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1.
Chem Commun (Camb) ; 2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-32016254

RESUMO

This work demonstrates a general and effective approach to activate inert polymer chains for further reactions through electrochemically driven radical generation and radical transfer reactions. The generated radical-containing polymer chains show capacity for further polymer reactions and preparation of polymer hybrids.

2.
Nanomaterials (Basel) ; 9(11)2019 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-31717767

RESUMO

This study demonstrated the processability of sulfur copolymers (SDIB) into polymer blend with polybenzoxazines (PBz) and their compatibility with the electrospinning process. Synthesis of SDIB was conducted via inverse vulcanization using elemental sulfur (S8). Polymer blends produced by simply mixing with varying concentration of SDIB (5 and 10 wt%) and fixed concentration of PBz (10 wt%) exhibited homogeneity and a single-phase structure capable of forming nanofibers. Nanofiber mats were characterized to determine the blending effect on the microstructure and final properties. Fiber diameter increased and exhibited non-uniform, broader fiber diameter distribution with increased SDIB. Microstructures of mats based on SEM images showed the occurrence of partial aggregation and conglutination with each fiber. Incorporation of SDIB were confirmed from EDX which was in agreement with the amount of SDIB relative to the sulfur peak in the spectra. Spectroscopy further confirmed that SDIB did not affect the chemistry of PBz but the presence of special interaction benefited miscibility. Two distinct glass transition temperatures of 97 °C and 280 °C indicated that new material was produced from the blend while the water contact angle of the fibers was reduced from 130° to 82° which became quite hydrophilic. Blending of SDIB with component polymer proved that its processability can be further explored for optimal spinnability of nanofibers for desired applications.

3.
ACS Omega ; 4(4): 7884-7890, 2019 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-31459875

RESUMO

Meldrum's acid (MA) is utilized as a monomer to polymerize with diisocyanates to result in polyamides, containing MA moieties at polymer chains. This reaction is also employed to prepare isocyanate-terminated polyamide segments which are utilized as a precursor for preparation of MA-containing polyurethanes. Based on the thermolysis reaction of MA groups, followed by ketene dimerization reaction, the reactive polyamides and polyurethanes show self-cross-linkable features. The cross-linked polyurethanes exhibit good film formability, thermal stability, and mechanical properties. A new MA-based polymerization method and a novel synthesis route for preparation of reactive polyamides and polyurethanes are demonstrated.

4.
J Am Geriatr Soc ; 67(11): 2298-2304, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31335969

RESUMO

OBJECTIVES: Whether early medication reconciliation and integration can reduce polypharmacy and potentially inappropriate medication (PIM) in the emergency department (ED) remains unclear. Polypharmacy and PIM have been recognized as significant causes of adverse drug events in older adults. Therefore, this pilot study was conducted to delineate this issue. DESIGN: An interventional study. SETTING: A medical center in Taiwan. PARTICIPANTS: Older ED patients (aged ≥65 years) awaiting hospitalization between December 1, 2017, and October 31, 2018 were recruited in this study. A multidisciplinary team and a computer-based and pharmacist-assisted medication reconciliation and integration system were implemented. MEASUREMENTS: The reduced proportions of major polypharmacy (≥10 medications) and PIM at hospital discharge were compared with those on admission to the ED between pre- and post-intervention periods. RESULTS: A total of 911 patients (pre-intervention = 243 vs post-intervention = 668) were recruited. The proportions of major polypharmacy and PIM were lower in the post-intervention than in the pre-intervention period (-79.4% vs -65.3%; P < .001, and - 67.5% vs -49.1%; P < .001, respectively). The number of medications was reduced from 12.5 ± 2.7 to 6.9 ± 3.0 in the post-intervention period in patients with major polypharmacy (P < .001). CONCLUSION: Early initiation of computer-based and pharmacist-assisted intervention in the ED for reducing major polypharmacy and PIM is a promising method for improving geriatric care and reducing medical expenditures. J Am Geriatr Soc 67:2298-2304, 2019.

