Increase In Water Contact Angle Research Articles

Novel trifluoropropoxy-substituted asymmetric carbazole derivatives as efficient and hydrophobic hole transporting materials for high-performance and stable perovskite solar cells

For highly efficient and stable perovskite solar cells (PSCs), small molecular hole transporting materials (HTMs) with high glass transition temperature, hydrophobicity, excellent film-formation and excellent hole mobility is highly desireable. However, developing a single molecule, which could meet all the above mention properties, is challenging. Herein, novel small molecules were design and synthesized, which show a suitable HOMO energy level and fulfill the above metioned properties simultaneously. For this purpose, we incorporate a hydrophobic trifluoropropoxy-terminal group to diphenylamine in SGT-405(3,6), a carbazole-based promising non-spiro-type small molecular HTM with excellent performance and low-cost, leading to two new HTMs (SGT-405s(C2,CF3) and SGT-405d(C2,CF3)). Among them SGT-405s(C2,CF3) showed an excellent hole mobility of 3.32 × 10–4 cm2 V−1 s−1, a remarkable high Tg of 183 ℃ and increased water contact angle of 87° compared to that of spiro OMeTAD (77.7°). Due to these superior properties, compared to those of spiro-OMeTAD, PSCs based on SGT-405s(C2,CF3) showed a remarkable power conversion efficiency (PCE) of 20.14%, which is higher than that of spiro-OMeTAD (18.97%), together with enhanced long-term and thermal stability. Our work revealed for the first time that trifluoropropoxy is a potential terminal group and an effective strategy for the design of new HTMs possessing superior properties in terms of glass transition temperature, hydrophobicity and film formation, for realizing efficient PSCs with enhanced moisture and thermal stability, simultaneously.

Water-Repellent Characteristics of Beech Wood Coated with Parylene-N.

In recent years, awareness regarding sustainability and the responsible usage of natural resources has become more important in our modern society. As a result, wood as a building material experiences a renaissance. However, depending on the use case, protective measures may be necessary to increase wood’s durability and prolong its service life. The chemical vapor deposition (CVD) of parylene-N layers offers an interesting alternative to solvent-based and potentially environmentally harmful coating processes. The CVD process utilized in this study generated transparent, uniform barrier layers and can be applied on an extensive range of substrates without the involvement of any solvents. In this study, European beech wood samples (Fagus sylvatica L.) were coated with parylene-N using the CVD process, with paracyclophane as a precursor. The aim of the study was to analyze the water absorption of beech wood, in relation to the different layer thicknesses of parylene-N. Therefore, four different coating thicknesses from 0.5 to 40 μm were deposited, depending on the initial amount of precursor used. The deposited layers were analyzed by reflection interference spectroscopy and scanning electron microscopy, and their chemical structures and compositions were investigated by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Due to the chemical structure of parylene-N, the deposited layers led to a significantly increased water contact angle and reduced the water uptake by 25–34% compared to the uncoated reference samples. A linear correlation between layer thickness and water absorption was observed. The coating of wood with parylene-N provides a promising water barrier, even with thin layers.

New promising antimicrobial material based on thermoplastic polyurethane modified with polymeric biocide polyhexamethylene guanidine hydrochloride

