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1.
Molecules ; 29(11)2024 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-38893367

RESUMO

Silver iodide is a prototype compound of superionic conductors that allows ions to flow through its structure. It exhibits a first-order phase transition at 420 K, characterized by an abrupt change in its ionic conductivity behavior, and above this temperature, its ionic conductivity increases by more than three orders of magnitude. Introducing small concentrations of carbon into the silver iodide structure produces a new material with a mixed conductivity (ionic and electronic) that increases with increasing temperature. In this work, we report the experimental results of the ionic conductivity as a function of the reciprocal temperature for the (AgI)x - C(1-x) mixture at low carbon concentrations (x = 0.99, 0.98, and 0.97). The ionic conductivity behavior as a function of reciprocal temperature was well fitted using a phenomenological model based on a random variable theory with a probability distribution function for the carriers. The experimental data show a proximity effect between the C and AgI phases. As a consequence of this proximity behavior, carbon concentration or temperature can control the conductivity of the (AgI)x - C(1-x) mixture.

2.
Exp Parasitol ; 238: 108261, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35460696

RESUMO

Toxoplasma gondii, as other apicomplexa, employs adhesins transmembrane proteins for binding and invasion to host cells. Search and characterization of adhesins is pivotal in understanding Apicomplexa invasion mechanisms and targeting new druggable candidates. This work developed a machine learning software called ApiPredictor UniQE V2.0, based on two approaches: support vector machines and multilayer perceptron, to predict adhesins proteins from amino acid sequences. By using ApiPredictor UniQE V2.0, five SAG-Related Sequences (SRSs) were identified within the Toxoplasma gondii proteome. One of those candidates, TgSRS12B, was cloned in plasmid pEXP5-CT/TOPO and expressed in E. coli BL21 DE3. The resulting recombinant protein was purified via affinity chromatography. Co-precipitation assays in CaCo and Muller cells showed interactions between TgSRS12B-His-tagged and the membrane fractions from both human cell lines. In conclusion, we demonstrated that ApiPredictor UniQE V2.0, a bioinformatic free software, was able to identify TgSRS12B as a new adhesin protein.


Assuntos
Toxoplasma , Escherichia coli/metabolismo , Humanos , Aprendizado de Máquina , Plasmídeos/genética , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Toxoplasma/genética , Toxoplasma/metabolismo
3.
Cardiol Young ; : 1-3, 2022 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-35450546

RESUMO

Primary cardiac tumours are uncommon in the paediatric population, accounting for fewer than 0.5% of paediatric cases of cardiac disease. Right ventricular tumours, including myxomas, are particularly rare and may be asymptomatic or demonstrate varying degrees of cardiac dysfunction based on the location and size of the tumour, inducing conduction abnormalities, syncope, embolism, and potentially, sudden death. We report a rare case of right ventricular myxoma causing severe right ventricular outflow tract obstruction and surgical intervention in a paediatric patient.

4.
Molecules ; 27(18)2022 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-36144865

RESUMO

The superionic conductor, solid state, and body-centered cubic structure, silver iodide at room temperature, has been studied via molecular dynamics simulations. The calculated results using pairwise Coulomb-Buckingham potential, zero pressure on the sample, a semi-rigid model system of 1000 Ag and 1000 I ions, (NVE) as a statistical ensemble, and an effective charge of Z=0.63 for the pairs Ag-Ag and I-I, were found to be consistent with experimental data and one study using Z=0.60, different potential, and simulation software. For the pair Ag-I, there is a discrepancy due to the high silver ion diffusion. The calculated value of the diffusion constant of the silver ion is greater than iodide ion. The dynamic transport properties (mean square displacement, velocity autocorrelation function) results indicated typical behavior reported by other authors, using different potentials in their DM simulations for iodine and silver ions.

