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1.
Materials (Basel) ; 11(3)2018 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-29495571

RESUMO

An innovative recycling process for thermoset polymer composites developed by Connora Technologies (Hayward, CA, USA) was studied. The process efficacy has already been tested, and it is currently working at the plant level. The main aspect investigated in the present paper was the environmental impact by means of the Life Cycle Assessment (LCA) method. Because of the need to recycle and recover materials at their end of life, the Connora process creates a great innovation in the market of epoxy composites, as they are notoriously not recyclable. Connora Technologies developed a relatively gentle chemical recycling process that induces the conversion of thermosets into thermoplastics. The LCA demonstrated that low environmental burdens are associated with the process itself and, furthermore, impacts are avoided due to the recovery of the epoxy-composite constituents (fibres and matrix). A carbon fibre (CF) epoxy-composite panel was produced through Vacuum Resin Transfer Moulding (VRTM) and afterwards treated using the Connora recycling process. The LCA results of both the production and the recycling phases are reported.

2.
Chem Commun (Camb) ; 47(2): 665-7, 2011 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-21113530

RESUMO

Acid-degradable microcapsules were prepared via an interfacial polymerization. Degradation of the thin wall of the capsules leads to all-or-nothing cargo release. The only byproducts of degradation are acetone, and a non-toxic triamide. Proof-of-concept experiments showed that cargo can be delivered to and released in cells.


Assuntos
Ácidos/química , Cápsulas/química , Portadores de Fármacos/química , Materiais Biocompatíveis/química , Linhagem Celular Tumoral , Humanos , Concentração de Íons de Hidrogênio , Cinética , Paclitaxel/administração & dosagem
3.
J Am Chem Soc ; 132(20): 6890-1, 2010 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-20438114

RESUMO

The patterning of a surface with more than one type of functionality in spatially resolved fashion is described. A scanning probe was used to create patterns composed of two orthogonal types of functionality within a dense, electrochemically active mixed monolayer via a simple modulation of the applied surface bias. One reductive pathway produces surface-bound amine moieties while the other creates an oxidized surface. The two newly created surface functionalities can each be used independently to locally deposit complementary materials such as electron- or hole-transporting molecules via self-assembly.


Assuntos
Nanotecnologia/métodos , Aminas/química , Benzoquinonas/química , Eletroquímica , Microscopia de Força Atômica , Oxirredução , Oxigênio/química , Silanos/química , Propriedades de Superfície
4.
J Am Chem Soc ; 131(38): 13586-7, 2009 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-19736938

RESUMO

We report the development of phototriggerable microcapsules and demonstrate the concept of protection and remote release of chemical species. Light-rupturable, liquid-filled microcapsules were prepared by coencapsulation of carbon nanotubes using a simple and robust interfacial polymerization technique. The incorporation of carbon nanotubes endows the microcapsules with the ability to respond to an external optical event. The triggered release of the liquid contents for the microcapsules may be achieved either in air or within a liquid medium via irradiation with a near-IR laser. Rupture of the impermeable shell-wall under irradiation is presumed to be due to an increase in internal pressure due to optothermal heating of the CNTs. The storage and triggered release of reactive small molecules and catalysts was demonstrated in the context of remotely initiated "click" reaction and ring-opening metathesis polymerization.


Assuntos
Cápsulas/química , Luz , Nanotubos de Carbono/química , Lasers , Microscopia Eletrônica de Varredura , Nylons/química , Processos Fotoquímicos , Tolueno/química
5.
J Am Chem Soc ; 131(15): 5396-8, 2009 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-20560635

RESUMO

As energy demands increase, new, more direct, energy collection and utilization processes must be explored. We present a system that intrinsically combines the absorption of sunlight with the production of useful work in the form of locomotion of objects on liquids. Focused sunlight is locally absorbed by a nanostructured composite, creating a thermal surface tension gradient and, subsequently, motion. Controlled linear motion and rotational motion are demonstrated. The system is scale independent, with remotely powered and controlled motion shown for objects in the milligram to tens of grams range.


