studied, leading to the determination of the activation energy, the enthalpy of activation and the entropy of activation.
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Anisotropic particles, in shape or chemistry, have raised enthusiasm since they interact with their surrounding in unique ways, leading to complex assemblies that can be used in applications ranging ...from energy to health. In this study, two different types of polymeric nanoparticles, blend-type with two hydrophobic polymers and Janus type with hydrophobic and hydrophilic parts were produced thanks to an emulsification elongational-flow microprocess. Particles with controlled sizes and size distribution were successfully produced in one step and the effect of material (e.g. polymers’ composition and concentration, solvent) and process (e.g. flow rates, emulsification time) parameters on nanoparticles’ characteristics were thoroughly studied. Particles’ diameter ranged from 90 to 200 nm, depending on the aforementioned parameters.
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Janus polymeric nanoparticles have attracted much attention for their wide range of applications in various fields due to the presence of two domains with different chemistries, compositions or ...functionalities. This type of particles is obtained by various conventional methods which require several steps (the particle elaboration and the surface functionalization), sometimes leading to the elaboration of emulsions with large and multimodal sizes distributions. Various physical and chemical parameters influence the particles size, morphology and stability.
In this study, we propose to prepare polymeric Janus nanoparticles (JNPs) by a one-step method from a mixture of two different polymers and to compare several emulsification-evaporation processes (sonication, shear mixing and elongational-flow micromixing).
The possibility to obtain monomodal JNPs (diameter lower than 200 nm) with a hydrophobic domain (poly(lactic-co-glycolic acid), PLGA) and a hydrophilic charged domain (based on poly(styrene sulfonate), PSS) was demonstrated only with the elongational-flow micromixer.
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Stimuli‐responsive materials have properties that depend on the environment in which they are used. In most cases, the material itself is formulated to react to the corresponding stimulus. However, ...many phenomena occur at the surface of the material. In this context, the design and the investigation of the reactivity of stimuli‐responsive surfaces are particularly interesting. More precisely, this review focuses on functional coatings that react via Diels–Alder (DA) chemistry, a thermoreversible reaction between a diene and a dienophile. According to the nature of the substrate, these coatings are mainly based on self‐assembled monolayers or silane assemblies, on polydopamine derivatives, or on polymer thin films deposited by vapor‐phase processes including plasma polymerization. The different works discussed here show that interfacial thermoreversible reactions occur between a DA‐functionalized surface and a DA reactant in solution but also between two solid substrates are possible. The direct cycloaddition is always described in the cited papers but the reversibility of the reaction is less discussed. The latter however remains very challenging for smart applications in material science.
This review reports on the fabrication of functional surfaces with thermoreversible properties and the understanding of their reactivity via the Diels–Alder reaction. Based on various functionalization processes, the designed surfaces have various physico‐chemical properties, leading to different Diels–Alder reactivity. The direct cycloaddition is always described in the cited papers but the reversibility of the reaction is less discussed.
Biodegradable polymeric nanoparticles are considered as promising drug delivery systems due to their high potential in tuning the release and alleviate side effects. However, particle greater than ...200 nm can be detected by the immune system. Thus, this paper focuses on the elaboration of size-controlled nanoparticles of poly (lactic-co-glycolic acid) smaller than 200 nm encapsulating a model drug. For this purpose, the biodegradable polymer was first solubilized in ethyl acetate and then dispersed into water by different nanoemulsification devices: shear mixer, sonicator and elongational-flow reactor and micromixer. Last two devices showed the capacity to produce monomodal nanoparticles of targeted size range at different continuous to disperse phase volume ratios. On a second part, nanoparticles produced with the micromixer were employed as nanocarriers for rifampicin, a hydrophobic antibiotic. These drug-loaded nanoparticles were produced at different drug concentrations to study the effect of drug load on the particle properties. Different techniques such as dynamic light scattering, transition electron microscopy and ultraviolet spectroscopy were employed to thoroughly characterize the nanoparticle diameter, size dispersity and morphology, drug encapsulation efficiency and in vitro drug release profile. Nanoparticles produced with the micromixer, following a new phase pre-saturation approach, had a highly monomodal diameter as low as 63 nm and an encapsulation efficiency of 40% at 5% w/v drug load was measured. Drug release tests under sink conditions showed 44% ± 2% cumulative drug release within 8 days.