New antimicrobial polymer composite based on commercial polyurethane (PU) Laripur®LPR9020 and polymeric biocide polyhexamethylene guanidine hydrochloride (PHMG-Cl) has been prepared by solvent casting method. Modified PU films containing from 1 to 4 wt% of PHMG-Cl were characterized in terms of mechanical, thermal and surface properties, biocide release behavior, as well as antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacterial strains. The results of mechanical testing indicate that the introduction of PHMG-Cl did not cause noticeable changes in the tensile strength of PU films, but improved their elasticity by at least 20–30%. The surface of PU/PHMG-Cl films was found to possess significantly higher hydrophobicity than neat polymer that is manifested in sharply increased water contact angle value from 72° for neat PU to 95° for PU/PHMG-Cl (2%). According to thermogravimetric analysis data, PU/PHMG-Cl composites are thermally stable to at least 300 °C which indicate their availability for melt processing by common methods. The results of differential scanning calorimetry showed reduction of both glass transition and melting temperatures of PU by more than 7 °C when contained only 1% of PHMG-Cl.Gradual release of polymeric biocide from modified PU films into water has been detected spectrophotometrically. The total biocide release ratio was found to be in the range from 29% to 48% after 50 hours immersion, depending on its content in polymer composite. PU/PHMG-Cl films showed much lower leaching rate into physiological saline solution compared to pure water (from 10% to 21% after 50 hours), which may be caused by poor solubility of polymeric biocide in sodium chloride solutions.The study of antibacterial activity of modified PU films using both disc agar diffusion and contact methods indicate high efficacy against tested microorganisms when contained 3% of polymeric biocide. So, this approach, based on the modification of PU resin with polymeric biocide PHMG-Cl, has been discussed in terms of potential medical applications when biocide release system or contact active material are necessary.

Physicochemical and antimicrobial properties of chitosan composite films incorporated with glycerol monolaurate and nano-TiO2

Antimicrobial composite films for active food packaging were developed based on chitosan, glycerol monolaurate (GML), and nano-TiO2. The rheological, morphological, physical, and antimicrobial properties of chitosan-based composite films doped with GML and nano-TiO2 were investigated. All film-forming solutions showed typical pseudoplastic properties, and the viscosity of film-forming solutions increased after the addition of GML. The chitosan films incorporated with GML were transparent, and the transparency of films decreased after adding nano-TiO2. The chitosan-TiO2 composite film containing 1.5% GML exhibited the highest UV–vis barrier properties. Scanning electron microscopy images showed that the surface of films containing GML presented a rough structure, and the changes in the microstructure of films were also confirmed by the results obtained using atomic force microscopy. The addition of GML and nano-TiO2 improved the water-resistance and the barrier properties of the chitosan film. Increasing the GML content resulted in increased water contact angle and decreased the permeability of water vapor, oxygen, and carbon dioxide of composite films. Moreover, the incorporation of GML reduced the tensile strength of composite films. Fourier transform infrared spectroscopy and X-ray diffraction indicated that the interaction among chitosan, GML, and nano-TiO2 could be established through non-covalent bonds. Notably, chitosan-based composite films doped with GML and nano-TiO2 exhibited strong antimicrobial activity, and the film containing 1.5% GML was the most effective. The structure of bacterial cells was injured by the composite films. Overall, the developed composite films exhibited excellent functional properties and could be potential targets for bioactive packaging.

Water resistance and characteristics of asphalt surfaces treated with micronized-recycled-polypropylene waste: Super-hydrophobicity

Research studies have shown that superhydrophobic (SH) surfaces possessed better and enhance water-resistance, anti-icing, anti-corrosion, and even self-cleansing properties than non-SH surfaces. Although asphalt binder is widely used for waterproofing and damp-proofing application, it was established that asphalt binder is only hydrophobic not SH. The potential use of micronized recycled-polypropylene (RPP) to boost the properties of the asphalt binder to SH has been examined in this study. Micronized RPP were obtained by milling and sieving of polypropylene plastic waste. Two different sizes of the micronized RPP (maximum size of 177 and 149 µm) were thermally fused on to the surface of asphalt substrates at 100 °C, for curing durations of 25, 40, and 55 min. Surface profile and water contact angle (WCA) of the RPP-treated asphalt substrates were evaluated using 3D profilometer and video contact angle measurements respectively. Surface morphology of the micronized RPP and the treated asphalt substrates was also examined using scanning electron microscope (SEM). RPP-treatment of the asphalt substrates resulted in their transformation from hydrophobic to SH WCA range. Highest improvement in average WCA of 156° from 110° (41.81% increase) was observed for substrate treated with micronized RPP having maximum size of 177 µm, and cured for 55 min. This corresponds to 86.81% drop in work of adhesion. The increase in WCA was found to be due to stretching and profile transformation of the asphalt substrates surface, which occur as a result of the RPP particles embedment. Statistical analysis showed that both the curing duration and size of the RPP have significant influence on the profile and the WCA of the treated asphalt substrates. Re-evaluation of the treated asphalt substrates after 12 months of exposure revealed that higher mass accumulation of the RPP on the asphalt surface yielded more stable WCA over time.