5.
Hua Xi Kou Qiang Yi Xue Za Zhi ; 36(4): 435-440, 2018 Aug 01.
Artigo em Chinês | MEDLINE | ID: mdl-30182573

RESUMO

Deciduous teeth are the first dentition of humans and play an important role in children's physical and mental development. Dental caries are one of the most common oral diseases in children. According to the data of the World Health Organization, 60%-90% of school children worldwide develop dental caries. In China, dental caries of primary teeth feature high incidence and low rate of visits. Without timely treatment, the deep caries lesions of primary teeth can lead to teeth defect, pulpitis, apical periodontitis, and maxillofacial space infection. Moreover, the premature loss of deciduous teeth can cause malocclusion and eruption disorder of subsequent permanent teeth. These conditions all cause considerable effects on children's oral health and physical and mental development. Performing active and effective measures to treat deciduous teeth with deep caries lesions is important to maintain the integrity and normal physiological function of dentition and facilitate normal eruption of permanent teeth. The current situation of indirect pulp therapy in China was studied in this paper. Basic concepts, including indirect pulp capping, interim therapeutic restoration, partial caries removal, stepwise caries removal, and atraumatic restorative therapy, have been defined by consulting domestic and foreign literature. A theoretical basis for improving the clinical pathway of deciduous teeth with deep caries lesions is provided by explaining the technical connotation and therapeutic importance of indirect pulp therapy in primary teeth.


Assuntos
Cárie Dentária , Capeamento da Polpa Dentária , Criança , China , Assistência Odontológica , Cárie Dentária/terapia , Restauração Dentária Permanente , Humanos , Dente Decíduo
6.
Macromol Rapid Commun ; 39(8): e1700832, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29450931

RESUMO

A novel approach to preparing polymeric materials using elemental sulfur as a feedstock through the newly developed sulfur radical transfer and coupling (SRTC) reaction is reported herein. Polybenzoxazines with high sulfur contents are prepared using the SRTC reaction with benzoxazine compounds as the radical acceptors. The reactions between elemental sulfur and benzoxazine rings are analyzed with Fourier transform infrared (FTIR), 1 H NMR, and 13 C DEPT spectroscopies to elucidate the SRTC reaction mechanism. Moreover, the prepared polybenzoxazine-sulfur hybrid materials show attractive repairing properties based on the dynamic S-S linkages. An effective reaction mechanism and the prepared repairable sulfur-possessing polymeric materials are demonstrated.


Assuntos
Benzoxazinas/química , Polímeros/química , Enxofre/química
7.
ACS Omega ; 3(4): 4641-4646, 2018 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-31458684

RESUMO

On the basis of the reaction between ketene and alcohol groups to result in an ester linkage and Meldrum's acid as an effective precursor of ketene group, a bifunctional aliphatic Meldrum's acid compound (BisMA) is synthesized and used as a monomer to react with ethylene glycol and glycerol for the preparation of linear and cross-linked aliphatic polyesters, respectively. A 62 and 35 wt % of biodegradation fraction have been recorded on the linear and cross-linked aliphatic polyesters after an 8 week biodegradation test, respectively, to demonstrate the good biodegradability of the synthesized polyesters. In addition to conventional linear biodegradable polyesters, this synthetic route also provides a new and convenient method for preparation of cross-linked biodegradable polyesters. The types of the required monomers and reaction methods for preparation of the cross-linked biodegradable polyesters are similar to those used for conventional thermosetting resins. An integration of biodegradable polymers and thermosetting resins in polymer chemistry has been demonstrated.

8.
Macromol Rapid Commun ; 38(15)2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28582606

RESUMO

In this work, the incorporation of a 2,2,6,6-tetramethylpiperydinyl-1-oxyl (TEMPO) group to a benzoxazine ring is performed using a one-pot synthesis for the preparation of TEMPO-functionalized benzoxazine compounds and polymers as reactive and crosslinkable initiators for nitroxide-mediated polymerization (NMP). The TEMPO-functionalization reaction of benzoxazine, traced with 1 H NMR, is conducted with sequential radical transfer and coupling reactions. Moreover, polystyrene-grafted polybenzoxazine copolymers are prepared with the TEMPO-benzoxazine initiator and NMP of styrene. The polymerization system exhibits the characteristics of controlled radical polymerization, including controlled molecular weights of products and ability for sequential polymerization. Moreover, based on the chemical reactivity and crosslinking ability of benzoxazine groups, the synthesis route developed in this work will widen the scope of the design and synthesis of functional and high-performance polymers.


