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1.
Front Physiol ; 9: 1062, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30158873

RESUMO

Objectives: To evaluate the physiological requirements imposed by the current mountain biking Cross-Country Olympic (XCO) format. Methods: Sixteen Cross-Country cyclists competing at national or international level participated in this study. All participants completed a simulated and a real official race on a cycling-accredited race track. Oxygen consumption (O2) and heart rate (HR) values expressed as %O2max and %HRmax, respectively, were divided into three physiological intensity zones. The first zone (Z1) was the physiological region below VT1, the second zone (Z2) corresponded to a region between VT1 and VT2, and the third zone (Z3) was located between VT2 and VO2max. For power output, an additional fourth zone was considered above maximal aerobic power (MAP). Results: When competing in the current XCO format, 37.0 ± 17.9% of the race is performed above the second ventilatory threshold at a mean intensity of 87% O2max and 25% of the race was spent above MAP. This contribution varied between laps, with a very high intensity during the first lap and more aerobic subsequent laps. The durations of most of the periods beyond MAP oscillated between 5 and 30 s. Between these short, repeated bursts, low-intensity periods of exercise were recorded. Conclusion: The current XCO race format is an acyclical and intermittent exercise comparable to high-intensity team sports. Moreover, our results highlight the relevance of O2 values when analyzing XCO performance, they should be combined with commonly used HR and/or power output data.

2.
Bioorg Med Chem ; 24(22): 5685-5692, 2016 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-27647371

RESUMO

To discover new molecules with an inhibitory activity of melanogenesis a hundred of scorpions, snakes, spiders and amphibians venoms were screened for their capacity to inhibit mushroom tyrosinase using 3,4-l-dihydroxyphenylalanine (l-DOPA) as substrate. The Argiope lobata spider venom proved to be the most active. HPLC fraction containing Argiotoxine-636 (ArgTX-636), a polyamine known for its numerous biological activities, was found to also show a good regulation activity of melanogenesis by inhibiting DOPA and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) oxidases activities, wore by tyrosinase (TYR) and tyrosinase-related protein 1 (TRP-1), respectively. Our results demonstrate that ArgTX-636 reduced the mushroom tyrosinase activity in a dose-dependent way with a maximal half inhibitory concentration (IC50) value of 8.34µM, when l-DOPA is used as substrate. The Lineweaver-Burk study showed that ArgTX-636 is a mixed type inhibitor of the diphenolase activity. Moreover, ArgTX-636 inhibits DHICA oxydase activity of mushroom tyrosinase activity with IC50 at 41.3µM. ArgTX-636 has no cytotoxicity in B16F10 melanoma cells at concentrations up to 42.1µM. The effect of ArgTX-636 on melanogenesis showed that melanin production in B16F10 melanoma cell decreased by approximatively 70% compared to untreated cells. ArgTX-636 displayed no significant effect on the TYR expression while the protein level of TRP-1 decreased in B16F10 cells. Thus, ArgTX-636 could have particular interest for cosmetic and/or pharmaceutical use in order to reduce important dermatoses in black and mixed skins.


Assuntos
Ácidos Indolacéticos/farmacologia , Melaninas/antagonistas & inibidores , Poliaminas/farmacologia , Venenos de Aranha/química , Animais , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ácidos Indolacéticos/química , Ácidos Indolacéticos/isolamento & purificação , Melaninas/metabolismo , Camundongos , Estrutura Molecular , Poliaminas/química , Poliaminas/isolamento & purificação , Relação Estrutura-Atividade
3.
Vaccine ; 34(15): 1810-5, 2016 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-26902547

