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1.
Int J Mol Sci ; 22(15)2021 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-34361016

RESUMO

Although small water clusters (SWCs) are important in many research fields, efficient methods of preparing SWCs are still rarely reported, which is mainly due to the lack of related materials and understanding of the molecular interaction mechanisms. In this study, a series of functional molecules were added in water to obtain small water cluster systems. The decreasing rate of the half-peak width in a sodium dodecyl sulfate (SDS)-water system reaches ≈20% at 0.05 mM from 17O nuclear magnetic resonance (NMR) results. Based on density functional theory (DFT) and molecular dynamics (MD) simulation calculation, it can be concluded that functional molecules with stronger negative electrostatic potential (ESP) and higher hydrophilicity have a stronger ability to destroy big water clusters. Notably, the concentrations of our selected molecule systems are one to two magnitudes lower than that of previous reports. This study provides a promising way to optimize aqueous systems in various fields such as oilfield development, protein stability, and metal anti-corrosion.


Assuntos
Interações Hidrofóbicas e Hidrofílicas , Simulação de Dinâmica Molecular , Dodecilsulfato de Sódio/química , Espectroscopia de Ressonância Magnética , Eletricidade Estática , Água/química
2.
Int J Mol Sci ; 22(12)2021 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-34208767

RESUMO

Promoting fluid transportation in porous media has important applications in energy, pedology, bioscience, etc. For this purpose, one effective way is to prevent swelling through surface modification; however, it is far from enough in real cases, such as ultra-low permeability reservoirs and tight oils. In this study, we considered the comprehensive effects of inhibiting clay swelling, flocculation performance, reducing water clusters and interfacial tension and developed a series of imidazole-based tetrafluoroborate ionic liquids (ILs) with different lengths of alkyl chains. Through measurements of anti-swelling rates, XRD, SEM, 17O NMR, molecular dynamics simulation, zeta potential, flocculation evaluation, interfacial tension and a core flooding experiment based on ultra-low permeability reservoirs, the relationships between the molecular structure and physicochemical properties of ILs have been revealed. Interestingly, one of the selected ILs, imidazole-based tetrafluoroborate ILs (C8-OMImBF4), shows excellent performance, which is helpful to design an effective strategy in promoting fluid transportation in narrow spaces.


Assuntos
Argila/química , Imidazóis/química , Líquidos Iônicos/química , Água/química , Algoritmos , Fenômenos Químicos , Modelos Moleculares , Modelos Teóricos , Conformação Molecular , Estrutura Molecular , Difração de Raios X
3.
Sci Rep ; 10(1): 16565, 2020 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-33024159

RESUMO

Pickering emulsions with on-off properties provide significant advantages over simple solid-stabilized emulsions for the development of novel materials, such as oil-displacing agents for enhanced oil recovery and templates for the fabrication of porous materials. However, the irreversible adsorption of particles as emulsion stabilizers endows the Pickering emulsions with kinetically stable property, resulting in a huge challenge to break the stability. Here we fabricated microscale Pickering emulsions, by the use of paramagnetic particles, which possess excellent stability for several months and more interestingly perform complete demulsification under controllable magnetic fields in several minutes. The alternating asymmetrical magnetic field endows oil-in-water droplets ''big'' N and S poles on the outer particle layers, and attracts the solid particles to the bottom of the vial after the coalescence and the deformation of the droplets, bringing the prevention of re-emulsion and the cyclic utilization. This facile strategy to produce stable Pickering emulsions with a magnetic-response opens a promising avenue for various practical applications including oil recovery, wastewater treatment, and sludge removal.