Assuntos
Fontes Geradoras de Energia , Movimento (Física) , Luz Solar , Tensão Superficial , Nanocompostos/efeitos da radiação , Fenômenos Físicos , Rotação , Energia Solar
6.
J Am Chem Soc ; 130(13): 4238-9, 2008 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-18331043

RESUMO

A facile patterning method for the functionalization of vertically aligned carbon nanotubes is described. Modification of the surface of nanotube forests with hydrophilic, hydrophobic, or polymerizable small molecules was achieved via UV-triggered attachment of perfluoroarylazides. Multiple functionalizations of the tube surface can be achieved. Macro- and micropatterning of forest substrates were demonstrated. Superhydrophobic surfaces containing superhydrophilic regions were prepared.


Assuntos
Azidas/química , Nanotubos de Carbono/química , Azidas/efeitos da radiação , Interações Hidrofóbicas e Hidrofílicas , Nanotubos de Carbono/efeitos da radiação , Tamanho da Partícula , Propriedades de Superfície , Raios Ultravioleta , Molhabilidade
7.
J Am Chem Soc ; 129(38): 11750-5, 2007 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-17803274

RESUMO

This paper describes the development of a new catalytic transformation, the ruthenium-catalyzed decarbonylative arylation of cyclic 2-amino esters, which replaces the ester group with an aryl ring at the sp3 carbon center. For example, proline ester amidine 1 is converted to 2-arylpyrrolidine 3 in the presence of arylboronic acids or esters as arene donors and Ru(3)(CO)(12) as the catalyst. This process provides a rapid access to a variety of 2-arylpyrrolidines and piperidines from commercially available proline, hydroxyproline, and pipecolinate esters. The examination of the substrate scope also showed that many arene boronic acids and boronate esters serve as coupling partners. The high chemoselectivity of this process was demonstrated and ascribed to the significant rate difference between the decarbonylative arylation and the C-H arylation. The decarbonylative arylation complements the C-H arylation, since the latter process lacks control over the extent of functionalization, affording a mixture of mono- and bis-arylpyrrolidines. When applied in tandem, these two processes provide 2,5-diarylpyrrolidines in two steps from the corresponding proline esters. It was also demonstrated that the required amidine or iminocarbamate directing group fulfills two major functions: first, it is essential for the ester activation step, which occurs via the coordination-assisted metal insertion into the acyl C-O bond; second, it facilitates the decarbonylation, via the stabilization of a metallacycle intermediate, assuring the formation of the 2-arylated products instead of the corresponding ketones observed before by others.


Assuntos
Carbono/química , Ésteres/síntese química , Hidrocarbonetos Aromáticos/química , Cetonas/química , Piperidinas/síntese química , Pirrolidinas/síntese química , Rutênio/química , Ácidos Borônicos/química , Catálise , Ésteres/química , Hidroxiprolina/química , Modelos Químicos , Prolina/química , Estereoisomerismo
8.
J Am Chem Soc ; 128(44): 14220-1, 2006 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-17076471

RESUMO

A new ruthenium-catalyzed direct sp3 C-H to C-C bond transformation is disclosed. Specifically, a method for the alpha-arylation of cyclic amines, containing either permanent (pyridine, pyrimidine) or removable (amidine) directing groups, is described. This cross-coupling reaction involves heating amine substrates with arylboronate ester at 150 degrees C in a ketone solvent with a catalytic amount of ruthenium carbonyl [Ru3(CO)12]. Arylboronate esters containing either electron-withdrawing or electron-donating substituents could be efficiently coupled. Heteroarene boronates were also effective donors.


Assuntos
Amidinas/química , Carbono/química , Hidrocarbonetos Aromáticos/química , Hidrogênio/química , Piperidinas/química , Pirrolidinas/química , Estrutura Molecular , Estereoisomerismo
9.
Org Lett ; 7(24): 5429-31, 2005 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-16288523

RESUMO

[reaction: see text] The scope and limitations of intramolecular hydro-O-alkylation of aldehyde substrates leading to spiroketals and bicyclic ketals and aminals is reported. The direct transformation of tertiary and sterically hindered secondary sp(3) C-H bonds into C-O bonds under the action of a catalytic amount of a variety of Lewis acids is described. The mechanism of these transformations is proposed to involve a tandem hydride transfer/cyclization sequence.