RESUMO

Scorpion envenoming represents a public health issue in subtropical regions of the world. Treatment and prevention need to promote antitoxin immunity. Preserving antigenic presentation while removing toxin effect remains a major challenge in toxin vaccine development. Among particulate adjuvant, particles prepared with poly (D,L-lactide) polymer are the most extensively investigated due to their excellent biocompatibility and biodegradability. The aim of this study is to develop surfactant-free PLA nanoparticles that safely deliver venom toxic fraction to enhance specific immune response. PLA nanoparticles are coated with AahG50 (AahG50/PLA) and BotG50 (BotG50/PLA): a toxic fraction purified from Androctonus australis hector and Buthus occitanus tunetanus venoms, respectively. Residual toxicities are evaluated following injections of PLA-containing high doses of AahG50 (or BotG50). Immunization trials are performed with the detoxified fraction administered alone without adjuvant. A comparative study of the effect of Freund is also included. The neutralizing capacity of sera is determined in naive mice. Six months later, immunized mice are challenged subcutaneously with increased doses of AahG50. Subcutaneous lethal dose 50 (LD50) of AahG50 and BotG50 is of 575 µg/kg and 1300 µg/kg respectively. By comparison, BotG50/PLA is totally innocuous while 50% of tested mice survive 2875 µg AahG50/kg. Alhydrogel and Freund are not able to detoxify such a high dose. Cross-antigenicity between particulate and soluble fraction is also, ensured. AahG50/PLA and BotG50/PLA induce high antibody levels in mice serum. The neutralizing capacity per mL of anti-venom was 258 µg/mL and 186 µg/mL calculated for anti-AahG50/PLA and anti-BotG50/PLA sera, respectively. Animals immunized with AahG50/PLA are protected against AahG50 injected dose of 3162 µg/kg as opposed all non-immunized mice died at this dose. We find that the detoxification approach based PLA nanoparticles, benefit the immunogenicity and protective efficacy of venom immunogen.


Assuntos
Antivenenos/uso terapêutico , Materiais Biocompatíveis/química , Imunoterapia Ativa , Poliésteres/química , Venenos de Escorpião/imunologia , Adjuvantes Imunológicos/química , Animais , Antivenenos/química , Feminino , Camundongos , Nanopartículas/química , Testes de Neutralização , Escorpiões , Testes de Toxicidade
4.
Chem Commun (Camb) ; 50(21): 2744-7, 2014 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-24476638

RESUMO

Intermolecular radical 1,2-addition (IRA) of N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)aminoxyl (SG1) based alkoxyamines onto activated olefins is used as a tool for peptide ligation. This strategy relies on simple peptide pre-derivatization to obtain (i) a SG1 nitroxide functionalized resin peptide at its N-terminus (SG1-peptide alkoxyamine), (ii) a vinyl functionalized peptide (either at its C-terminus or N-terminus), and does not require any coupling agents.


Assuntos
Aminas/química , Radicais Livres/química , Oligopeptídeos/química , Organofosfonatos/química , Alcenos/química
5.
Clin Cancer Res ; 19(22): 6138-50, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-24100627

RESUMO

PURPOSE: To study the role of the adrenomedullin system [adrenomedullin and its receptors (AMR), CLR, RAMP2, and RAMP3] in prostate cancer androgen-independent growth. EXPERIMENTAL DESIGN: Androgen-dependent and -independent prostate cancer models were used to investigate the role and mechanisms of adrenomedullin in prostate cancer hormone-independent growth and tumor-associated angiogenesis and lymphangiogenesis. RESULTS: Adrenomedullin and AMR were immunohistochemically localized in the carcinomatous epithelial compartment of prostate cancer specimens of high grade (Gleason score >7), suggesting a role of the adrenomedullin system in prostate cancer growth. We used the androgen-independent Du145 cells, for which we demonstrate that adrenomedullin stimulated cell proliferation in vitro through the cAMP/CRAF/MEK/ERK pathway. The proliferation of Du145 and PC3 cells is decreased by anti-adrenomedullin antibody (αAM), supporting the fact that adrenomedullin may function as a potent autocrine/paracrine growth factor for prostate cancer androgen-independent cells. In vivo, αAM therapy inhibits the growth of Du145 androgen-independent xenografts and interestingly of LNCaP androgen-dependent xenografts only in castrated animals, suggesting strongly that adrenomedullin might play an important role in tumor regrowth following androgen ablation. Histologic examination of αAM-treated tumors showed evidence of disruption of tumor vascularity, with depletion of vascular as well as lymphatic endothelial cells and pericytes, and increased lymphatic endothelial cell apoptosis. Importantly, αAM potently blocks tumor-associated lymphangiogenesis, but does not affect established vasculature and lymphatic vessels in normal adult mice. CONCLUSIONS: We conclude that expression of adrenomedullin upon androgen ablation in prostate cancer plays an important role in hormone-independent tumor growth and in neovascularization by supplying/amplifying signals essential for pathologic neoangiogenesis and lymphangiogenesis. Clin Cancer Res; 19(22); 6138-50. ©2013 AACR.