5.
Fetal Diagn Ther ; 46(1): 45-57, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30223262

RESUMO

INTRODUCTION: In a pilot study of chronic maternal hyperoxygenation (CMH) in left heart hypoplasia (LHH), we sought to determine effect estimates of CMH on head size, vascular resistance indices, and neurodevelopment compared to controls. MATERIAL AND METHODS: Nine gravidae meeting the inclusion criteria (fetal LHH, ≥25.9 weeks' gestation, and ≥10% increase in percent aortic flow after acute hyperoxygenation) were prospectively enrolled. Controls were 9 contemporary gravidae with fetal LHH without CMH. Brain growth and Doppler-derived estimates of fetal cerebrovascular and placental resistance were blindly evaluated and compared using longitudinal regression. Postnatal anthropomorphic and neurodevelopmental assessments were compared. RESULTS: There was no difference in baseline fetal measures between groups. There was significantly slower biparietal diameter (BPD) growth in the CMH group (z-score change -0.03 ± 0.02 vs. +0.09 ± 0.05 units/week, p = 0.02). At 6 months postnatal age, the mean head circumference z-score in the CMH group was smaller than that of controls (-0.20 ± 0.58 vs. +0.85 ± 1.11, p = 0.048). There were no differences in neurodevelopmental testing at 6 and 12 months. DISCUSSION: In this pilot study, relatively diminished fetal BPD growth and smaller infant head circumference z-scores at 6 months were noted with in utero CMH exposure.


Assuntos
Circulação Cerebrovascular , Síndrome do Coração Esquerdo Hipoplásico/fisiopatologia , Oxigênio/uso terapêutico , Resistência Vascular , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Encéfalo/crescimento & desenvolvimento , Feminino , Feto , Humanos , Troca Materno-Fetal , Projetos Piloto , Gravidez , Fluxo Pulsátil , Análise de Regressão , Ultrassonografia Pré-Natal , Artérias Umbilicais/diagnóstico por imagem , Artérias Umbilicais/fisiopatologia
6.
Pediatr Dermatol ; 35(3): e155-e158, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29575091

RESUMO

We describe the difficulties of treating acne in a series of female-to-male transgender adolescents, including concerns about potential hepatotoxicity with concomitant use of testosterone with isotretinoin or tetracyclines. Acne is a foreseeable adverse effect of testosterone treatment in transgender adolescents, so monitoring for acne is advised. The treatment of acne in transgender adolescents is important given that severe acne and transgenderism are associated with higher rates of depression and suicide.


Assuntos
Acne Vulgar/tratamento farmacológico , Doxiciclina/uso terapêutico , Isotretinoína/uso terapêutico , Testosterona/efeitos adversos , Pessoas Transgênero , Acne Vulgar/etiologia , Adolescente , Antibacterianos/uso terapêutico , Fármacos Dermatológicos/uso terapêutico , Feminino , Humanos , Masculino
7.
Cardiol Young ; 27(9): 1853-1856, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28651676

RESUMO

Anomalous origin of the left coronary artery from the right pulmonary artery in single ventricles is a very rare congenital anomaly. Failure to recognise it preoperatively may lead to adverse outcomes, including death. We report the case of a neonate with a univentricular heart in the form of a double-outlet right ventricle, mitral atresia with discrete coarctation of the aorta, and an incidental intraoperative finding of an anomalous origin of the left coronary artery from the right pulmonary artery. The patient underwent a successful repair with an uneventful postoperative course.


Assuntos
Coartação Aórtica/diagnóstico por imagem , Coartação Aórtica/cirurgia , Anomalias dos Vasos Coronários/diagnóstico por imagem , Anomalias dos Vasos Coronários/cirurgia , Ventrículos do Coração , Artéria Pulmonar , Anormalidades Múltiplas , Procedimentos Cirúrgicos Cardiovasculares/métodos , Ecocardiografia , Feminino , Ventrículos do Coração/anormalidades , Ventrículos do Coração/diagnóstico por imagem , Ventrículos do Coração/cirurgia , Humanos , Recém-Nascido , Artéria Pulmonar/anormalidades , Artéria Pulmonar/diagnóstico por imagem , Artéria Pulmonar/cirurgia , Resultado do Tratamento
8.
Birth Defects Res A Clin Mol Teratol ; 106(9): 739-48, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27296724

