Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 6 de 6
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Angew Chem Int Ed Engl ; 58(34): 11768-11773, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31216118

RESUMO

α-Alkylidene cyclic carbonates (αCCs) recently emerged as attractive CO2 -sourced synthons for the construction of complex organic molecules. Herein, we report the transformation of αCCs into novel families of sulfur-containing compounds by organocatalyzed chemoselective addition of thiols, following a domino process that is switched on/off depending on the desired product. The process is extremely fast and versatile in substrate scope, provides selectively linear thiocarbonates or elusive tetrasubstituted ethylene carbonates with high yields following a 100 % atom economy reaction, and valorizes CO2 as a renewable feedstock. It is also exploited to produce a large diversity of unprecedented functional polymers. It constitutes a robust platform for the design of new sulfur-containing organic synthons and important families of polymers.

2.
Macromol Rapid Commun ; 40(1): e1800545, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30284334

RESUMO

The performance of lithium- and sodium-ion batteries relies notably on the accessibility to carbon electrodes of controllable porous structure and chemical composition. This work reports a facile synthesis of well-defined N-doped porous carbons (NPCs) using a poly(ionic liquid) (PIL) as precursor, and graphene oxide (GO)-stabilized poly(methyl methacrylate) (PMMA) nanoparticles as sacrificial template. The GO-stabilized PMMA nanoparticles are first prepared and then decorated by a thin PIL coating before carbonization. The resulting NPCs reach a satisfactory specific surface area of up to 561 m2 g-1 and a hierarchically meso- and macroporous structure while keeping a nitrogen content of 2.6 wt%. Such NPCs deliver a high reversible charge/discharge capacity of 1013 mA h g-1 over 200 cycles at 0.4 A g-1 for lithium-ion batteries, and show a good capacity of 204 mA h g-1 over 100 cycles at 0.1 A g-1 for sodium-ion batteries.


Assuntos
Carbono/química , Fontes de Energia Elétrica , Líquidos Iônicos/química , Lítio/química , Polímeros/química , Sódio/química , Tamanho da Partícula , Porosidade , Propriedades de Superfície
3.
Adv Mater ; 29(40)2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28869678

RESUMO

Redox-active catechols are bioinspired precursors for ortho-quinones that are characterized by higher discharge potentials than para-quinones, the latter being extensively used as organic cathode materials for lithium ion batteries (LIBs). Here, this study demonstrates that the rational molecular design of copolymers bearing catechol- and Li+ ion-conducting anionic pendants endow redox-active polymers (RAPs) with ultrarobust electrochemical energy storage features when combined to carbon nanotubes as a flexible, binder-, and metal current collector-free buckypaper electrode. The importance of the structure and functionality of the RAPs on the battery performances in LIBs is discussed. The structure-optimized RAPs can store high-capacities of 360 mA h g-1 at 5C and 320 mA h g-1 at 30C in LIBs. The high ion and electron mobilities within the buckypaper also enable to register 96 mA h g-1 (24% capacity retention) at an extreme C-rate of 600C (6 s for total discharge). Moreover, excellent cyclability is noted with a capacity retention of 98% over 3400 cycles at 30C. The high capacity, superior active-material utilization, ultralong cyclability, and excellent rate performances of RAPs-based electrode clearly rival most of the state-of-the-art Li+ ion organic cathodes, and opens up new horizons for large-scalable fabrication of electrode materials for ultrarobust Li storage.

4.
ACS Macro Lett ; 6(2): 121-126, 2017 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-35632880

RESUMO

Poly(ionic liquid)s (PILs) have attracted considerable attention as innovative single-ion solid polyelectrolytes (SPEs) in substitution to the more conventional electrolytes for a variety of electrochemical devices. Herein, we report the precise synthesis, characterization, and use as single-ion SPEs of a novel double PIL-based amphiphilic diblock copolymer (BCP), i.e., where all monomer units are of N-vinyl-imidazolium type, with triethylene glycol pendant groups in the first block and a statistical distribution of N-vinyl-3-ethyl- and N-vinyl-3-perfluorooctyl-imidazolium bromides in the second block. BCP synthesis is achieved directly in water by a one-pot process, by cobalt-mediated radical polymerization-induced self-assembly (CMR-PISA). A subsequent anion exchange reaction substituting bis(trifluoromethylsulfonyl)imide (Tf2N-) for bromide (Br-) counter-anions leads to PIL BCPs with two different lengths of the first block. They demonstrate ionic conductivity σDC = 1-3 × 10-7 S cm-1, as determined by broadband dielectric spectroscopy at 30 °C (under anhydrous conditions), and exhibit wide electrochemical stability (up to 4.8 V versus Li+/Li) and form free-standing films with mechanical properties suited for SPE applications (Young's modulus = 3.8 MPa, elongation at break of 250%) as determined by stress/strain experiments.

5.
Chem Commun (Camb) ; 47(38): 10683-5, 2011 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-21881675

RESUMO

Hydrogen bonded assemblies are usually decomposed by polar organic solvents. However, we have succeeded in preparing a strongly associated supramolecular polymer which forms viscous solutions in competitive solvents such as tetrahydrofuran.

6.
Macromol Biosci ; 5(4): 299-305, 2005 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-15818582

RESUMO

Amphiphilic and biodegradable micelles and nanoparticles designed as potential drug carriers were prepared from biodegradable statistical and block copolyesters obtained by a living anionic ring-opening process. These novel materials display amphiphilic properties arising from the joint presence of hydrophilic poly((RS)-3,3-dimethylmalic acid) and hydrophobic poly(hexyl (RS)-3,3-dimethylmalate) segments. Micelles obtained from a well-defined block copolymer have been characterized by their critical aggregation concentration, and nanoparticles derived from statistical copolymer have been analyzed by transmission electron microscopy (TEM).


Assuntos
Portadores de Fármacos/química , Malatos/química , Nanoestruturas/química , Polímeros/química , Portadores de Fármacos/síntese química , Micelas , Microscopia Eletrônica , Nanoestruturas/ultraestrutura , Polímeros/síntese química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...