Assuntos
Adrenomedulina/metabolismo , Linfangiogênese , Neovascularização Patológica , Neoplasias de Próstata Resistentes à Castração/metabolismo , Adrenomedulina/antagonistas & inibidores , Adrenomedulina/imunologia , Androgênios , Animais , Anticorpos/imunologia , Apoptose/imunologia , Proteína Semelhante a Receptor de Calcitonina , Proteínas de Transporte/metabolismo , Castração , Linhagem Celular Tumoral , Movimento Celular/imunologia , Proliferação de Células , AMP Cíclico/metabolismo , Células Endoteliais/imunologia , Humanos , Masculino , Camundongos , Camundongos Nus , Invasividade Neoplásica , Transplante de Neoplasias , Pericitos/imunologia , Proteína 2 Modificadora da Atividade de Receptores/metabolismo , Proteína 3 Modificadora da Atividade de Receptores/metabolismo , Receptores de Adrenomedulina/imunologia , Receptores da Calcitonina/metabolismo , Transdução de Sinais/imunologia , Transplante Heterólogo
6.
Macromol Biosci ; 13(9): 1213-20, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23825039

RESUMO

Glycopolymer-corona-based micelles are obtained in a one-pot procedure, through reaction of D-mannosamine or D-glucosamine with the N-succinimidyl (NS) esters of a poly(D,L-lactide)-block-poly(N-acryloxysuccinimide-co-N-vinylpyrrolidone) (PLA-b-P(NAS-co-NVP)) amphiphilic copolymer (presenting quasi-alternating NAS/NVP units) in dimethyl sulfoxide (DMSO), followed by nanoprecipitation and dialysis against water. The glycopolymer micelles exhibit a higher CMC and size than those obtained from unmodified copolymer, due to increased hydrophilicity of the external block as a result of sugar derivatization, and the availability of the sugars at the micelle surface is evidenced through interactions with Concanavalin A (Con A) lectin, as attested by turbidimetric measurements and enzyme-linked lectin assay (ELLA). Interestingly, the glycopolymer micelles can be further used for hydrophobic molecule encapsulation and release, as shown with imiquimod, while keeping their interactions with con A intact. It is concluded that the PLA-based amphiphilic/reactive copolymer represents a versatile platform for glycopolymer-based micelle constructs for drug/vaccine delivery.


Assuntos
Micelas , Poliésteres/química , Polímeros/química , Pirrolidinonas/química , Absorção , Aminoquinolinas/farmacologia , Concanavalina A/farmacologia , Concentração de Íons de Hidrogênio , Imiquimode , Espectroscopia de Ressonância Magnética , Nefelometria e Turbidimetria , Oxazinas/metabolismo , Espectrometria de Fluorescência
7.
Nat Mater ; 12(5): 452-7, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23542871

RESUMO

Electrochemical energy storage is one of the main societal challenges of this century. The performances of classical lithium-ion technology based on liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues. Solid polymer electrolytes would be a perfect solution to those safety issues, miniaturization and enhancement of energy density. However, as in liquids, the fraction of charge carried by lithium ions is small (<20%), limiting the power performances. Solid polymer electrolytes operate at 80 °C, resulting in poor mechanical properties and a limited electrochemical stability window. Here we describe a multifunctional single-ion polymer electrolyte based on polyanionic block copolymers comprising polystyrene segments. It overcomes most of the above limitations, with a lithium-ion transport number close to unity, excellent mechanical properties and an electrochemical stability window spanning 5 V versus Li(+)/Li. A prototype battery using this polyelectrolyte outperforms a conventional battery based on a polymer electrolyte.