In this study, size-controlled nanoparticles of poly(lactic-co-glycolic acid) smaller than 200 nm encapsulate a model drug: the rifampicin, a hydrophobic antibiotic. For this purpose, the biodegradable polymer was first solubilized in ethyl acetate and then dispersed into water by different nanoemulsification devices: shear mixer, sonicator and elongational-flow reactor and micromixer. On a second part, nanoparticles produced with the micromixer were employed as nanocarriers for rifampicin. These drug-loaded nanoparticles were produced at different drug concentrations to study the effect of drug load on particle’s properties: size, encapsulation efficiency and drug release. Display omitted
•One-step encapsulation of hydrophobic drug can be proceeded by microfluidics.•Poly (lactic-co-glycolic acid) is used as drug carrier.•Different emulsification devices led to various particles sizes smaller than 200 nm.•Phase saturation approach enables the production of highly monomodal particles.
Surface functionalization is an interesting way to elaborate new smart materials. In this work, a two-step surface modification, based on pulsed plasma polymerization, was used to design functional ...surfaces able to react by Diels–Alder reaction (a diene–dienophile cycloaddition). The reactivity of furan-functionalized (diene) surfaces with a maleimide-derivative (dienophile) was studied. The determination of the rate constants led to the determination of the activation energy, the enthalpy of activation, and the entropy of activation. These results were then compared to those obtained in solution. For the first time, it was possible to understand the role played by molecule confinement (close to the surface) on the Diels–Alder reactivity.
Les problématiques liées aux surfaces et interfaces prennent de plus en plus d’importance dans de nombreux secteurs, aussi bien académiques qu’industriels. Dans de nombreuses applications, il n’est ...parfois pas nécessaire de conférer la réactivité désirée à la totalité du volume du matériau : une surface aux propriétés bien contrôlées peut suffire.Lieu de discontinuité des propriétés d’un matériau, la surface possède un comportement qui lui est propre, généralement apporté par une étape de fonctionnalisation. Dans ce contexte, ce travail de thèse vise à élaborer des surfaces polymères aux propriétés thermoréversibles, de comprendre les mécanismes réactionnels mis en jeu aux interfaces et de proposer de nouvelles surfaces aux pouvoirs adhésifs réversibles.Il existe de nombreuses techniques permettant de modifier la surface des matériaux. La littérature est abondante et variée, on y trouve notamment des techniques visant à introduire des groupements fonctionnels à la surface d’un substrat. Parmi elles, la polymérisation plasma est une technique de dépôt chimique en phase vapeur, sans solvant, permettant le dépôt de films minces de polymères aux propriétés physico-chimiques contrôlées sur une grande variété de matériaux. Le plasma, état très excité de la matière, est généré grâce à un champ électromagnétique. C’est cette technique de fonctionnalisation qui a été choisie dans ce travail de thèse dans le but de déposer un film mince de polymère possédant des propriétés thermoréversibles sur divers substrats.Les propriétés de thermoréversibilité sont apportées grâce à la présence de groupements furanes, capables de réagir avec un diénophile par une réaction de Diels-Alder (DA). Cette réaction, dite « click », entre un diène et un diénophile a été décrite pour la première fois en 1928 par Otto Diels et Kurt Alder, et fut à l’origine de l’obtention de leur Prix Nobel en 1950. Dans la littérature, les études sur la réaction de DA sont majoritairement réalisées en solution voire sur des matériaux massifs. Cette chimie a été beaucoup moins étudiée sur/dans des films minces, où la notion de confinement prend toute son importance. C’est dans ce contexte que se posent ces travaux de thèse.Dans un premier temps, une étude expérimentale approfondie sur la réactivité de DA (étude cinétique et thermodynamique) a été réalisée. Des polymères plasma ayant des propriétés physico-chimiques variées ont été synthétisés et un couple diène/diénophile modèle, le furane présent dans le polymère plasma et l’anhydride maléique en solution, a été choisi. La compréhension de la réactivité interfaciale de DA sur des polymères plasma constitue la première grande partie de cette thèse. Diverses méthodes de caractérisation des propriétés du film mince fonctionnel (spectroscopie infrarouge, spectrométrie photo-électronique X, mesures d’angle de contact, mesures par microbalance à cristal de quartz avec dissipation, microscopie à force atomique et ellipsométrie) ont été utilisées pour confirmer dans un premier temps la faisabilité du procédé de fonctionnalisation basé sur la polymérisation plasma puis de quantifier la réactivité interfaciale de DA. Dans une seconde partie, la méthodologie développée a été élargie à la compréhension de la réactivité interfaciale de DA et rétro-DA mettant en jeu un autre couple diène/diénophile, à savoir le furane (toujours greffé sur le polymère plasma) et le maléimide (en solution). Enfin, le greffage du maléimide sur un substrat a permis de s’interroger sur la faisabilité d’une adhésion covalente réversible, à l’échelle moléculaire mais aussi macroscopique, entre deux substrats solides fonctionnalisés, l’un avec des groupements furanes, l’autre avec des groupements maléimides. ...
