Hydrophobic Chemical Groups Research Articles

Superhydrophobic ceramic membrane coupled with a biphasic solvent for efficient CO2 capture

An innovative strategy was proposed by integration of membrane contactor (MC) with biphasic solvent for efficient CO2 capture from flue gas. The accessible fly ash-based ceramic membrane (CM) underwent hydrophobic modification through silane grafting, followed by fluoroalkylsilane decoration, to prepare the superhydrophobic membrane (CSCM). The CSCM significantly improved resistance to wetting by the biphasic solvent, consisting of amine (DETA) and sulfolane (TMS). Morphological characterizations and chemical analysis revealed the notable enhancements in pore structure and hydrophobic chemical groups for the modified membrane. Predictions of wetting/bubbling behavior based on static wetting theory referred the liquid entry pressure (LEP) of CSCM increased by 20 kPa compared to pristine CM. Compared with traditional amine solvents, the biphasic solvent presented the expected phase separation. Performance experiments demonstrated that the CO2 capture efficiency of the biphasic solvent increased by 7%, and the electrical energy required for desorption decreased by 32%. The 60-h continuous testing and supplemental characterization of used membrane confirmed the excellent adaptability and durability of the CSCMs. This study provides a potential approach for accessing hydrophobic ceramic membranes and biphasic solvents for industrial CO2 capture.

Fabrication of highly luminescent and thermally stable composites of sulfur nanodots through surface modification and assembly.

Sulfur nanodots (S-dots) have emerged as a promising luminescent material to excel over traditional heavy metal-based quantum dots. However, their relatively low emission efficiency and poor thermal stability in the solid state have limited their wide applications in photoelectric devices. In this work, highly luminescent, with a photoluminescence quantum yield higher than 50%, and thermally stable composites of S-dots were produced through modulating their surface states and aggregation behaviors by introducing pyromellitic dianhydride (PMDA) and benzoyleneurea (BEU), respectively. PMDA eliminated the relatively short-lived surface states and defects on the surface of S-dots and BEU regulated the aggregation states and facilitated the energy transfer from BEU to S-dots. The as-obtained composites also showed significantly improved thermal stability compared to S-dots, aided by the hydrophobic chemical groups and dense matrix of PMDA and BEU, which extended their applications in fabricating light-emitting diodes. Our presented results provide a new approach to produce highly luminescent S-dots, which widen their applications in the fields of bioimaging, sensing, photoelectric devices, and environmental science.

Design of Cell-Adhesive Shellac Derivatives and Endowment of Photoswitchable Cell-Adhesion Properties.

The emergence of new biodegradable cell-adhesion materials is an attractive topic in biomaterial chemistry, particularly for the development of cell incubation scaffolds and drug encapsulation materials used in in situ regenerative therapy. Shellac is a natural resin with unique film-forming properties and high miscibility with various chemicals, in addition to being biodegradable and nontoxic to biological systems. However, since native shellac does not adhere to mammalian cells, there have been no reports of using shellac to develop cell-adhesive biomaterials. In this study, we report on the development of cell-adhesive shellac derivatives through slight chemical modification. Shellac is a mixture of oligoesters that consists of hydroxyl fatty acids and resin acids, and therefore, all oligomers have one carboxylic acid group at the terminal. We discovered that a simple modification of hydrophobic chemical groups, particularly those containing aromatic groups in the ester form, could dramatically improve cell-adhesion properties for mammalian cells. Furthermore, by using photocleavable esters containing aromatic groups, we successfully endowed photoswitchable properties in cell adhesion. Given that shellac is a low-cost, biodegradable, and nontoxic natural resin, the modified shellacs have the potential to become new and attractive biomaterials applicable to in situ regenerative therapy.

Unraveling the Influence of K280 Acetylation on the Conformational Features of Tau Core Fragment: A Molecular Dynamics Simulation Study.