8.
Colloids Surf B Biointerfaces ; 103: 298-303, 2013 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-23277324

RESUMO

Efficient biomolecule conjugation to the surface of biodegradable colloidal carriers is crucial for their targeting efficiency in drug/vaccine delivery applications. We here propose a potent strategy to drastically improve peptide immobilization on biodegradable polylactide (PLA) nanoparticles (NPs). Our approach particularly relies on the use of an amphiphilic block copolymer PLA-b-poly(N-acryloxysuccinimide-co-N-vinylpyrrolidone) (PLA-b-P(NAS-co-NVP)) as NP surface modifier, whose the N-succinimidyl (NS) ester functions of the NAS units along the polymer chain ensure N-terminal amine peptide coupling. The well-known immunostimulatory peptide sequence derived from the human interleukin 1ß (IL-1ß), VQGEESNDK, was coupled on the NPs of 169 nm mean diameter in phosphate buffer (pH 8, 10 mM). A maximum amount of 2 mg immobilized per gram of NPs (i.e. 0.042 peptidenm(-2)) was obtained. Introduction of a three lysine tag at the peptide N-terminus (KKKVQGEESNDK) resulted in a dramatic improvement of the immobilized peptide amounts (27.5 mg/g NP, i.e. 0.417 peptidenm(-2)). As a comparison, the density of tagged peptide achievable on surfactant free PLA NPs of similar size (140 nm), through classical EDC or EDC/NHS activation of the surface PLA carboxylic end-groups, was found to be 6 mg/g NP (i.e. 0.075 peptidenm(-2)), showing the decisive impact of the P(NAS-co-NVP)-based hairy corona for high peptide coupling. These results demonstrate that combined use of lysine tag and PLA-b-P(NAS-co-NVP) surfactant represents a valuable platform to tune and optimize surface bio-functionalization of PLA-based biodegradable carriers.


Assuntos
Portadores de Fármacos/química , Ésteres/química , Lisina/metabolismo , Nanopartículas/química , Peptídeos/metabolismo , Poliésteres/química , Tensoativos/química , Acrilamidas/química , Sequência de Aminoácidos , Biodegradação Ambiental , Morte Celular/efeitos dos fármacos , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Cromatografia de Fase Reversa , Coloides , Humanos , Proteínas Imobilizadas/metabolismo , Dados de Sequência Molecular , Nanopartículas/toxicidade , Tamanho da Partícula , Peptídeos/química , Pirrolidinonas/química , Eletricidade Estática
9.
Dalton Trans ; 42(13): 4479-86, 2013 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-23338614

RESUMO

The first reported combination of regioselective hydro-defluorination and a ligand exchange reaction during the syntheses of neutral iridium(III) complexes is presented. Surprisingly, loss of one fluorine atom per ligand combined with a complete ligand exchange reaction on the transition metal were jointly observed during a bridge-splitting and substitution reaction of two different dimeric iridium(III) precursor complexes with two different ancillary ligands. The regioselectivity of defluorination was evidenced in both cases. The reaction time was identified as a factor strongly impacting the kinetics of the thermally induced reaction.

10.
Chemistry ; 19(4): 1373-84, 2013 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-23203604

RESUMO

A series of styrene-substituted 1,3,4-oxadiazoles has been designed and investigated as new low-molecular-weight organogelators. The photophysical properties of the resulting thermoreversible organogels have been characterized by UV/Vis absorption and luminescence spectroscopies. Surprisingly, the gelation ability of the oxadiazoles depended on the presence of the styrene moiety as gelation of the investigated oxadiazoles did not take place in its absence. Gel formation was accompanied by a modification of the fluorescence of the organogelators in the supramolecular state. UV irradiation of the gels caused a rearrangement of the immobilized 1,3,4-oxadiazoles bearing a styrene moiety by a tandem [4+2] and [3+2] cascade reaction. Structure modification and color change of the gels were also evident upon irradiation.

11.
Angew Chem Int Ed Engl ; 51(29): 7166-70, 2012 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-22696305

RESUMO

When pressure is applied to dynamic interactive membranes consisting of micelles composed of a triblock copolymer, their morphologies can be fine-tuned. Membranes with a range of porosities are accessible which can regulate and thereby control filtration performance and also display effective autonomous healing.

12.
Chem Commun (Camb) ; 47(38): 10698-700, 2011 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-21892484

RESUMO

Two iridium(III) soft salts based on ion-paired dinuclear cationic and mononuclear anionic complexes were designed and investigated as phosphorescent emitters for solution processed OLEDs. New dinuclear cationic complexes were prepared with two different bridging ligands, a carbazole and a phenylene spacer. Best devices were designed with the soft salt bearing a carbazole moiety.