4.
Materials (Basel) ; 13(16)2020 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-32784570

RESUMO

Although stimuli-responsive release systems have attracted great attention in medical applications, there has been no attempt at "precise" deep profile control based on such systems, which is greatly need to improve oil recovery. With this in mind, we provided a facile and simple strategy to prepare stimuli-responsive composite capsules of amphiphilic dendrimers-poly(styrene sulfonic acid) sodium/halloysite nanotubes (HNTs) via layer-by-layer (LbL) self-assembly technique, controlling the release crosslinking agent methenamine under different pH or salinity conditions. The release time of methenamine encapsulated in multilayer shells is about 40 h, which can be prolonged with the introduction of salt or shortened via the addition of acid, which accordingly induces the gelation of polyacrylamide (PAM) solutions, taking from a few hours to a dozen days. This study provided a novel approach for controllable release of chemical agents and controllable crosslinking of deep profiles in many application fields.

5.
Soft Matter ; 16(21): 4912-4918, 2020 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-32393946

RESUMO

Protein adsorption on polyelectrolyte (PE) surfaces has aroused intensive attraction, but there are still few investigations on tuning the protein adsorption at a solid surface by controllable layer structures and surface properties of PE adlayers. Furthermore, there is a lack of understanding regarding the correlation between molecular conformation and anticorrosion performance of composite materials. With this in mind, we synthesized a series of PEs and constructed 3,4-dihydroxy-l-phenylalanine (l-DOPA) adlayers on the PE surfaces, monitoring the whole adsorption process in situ. A highly charged cationic PE surface exhibits a low adhesion of DOPA molecules, leading to a loose structure, rough surface morphology, and strong solvation effects and, accordingly, this kind of multilayer provides a poor anticorrosion capacity. In comparison, amphiphilic and highly charged cationic PE surfaces are in favor of DOPA adsorption and the formation of compact and smooth multilayers due to cation-π and hydrophobic interactions between DOPA and PEs. Interestingly, one of the multilayers exhibits a remarkable enhancement of inhibition efficiency of about 460-fold compared with that of the bare substrate, which is much higher than that of other anticorrosion coatings reported previously. Our findings reveal the interaction mechanism between DOPA and PE surfaces to achieve the controllable adsorption of biomolecules, providing a promising way to optimize the layer structures to improve the anticorrosion capacity.


Assuntos
Di-Hidroxifenilalanina/química , Polieletrólitos/química , Adsorção , Corrosão , Interações Hidrofóbicas e Hidrofílicas
6.
ACS Appl Mater Interfaces ; 11(18): 16914-16921, 2019 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-30990008

RESUMO

Antiadhesion performance, stretchability, and transparency are highly desirable properties for materials and devices in numerous applications. However, the existing strategies for imparting materials with antiadhesion performance generally induce rigidity and opacity, and principle is yet to be provided for designing materials that combine these important parameters. Here, we show that four factors including a low surface energy, appropriate cross-linking, availability of a homogeneous and amorphous composite, and a smooth material surface can be used to design an intrinsically stretchable and transparent polymer film with antiadhesion performance against various liquids including water, diiodomethane, hexadecane, cooking oil, and pump oil. The film can be obtained via simply molding a waterborne polymer network at ambient temperature. Furthermore, the film can retain its antiadhesion performance and outstanding transparency even when it is subjected to large mechanical deformations reaching up to 1800%, and its maximal fracture strain exceeds 3000%. These design concepts offer a general platform for achieving multiple material functionalities, and may open new avenues for the surface functionalization of stretchable materials and devices.

7.
Langmuir ; 35(8): 3031-3037, 2019 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-30722665

RESUMO

Bacterial infection on biomaterial devices and the subsequent medical risks pose a serious problem in both human healthcare and industrial applications, resulting in a prevalence of various antimicrobial materials. Cationic amphiphilic polymer has been proposed to be a new generation of efficient antibacterial material, but the surface modified by such types of polymers still shows incomplete bactericidal ability and easily contaminated performance. With this in mind, a novel kind of geminized cationic amphiphilic polymer brush surface has been developed in this study, presenting a complete antibacterial activity, because of the synergistic biocidal effect of electrostatic and hydrophobic interactions, as well as the minimized contact area between bacteria and polymer surface. A structure self-adjustment process of polymer brush construction has been proposed, in which the mutual interference among cationic head groups can be avoided and the electrostatic repulsion and hydrophobic attraction can be balanced, in the formation of a smooth and tight surface. A self-cleaning capability of polymer surface has been performed via hydrolysis and degradation, maintaining a high antibacterial activity. Therefore, we provide a facile and possible manipulation strategy to fabricate super-antibacterial and self-cleaning surfaces in a wide range of biomedical and industrial applications.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Interações Hidrofóbicas e Hidrofílicas , Polímeros/química , Polímeros/farmacologia , Escherichia coli/efeitos dos fármacos , Modelos Moleculares , Conformação Molecular , Staphylococcus aureus/efeitos dos fármacos
8.
Molecules ; 24(1)2018 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-30577641

