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•SMPs are an emerging class of smart polymer materials with multi-responsiveness.•Recent trends in the field of SMPs (conception, fabrication, modeling) are outlined.•A new generation ...multi-functional SMPs containing nanosized fillers is described.•The nanocomposites have enhanced mechanical, thermal and shape-memory properties.•SMPs are of great interest to fundamental research and technological innovation.
Shape-memory polymers (SMPs) as stimuli-responsive shape-changing polymers are of great interest for fundamental research and technological innovation. In this contribution, a brief review of the recent trends in the field of SMPs is presented with particular focus on their structure, shape-memory effects and working mechanism. A special attention is paid to smart multi-responsive and multi-functional SMP materials as emerging technological class. They are mainly described as shape-memory nanocomposites (SMCs) where the incorporation of functional (in)organic nanofillers in the SMP matrices is purposely carried out. Potential applications of the SMCs-based materials as medical and biomimetic devices, self-healing systems, self-deployable structures, actuators, sensors, etc. or their direct implementation in the industry are finally outlined.
Environmental concerns along with the need to develop aliphatic polycarbonate materials free of any toxic compounds have driven scientists to implement macromolecular engineering processes by ...replacing potentially toxic and carcinogenic metal-based catalysts traditionally used for the ring-opening polymerization of cyclic carbonates by organic compounds. This issue is of particular importance as aliphatic polycarbonates are gaining increasing credibility for biomedical applications owing to their biocompatibility and bioresorbability. This review provides a complete account of the various metal-free catalysts that has been developed so far as well as comprehensive investigations on the related polymerization mechanisms.
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•Effect of lignin incorporation on thermal degradation and fire behavior of PLA.•Phosphorus/nitrogen modification of lignin: enhancement of its FR effect in PLA.•Use of several ...innovative and original techniques for lignins characterization.•Gases from thermal decomposition of lignins analyzed by TGA-MS.•Gases from combustion of lignins analyzed by cone calorimeter-FTIR.
The present study focuses on the use of lignin, which is the second most abundant constituent of the biomass, as sustainable flame retardant additive for polylactide (PLA). Indeed, thanks to its aromatic structure, lignin could be advantageously used, in polymeric matrices, as a char promotor agent that can allow some reduction of the combustion rate. An original and simple approach, based on a two-step phosphorus/nitrogen chemical modification, is proposed to enhance the flame retardant effect of lignin in PLA. This approach has been applied on two different lignins, i.e. kraft and organosolv lignins. The effect of the plant origin, extraction mode of lignin as well as it chemical modification on both its structure and properties was investigated by using several characterization techniques. Fire properties and thermal behavior of PLA composites containing 20 wt% of both untreated and treated lignins were characterized by using cone calorimeter, UL-94 and thermogravimetric analysis (TGA). Results showed that the incorporation of untreated lignins led to a flame retardant action in PLA thanks to the formation of char but also to a significant loss of the thermal stability of PLA and to an important decrease of its time to ignition. In contrast, both phosphorus/nitrogen chemically treated lignins were found to limit PLA thermal degradation during melt processing as well as during TG experiments and also to significantly improve fire retardant properties allowing to reach V0 classification at UL-94. In this paper we also deeply investigated the nature of the gases evolved during thermal decomposition of treated and untreated lignins by using TGA-Mass spectrometer and cone calorimeter – FTIR couplings.
Surface-functionalization mediated through “grafting from” methods is of considerable interest as means to tailor the chemical and physical properties of functional substrates in a reliable way. The ...resulting polymer brushes, obtained by a “grafting from” strategy, are composed of grafted polymer chains tethered from one of their extremities to a surface by a covalent bond. Tuning the molecular parameters of these polymeric brushes such as the nature of monomer, the grafting density, and the chain length as well as the design of micropatterned structures enables delicate modification of the properties of these substrates, paving the way to the development of functional surfaces. In this review, we highlight recent and most important approaches to form monolayers and to subsequently elaborate homogeneous and heterogeneous coatings of polymer brushes by surface-initiated polymerization. The control of initiator molecule assembly is particularly important for the final configuration of polymer brushes. We report the creation of homopolymers and block copolymers using major controlled polymerization techniques as well as lithographic techniques aiming at the design of polymeric (micro- or nano-) patterns.