Assuntos
Benzoxazinas/síntese química , Técnicas de Química Analítica/métodos , Óxidos N-Cíclicos/química , Benzoxazinas/química , Peso Molecular , Polimerização , Polímeros/química , Estireno/química
9.
Macromol Rapid Commun ; 38(10)2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28370775

RESUMO

This work demonstrates a new reactive and functional hybrid (S-MMA-POSS) of polyhedral oligomeric silsesquioxane (POSS) and sulfur prepared with a direct reaction between a multifunctional methacrylated POSS compound (MMA-POSS) and elemental sulfur (S8 ) through the "inverse vulcanization" process. S-MMA-POSS is an effective building block for imparting self-healing ability to the corresponding thermally crosslinked POSS-containing nanocomposites through a self-curing reaction and co-curing reaction with conventional thermosetting resins. Moreover, S-MMA-POSS is also a useful precursor for preparation of materials with high transparency in mid-infrared region.


Assuntos
Compostos de Organossilício/química , Enxofre/química , Teste de Materiais , Nanocompostos , Propriedades de Superfície
10.
Macromol Rapid Commun ; 38(4)2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28026084

RESUMO

In this work, a cocatalytic effect between Meldrum's acid (MA) and benzoxazine (Bz) compounds has been explored to build up a self-promoting curing system. Consequently, the MA/Bz reactive blend exhibits a relatively low reaction temperature compared to the required temperatures for the cross-linking reactions of the pure MA and Bz components. This feature is attractive for energy-saving processing issues. Moreover, the thermosetting resins based on the MA/Bz reactive blends have been prepared. The MA component can generate additional free volume in the resulting resins, so as to trap air in the resin matrix and consequently to bring low dielectric constants to the resins. The MA-containing agent is an effective modifier for benzoxazine resins to reduce their dielectric constants.


Assuntos
Benzoxazinas/química , Dioxanos/química , Resinas Sintéticas/síntese química , Temperatura , Catálise , Estrutura Molecular , Resinas Sintéticas/química
11.
J Hazard Mater ; 320: 187-193, 2016 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-27544731

RESUMO

Graphene oxide (GO)-based membranes provide an encouraging opportunity to support high separation efficiency for wastewater treatment. However, due to the relatively weak interaction between GO nanosheets, it is difficult for bare GO-based membranes to survive in cross-flow filtration. In addition, the permeation flux of the bare GO membrane is not high sufficiently due to its narrow interlayer spacing. In this study, GO membranes interlinked with multi-walled carbon nanotubes (MWCNTs) via covalent bonds were fabricated on modified polyacrylonitrile (PAN) supports by vacuum filtration. Due to the strong bonds between GO, MWCNTs and the PAN membrane, the membranes could be used for the treatment of simulated nuclear wastewater containing strontium via a cross-flow process. The result showed a high flux of 210.7L/(m2h) at 0.4MPa, which was approximately 4 times higher than that of commercial nanofiltration membranes. The improved water permeation was attributed to the nanochannels created by the interlinked MWCNTs in the GO layers. In addition, the hybrid membrane exhibited a high rejection of 93.4% for EDTA-chelated Sr2+ in an alkaline solution, and could also be used to separate Na+/Sr2+ mixtures. These results indicate that the MWCNTs-interlinked GO membrane has promising prospects for application in radioactive waste treatment.

12.
Macromol Rapid Commun ; 37(10): 845-50, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27027639

RESUMO

This work demonstrates a new halogenation reaction through sequential radical and halogen transfer reactions, named as "radical and atom transfer halogenation" (RATH). Both benzoxazine compounds and poly(2,6-dimethyl-1,4-phenylene oxide) have been demonstrated as active species for RATH. Consequently, the halogenated compound becomes an active initiator of atom transfer radical polymerization. Combination of RATH and sequential ATRP provides an convenient and effective approach to prepare reactive and crosslinkable polymers. The RATH reaction opens a new window both to chemical synthesis and molecular design and preparation of polymeric materials.


Assuntos
Halogenação , Polímeros/química , Radicais Livres/química , Polimerização
13.
Chem Commun (Camb) ; 51(64): 12760-3, 2015 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-26166203

RESUMO

This work demonstrates a new class of thermosetting resins, based on Meldrum's acid (MA) derivatives, which have high fractions of free volume and inherently low k values of about 2.0 at 1 MHz. Thermal decomposition of the MA groups evolves CO2 and acetone to create air-trapped cavities so as to reduce the dielectric constants.