RESUMO

Current approaches to dealing with the worldwide problem of marine biofouling are to impart chemical functionality to the surface or utilize microtopography inspired by nature. Previous reports have shown that only introducing a single method may not resist adhesion of mussels or inhibit biofouling in static forms. While it is promising to integrate two methods to develop an effective antifouling strategy, related basic research is still lacking. Here, we have fabricated engineered shark skin surfaces with different feature heights and terminated with different chemical moieties. Atomic force microscopy (AFM) with a modified colloid probe technique and quartz crystal microbalance with a dissipation n (QCM-D) monitoring method have been introduced to directly determine the interactions between adhesive proteins and functionalized surfaces. Our results indicate that the adhesion strength of probe-surface decreases with increasing feature height, and it also decreases from bare Si surface to alkyl and hydroxyl modification, which is attributed to different contact area domains and interaction mechanisms. Combining biomimetic microtopography and surface chemistry, our study provides a new perspective for designing and developing underwater anti-fouling materials.


Assuntos
Biomimética , Proteínas/química , Biomimética/instrumentação , Biomimética/métodos , Microscopia de Força Atômica , Técnicas de Microbalança de Cristal de Quartzo , Propriedades de Superfície
9.
Chem Commun (Camb) ; 54(76): 10679-10682, 2018 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-30137080

RESUMO

Magnetic-responsive switchable emulsions, which are stabilized by 3-aminopropyltriethoxy silane coated nanoparticles, have been developed in this study. The emulsions show excellent stability for dozens of days and more importantly perform complete demulsification on demand in several minutes. This study provides a facile and possible manipulation strategy to re-disperse the components, re-produce the stable emulsions, and re-trigger the demulsification performance without long-lasting effects.

10.
J Phys Chem B ; 122(25): 6648-6655, 2018 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-29897753

RESUMO

Amphiphilic poly(amidoamine) (PAMAM) dendrimers are a well-known dendritic family due to their remarkable ability to self-assemble on solid surface. However, the relationship between molecular conformation (or adsorption kinetics) of a self-assembled layer and molecular amphiphilicity of such kind of dendrimer is still lacking, which limits the development of modulating self-assembling structures and surface functionality. With this in mind, we synthesized a series of amphiphilic PAMAM-based dendrimers, denoted as G1C n, with different alkyl chains ( n = 8, 12, and 16), and investigated the molecular aggregation on silica surfaces by means of quartz crystal microbalance with dissipation, atomic force microscopy, and contact angle. After rinsing, remaining adsorption amounts of G1C12 were higher than those of G1C8 at high concentrations, suggesting that G1C12 adlayers were more stable due to the stronger intermolecular hydrophobic interactions, whereas it preferred to adopt the intramolecular hydrophobic interactions for G1C16, with low adsorption amounts and unstable adlayers. Bilayer-like structures were inferred in G1C8 and G1C12 adlayers with loose conformation, whereas monolayer structures were likely to exist in the sparse adsorption film of G1C16. Our results provided more detailed understanding of the effect of molecular structure on the self-assembled structures of amphiphilic dendrimers on solid surfaces, shedding light on the controlled microstructure and wettability of functional surface by modulating the length of hydrophobic chains of dendrimers and a potential application of dendrimer-substrate combinations.

