Letteratura scientifica selezionata sul tema "Copolymer/oligomers"

Block copolymers of poly(ethersulphone) (PES) oligomers with liquid crystalline polyester units were synthesized by the reaction of dihydroxy-terminated poly(ether sulphone) oligomers (number-average molecular weights: 704, 1,158 and 2570) and terephthaloyl bis(4-oxybenzoyl chloride), and their properties were investigated. The results indicated that the copolymer with PES segments of molecular weight of 704 possessed birefringent features when annealed at 360°C, while the copolymer with PES segments of molecular weight of 2,570 became isotropic. Also, the block copolymers had a better chemical resistance and high-temperature stability than PES.

Block copolymers of poly(ethersulphone) (PES) oligomers with liquid crystalline polyester units were synthesized by the reaction of dihydroxy-terminated poly(ether sulphone) oligomers (number-average molecular weights: 704, 1,158 and 2570) and terephthaloyl bis(4-oxybenzoyl chloride), and their properties were investigated. The results indicated that the copolymer with PES segments of molecular weight of 704 possessed birefringent features when annealed at 360°C, while the copolymer with PES segments of molecular weight of 2,570 became isotropic. Also, the block copolymers had a better chemical resistance and high-temperature stability than PES.

Oligo(acrylic acid) efficiently stabilizes polymeric particles, especially particles produced by reversible addition–fragmentation chain transfer (RAFT) (as hydrophilic block of an amphiphilic copolymer). Capillary electrophoresis (CE) has a far higher resolution power to separate these oligomers than the commonly used size exclusion chromatography. Coupling CE to electrospray ionization mass spectrometric detection unravels the separation mechanism. CE separates these oligomers, not only according to their degree of polymerization, but also according to their tacticity, in agreement with NMR analysis. Such analysis will provide insight into the role of these oligomers as stabilizers in emulsion polymerization, and into the mechanism of the RAFT polymerization with respect to degree of polymerization and tacticity.

Poly(phthalazinone ether nitrile) (PPEN) block copolymers containing polysiloxane were prepared so as to create a strongly hydrophobic polymer surface. The copolymers were synthesized from eugenol end-capped polydimethylsiloxane (PDMS) and fluoro-terminated PPEN oligomers by the aromatic nucleophilic substitution polycondensation in the presence of dimethyl sulfoxide/o-dichlorobenzene and K 2 CO 3 as solvents and catalyst, respectively. The resultant copolymers were characterized by FTIR, 1 H NMR, and gel permeation chromatography. XPS analysis results indicated that the copolymer film had a very rich PDMS segment surface. Atomic force microscopy further showed that there existed a continuous PDMS phase on the copolymer surface and PPEN as the dispersive particles was dispersed at diameters between 0.1 and 0.3 nm. The enrichment of PDMS in the copolymer surface could be responsible for an increase of surface water repellency (113.4°).

A series of conjugated, symmetrical, and ferrocene-containing main-chain monomers was prepared following a gentle coupling reaction. Ferrocene-containing oligomers with all-trans-configured vinylene bonds could be synthesized via acyclic diene metathesis (ADMET) polymerization. These oligomers had a larger Stokes shift (2400 to 2600 cm−1) and both exhibited stable and reversible electrochemistry. Meanwhile, the copolymerization of 1,1’-bis[1-methyl-2-(4-vinylphenyl)ethenyl]ferrocene with 2,7-divinyl-9,9-dioctylfluorene was achieved. The structurally regular copolymers proved their optical and electrochemical properties. The fluorescence intensity of the copolymer gradually enhanced with the increasing number of fluorene units. At the same time, it was also found that the color of the copolymers had a significant change from yellow-green to red.

ABSTRACTThe metal-catalyzed step-growth radical polymerization was achieved to enable two systems for preparing tailored polymeric structures, i.e., sequence-regulated vinyl copolymer and periodically-functionalized polymer. The former is a novel strategy for preparing sequence-regulated vinyl copolymers by step-polymerization of sequence-regulated vinyl oligomers prepared from common vinyl monomers as building blocks. The later deals the simultaneous chain- and step-growth radical polymerization, which resulted in the polymers with periodic functional groups.