14.
Langmuir ; 30(26): 7676-86, 2014 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-24927298

RESUMO

In this article, we report a novel, nanoprecipitation-based method for preparing silica nanoparticles with thiol and amine cofunctionalization. (3-Mercaptopropyl)trimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane (APTMS) were used as the organosilane precursors, which were subjected to acid-catalyzed polycondensation in an organic phase containing a water-miscible solvent (e.g., dimethyl sulfoxide). A pale colloidal solution could be immediately formed when the preincubated organic phase was directly injected into water. The initial composition ratio between MPTMS and APTMS is an important factor governing the formation of nanoparticles. Specifically, large, unstable micrometer-sized particles were formed for preparation using MPTMS as the sole silane source. In contrast, when APTMS was used alone, no particles could be formed. By reducing the fraction of APTMS (or increasing that of MPTMS) in the initial mixture of organosilanes, the formation of nanometer-sized particles occurred at a critical fraction of APTMS (i.e., 25%). Remarkably, a tiny fraction (e.g., 1%) of APTMS was sufficient to produce stable nanoparticles with a hydrodynamic diameter of about 200 nm. Other factors that would also affect particle formation were determined. Moreover, an interesting temperature effect on particle formation was observed. The TEM micrographs show spherical nanospheres with mean sizes of 130-150 nm in diameter. The solid-state (29)Si NMR spectra demonstrate that the hybrid silica materials contain fully and partially condensed silicon structures. The bifunctionalized silica nanoparticles have positive zeta potentials whose magnitudes are positively correlated with the amount of APTMS. The total thiol content, however, is negatively correlated with the amount of APTMS. The cationic nanoparticles can bind an antisense oligonucleotide in a composition-dependent manner.


Assuntos
Aminas/química , Nanopartículas/química , Dióxido de Silício/química , Compostos de Sulfidrila/química , Propilaminas/química , Silanos/química
15.
Langmuir ; 30(3): 812-22, 2014 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-24410024

RESUMO

Nitric oxide (NO) is a ubiquitous molecule in the body. Because of its multiple pathophysiologic roles, the potential for treating various diseases by the exogenous administration of NO has been under intensive investigation. However, the unstable, radical nature of NO poses a major challenge to the effective delivery of NO. Previously, silica nanoparticles synthesized by the traditional method have been developed into NO-carrying systems. In the present study, for the first time NO-carrying silica nanoparticles were prepared from a single silica precursor using a simple nanoprecipitation method. (3-Mercaptopropyl)-trimethoxysilane (MPTMS) was used as the sole silane source, which was subjected to acid-catalyzed S-nitrosation and condensation reactions in a one-pot organic phase. S-Nitroso silica nanoparticles (SNO-SiNPs) were then produced by injecting a smaller quantity of the organic phase into a larger amount of water without surfactants. Various preparation parameters were tested to obtain optimized conditions. Moreover, a phase diagram demonstrating the ouzo effect was constructed. The prepared SNO-SiNPs were spherical particles with a tunable size in the range of 100-400 nm. The nanoparticles in aqueous dispersions exhibited high colloid stability, possibly resulting from highly negatively charged surfaces. The result of solid-state (29)Si NMR shows the predominance of T(2) and T(3) silicon structures, suggesting that nanoparticles were formed from polycondensed silica species. In conclusion, NO-loaded silica nanoparticles have been directly prepared from a single silane precursor using a surfactant-free, low-energy, one-step nanoprecipitation approach. The method precludes the need for the initial formation of bare particles and subsequent functionalization steps.


Assuntos
Nanopartículas/química , Compostos Nitrosos/síntese química , Dióxido de Silício/química , Estrutura Molecular , Compostos Nitrosos/química , Tamanho da Partícula , Propriedades de Superfície
16.
ACS Appl Mater Interfaces ; 5(20): 9918-25, 2013 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-24047256

RESUMO

Electrically induced reversible reactions between ferrocene (Fc) and ß-cyclodextrin (ß-CD) groups have been utilized for preparation of poly(tetrafluoroethylene) (PTFE) membranes exhibiting electrically driven biofouling release properties. PTFE membrane is surface-modified with polymer chains possessing Fc pendant groups. The surface layer is then cross-linked with a difunctional ß-CD compound by means of the Fc/ß-CD complexation reaction. The electrically induced reversibly cross-linking and de-cross-linking behaviors of the surface layer of the modified PTFE membrane have been characterized with Fourier transform Infrared, X-ray photoelectron spectroscopy, and scanning electron microscopy. The surface-modified PTFE membrane has been fouled with protein absorption. Electrical treatment of the fouled membrane results in a protein detachment from the membrane surface driven by the surface structure change accompanied with the electrically induced de-cross-linking reaction of the Fc/ß-CD linkages. A smart membrane exhibiting a novel cleaning technology for membrane fouling has been developed.