11.
Soft Matter ; 14(16): 3090-3095, 2018 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-29611598

RESUMO

In this study, a novel supramolecular hydrogel, abbreviated as AGC16/NTS, was designed and constructed by the molecular self-assembly of a cationic gemini surfactant, 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylatedibromide (AGC16), and an anionic aromatic gelator, trisodium 1,3,6-naphthalenetrisulfonate (NTS). The AGC16/NTS hydrogel was able to form in a mass ratio range of AGC16 and NTS from 20 : 1 to 10 : 1. It was interestingly found that AGC16/NTS exhibited two phase transitions (gel-to-gel and gel-to-sol) observed by visual and rheological measurements during the heating process, which is rarely reported in the previous literature reports of hydrogels prepared using low molecular weight gelators. Cryogenic scanning electron microscopy (cryo-SEM), fluorescence emission spectroscopy and X-ray diffraction (XRD) were used to investigate the temperature-responsive properties and molecular self-assembly mechanism of the hydrogel AGC16/NTS. During the gel-to-gel transition process, the temperature-responsive changes in the visual appearance of AGC16/NTS (turbid to transparent) were clearly observed. Compared with the transparent gel, the turbid gel possesses higher mechanical strength and a much more compact network mophology due to stronger intermolecular hydrophobic association beetween gelators. The molecular self-assembly modes for the two different hydrogel states (turbid and transparent gel) were proposed, helping to further understand the hydrogel transition mechanisms at a molecular level.

12.
Environ Sci Pollut Res Int ; 25(14): 13823-13832, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29508202

RESUMO

Large quantities of construction and demolition (C&D) waste are generated in China every year, but their potential environmental impacts on the surrounding areas are rarely assessed. This study focuses on metals contained in C&D waste, characterizing the metal concentrations and their related environmental risks. C&D waste samples were collected in Shenzhen City, China, from building demolition sites, renovation areas undergoing refurbishment, landfill sites, and recycling companies (all located in Shenzhen city) that produce recycled aggregate, in order to identify pollution levels of the metals As, Cd, Cr, Cu, Pb, Ni, and Zn. The results showed that (1) the metal concentrations in most demolition and renovation waste samples were below the soil environmental quality standard for agricultural purposes (SQ-Agr.) in China; (2) Cd, Cu, and Zn led to relatively higher environmental risks than other metals, especially for Zn (DM5 tile sample, 360 mg/kg; R4 tile sample, 281 mg/kg); (3) non-inert C&D waste such as wall insulation and foamed plastic had high concentrations of As and Cd, so that these materials required special attention for sound waste management; and (4) C&D waste collected from landfill sites had higher concentrations of Cd and Cu than did waste collected from demolition and refurbishment sites.


Assuntos
Arsênio/análise , Indústria da Construção , Monitoramento Ambiental , Resíduos Industriais/análise , Metais Pesados/análise , China , Reciclagem , Instalações de Eliminação de Resíduos
13.
Soft Matter ; 14(4): 566-573, 2018 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-29334109

RESUMO

A novel supramolecular hydrogel was designed and constructed by molecular self-assembly of a cationic gemini surfactant, 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylate dibromide (AGC16), and an anionic aromatic compound, trisodium 1,3,6-naphthalenetrisulfonate (NTS). Owing to its unique structure, the hydrogel (abbreviated as AGC16/NTS) has the potential to be used as a multifunctional drug delivery system. The structure and properties of AGC16/NTS were characterized by rheological measurements, differential scanning calorimetry, variable-temperature 1H nuclear magnetic resonance, ultraviolet-visible spectroscopy, variable-temperature fluorescence emission spectroscopy, cryogenic scanning electron microscopy, transmission electron microscopy and X-ray diffraction methods. The rheological and DSC analysis results revealed that the gel AGC16/NTS was formed below 57 °C. It was found from UV-vis, fluorescence and 1H NMR spectroscopy characterization that aromatic π-π stacking and hydrophobic forces were indispensable to the formation of AGC16/NTS. The Cryo-SEM and TEM observation results indicated that gelators AGC16 and NTS self-assembled into one-dimensional fibers which further tightly intertwined to form a three-dimensional network structure. Based on the spectroscopic data and X-ray diffraction measurement results, a self-assembly model was proposed, helping to further understand the molecular self-assembly mechanism of AGC16/NTS. It was also found that the electrostatic force, hydrophobic force and π-π interaction were the three main driving forces for the gelation. The multiple non-covalent interactions between AGC16 and NTS endowed the hydrogel with excellent performance when the hydrogel was used as a carrier for drug delivery, due to multiple micro-domains within the same gel system. We further investigated the encapsulation and releasing properties of the hydrogel, using the hydrophobic model drug curcumin (Cur) and the model drug naproxen sodium (Npx) with aromatic ring structure. The fluorescence spectroscopy analysis confirmed that Npx was carried through aromatic π-π stacking and the 1H NMR measurement result revealed that Cur was encapsulated within the hydrophobic cavities of AGC16/NTS through hydrophobic interaction. Moreover, the drug release study results showed a sustained release of drugs from the hydrogel, indicating good application prospects in exploring new multifunctional drug delivery systems.