Surface Modification of (Non)-Fluorinated Vitrimers through Dynamic Transamination.

Surface modifications are typically permanent in shape and chemistry. Herein, vinylogous urethane (VU) chemistry is presented as an easily accessible and versatile platform for rapid, facile, and reworkable surface modification. It is demonstrated that both physical and chemical post-modification of permanent, yet dynamic elastic polymer networks are achieved. Surface patterns with high regularity are created, both via a straightforward replication process using a polydimethylsiloxane stamp (resolution ca. 10-100µm) as well as using thermally activated nano-imprint lithography (NIL) to form hole, pillar, or line patterns (ca. 300nm) in elastic VU-based vitrimers. The tunable, rapid exchange allows patterning at 130°C in less than 15min, resulting in an increased water contact angle and surface-structure induced light reflection. Moreover, it is also demonstrated that the use of a single dynamic covalent chemistry makes it possible to strongly adhere to fluorinated and non-fluorinated materials based on incompatible matrices, causing cohesive failure in a peel test. In a topography scan, the visibly transparent interface is shown to possess a continuous phase without a gap, while maintaining distinctively separated (non)-fluorinated domains. Finally, this approach allowed for a straightforward coating of a non-fluorinated material with a fluorinated monomer to minimize the overall fluorinated content.

Explication of hydrophobic silica as effective pore former for membrane fabrication

Membrane development is one of the key aspects to enhance the productivity of a filtration process. This study evaluates a hydrophobic silica as pore former for fabrication of polyvinylidene difluoride (PVDF) membrane for liquid based filtration and compare it with a hydrophilic silica. Membranes incorporated with hydrophobic (M-series) and hydrophilic silica (N-series) with loadings of 1, 2 and 3 wt% in the dope solution were fabricated, characterized and subjected to filtration tests using feeds of pure water, raw wastewater, secondary effluent, microalgae solution and activated sludge. Results show that the hydrophobic silica remained within the membrane matrix (7.24% of elemental Si by EDS), almost three-fold higher than the hydrophilic silica (2.48%). It turned the membrane surface to be more hydrophobic ascribed by increasing water contact angle from 87° from the pristine PVDF membrane up to 97° for the membrane with the highest loading of hydrophobic silica. On the other hand, the addition of hydrophilic decreased the contact angle down to 67° for the membrane with the highest loading. Loading hydrophobic silica enhanced the dope solution viscosities up to 1825–2000 cP, upon dropwise addition of nonsolvent (water), whereas the viscosity remained at 880–950cP for the hydrophilic silica. Addition of hydrophobic silica increased the number of surface pore without significantly altering the pore size of about 0.12 µm. On the other hand, an increase in the pore size (up to 0.33 µm) was observed when hydrophilic silica was added. Despite the smaller pore size, the pure water permeance of the hydrophobic silica loaded membranes (450–984 L/m2hbar) outperformed the hydrophilic silica loaded membranes (420–600 L/m2hbar) due to their higher surface porosities thanks to the higher number of surface pores. The filtration results of multiple feeds showed the advantages of loading more hydrophobic silica in improving the hydraulic performance. The findings demonstrate the efficacy of hydrophobic silica as pore former in PVDF membrane fabrication.