13.
Macromol Biosci ; 11(9): 1175-84, 2011 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-21681960

RESUMO

The properties of poly(D,L-lactide)-block-poly(2-hydroxyethyl acrylate) (PLA-b-PHEA) block copolymers by means of in vitro / in vivo (rat) degradation are investigated and compared to those of PLA homopolymer. Over 12 weeks, we observe mass loss and molecular weight decrease. In vitro and in vivo findings are very similar for each polymer tested. When a short PHEA block is used (PLA-b-PHEA 15 000-3 000 g · mol(-1) , 85/15 wt%), the degradation process is found to be very similar to that of homo-PLA, and to be typical of a bulk erosion mechanism, with no mass loss observed until week 7 and continuous decrease of molar mass within this timeframe. For a longer PHEA block length within the block copolymer (PLA-b-PHEA 15 000-7 500 g · mol(-1) , 65/35 wt%), the degradation mechanism is modified, with a significant mass loss observed at early times and only a slight decrease in molar mass. The latter finding is related to the pronounced hydrophilicity and softness of the material induced by the PHEA block, which allow easy diffusion and rapid leakage of the degradation residues from the material towards the aqueous medium. Schwann cells are found to better adhere on spin-coated films of PLA-b-PHEA (85/15 wt%) than on PLA ones. These results show the potential of such hydrophilized PLA-based copolymers for use in peripheral nerve repair.


Assuntos
Materiais Biocompatíveis/química , Regeneração Nervosa/fisiologia , Poliésteres/química , Poli-Hidroxietil Metacrilato/análogos & derivados , Polímeros/química , Animais , Materiais Biocompatíveis/metabolismo , Adesão Celular , Masculino , Teste de Materiais , Estrutura Molecular , Peso Molecular , Poli-Hidroxietil Metacrilato/química , Poli-Hidroxietil Metacrilato/metabolismo , Polímeros/metabolismo , Ratos , Ratos Endogâmicos Lew , Ratos Sprague-Dawley , Células de Schwann/citologia , Propriedades de Superfície
14.
Org Biomol Chem ; 9(8): 2892-8, 2011 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-21373661

RESUMO

The search for photosensitive alkoxyamines represents a huge challenge. The key parameters governing the cleavage process remain unknown. The dissociation process of light sensitive alkoxyamines is studied as a function of their chemical structures. The photochemical properties of 6 selected compounds are investigated by ESR and laser flash photolysis. It is found that (i) the selectivity of the cleavable N-O vs. C-O bond and (ii) the efficiency of the nitroxide formation are strongly related to the alkoxyamine structure. The distance between the chromophore and the aminoxy group is a key parameter for an efficient pathway of the radical generation as displayed by the photopolymerization ability of these alkoxyamines.

15.
Int Orthop ; 35(12): 1777-82, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21365193

RESUMO

PURPOSE: Our goal was to evaluate the five-year follow-up results of the Scorpio single radius total knee arthroplasty. METHOD: We performed a retrospective study based upon a multicentre database to evaluate the minimum five-year follow-up clinical and radiological results of 747 patients (831 knees) who underwent primary Scorpio single radius total knee arthroplasty. RESULTS: The mean age of the patients was 71.9 years. At a minimal five-year follow-up, 141 patients were lost to follow-up, 83 patients had died, eight patients had undergone revision of a component, and the remaining 589 patients (602 knees) had a complete clinical and radiological evaluation after a median of six years (range, 5-8). The mean clinical component of the knee score was 92.2 points, and the mean functional component of the knee score was 76.9 points. At last follow-up, 530 of the 602 knees were rated as excellent or good. Only four knees developed patellar complications requiring revision. The survival rate at six years was 95.2% ± 1.9% and 98.3% ± 0.6 with revision for any reason and revision for mechanical failure as the end point, respectively. CONCLUSION: This medium-term study indicates favourable clinical and radiological results for this single flexion-extension radius design arthroplasty, with a low complication rate on the patellar side.


Assuntos
Artroplastia do Joelho/métodos , Artropatias/cirurgia , Articulação do Joelho/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Artroplastia do Joelho/efeitos adversos , Bases de Dados Factuais , Feminino , Humanos , Artropatias/fisiopatologia , Articulação do Joelho/fisiopatologia , Masculino , Pessoa de Meia-Idade , Avaliação de Resultados em Cuidados de Saúde , Complicações Pós-Operatórias , Amplitude de Movimento Articular , Reoperação , Estudos Retrospectivos , Resultado do Tratamento
16.
Peptides ; 32(4): 656-63, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21262299

RESUMO

AaCtx is the first chlorotoxin-like peptide isolated from Androctonus australis scorpion venom. Its amino acid sequence shares 70% similarity with chlorotoxin from Leiurus quinquestriatus scorpion venom, from which it differs by twelve amino acids. Due to its very low concentration in venom (0.05%), AaCtx was chemically synthesized. Both native and synthetic AaCtx were active on invasion and migration of human glioma cells. However, their activity was found to be lower than that of chlorotoxin. The molecular model of AaCtx shows that most of amino acids differing between AaCtx and chlorotoxin are localized on the N-terminal loop and the α-helix. Based on known compounds that block chloride channels, we suggest that the absence of negative charged amino acids on AaCtx structure may be responsible for its weak activity on glioma cells migration and invasion. This finding serves as a starting point for structure-function relationship studies leading to design high specific anti-glioma drugs.