Assuntos
Incrustação Biológica/prevenção & controle , Membranas Artificiais , Politetrafluoretileno/química , Absorção , Eletricidade , Compostos Ferrosos/química , Metalocenos , Proteínas/química , Proteínas/metabolismo , Propriedades de Superfície , beta-Ciclodextrinas/química
17.
Macromol Rapid Commun ; 34(8): 689-94, 2013 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-23495104

RESUMO

In this paper, self-assembled polymeric toroids formed by a temperature-driven process are reported. Rhodamine B (RhB) end-capped poly(N-isopropylacrylamide) (PNIPAAm) demonstrating a lower critical solution temperature (LCST) is prepared. In a two-phase system, the polymer in the aqueous phase could move to the chloroform phase on raising the temperature above its LCST. This temperature-driven process results in the formation of polymeric toroids in the chloroform phase, and the strategy affords a new pathway to toroidal self-assembly of polymers. Moreover, the photoluminescent behavior of the RhB end-capped PNIPAAm species formed by the process is also studied and discussed.


Assuntos
Acrilamidas/química , Polímeros/química , Rodaminas/química , Resinas Acrílicas , Clorofórmio/química , Espectrofotometria Ultravioleta , Temperatura , Água/química
18.
ACS Appl Mater Interfaces ; 3(7): 2204-8, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21644521

RESUMO

We report a thermally-induced increase of electrical conductivity of polymer/multiwalled carbon nanotube (MWCNT) composites using Diels-Alder-adduct-modified MWCNTs as additives. Thermal treatments of the composites induce the defunctionalization of the modified MWCNTs through retro-DA reaction, consequently to recover the electrical conductivity of MWCNTs and to increase the conductivity of PVDF/MWCNT composites. For the composites possessing 0.5 wt % of MWCNTs, thermal treatment increases the electrical conductivity from 2 × 10(-12) S cm(-1) to 4 × 10(-8) S cm(-1) and significantly reduces the value of percolation threshold. Meanwhile, the thermal treatment does not alter the mechanical properties of the composites.

19.
Langmuir ; 27(9): 5445-55, 2011 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-21449586

RESUMO

In this work, the hemocompatibility of PEGylated poly(vinylidene fluoride) (PVDF) microporous membranes with varying grafting coverage and structures via plasma-induced surface PEGylation was studied. Network-like and brush-like PEGylated layers on PVDF membrane surfaces were achieved by low-pressure and atmospheric plasma treatment. The chemical composition, physical morphology, grafting structure, surface hydrophilicity, and hydration capability of prepared membranes were determined to illustrate the correlations between grafting qualities and hemocompatibility of PEGylated PVDF membranes in contact with human blood. Plasma protein adsorption onto different PEGylated PVDF membranes from single-protein solutions and the complex medium of 100% human plasma were measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Hemocompatibility of the PEGylated membranes was evaluated by the antifouling property of platelet adhesion observed by scanning electron microscopy (SEM) and the anticoagulant activity of the blood coagulant determined by testing plasma-clotting time. The control of grafting structures of PEGylated layers highly regulates the PVDF membrane to resist the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. It was found that PVDF membranes grafted with brush-like PEGylated layers presented higher hydration capability with binding water molecules than with network-like PEGylated layers to improve the hemocompatible character of plasma protein and blood platelet resistance in human blood. This work suggests that the hemocompatible nature of grafted PEGylated polymers by controlling grafting structures gives them great potential in the molecular design of antithrombogenic membranes for use in human blood.


Assuntos
Materiais Biocompatíveis/química , Incrustação Biológica/prevenção & controle , Membranas Artificiais , Plasma/metabolismo , Polivinil/química , Atmosfera , Humanos , Propriedades de Superfície
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