Fabrication of transparent silica-silica nanotube/PFTS nano-composite thin films with superhydrophobic, oleophobic, self-cleaning and anti-icing properties

Light on optoelectronic devices and solar panels is lost both through reflection at the air/glass interface of the cover glass and through scattering or absorption by accumulated dust, dirt and ice. Therefore, the transparent superhydrophobic thin films can resolve these problems. In this research, silica-silica nanotube nanocomposite thin films were applied on glass substrates by a sol–gel method. To modify the nanocomposite thin film, the samples were immersed in a PFTS solution. The morphology, chemical composition and transparency of the thin films were investigated using FE-SEM, FTIR and UV–VIS–NIR spectrophotometer methods. The water and oil contact angles on the thin film surfaces was measured using a contact angle analyzer. The self-cleaning and stability of the thin films were investigated. The water contact angle results indicated that silica nanotube/PFTS thin films increased water contact angle of the glass substrate from 16° to 152°. The transmittance of the silica-silica nanotube/PFTS coated glass substrate was measured as 87% at 550 nm. The icing test results showed that superhydrophobic coating increased icing time during ice formation on the glass surface from 102 to 874 s.

The effect of ambient air plasma generated by coplanar and volume dielectric barrier discharge on the surface characteristics of polyamide foils

This study targeted wettability and adhesion enhancement of polyamide (PA) foil surface by plasma treatment at atmospheric pressure. Volume dielectric barrier discharge (VDBD) and diffuse coplanar surface barrier discharge (DCSBD) were applied in ambient air using exposure times 0.25–2 s. Water contact angle (WCA) measurements proved that both plasma sources achieved significant wettability improvement of PA 6 foil surface immediately after treatment. However, the durability of this hydrophilic effect was much more pronounced with the DCSBD, compared to the VDBD. The lowest registered drop of WCA after DCSBD treatment was from the initial 65° to 28°, which even after one month of storage recovered only to 44°. In contrast, the VDBD treatment at similar parameters resulted in the WCA increase from 45° to 54° already after the first day of ageing. The XPS analysis of oxygen-based polar functional groups incorporated onto the treated PA 6 surface proved higher efficiency of DCSBD plasma. Moreover, the degree of surface oxidation was raised by increasing DCSBD's input power. Tape peel test revealed adhesion improvement achieved only with DCSBD, which had a growing tendency with increasing exposure time and input power. SEM did not show any noticeable damage of surface after the applied plasma treatments.

Effects of the curing atmosphere on the structures and properties of polybenzoxazine films

The effects of four different curing atmospheres, i.e., static air, circulating air, nitrogen and vacuum, on the polymerization mechanism, chemical structure, hydrogen bonding, mechanical property, thermal property, water contact angle, etc., of the polybenzoxazine films were systematically studied. It was found that curing in air caused more oxidation and decomposition, generating more benzoquinones, carbonyl groups and iminium ions in the resultant polybenzoxazine films. Consequently, the films cured in air were less cross-linked, darker in color and more brittle. The films cured in static air (SA) showed tensile strength and elongation at break of 12.59 MPa and 2.16%, respectively, which were 61.24 MPa and 2.74% lower than those of the films cured in nitrogen (N2). Moreover, it was demonstrated that more intramolecular rigid –OH···N hydrogen bonding was formed in the films cured in air, which was believed to be the fundamental reason for the lower chemical cross-linking density and poorer toughness. Nevertheless, these films showed higher char yield due to the formation of more thermally stable groups in oxidation process. Further investigation on chemical structures, hydrogen bonding and water contact angles of the upper and lower surfaces of the films revealed that the upper surfaces were more inclined to be oxidized and decomposed during curing and more intramolecular hydrogen bonding (–OH···N HB) was formed on upper surfaces, which led to increased water contact angles.

Aging effect of plasma-treated carbon surfaces: An overlooked phenomenon

Carbon surfaces become significantly activated with plasma treatment enhancing the surface energy, wettability, and bio-conjugation. However, the activated surfaces are influenced by aging effect or reorientation phenomenon, a rarely reported occurrence, that refers to the loss of surface activity with time. Generated plasma-activated surface functional groups suffer from a brief shelf life as they reorient themselves to occupy lower states of energy. This study thoroughly assesses plasma-treated pyrolyzed carbon platforms with O2, N2, and Ar plasma radiations over 3 weeks. Pristine, immediately treated, and aged carbon samples were analyzed by SEM, AFM, WCA, and XPS to observe physical and chemical changes of the surfaces. Moreover, the electrochemical analyses demonstrated radical alterations of the surface characteristics immediately after the treatment; an activation which did not last long regardless of the plasma choice. With time, clear signs of surface inactivation were recorded manifesting in the form of decreased roughness, increased water contact angle, and major alterations of surface chemical composition, capacitance, and resistance. Our observations confirm that the plasma-treated carbon samples return to the pristine surface characteristics within a brief period of time thus demonstrating the loss of surface activity irrespective of the treatment choice.