RESUMO

BACKGROUND: The role of prenatal diagnosis in reducing neonatal mortality from transposition of the great arteries (TGA) is controversial. Factors affected by prenatal diagnosis such as proximity at birth to a cardiac surgical center (CSC) and CSC volume are associated with mortality in congenital heart disease. The purpose of the study was to determine the associations between prenatal diagnosis, distance from birthplace to a CSC, CSC TGA volume, and neonatal mortality in patients with TGA. METHODS: The Texas Birth Defects Registry was queried for all live born infants with TGA from 1999 to 2007. Four hundred sixty-eight cases of TGA were included. RESULTS: Forty-eight patients (10.3%) were prenatally diagnosed, and 20 patients died before age 28 days (4.3%). Neither prenatal diagnosis nor close proximity to a CSC at birth (p > 0.05) were associated with decreased mortality. Low CSC TGA volume was associated with increased mortality (p < 0.0002). Mortality at the CSCs with <5 patients per year was 9.6%; CSCs with 5 to 10 patients per year had 0% mortality, and those with >10 patients per year had 2.3% mortality. In multivariable logistic regression, only preterm birth (odds ratio, 7.05; 95% confidence interval, 4.13-12.05) and lower CSC volume (p < 0.001) were associated with neonatal mortality, although prenatal diagnosis attenuated the detrimental association of lower volume CSCs with higher mortality (p for interaction = 0.047). CONCLUSION: Lower CSC TGA patient volume was associated with higher neonatal mortality. Prenatal diagnosis may improve survival in lower volume CSCs. Birth Defects Research (Part A) 106:739-748, 2016. © 2016 Wiley Periodicals, Inc.


Assuntos
Mortalidade Infantil , Complicações na Gravidez , Diagnóstico Pré-Natal , Transposição dos Grandes Vasos , Feminino , Humanos , Lactente , Masculino , Gravidez , Complicações na Gravidez/diagnóstico , Complicações na Gravidez/mortalidade , Complicações na Gravidez/patologia , Complicações na Gravidez/fisiopatologia , Transposição dos Grandes Vasos/diagnóstico , Transposição dos Grandes Vasos/mortalidade , Transposição dos Grandes Vasos/patologia , Transposição dos Grandes Vasos/fisiopatologia
9.
Pediatr Dermatol ; 31(1): e6-9, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-23937359

RESUMO

Systemic polyarteritis nodosa (PAN) is a vasculitis that affects small to medium-size arteries. Onset in childhood is rare and can cause significant morbidity. Often, cutaneous manifestations can provide early clues toward diagnosis. This article describes a case of childhood systemic PAN that presented with fever, a necrotic skin lesion, and oral ulceration. Intestinal perforation complicated this case. Prompt recognition of childhood PAN is important to prevent serious complications.


Assuntos
Imunossupressores/uso terapêutico , Poliarterite Nodosa/diagnóstico , Poliarterite Nodosa/tratamento farmacológico , Pré-Escolar , Colo/patologia , Diagnóstico Precoce , Humanos , Masculino , Morbidade , Poliarterite Nodosa/patologia , Pele/patologia
10.
ACS Catal ; 14(3): 1363-1374, 2024 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-38327648

RESUMO

Low molar mass, hydroxyl end-capped polymers, often termed "polyols," are widely used to make polyurethanes, resins, and coatings and as surfactants in liquid formulations. Epoxide/anhydride ring-opening copolymerization (ROCOP) is a controlled polymerization route to make them, and its viability depends upon catalyst selection. In the catalysis, the polyester polyol molar masses and end-groups are controlled by adding specific but excess quantities of diols (vs catalyst), known as the chain transfer agent (CTA), to the polymerizations, but many of the best current catalysts are inhibited or even deactivated by alcohols. Herein, a series of air-stable Al(III)/K(I) heterodinuclear polymerization catalysts show rates and selectivity at the upper end of the field. They also show remarkable increases in activity, with good selectivity and control, as quantities of diol are increased from 10-400 equiv. The reactions are accelerated by alcohols, and simultaneously, their use allows for the production of hydroxy telechelic poly/oligoesters (400 < Mn (g mol-1) < 20,400, D < 1.19). For example, cyclohexene oxide (CHO)/phthalic anhydride (PA) ROCOP, using the best Al(III)/K(I) catalyst with 200 equiv of diol, shows a turnover frequency (TOF) of 1890 h-1, which is 4.4× higher than equivalent reactions without any diol (Catalyst/Diol/PA/CHO = 1:10-400:400:2000, 100 °C). In all cases, the catalysis is well controlled and highly ester linkage selective (ester linkages >99%) and operates effectively using bicyclic and/or biobased anhydrides with bicyclic or flexible alkylene epoxides. These catalysts are recommended for future production and application development using polyester polyols.