Assuntos
Portadores de Fármacos/química , Hidrogéis/química , Curcumina/química , Liberação Controlada de Fármacos , Modelos Moleculares , Conformação Molecular , Naproxeno/química , Reologia
14.
Soft Matter ; 14(3): 405-410, 2018 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-29239453

RESUMO

A pH and salt dually responsive emulsion has been designed on the basis of a novel amphiphilic macromolecule. It was found that the water separation of an oil-in-water emulsion reached up to ∼60% after standing for 10 min at low pH. 2-(Diethylamino)ethyl methacrylate (DEA) residues were found to induce the macromolecules to protonate and to be hydrophilic at pH values between 2 and 6, resulting in dewetting from oil droplet surfaces in water. Besides, the macromolecules form aggregates with different structures at the water/oil interface, depending on the pH value or salt concentration of the emulsion system, enabling the system to be demulsified in response to the pH or salt stimulus. The experimental results also showed that with the addition of aluminium chloride at 100 mg L-1, the water separation was about 70% after 20 min. A possible mechanism with respect to demulsifying was proposed on the basis of an "ion bridge" among sodium acrylate (SA) residues, inducing the macromolecules to "cross-link" and become insoluble, and leading to oil/water separation. Furthermore, at a fixed pH of 5, addition of salt to the aqueous dispersion increased the degree of oil-water interfacial activity and batch emulsions were significantly unstable to coalesce at a low salinity of 25-50 mg L-1. This finding presents a new manipulation on emulsion stability and potential applications in the fields of oil recovery, wastewater treatment, sludge removal, and so on.

15.
Polymers (Basel) ; 10(2)2018 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-30966199

RESUMO

The mixing of polymers and nanoparticles is opening pathways for engineering flexible composites that exhibit advantageous functional properties. To fabricate controllable assembling nanocomposites for efficiently encapsulating methenamine and releasing them on demand, we functionalized the surface of natural halloysite nanotubes (HNTs) selectively with polymerizable gemini surfactant which has peculiar aggregation behavior, aiming at endowing the nanomaterials with self-assembly and stimulative responsiveness characteristics. The micromorphology, grafted components and functional groups were identified using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The created nanocomposites presented various characteristics of methenamine release with differences in the surface composition. It is particularly worth mentioning that the controlled release was more efficient with the increase of geminized monomer proportion, which is reasonably attributed to the fact that the amphiphilic geminized moieties with positive charge and obvious hydrophobic interactions interact with the outer and inner surface in different ways through fabricating polymeric shell as release stoppers at nanotube ends and forming polymer brush into the nanotube lumen for guest immobilization. Meanwhile, the nanocomposites present temperature and salinity responsive characteristics for the release of methenamine. The combination of HNTs with conjugated functional polymers will open pathways for engineering flexible composites which are promising for application in controlled release fields.