Surface Laser-Marking and Mechanical Properties of Acrylonitrile-Butadiene-Styrene Copolymer Composites with Organically Modified Montmorillonite.

In this study, organically modified montmorillonite (OMMT) was prepared by modifying MMT with a cationic surfactant cetyltrimethylammonium bromide (CTAB). The obtained OMMT of different loading contents (1, 2, 4, 6, and 8 wt %) was melt-blended with poly(acrylonitrile-co-butadiene-co-styrene) (ABS) to prepare a series of ABS/OMMT composites, which were laser marked using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser beam of 1064 nm under different laser current processes. X-ray diffraction (XRD), color difference spectrometer, optical microscope, water contact angle tests, scanning electron microscope (SEM), and Raman spectroscopy were carried out to characterize the morphology, structure, and properties of the laser-patterned ABS composites. The effects of the addition of OMMT and the laser marking process on the mechanical properties of ABS/OMMT composites were investigated through mechanical property tests. The results show that the obtained ABS/OMMT composites have enhanced laser marking performance, compared to the ABS. When the OMMT content is 2 wt % and the laser current intensity is 9 A, the marking on ABS composites has the highest contrast (ΔE = 36.38) and sharpness, and the quick response (QR) code fabricated can be scanned and identified with a mobile app. SEM and water contact angle tests showed that the holes, narrow cracks, and irregular protrusion are formed on the composite surface after laser marking, resulting in a more hydrophobic surface and an increased water contact angle. Raman spectroscopy and XRD indicate that OMMT can absorb the near-infrared laser energy, undergo photo thermal conversion, and cause the pyrolysis and carbonization of ABS to form black marking, and the crystal structure itself does not change significantly. When the 2 wt % of OMMT is loaded, the tensile strength, elongation at break, and impact strength of ABS/OMMT are increased by 15, 20, and 14%, respectively, compared to ABS. Compared with the unmarked ABS/OMMT, the defects including holes and cracks generated on the surface of the marked one lead to the decreased mechanical property. The desirable combination of high contrast laser marking performance and mechanical properties can be achieved at an OMMT loading content of 2 wt % and a laser current intensity of 9 A. This research work provides a simple, economical, and environmentally friendly method for laser marking of engineering materials such as ABS.

Effect of sulfur nanoparticles on properties of alginate-based films for active food packaging applications

Sulfur nanoparticles (SNPs) were prepared and embedded in calcium cross-linked alginate films in varying concentration, and their effect on the functional properties of the films were studied. The FE-SEM image showed uniform dispersion of up to 2 wt% of SNPs, above which aggregation was observed. The addition of 2 wt% of SNPs showed the best results of the tensile and water vapor barrier properties, with an increase in 12% and 41%, respectively. The surface color of the films changed significantly by the addition of SNPs with a decrease in transparency. However, the UV barrier properties showed a considerable increase of 99%. In addition, the incorporation of SNPs increased the hydrophobicity of the film, which was evident by the increased water contact angle and decreased moisture content of the film, as indicated by the thermal analysis results. The antimicrobial activity of alginate/SNPs composite film was tested against foodborne pathogenic bacteria, E. coli and L. monocytogenes. The nanocomposite film did not completely destroy E. coli but showed a bacteriostatic activity to reduce the 60% of bacterial colonies. However, the activity against L. monocytogenes was found to be highly bactericidal at the highest nanoparticle concentration, where a 100% bacterial elimination was observed after 12 h of exposure. Thus, the alginate/SNPs composite film can be used for the packaging of frozen foods with high moisture content that are susceptible to Listeria monocytogenes contamination, such as meat products.