11.
Materials (Basel) ; 16(4)2023 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-36836991

RESUMO

Copper oxide is a widely studied compound in wastewater decontamination, hydrogen production, solar cell production, and sensor fabrication. In recent years, many architectures and structures with the potential for developing clean technologies have been synthesized. A procedure by thermal oxidation to grow electrical insolate Cu2O films on copper surfaces in an air atmosphere was developed. The results of the morphological and structural characterization of the copper oxide layers evidence the presence of Cu2O polycrystalline films. The films have polyhedral architectures of approximately 1.4 µm thickness and are electrically insulating. A novel copper resistive furnace was built using this copper oxide film which was used as an electrical insulator between the electrical resistance of the heater and the surface of the copper thermal block. The application improves the efficiency of the resistive furnace in terms of the temperature reached and the thermal coupling response time relative to the performance of conventional furnaces using ceramic insulation. Over the entire operating temperature range explored for the same power supply, the copper oxide-coated furnace achieved higher temperatures and faster response times than the traditionally coated furnace.

12.
Chem Sci ; 14(40): 11273-11282, 2023 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-37860667

RESUMO

Ring-opening metathesis polymerization (ROMP) is a versatile method for synthesizing complex macromolecules from various functional monomers. In this work, we report the synthesis of water-soluble and degradable bottlebrush polymers, based on polyphosphoesters (PPEs) via ROMP. First, PPE-macromonomers were synthesized via organocatalytic anionic ring-opening polymerization of 2-ethyl-2-oxo-1,3,2-dioxaphospholane using N-(hydroxyethyl)-cis-5-norbornene-exo-2,3-dicarboximide as the initiator and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the catalyst. The resulting norbornene-based macromonomers had degrees of polymerization (DPn) ranging from 25 to 243 and narrow molar mass dispersity (D ≤ 1.10). Subsequently, these macromonomers were used in ROMP with the Grubbs 3rd-generation bispyridyl complex (Ru-G3) to produce a library of well-defined bottlebrush polymers. The ROMP was carried out either in dioxane or in aqueous conditions, resulting in well-defined and water-soluble bottlebrush PPEs. Furthermore, a two-step protocol was employed to synthesize double hydrophilic diblock bottlebrush copolymers via ROMP in water at neutral pH-values. This general protocol enabled the direct combination of PPEs with ROMP to synthesize well-defined bottlebrush polymers and block copolymers in water. Degradation of the PPE side chains was proven resulting in low molar mass degradation products only. The biocompatible and biodegradable nature of PPEs makes this pathway promising for designing novel biomedical drug carriers or viscosity modifiers, as well as many other potential applications.

13.
Dalton Trans ; 52(9): 2722-2734, 2023 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-36748862

RESUMO

The synthesis of a series of ferrocenylvinylketenes as stable η4-[Fe(CO)3] complexes (3a-f) was successfully accomplished through the reaction of η2-[Fe(CO)4] complexes under mild carbonylation conditions. The reactivity of 3a-f under thermal conditions afforded the unexpected formation of a novel family of (µ2,η3-allyl-η5-oxapentadienyl)diiron pentacarbonyl complexes 5a-f proposed to be formed by a sequence metathesis-haptotropic rearrangement between the starting η4-vinylketene iron(0) complex 3 and a η4-vinylcarbene iron(0) complex trapped in situ after a reversible carbonylation process favored by the thermal conditions. An electron density distribution analysis (EDD) of 5e using high-resolution X-ray diffraction data in combination with the DFT framework was performed to understand the electronic communication between the two iron fragments.