Les matériaux hybrides organiques-inorganiques à l'échelle nanométrique (nanoMOFs) ont montré un potentiel significatif dans le domaine de la libération contrôlée de médicaments (DDS) en raison de leurs propriétés avantageuses, notamment des compositions modulables, une porosité importante, de grandes surfaces spécifiques, de bonnes biocompatibilités et dégradabilités. Parmi la famille de nanoMOFs, le MIL-100(Fe) (MIL signifie Matériaux de l'Institut Lavoisier), construit à partir de trimères de fer et de ligands organiques (trimésate), a été largement étudié, avec des données bien documentées sur la toxicité in vivo et la biocompatibilité, ce qui en fait un candidat très attractif pour des applications biomédicales. Nous avons rédigé deux articles de synthèse qui détaillent la synthèse et les applications des nanoMOFs dans le domaine biomédical. Ce travail nous a permis de cerner plusieurs défis qui subsistent encore dans l'application biomédicale et la production à grande échelle des nanoMOFs MIL-100(Fe). Tout d'abord, il est essentiel d'améliorer la stabilité des nanoMOFs pendant leur conservation et dans de milieux biologiques, en vue d'une utilisation industrielle ultérieure. De plus, les méthodes de synthèse des nanoMOFs MIL-100(Fe) nécessitent une optimisation pour répondre aux exigences de la production à grande échelle non consommatrice d'énergie et “verte” (sans solvants organiques toxiques). Pour tenter de pallier à ces problèmes, nous proposons la modification de la surface des nanoMOFs MIL-100(Fe) avec des copolymères ou oligomères biocompatibles afin d'améliorer leur stabilité et leur biocompatibilité in vitro/in vivo. En outre, nous avons optimisé la stratégie de synthèse des nanoMOFs à base de trimésate de fer pour permettre une production simple, écologique, continue, respectueuse de l'environnement et à faible consommation d'énergie. Tout d'abord, nous avons conçu et synthétisé une famille de copolymères de type peigne qui comportent des chaines de poly(éthylène glycol) (PEG), des fonctions alendronate pour permettre un bon anchrage aux MOFs, et des molécules fluorescentes afin de permettre une bonne détection des nanoparticules composites. L'association de ces matériaux est extrêmement rapide (10 secondes) et les rendements avoisinent les 100%. Tous les composants des copolymères peigne jouent un role dans ce processus efficace de recouvrement. Les MIL-100(Fe) revêtus de copolymères ont non seulement démontré une excellente stabilité, mais aussi un caractère “furtif” évitant la reconnaissance par les macrophages. Les nanoMOFs ont été obtenus par une synthèse micro-onde usuelle, mais nécessitant un grand apport d'énergie et des températures élevées (130 °C). Dans un effort d'optimiser la synthèse, nous avons exploré des méthodes nouvelles opérant à température ambiante. Tout d'abord nous avons utilisé des modulateurs afin de contrôler la taille des nanoMOFs à température ambiante. En faisant varier les rapports molaires (R) de l'acide acétique (modulateur) et de l'acide trimésique (ligand organique), nous avons obtenu des nanoMOFs avec des diamètres hydrodynamiques allant de 40 à 200 nm. Nous avons ensuite recouvert ces nanoparticules avec des oligomères à base de cyclodextrine, afin d'obtenir une bonne stabilité sans compromettre leur capacité d'encapsulation de molécules actives. Ces études proposent des méthodes vertes et ouvrent la voie à la production à grande échelle des nanoMOFs à base de trimésate de fer
Nanoscale metal-organic frameworks (nanoMOFs) have shown significant promise as drug delivery systems (DDS) due to their advantageous properties, including tunable compositions, uniform porosity, large surface areas, biocompatibility, and degradability. Among these, MIL-100(Fe) (MIL stands for Materials of the Lavoisier Institute) nanoMOFs, constructed from trimesate organic linkers and iron trimers, have been extensively studied. We reviewed here in detail their well-documented in vivo toxicity and biocompatibility data, making them highly attractive candidates for drug delivery applications. We highlighted several challenges which remain in the biomedical application and large-scale production of MIL-100(Fe) nanoMOFs. First, improving the storage stability of MIL-100(Fe) is essential for further use. Additionally, the synthesis methods for MIL-100(Fe) nanoMOFs need optimization to meet the demands of green (organic solvent free) large-scale production. To address these issues, we propose the surface modification of MIL-100(Fe) nanoMOFs with biocompatible copolymers or oligomers to enhance their stability and biocompatibility. Furthermore, we have investigated novel synthesis strategies for MIL-100(Fe) nanoMOFs to enable simple, green, environmentally friendly, and low-energy production. We designed and synthesized a family of comb-like copolymers, comprising grafted: i) “x” (0-6) alendronate (Ale) anchoring units; ii) “y” (up to 45) poly(ethylene glycol) (PEG) side chains with molecular weight of zK (z=0.5, 2, 5), and iii) fluorescent Alexa Fluor (F) moieties. The resulting FAlexPEGzKy copolymers spontaneoulsy adsorbed onto the nanoMOF's surface in aqueous media, reaching ~100% efficiency. We highlighted the cooperative effects of each component of the FAlexPEGzKy copolymers in the association process. The coating occurred in the top layers without affecting the nanoMOF's crystallinity. The composition of the FAlexPEGzKy copolymers was optimized to ensure a good stability in biological media, despite the non covalent nature of the coating. In addition, the copolymer-coated MIL-100(Fe) nanoMOFs not only exhibited excellent storage stability but also demonstrated a “stealth effect” in macrophage J774 cells, as shown by confocal studies and iron quantification in the cells. In these studies, MIL-100(Fe) nanoMOFs were prepared by a conventional microwave hydrothermal procedure at high temperature (130 °C). To optimize the process, we investigated the possibilities to obtain MIL-100(Fe) nanoMOFs at room temperature. We used modulators in an attempt to control the size of the nanoMOFs. By varying the molar ratio (R) of acetic acid (modulator) to trimesic acid (organic linker), we obtained MIL-100(Fe) nanoMOFs with hydrodynamic diameters ranging from 40 to 200 nm. However, the resulting MIL-100(Fe) nanoMOFs needed also to be coated to avoid their aggregation. The coatings based on crosslinked cyclodextrins did not compromise the drug-loading capacity of the nanoMOFs. In a nutshell, this work presents novel strategies to construct nanoMOFs in a lego-type manner, using materials prepared mostly using “green” chemistry