Abnormal aggregation of the microtubule-associated protein Tau is closely associated with tauopathies, including Alzheimer’s disease and chronic traumatic encephalopathy. The hexapeptide 275VQIINK280 (PHF6*), a fibril-nucleating core motif of Tau, has been shown to play a vital role in the aggregation of Tau. Mounting experiment evidence demonstrated the acetylation of a single-lysine residue K280 in the PHF6* was a critical event for the formation of pathological Tau amyloid deposits. However, the underlying mechanisms by which K280 acetylation affects Tau aggregation at the atomic level remain elusive. In this work, we performed replica exchange molecular dynamics simulations to investigate the influence of acetylation of K280 on the aggregation of PHF6*. Our simulations show that acetylation of K280 not only enhances the self-assembly capability of PHF6* peptides but also increases the β-sheet structure propensity of the PHF6*. The inter-molecular interactions among PHF6* peptides are strengthened by the acetylation of K280, resulting in an increased ordered β-sheet-rich conformations of the PHF6* assemblies along with a decrease of the structural diversity. The residue-pairwise contact frequency analysis shows that K280 acetylation increases the interactions among the hydrophobic chemical groups from PHF6* peptides, which promotes the aggregation of PHF6*. This study offers mechanistic insights into the effects of acetylation on the aggregation of PHF6*, which will be helpful for an in-depth understanding of the relationship between acetylation and Tau aggregation at the molecular level.

Fast enhancement on hydrophobicity of poplar wood surface using low-pressure dielectric barrier discharges (DBD) plasma

The hydrophilicity of woody products leads to deformation and cracks, which greatly limits its applications. Low-pressure dielectric barrier discharge (DBD) plasma using hexamethyldisiloxane was applied in poplar wood surface to enhance the hydrophobicity. The chemical properties, micro-morphology, and contact angles of poplar wood surface before and after plasma treatment were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDX), atomic force microscopy (AFM), and optical contact angle measurement (OCA). Moreover, tinfoil film was used as the base to reveal the enhancement mechanism. The results showed that hexamethyldisiloxane monomer is first broken into several fragments with active sites and hydrophobic chemical groups. Meanwhile, plasma treatment results in the formation of free radicals and active sites in the poplar wood surface. Then, the fragments are reacted with free radicals and incorporated into the active sites to form a network structure based on the linkages of Si-O-Si and SiOC. Plasma treatment also leads to the formation of acicular nano-structure in poplar wood surface. These facts synergistically enhance the hydrophobicity of poplar wood surface, demonstrating the dramatically increase in the equilibrium contact angle by 330%.

Ordered Micro/Nanostructures with Geometric Gradient: From Integrated Wettability "Library" to Anisotropic Wetting Surface.

Geometric gradients within ordered micro/nanostructures exhibit unique wetting properties. Well-defined and ordered microsphere arrays with geometric gradient (OMAGG) are successfully fabricated through combining colloidal lithography and inclined reactive ion etching (RIE). During the inclined RIE, the graded etching rates in vertical direction of etcher chamber are the key to generating a geometric gradient. The OMAGG can be used as an effective mask for the preparation of micro/nanostructure arrays with geometric gradient by selective RIE. Through this strategy, a well-defined wettability "library" with graded silicon cone arrays is fabricated, and the possibility of screening one desired "book" from the designated wettability "library" is demonstrated. Meanwhile, the silicon cone arrays with geometric gradient (SCAGG) can be applied to control the wetting behavior of water after being modified by hydrophilic or hydrophobic chemical groups. Based on this result, a temperature-responsive wetting substrate is fabricated by modifying poly n-isopropyl acrylamide (PNIPAM) on the SCAGG. These wettability gradients have great potential in tissue engineering, microfluidic devices, and integrated sensors.

Controlled hydrophilic/hydrophobic property of silica films by manipulating the hydrolysis and condensation of tetraethoxysilane

Controlling surface wettability is an important road to afford the materials with anticipated functional properties, such as anti-fogging, anti-icing and self-cleaning. Manipulating the surface topography and chemical composition is a promising strategy to achieve the expected functional properties. Herein, we concurrently realized the control of surface topography and chemical composition of the film materials via exploiting a simply one step method through the hydrolysis and condensation of tetraethoxysilane (TEOS) to form silica sol-gel films. By adjusting the amount of water, TEOS and basic catalyst, the hydrophilic or hydrophobic chemical groups on the silica particles surface were well controlled. As a result, the sol-gel silica films exhibiting a controllable and wide range contact angles from 7.7±1.5° to 121.6±1.8° were obtained by this simple one-step method. The inorganic nonmetallic, metallic and polymer materials surface could maintain different wettability by the modification of controlled wettability silica films. Furthermore the wettability of silica film could be easily changed from hydrophobicity to superhydrophilicity through a heat-treatment due to the decrease of hydrophobic chemical groups conforming to the time-temperature equivalence principle. Raising temperature and extending holding time were equivalent to chemical bond breaking which result in the wettability change of silica films.