14.
Nefrologia ; 2023 Apr 06.
Artigo em Espanhol | MEDLINE | ID: mdl-37359780

RESUMO

Background and objectives: Acute kidney injury (AKI) is common among hospitalized patients with COVID-19 and associated with worse prognosis. The Spanish Society of Nephrology created the AKI-COVID Registry to characterize the population admitted for COVID-19 that developed AKI in Spanish hospitals. The need of renal replacement therapy (RRT) therapeutic modalities, and mortality in these patients were assessed. Material and method: In a retrospective study, we analyzed data from the AKI-COVID Registry, which included patients hospitalized in 30 Spanish hospitals from May 2020 to November 2021. Clinical and demographic variables, factors related to the severity of COVID-19 and AKI, and survival data were recorded. A multivariate regression analysis was performed to study factors related to RRT and mortality. Results: Data from 730 patients were recorded. A total of 71.9% were men, with a mean age of 70 years (60-78), 70.1% were hypertensive, 32.9% diabetic, 33.3% with cardiovascular disease and 23.9% had some degree of chronic kidney disease (CKD). Pneumonia was diagnosed in 94.6%, requiring ventilatory support in 54.2% and admission to the ICU in 44.1% of cases.The median time from the onset of COVID-19 symptoms to the appearance of AKI (37.1% KDIGO I, 18.3% KDIGO II, 44.6% KDIGO III) was 6 days (4-10). A total of 235 (33.9%) patients required RRT: 155 patients with continuous renal replacement therapy, 89 alternate-day dialysis, 36 daily dialysis, 24 extended hemodialysis and 17 patients with hemodiafiltration. Smoking habit (OR 3.41), ventilatory support (OR 20.2), maximum creatinine value (OR 2.41) and time to AKI onset (OR 1.13) were predictors of the need for RRT; age was a protective factor (0.95). The group without RRT was characterized by older age, less severe AKI, shorter kidney injury onset and recovery time (p < 0.05). 38.6% of patients died during hospitalization; serious AKI and RRT were more frequent in the death group. In the multivariate analysis, age (OR 1.03), previous chronic kidney disease (OR 2.21), development of pneumonia (OR 2.89), ventilatory support (OR 3.34) and RRT (OR 2.28) were predictors of mortality while chronic treatment with ARBs was identified as a protective factor (OR 0.55). Conclusions: Patients with AKI during hospitalization for COVID-19 had a high mean age, comorbidities and severe infection. We defined two different clinical patterns: an AKI of early onset, in older patients that resolves in a few days without the need for RRT; and another more severe pattern, with greater need for RRT, and late onset, which was related to greater severity of the infectious disease. The severity of the infection, age and the presence of CKD prior to admission were identified as risk factors for mortality in these patients. In addition chronic treatment with ARBs was identified as a protective factor for mortality.

16.
Foods ; 11(21)2022 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-36359964

RESUMO

With the objective of evaluating the quality parameters of raw milk in Ecuador between 2010 and 2020, a systematic review and meta-analysis of 73 studies on raw milk produced in different regions of Ecuador was performed. Under the random effects model, effect size and heterogeneity were determined vs. climatic region both among analyses and studies, with Cochran's Q, I2 and Tau (π) statistics. For all the variables, it was observed that there was great heterogeneity (I2 > 90%) among the studies; additionally, it was found that climatic region had an influence only among the variables arsenic, mercury, pH and total solids, and it was greater in the coastal region than the Inter-Andean region. The mean values of the physicochemical characteristics of the milk (titratable acidity, ash, cryoscopy, fat, lactose, pH, protein, non-fat solids and total solids) in the great majority of these studies were within the range allowed by Ecuadorian regulations. As for the hygienic quality of raw milk (total bacterial count, somatic cell count and presence of reductase), although the mean values were within those determined by local legislation, it should be noted that the range established by Ecuadorian regulations is relatively much higher compared to other regulations, which possibly means that there is a high presence of bacteria and somatic cells in raw milk. Finally, the presence of several adulterants (added water) and contaminants (AFM1, antibiotics and heavy metals) was confirmed in the milk, in addition to other substances such as eprinomectin, zearalenone and ptaquilosides, whose presence can be very dangerous, because they can be hepatotoxic, immunotoxic and even carcinogenic. In conclusion, there is great variability among the studies reviewed, with the physicochemical characteristics being the most compliant with Ecuadorian legislation; the hygienic characteristics, adulterants and contaminants of raw milk require greater attention by producers and local authorities, so that they do not harm the health of consumers and the profitability of producers in Ecuador.