Assuntos
Peptídeos/química , Peptídeos/isolamento & purificação , Venenos de Escorpião/química , Sequência de Aminoácidos , Animais , Adesão Celular , Linhagem Celular Tumoral , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Humanos , Masculino , Camundongos , Modelos Moleculares , Dados de Sequência Molecular , Peptídeos/síntese química , Peptídeos/toxicidade , Homologia de Sequência de Aminoácidos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
17.
Chem Soc Rev ; 40(5): 2189-98, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21234490

RESUMO

Due to the academic and industrial interest of Nitroxide Mediated Polymerization (NMP), a lot of investigations have focused on the kinetics of this process. During the last decade, although the simplified kinetic scheme--equilibrium reactions between dormant species (alkoxyamine) and active species (alkyl radicals and nitroxides), propagation reaction of the macro-alkyl radical, and termination reactions--was suitable to predict the main trends at the macromolecular level, it has become obvious that it was not sufficient to describe all the kinetic effects involved in the NMP process. Indeed, like the conventional radical polymerization, NMP should be described as a 3 stage process including initiation, propagation, and self- and cross-termination. These two types of radical polymerization differ by the occurrence during NMP of an activation/deactivation process involving the dormant species in both the initiation and propagation stages. Evidence is provided of the importance of the rate of homolysis of the initiator (alkoxyamines) and of the rate of the first alkyl radical addition onto the monomer for the success of NMP. Thus, the fundamental kinetics of the main reactions involved in NMP as well as side-reactions are also discussed in this tutorial review.

18.
Macromol Rapid Commun ; 31(15): 1383-8, 2010 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-21567541

RESUMO

The photochemical properties of two new photocleavable alkoxyamines bearing a benzophenone-derived chromophore were studied by electron spin resonance (ESR). The CO bond cleavage has been demonstrated and the photolysis rate constants (k(d) ) determined over a large range of light intensity through the monitoring of the nitroxide concentration in aerated conditions. The obtained kinetic data highlight for the first time the linear dependence of k(d) on the light intensity for alkoxyamines: this should be a driving factor for nitroxide mediated radical photopolymerization (NMP(2) ).

19.
Macromol Rapid Commun ; 31(21): 1909-13, 2010 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-21567612

RESUMO

New photosensitive alkoxyamines have been designed using molecular orbital calculations to improve the selective CO versus NO cleavage. The targeted light-sensitive alkoxyamine is synthesized in one step and its reactivity under UV has been investigated using both ESR and LFP. The ability of this alkoxyamine to control the photopolymerization of n-butyl acrylate is evidenced through a process called nitroxide-mediated photopolymerization NMP(2) . The selected alkoxyamine is finally used to prepare covalently bonded multilayered micropatterns. This original application highlights the high potential of this technique for some specific applications that require spatial control.

20.
J Chromatogr A ; 1216(47): 8386-90, 2009 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-19818445

RESUMO

We propose a fast, reliable chromatographic method to determine the grafting yield of a Polybutadiene-graft-Polystyrene (PB-g-PS) copolymer synthesized in our laboratory for High Impact Polystyrene applications. We used Liquid Chromatography at Critical Conditions of PS to separate non-grafted PS from graft product and ungrafted PB. Separation between grafted copolymer and non-grafted PS was very efficient and thanks to linearity of UV-detector response, we could quantify the amount of grafted PS in the copolymer, as well as calculate the grafting yield. Results shown here are for DOW BR1202D high-cis PB and BASF CB529T low-cis PB, Luperox TBIC M75 initiator at 8 x 10(-4) mol L(-1) and 125 degrees C reaction temperature.


Assuntos
Butadienos/química , Cromatografia em Gel/métodos , Elastômeros/química , Polímeros/síntese química , Poliestirenos/química , Ressonância Magnética Nuclear Biomolecular
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