16.
Environ Sci Pollut Res Int ; 24(36): 28197-28204, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29022173

RESUMO

The used electronic product (UEP) has attracted the worldwide attentions because part of e-waste may be exported from developed countries to developing countries in the name of UEP. On the basis of large foreign trade data of electronic products (e-products), this study adopted the trade data approach (TDA) to quantify the potential exports of UEP in Macau, taking a case study of personal computers (PCs). The results show that the desktop mainframes, LCD monitors, and CRT monitors have more low-unit-value trades with higher trade volumes in the past 10 years, while the laptop and tablet PCs, as the newer technologies, owned the higher ratios of the high-unit-value trades. During the period of 2005-2015, the total mean exports for used laptop and tablet PCs, desktop mainframes, and LCD monitors were approximately 18,592, 79,957, and 43,177 units, respectively, while the possible export volume of used CRT monitors was higher, up to 430,098 units in 2000-2010. Noticed that these potential export volumes could be the lower bound because not all used PCs may be shipped using the PC trade code. For all the four kinds of used PCs, the majority (61.6-98.82%) of the export volumes have gone to Hong Kong, followed by Mainland China and Taiwan. Since 2011, there was no CRT monitor export; however, the other kinds of used PC exports will still exist in Macau in the future. The outcomes are helpful to understand and manage the current export situations of used products in Macau, and can also provide a reference for other countries and regions.


Assuntos
Comércio , Resíduo Eletrônico , Microcomputadores/economia , Países em Desenvolvimento , Macau , Propriedade
17.
Waste Manag ; 68: 498-507, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28756124

RESUMO

Many studies show that high levels of many toxic metals and persistent and bio-accumulative chemicals have been found in electronic waste (e-waste) dismantling sites and their surrounding environmental media. Both flame-retardant plastic housing materials and printed circuit boards (PCBs) could be the major contributors. However, relatively little work has focused on the use or content of toxic substances and their changing in scrap housing materials and PCBs from home appliances. This study evaluated the existence of brominated flame retardants (BFRs, including polybrominated diphenyl ethers (PBDEs) and Tetrabromobisphenol-A (TBBPA)) in housing plastics and PCBs from home appliances collected from various e-waste recyclers in China. These were then analyzed for the potential migration of BFRs from the e-waste components into their recycled products. The results show that both PBDEs and TBBPA were found with high level in most of e-waste samples, indicating that the widespread use of BFRs in home appliances are entering into the end-of-life stage. For the plastics samples, CRT TVs and LCD monitors should be given priority for the control of BFRs. Regarding PBDEs, the dominant congeners of BDE-209 in the plastics samples contributed 90.72-93.54% to the total concentrations of PBDEs, yet there are large variations for PCBs samples: BDE-28, -47, -99, and -153 were also important congeners compositions, except for BDE-209. Compared with previous studies, the BFRs concentrations in current Chinese e-waste are trending to decline. This study also found that BFRs in housing plastics and PCBs will be transferred into the recycled products with other purpose use, and the new products could have highly enriched capacities for BFRs. The obtained results could be helpful to manage e-waste and their components properly in order to minimize associated environmental and health risks of BFRs, particularly for their further reuse.


Assuntos
Resíduo Eletrônico , Retardadores de Chama/análise , China , Monitoramento Ambiental , Éteres Difenil Halogenados , Bifenil Polibromatos
18.
Soft Matter ; 13(9): 1881-1887, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-28180226