17.
Microbiol Res ; 264: 127145, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-35973364

RESUMO

BACKGROUND: Data regarding humoral and cellular response against SARS-CoV-2 in children are scarce. We analysed seroconversion rate, decrease of anti-RBD IgG antibodies over time and T-cell response in paediatric patients who suffered COVID-19. METHODS: Longitudinal study of paediatric patients COVID-19 diagnosed by positive molecular assay in nasopharyngeal swabs. Blood samples were drawn 1-2 months and 6-7 months after acute infection. Anti-RBD IgG were determined using the Alinity® SARS-CoV-2 IgG II Quant assay (Abbott). Cellular immune response was analysed by T-SPOT® SARS-CoV-2 assay kit (Oxford Immunotec Ltd.). RESULTS: 27/39 (69,2%) patients seroconverted. Despite a significant decrease in antibody levels over time (p < 0,01), no children seroreverted between first and second visits. Only 6/16 (37,2%) children under 6 years-old were seropositive compared to 21/23 (91,3%) over 6 years-old (p < 0,01). Highest antibody levels were found in seropositive younger children (p = 0,036). Thirteen (33,3%) children showed T-cell response. Among participants showing humoral response, no cellular response was detected in 14 (51,9%). CONCLUSIONS: Anti-RBD IgG antibodies persistence at 6-7-months after SARS-CoV-2 infection was observed. A different IgG response was found depending on age. As measured by T-SPOT, most patients did not display cellular response 6-7 months after infection.


Assuntos
COVID-19 , Anticorpos Antivirais , Criança , Pré-Escolar , Humanos , Imunoglobulina G , Estudos Longitudinais , SARS-CoV-2
18.
An Pediatr (Engl Ed) ; 96(4): 349.e1-349.e11, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35534418

RESUMO

Some people, including minors, have a gender identity that does not correspond to the sex assigned at birth. They are known as trans* people, which is an umbrella term that encompasses transgender, transsexual, and other identities not conforming to the assigned gender. Healthcare units for trans* minors require multidisciplinary working, undertaken by personnel expert in gender identity, enabling, when requested, interventions for the minor and their social-familial environment, in an individualized and flexible way during the gender affirmation path. This service model also includes hormonal treatments tailored as much as possible to the individual's needs, beyond the dichotomic goals of a traditional binary model. This guide addresses the general aspects of professional care of trans* minors and presents the current evidence-based protocol of hormonal treatments for trans* and non-binary adolescents. In addition, it details key aspects related to expected body changes and their possible side effects, as well as prior counselling about fertility preservation.


Assuntos
Disforia de Gênero , Guias de Prática Clínica como Assunto , Pessoas Transgênero , Transexualidade , Adolescente , Feminino , Disforia de Gênero/tratamento farmacológico , Identidade de Gênero , Humanos , Masculino , Menores de Idade , Transexualidade/terapia
19.
Dalton Trans ; 51(17): 6868-6875, 2022 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35439809

RESUMO

Iodine promotes the in situ formation of iron(II) species from η4-vinylketene[Fe(CO)3] (3a-h) as a key intermediate for the synthesis of 2(5H)-furanones (4a-h) by a sequential water-insertion/carbon-oxygen coupling under mild reaction conditions. Compounds 4a-h were obtained in good to excellent yields. A possible reaction pathway was also proposed by DFT calculations. This methodology can be extended to the synthesis of (5H)-pyrrol-2-ones using anilines, with moderate yields and a few limitations.

20.
ACS Macro Lett ; 10(10): 1273-1279, 2021 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-35549040

RESUMO

Reversible addition-fragmentation chain transfer (RAFT) polymerization has become a straightforward approach to block copolymers using a wide variety of functional vinyl monomers. Polyphosphoester (PPE) macroinitiators from ring-opening polymerization (ROP) of their corresponding cyclic phosphoesters have been previously prepared for atom transfer radical polymerization; however, to date, these biodegradable macroinitiators for RAFT polymerization have not been reported. Herein, a macromolecular RAFT-chain transfer agent (CTA) based on poly(ethyl ethylene phosphonate) was prepared by the organocatalytic ROP of 2-ethyl-2-oxo-1,3,2-dioxaphospholane using 2-cyano-5-hydroxypentan-2-yl dodecyl trithiocarbonate as the initiator and 1,8-diazabycyclo[5.4.0]undec-7-ene as the catalyst. Precise macro-CTAs of degrees of polymerization (DPn) from 34 to 70 with D ≤ 1.10 were prepared and used in the dioxane solution RAFT polymerization of acrylamide, acrylates, methacrylates, and 2-vinylpyridine to yield a library of well-defined block copolymers. Additionally, the PPE-based macro RAFT-CTA was used as a nonionic surfactant in a typical aqueous emulsion polymerization of styrene to produce well-defined nanoparticles with the hydrophilic PPEs on their surface as the stabilizing agent. This general protocol allowed the combination of polyphosphoesters with RAFT polymerization.


Assuntos
Compostos Organofosforados , Polímeros , Substâncias Macromoleculares , Polimerização , Cloreto de Polivinila
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