Assuntos
Aldeídos/química , Alquilação , Catálise , Ciclização , Indicadores e Reagentes , Estrutura Molecular , Temperatura Ambiente
10.
J Am Chem Soc ; 127(35): 12180-1, 2005 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-16131169

RESUMO

A practical method for the intramolecular hydroalkylation of electron-deficient olefins has been developed. The direct transformation of benzylic, tertiary, and sterically hindered secondary sp3 C-H bonds into C-C bonds under the action of a catalytic amount of a variety of Lewis acids is described. The mechanism of these transformations is proposed to involve a tandem hydride transfer/cyclization sequence.


Assuntos
Ácidos/química , Alcenos/química , Carbono/química , Hidrogênio/química , Alquilação , Catálise , Elétrons , Modelos Químicos , Oxirredução , Temperatura Ambiente
11.
J Am Chem Soc ; 126(21): 6556-7, 2004 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-15161275

RESUMO

We herein present a new oxidative cyclization of alkene-amide substrates under neutral and catalytic conditions. This overall transformation requires tandem sp3 C-H activation (at the position adjacent to the amide nitrogen) and C-C bond formation. Specifically, pyrrolidine 1 was converted to pyrrolizidinone 3 and indolizidinone 4 in 66% and 17% yield, respectively, in the presence of [Ir(coe)2Cl]2, the carbene ligand IPr (1:1 metal/ligand ratio, 5-10 mol % of Ir), and the hydrogen acceptor (NBE or TBE, 3-10 equiv). The results presented in this study suggest that complex 10 [IPr-Ir(Cl)(substrate)] is the key intermediate in the catalytic cycle. On the mechanistic front, the key advance was the ability to facilitate C-H activation and alkene insertion in tandem, and in preference to beta-hydride elimination, in the context of amide substrates. With respect to complex synthesis, catalytic and neutral conditions of this method unlock new exciting opportunities as illustrated by regioselective cyclization of the proline-derived substrate 16.


Assuntos
Alcenos/química , Amidas/química , Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Catálise , Ciclização , Indóis/química , Estrutura Molecular , Compostos Organometálicos/química , Oxirredução , Pirróis/química , Rutênio/química
12.
Org Lett ; 6(4): 581-4, 2004 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-14961628

RESUMO

[reaction: see text] We herein report that RuCl(3)/AgOTf has proven to be a hydroarylation catalyst with an efficiency and scope superior to previously known methods. This catalyst demonstrated consistent performance with arene-ene substrates of diverse structural features, providing good to excellent yields of cyclization products (chromanes, tetralins, terpenoids, dihydrocoumarins).


Assuntos
Alcenos/síntese química , Cromanos/síntese química , Cumarínicos/síntese química , Rutênio/química , Terpenos/síntese química , Tetra-Hidronaftalenos/síntese química , Catálise , Ciclização , Indicadores e Reagentes
13.
Org Lett ; 5(22): 4053-5, 2003 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-14572247

RESUMO

[reaction: see text]. A concise total synthesis of (+/-)-deguelin was achieved with a longest linear sequence of six steps in 68% yield. A key step was the platinum-catalyzed 6-endo hydroarylation of an alkynone intermediate.


Assuntos
Rotenona/análogos & derivados , Rotenona/síntese química , Hidrocarbonetos Aromáticos com Pontes/química , Catálise , Ciclização , Estrutura Molecular , Compostos de Platina/química , Rotenona/química
14.
Org Lett ; 5(7): 1055-8, 2003 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-12659572

RESUMO

[reaction: see text] We herein report that PtCl(4) has proven to be a hydroarylation catalyst with an efficiency and substrate scope superior to previously known methods. This catalyst demonstrated consistent performance with arene-yne substrates of diverse structural features, including propargyl ethers, propargylamines, and alkynoate esters, providing good to excellent yields of the 6-endo products (chromenes, dihydroquinolines, and coumarins). In contrast, Pt(II), Pd(II), and Ga(III) salts were shown to be sensitive to the substitution on the alkyne moiety.

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