RESUMO

An efficient method was developed to encapsulate water insoluble organic particles of Sudan red III (SR) in aqueous suspensions by using a polymerizable cationic gemini surfactant, 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-(propylacrylate dibromide) (AGC16). The AGC16 coated SR microcapsules (AGC16@SR) were prepared by absorption of AGC16 on the surface of SR, followed by in situ homopolymerization (PAGC16). Several measurements, including transmission and scanning electron microscopy, isothermal titration calorimetry, zeta potential, electron paramagnetic resonance and small angle X-ray scattering, were performed to determine the adsorption amount of AGC16, and the layer structures and the molecular assembly mechanism in the AGC16@SR and PAGC16@SR systems, respectively. For comparison purposes, the polymerizable cationic surfactant with one head group and a single alkyl chain, acryloyloxyethyl-N,N-dimethyl-N-cetylammonium bromide (referred to as ASC16), as well as the systems of ASC16@SR and PASC16@SR were also investigated in parallel. It was found that AGC16 molecules and their aggregates were simultaneously assembled into a shell layer, in which the saturated adsorption amount of AGC16 on SR is less than 1/2 that of ASC16, but the assembly layer of AGC16 is more hydrophobic with greater packing tightness compared with that of ASC16. It was also revealed that after in situ homopolymerization, the microcapsule shell becomes more compact. In the case of PAGC16@SR, the layers show higher surface roughness and irregularity compared with that of PASC16@SR. Moreover, the sustained release behavior of SR was also evaluated. The results revealed that PAGC16@SR performed well for SR controlled release, which was sorted by release performance as the following sequence: PAGC16@SR > AGC16@SR > PASC16@SR > ASC16@SR. Thus, the polymerizable cationic gemini surfactant holds substantial potential to be developed as an ideal candidate of soft matter to construct efficient controllable release systems.

19.
J Phys Chem B ; 120(42): 10990-10999, 2016 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-27704826

RESUMO

The adsorption kinetics and equilibrium of amphiphilic dendrimers based on poly(amidoamine) modified with a dodecyl chain, GnQPAMC12 (n represents the generation number), with different generation numbers at a silica-water interface have been investigated. The effect of molecular shape with different charge characteristics on the adsorption kinetics, adsorption isotherms, and the conformation of a self-assembled layer has been elucidated. For the adsorption kinetics, two steps were observed including the adsorption of individual molecules at concentrations below the critical micelle concentration (cmc) and the predominant adsorption of aggregates above the cmc. However, the adsorption isotherm, as a function of the generation number, presented an exceptional characteristic, in which a decrease in adsorption mass with different levels occurred in a high generation of amphiphilic dendrimers, depending on the balance of hydrophobic interaction and electrostatic repulsion. Atomic force microscopy imaging showed that flattened films with pores (spacing) of various shapes and roughness of 3-4 nm were formed, of which the pores (spacing) decreased obviously as the generation number increased. The addition of electrolyte (NaBr) has a great effect on the film morphology formed by the G3QPAMC12 dendrimer adsorbed at the silica-water interface, showing that the film became closer with smaller pores with increased NaBr concentration.

20.
Langmuir ; 32(44): 11485-11491, 2016 11 08.
Artigo em Inglês | MEDLINE | ID: mdl-27755878

RESUMO

The adsorption process of a geminized amphiphilic polyelectrolyte, comprising double elementary charges and double hydrophobic tails in each repeat unit (denoted as PAGC8), was investigated and characterized by means of quartz crystal microbalance with dissipation (QCM-D), ellipsometry, and atomic force microscopy (AFM). By comparison, the self-assembly behaviors of a traditional polyelectrolyte without hydrophobic chains (denoted as PASC1) and an amphiphilic polyelectrolyte with a single hydrophilic headgroup and hydrophobic tail in each repeat unit (denoted as PASC8) at the solid/liquid interface were also investigated in parallel. A two-regime buildup was found in both amphiphilic systems of PASC8 and PAGC8, where the first regime was dependent on electrostatic interactions between polyelectrolytes and oppositely charged substrates, and the rearrangements of the preadsorbed chains and their aggregation behaviors on surface dominated the second regime. Furthermore, it was found that the adsorbed amount and conformation changed as a function of the charge density and bulk concentrations of the polyelectrolytes. The comparison of the adsorbed mass obtained from QCM-D and ellipsometry allowed calculating the coupling water content which reached high values and indicated a flexible aggregate conformation in the presence of PAGC8, resulting in controlling the suspension stability even at an extremely low concentration. In order to provide an insight into the mechanism of the suspension stability of colloidal dispersions, we gave a further explanation with respect to the interactions between surfaces in the presence of the geminized polyelectrolyte.

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