Designing superhydrophobic and flame retardant photo-cured hybrid coatings

The study investigates the effect of the addition of phenyl phosphine oxide (DAPPO) with acrylate functionality, polyhedral oligomeric silsesquioxane (POSS) (acr-POSS) with acrylate functionality and 1H,1H,2H,2H-Perfluorodecyl acrylate (PFOA) on the superhydrophobicity and fire-resistance of photo-curable urethane-acrylate coatings. The addition of DAPPO to urethane-acrylate (50 wt.%) improved flame resistance. The additions of acr-POSS and PFOA improved surface hydrophobicity through increasing surface roughness by the addition of acr-POSS and decreasing surface energy by the addition of PFOA. The flammability and surface properties of the photo-curable hybrid coatings were evaluated by measuring limiting oxygen index (LOI) and water contact angle (WCA), respectively. Compared with the only urethane-acrylate-containing coating, the final hybrid coating had an increased water contact angle from 72.7°±2 to 147.2°±2 and increased LOI from 17,0 ± 0.08–24,3 ± 0.08. In the final hybrid coating, extinguishing occurred in less than 10 s.

Self-cleaning of glass surface to maximize the PV cell efficiency

Photovoltaic (PV) modules are widely used for harnessing solar energy which ensure maximum output when their glass surface is clean. However, PV modules are open to dust, grime and other contaminations which get deposited on their surface causing reduction in transmittance and hence their efficiency reduces. It is therefore required to clean the glass surface of PV modules time to time either manually by labor or using some special arrangements such as automated systems. However, these techniques are either laborious or require extra energy. Therefore, another solution to offset such complications is to use chemical coatings which ensure self-cleaning of glass surface by increasing water contact angle. In the present study, two types of water repellent chemicals (such as trimethylchlorosilane and hexamethyldisilazane) have been used to coat the glass surface using dip coating technique. The performance of such coated glass slides has been investigated using some important characterization techniques, such as finding transmittance by spectrophotometer and measuring water contact angle using a high resolution camera. Moreover, the self-cleaning effect has been observed using a microbalance to measure dust on coated glass exposed to open atmosphere and compared with uncoated glass. The results revealed that these coatings have increased the water contact angle up to 149% which reduces friction between the glass surface and water droplets. Moreover, the friction reduction helps in mobility of water droplets which in turn can easily carry out dust along with them, thus improving the efficiency of PV module.

Exploring in situ integration of pongamia oil to improve barrier properties of polyurethane coatings

AbstractPolyurethane coatings have been the focus of continuous innovation, such as bio‐based coatings and self‐healing coatings. This study investigates the route achieving superior coatings by in situ integration of pongamia oil during the curing process. Stronger urethane and carbonyl bonds for these oil‐modified coatings are observed using Fourier transform infra‐red spectroscopy. Thermogravimetric analysis reveals an increase in their thermal stability. A sustained high coating resistance and an increased Bode impedance (by ∼102 Ω cm2) for the oil‐modified coatings is observed using electrochemical impedance spectroscopy, which is corroborated by the cyclic corrosion test. Scanning electron microscopy depicts a roughened coating morphology with an increased water contact angle due to the integrated oil‐polyurethane polymer chains. Further, a preliminary computational fluid dynamics confirms this inhibited electrolyte mass flow through an oil‐modified coating with denser regions as compared to a clear coating. A consolidated schematic model incorporating the experimental and simulation results is proposed.

Cotton Fiber-Based Sorbents for Treating Crude Oil Spills.