Novel potentially biobased aliphatic–aromatic copolyesters poly(butylene succinate-co-butylene furandicarboxylate) (PBSFs) in full composition range were successfully synthesized from ...2,5-furandicarboxylic acid (FA), succinic acid (SA), and 1,4-butanediol (BDO) via an esterification and polycondensation process using tetrabutyl titanate (TBT) or TBT/La(acac)3 as catalyst. The copolyesters were characterized by size exclusion chromatography (SEC), Fourier transform infrared (FTIR), 1H NMR, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and their tensile properties were also evaluated. The weight average molecular weight (M w) ranges from 39 000 to 89 000 g/mol. The copolyesters are random copolymers whose composition is well controlled by the feed ratio of the diacid monomers. PBSFs have excellent thermal stability. The glass transition temperature (T g) increases continuously with ϕBF and agrees well with the Fox equation. The crystallizability and T m decrease with increasing butylene furandicarboxylate (BF) unit content (ϕBF) from 0 to 40 mol %, but rise again at ϕBF of 50–100 mol %. Consequently, the tensile modulus and strength decrease, and the elongation at break increases with ϕBF in the range of 0–40 mol %. At higher ϕBF, the modulus and strength increase and the ultimate elongation decreases. Thus, depending on ϕBF, the structure and properties of PBSFs can be tuned ranging from crystalline polymers possessing good tensile modulus (360–1800 MPa) and strength (20–35 MPa) to nearly amorphous polymer of low T g and high elongation (∼600%), and therefore they may find applications in thermoplastics as well as elastomers or impact modifiers.
Renewable and biodegradable UV-blocking films are in high demand for the increasing need of sustainable environment. Lignin can offer significant UV absorption, but it deteriorates the mechanical ...properties of films at a high content. In this effort, biobased 10-undecenoic and oleic acids were successfully grafted on soda lignin via solvent- and catalyst-free processes, as confirmed by 31P and 1H NMR and Fourier transform infrared (FTIR). The resulting lignin ester derivatives and neat lignin were then melt-blended with a biodegradable poly(butylene adipate-co-terephthalate) (PBAT) to prepare UV-protective films. The incorporation of the modified lignins into the PBAT matrix exhibited good dispersion of lignin particles with almost unaffected tensile properties as well as good thermal stability for up to 20 wt % loading of lignin derivatives. The resulting films showed excellent UV-barrier property with 10 wt % lignin loading, having full protection in the whole UV-irradiation range (280–400 nm). The UV protection of prepared films proved persistent even after UV irradiation for 50 h, and their transparency was evidently enhanced. This work demonstrates a very promising procedure to produce high-performance and biodegradable PBAT–lignin UV-blocking films.
Biodegradable and renewable UV-shielding films are highly demanded to meet the increasing sustainable requirement for the environment. Lignin as a natural broad UV blocker has gained considerable ...attention; however, the poor dispersibility within synthetic polymers limited its applications. Thus, a bioinspired melanin-like polydopamine thin layer was incorporated for the first time with lignin nanoparticle (LNP) in this effort, forming a UV-blocking core–shell lignin–melanin nanoparticle (LMNP) with higher compatibility and durability. Subsequently, LNP, LMNP, melanin nanoparticles (MNP), and a mix of LNP and MNP (MixNP) were compounded with poly(butylene adipate-co-terephthalate) (PBAT), to enhance the UV-barrier capability and photostability of PBAT films. The incorporated LMNPs were well distributed into PBAT, leading to improved tensile properties and thermal stability of the resulting films. All these films possessed remarkable UV-blocking capacity at NP concentration ranging from 0.5 to 5 wt %, blocking almost all of UV-A and more than 80% of UV-B light, while an appreciable optical transmittance could also be achieved. The PBAT–LMNP films displayed a high UV-shielding stability and the best retention in mechanical properties after UV exposure for 40 h. This work provides a very promising approach for fabricating biodegradable PBAT-based UV-blocking films for potential applications in agricultural or food packaging materials where the UV resistance is highly required.
S’initier par la pratique Dubois, Philippe R.
Politique et sociétés (Montréal),
2023, 2023-00-00, 20230101, Letnik:
42, Številka:
3
Journal Article
Recenzirano
Alors que le parcours aux cycles supérieurs en science politique est caractérisé par une forte compétition, les étudiant.e.s doivent s’initier rapidement aux rudiments de la recherche scientifique et ...publier durant leurs études. Ce court article plaide en faveur des projets autonomes extracurriculaires comme outil contribuant significativement à former la relève en recherche. Dans une perspective d’apprentissage par la pratique, collaborer à des activités étudiantes de diffusion de la recherche peut avoir des retombées positives sur le plan des connaissances et des compétences qui préparent au rôle de chercheur.euse. C’est aussi l’occasion de développer une meilleure compréhension générale des normes et des usages propres à la discipline. Cela peut rendre plus accessible le monde de la recherche à des personnes non initiées, désavantagées ou sous-représentées. Ainsi, les institutions d’enseignement supérieur ont intérêt à soutenir ce genre d’initiatives afin d’offrir une meilleure formation à leurs étudiant.e.s en complément au cursus officiel et ce, à tous les cycles d’études.
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