A novel fabrication of a superhydrophobic surface with highly similar hierarchical structure of the lotus leaf on a copper sheet

A novel and facile avenue was developed to successfully fabricate a regular hierarchical surface structure on a copper sheet via the combination of polydimethylsiloxane (PDMS) template and chemical etching method in this paper. The as-prepared hierarchical surface structure was comprised of uniform-sized microprotrusions and nanostructures which was similar to the natural lotus leaf. After modified by stearic acid, the surface was covered with a layer of hydrophobic chemical groups and became superhydrophobic. The values of its water contact angle and sliding angle were about 153° and 7°, respectively. Its wettability kept rather stable when it was exposed to humid conditions for 3 months. This study provides a new way to fabricate uniform surface microstructures that are highly similar to natural biological surfaces on metal materials.

Modificação das propriedades das fibras de curauá por acetilação

Nos compósitos cimentíceos as fibras vegetais podem sofrer vários graus de degradação quando expostas ao ambiente alcalino. O meio alcalino degrada os componentes macromoleculares das fibras, principalmente pela solubilização da lignina e a desfibrilação da celulose, comprometendo suas propriedades físicas e mecânicas. A resistência das fibras vegetais ao ataque alcalino pode ser aumentada por meio de tratamentos químicos superficiais como a acetilação que apresenta capacidade de reduzir a natureza higroscópica de compostos lignocelulósicos pela introdução de grupos funcionais hidrofóbicos em sua estrutura química. Objetivou-se, então neste trabalho, a aplicação do tratamento de acetilação em diferentes níveis, visando melhorias na durabilidade das fibras. O tratamento de acetilação nas fibras de curauá foi aplicado em diferentes temperaturas e tempos reacionais e sua eficiência, considerando-se a redução da hidrofilicidade e a manutenção do desempenho físico-mecânico das fibras, foi avaliada pelos ensaios de absorção de água por imersão, resistência mecânica, espectroscopia de infravermelho, microscopia eletrônica de varredura, análise termogravimétrica e difratometria de raios-x. Quando acetiladas, as fibras de curauá apresentaram absorções até 55% menores que nas fibras não tratadas. As perdas na resistência mecânica foram próximas aos 52%. O tratamento de acetilação agregou grupos químicos hidrofóbicos na composição e alterou o caráter cristalino das fibras.

Hydrophobic Gating in Synthetic Nanopores

In nature, nanopores play a critical role in a number of vital biological functions and understanding this role is just as critical. These pores can be ion selective based on their size and/or surface charge, but further functionality is achieved by modulating, or gating, their conductance state. The conductivity of a particular nanochannel can be controlled in a number of ways, including mechanically, chemically and electrically. By studying these phenomena in model systems, we may be able to take large steps towards understanding the underlying fundamental physics phenomena behind these mechanisms. Here, we present what we believe to be the first study to show the gating of a synthetic channel based on its hydrophobicity, which has been observed to be a natural gating mechanism in mechanosensitive channels.Using nanopores prepared in polyethylene terephthalate (PET) by the track-etching technique, we show that it is possible to decorate the pore surface with hydrophobic chemical groups and that these significantly alter the properties of the pore. Prior to modification, aqueous electrolytic solutions are able to conduct readily through the pore, but afterwards, the pore demonstrates closed and open states. This behavior is also observed to be voltage dependent. Increasing voltage increases the probability of the pore to be in the open states. There is also a voltage range where the pore does not conduct at all. The hydrophobic gating was studied as a function of pore diameter and charge of the residual groups.

Hybrid Layer as a Dentin‐Bonding Mechanism

A number of mechanisms (both mechanical and chemical) have been proposed as the cause of dentin adhesion. Extensive research in Japan during the past 10 years has shown that strong, long-lived bonds between resin and living dentin will form when a monomer such as 4-META, which contains both hydrophilic and hydrophobic chemical groups, penetrates the tissue and polymerizes in situ. This resin-impregnation creates a transitional "hybrid" layer, that is neither resin nor tooth, but a hybrid of the two. The thin layer of resin-reinforced dentin locks the two dissimilar substances together on a molecular level, sealing the surface against leakage and imparting a high degree of acid resistance.