Wood and plant fibers have been studied as natural sorbent materials for treating aquatic oil spills; however, the effectiveness of these materials is limited by their tendency to absorb water as well as oil. Chemical pretreatment of cotton fibers with fatty acids was examined as a means of enhancing the performance of cotton as a sorbent for crude oil. A raw cotton fiber was chemically modified with C18 fatty acid by simple leaving group chemistry. Free surface hydroxyl groups were modified with long alkyl chains to create fibers that displayed increased water contact angles, indicative of a significant decrease in surface energy. The increased affinity for oil and corresponding repulsion of water on the individual modified fibers translated to greater sorption of oil and rejection of water by loose assemblies of fibers (i.e., balls or yarn) when compared with unmodified cotton. X-ray diffraction (XRD) pattern, Fourier transform infrared (FT-IR), 13C cross-polarization/magic angle spinning solid-state nuclear magnetic resonance (CP/MAS SSNMR), and scanning electron microscopy (SEM) showed that cotton fibers were significantly exfoliated by the intercalation of C18 fatty acids about 2.4 times in its diameter. In the presence of seawater, the highly oleophilic C18 fatty acid-modified cotton fiber showed a maximum oil sorption capacity of 35.58 g per gram of fiber, about ∼49% greater than that of the corresponding raw cotton fiber.

Modification of poly (lactic acid) through the incorporation of gum rosin and gum rosin derivative: Mechanical performance and hydrophobicity

AbstractThe modification of PLA by melt compound with gum rosin (GR) and pentaerythritol ester of GR (PEGR) was investigated by studying the mechanical and thermal performance, blends morphology, wettability, and water absorption. Standard testing specimens for characterization were made at a variate resin content of 5, 10, and 15 part per hundred resin (phr) and manufactured by injection molding. It was found that GR and PEGR had a lubricating effect in PLA polymeric chains, resulting in a remarkable increase of 790 and 193% in melt flow index with only 5 phr GR and PEGR contents, respectively. A significant change in more than 10° of increasing water contact angle was observed for PLA with 15 phr PEGR. Thermogravimetric analysis reveals that PEGR led to delayed PLA degradation/decomposition process to higher temperature, increasing the onset temperature (T5%) in more than 7°C for PLA with 15 phr PEGR.

Novel low‐dielectric‐constant fluorine‐functionalized polysulfone with outstanding comprehensive properties

AbstractIn this work, a series of fluorine‐functionalized polysulfone (F‐PSU) copolymers with intrinsic low dielectric constants (low ε) are reported, which are derived from the polycondensation reaction of 4,4′‐dichlorophenyl sulfone with bisphenol A and bisphenol F (BPF) compounds. The resulting F‐PSU copolymers show high glass transition temperatures (Tg) varying from 187 to 201 °C and are thermally stable up to 500 °C under an N2 atmosphere. The introduction of BPF units into the PSU copolymers imparts enhanced hydrophobic properties to the F‐PSU films with increased water contact angle values from 66.2° to 93.7°. Moreover, the dielectric constant and dielectric loss of the F‐PSU (sample V) film are as low as 2.2 and 0.003 at 1 kHz, respectively. Interestingly, the dielectric properties are relatively stable to near the glass transition temperature, which is because of the existence of BPF structures in the molecular backbone. Furthermore, the F‐PSU copolymers are soluble in common solvents and can be readily fabricated into flexible transparent films by the spin casting method. © 2020 Society of Chemical Industry

Superhydrophobic diamond-coated Si nanowires for application of anti-biofouling’

The effect of the surface wettability of plasma-modified vertical Si nanowire array on the bio-fouling performance has been investigated. The Si nanowires prepared by a metal-assisted chemical etching technique exhibit a super-hydrophilic surface. The treatment in CH4/H2 gas plasma environment leads to the decoration of graphite and diamond nanoparticles around Si nanowires. The detailed interface between graphite/diamond and Si nanowire was characterized by HRTEM technique. These surface-modified nanowire samples show an increased water contact angle with ultrananocrystalline diamond decorated ones being superhydrophobic. The immersion test in chlorella solution reveals that the diamond-coated Si nanowires possess the least attachment of chlorella in comparison with other Si nanowires. This result confirms that the coating of Si nanowires with diamond nanoparticles shows the best behavior in anti-biofouling. Importantly, this work provides a method fabricated super-hydrophobic surface for the application of biofouling prevention.