Should we adapt to materials or can we modify materials to obtain what we want and what we need? Since the beginning of humanity, natural materials (stone, wood, etc.) have allowed civilizations to develop. Thanks to the increase of knowledge in the field of materials and to the development of more and more sophisticated fabrication processes, civilizations have also allowed the development of materials such as metal alloys, ceramics and, more recently, synthetic polymers. Since the second-half of the 20th century, researchers and engineers have found interest in responsive materials and particularly responsive polymers, able to adapt to their surrounding environment such as the mostly studied poly(N-isopropylacrylamine). The number of studies to design new smart materials keeps increasing because they play an important role in the development of advanced technologies. Today, we can find smart materials in all areas of activity.According to the targeted application, different stimuli are considered and can be classified amongchemical or physical stimuli.Recently, chemical stimuli have been studied for various applications, such as the elaboration of pH-stimuli responsive materials to control drug delivery and separation processes. The presence of specific molecules, for instance containing polar groups or able to form hydrogen bonds, can also modify the properties of materials and may be used to induce self-healing processes. Biomolecules may also provide chemical signals for the selective conjugation of proteins or sugars. Besides, physical stimuli have also gained interest because they can be remotely applied. Indeed, electro- or magneto-active polymers respond to an applied electric or magnetic field by changing their size or shape for instance. They are used to elaborate sensors, robotic muscles, to store data and in nanomagnetic materials for various biomedical applications. Photo-sensitive polymers can change their physicochemical properties in response to light irradiation at a given wavelength and intensity. The photoresponsive polymers are broadly used in nano- or bio-technology, such as for bio-patterning and photo-triggered drug delivery. Another highly-studied physical stimulus consists in the variation of the environmental temperature. This method is used for drug delivery, in liquid chromatography to vary the power of separation without changing the column and/or the solvent composition or to elaborate self-healing materials (composites) thanks to weak (H-bonds) or covalent interactions forinstance.In the former examples, the whole composition of the system is usually specifically formulated to react to environmental conditions, although many phenomena locally occur at the surface of the material. This strategy is thus economically non-viable because only few percents of the material volume are exploited for their smart properties. Consequently, industrial renewal can be stimulated by the fabrication of stimuli-responsive coatings that could cover any material, preserving the characteristics of the bulk material and limiting the cost of these additional smart properties. ...
Functionalizing the surface of a material with a smart plasma polymer coating is an interesting alternative strategy to obtain a thermoresponsive material without changing its formulation. On the ...basis of a low-pressure plasma polymerization process, the present work first aims to fabricate polymer thin films that react via the well-known thermoreversible Diels–Alder (DA) reaction (diene/dienophile cycloaddition). A two-step surface modification process based on (pulsed) plasma polymerization enables the design of functional coatings that contain furan (diene) groups. The reactivity of these surfaces with maleic anhydride (dienophile) in solution is thoroughly investigated, mainly by studying the kinetics of the DA reaction by advancing contact angle measurements. The determination of rate constants of reactions at various temperatures leads to the quantification of thermodynamic parameters such as the activation energy of the reaction as well as the enthalpy and entropy of activation related to the formation of the transition-state complex involved in the DA reaction. More interestingly, the design of furan-functionalized coatings with various physicochemical properties enables the understanding of the role played by the density of functional groups and the cross-linking rate of the polymer on the interfacial reactivity. Thus, we show in this work how to control the interfacial DA reaction on plasma coatings by tailoring the operating conditions of plasma polymerization.
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