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Switchable mechanically induced changes in the wetting behavior of surfaces are of para-mount importance for advanced microfluidic, self‐cleaning and biomedical applications. In this work we show that the well‐known polydimethylsiloxane (PDMS) elastomer develops self‐patterning when it is coated with nanostructured TiO2 films prepared by physical vapor deposition at glancing angles and subsequently subjected to a mechanical deformation. Thus, unlike the disordered wrinkled surfaces typically created by deformation of the bare elastomer, well‐ordered and aligned micro‐scaled grooves form on TiO2/PDMS after the first post‐deposition bending or stretching event. These regularly patterned surfaces can be reversibly modified by mechanical deformation, thereby inducing a switchable and reversible wetting petal effect and the sliding of liquid droplets. When performed in a dynamic way, this mechanical actuation produces a unique capacity of liquid droplets (water and diiodomethane) transport and tweezing, this latter through their selective capture and release depending on their volume and chemical characteristics. Scanning electron and atomic force microscopy studies of the strained samples showed that a dual‐scale rough-ness, a parallel alignment of patterned grooves and their reversible widening upon deformation, are critical factors controlling this singular sliding behavior and the possibility to tailor their response by the appropriate manufacturing of surface structures. European Union 899352 Ministerio de Ciencia e Innovación PID2019- 110430GB-C21, PID2019-109603RA-I0, MAT2013-40852-R, MAT2013- 42900-P Ministerio de Economía y Competitividad 201560E055 Junta de Andalucía AT17-6079, P18-RT-3480

Herein, we report a method for in situ generation of N-aryliminium ions via reactions of N,N-dimethylanilines with diiodomethane. We used the method to prepare tetrahydroquinolines via one-pot three-component reactions between N,N-dimethylanilines, diiodomethane, and olefins. This transformation involves initial reaction of the aniline with diiodomethane to form an iodomethylammonium salt, which undergoes fragmentation accompanied by elimination of methyl iodide to give an N-aryliminium ion, which is trapped by the olefin via [4 + 2] cycloaddition to give the final product. This method for generating N-aryliminium ions requires neither a catalyst nor a strong oxidant, suggesting that it can be expected to find broad utility, especially for substrates that are sensitive to Lewis acids, transition metals, or strong oxidants.

Momenta of ions from diiodomethane molecules after multiple ionization by soft-X-ray free-electron-laser pulses are measured. Correlations between the ion momenta are extracted by covariance methods formulated for the use in multiparticle momentum-resolved ion time-of-flight spectroscopy. Femtosecond dynamics of the dissociating multiply charged diiodomethane cations is discussed and interpreted by using simulations based on a classical Coulomb explosion model including charge evolution.

Hypothesis Measuring contact angles made by liquids around individual carbon fibers (CFs) using the Wilhelmy technique is a conventional method to evaluate their surface properties. However, despite its apparent simplicity, inaccurate measurements of capillary forces and wetted lengths, due to the fineness of the CFs, as well as an improper selection of probe liquids can lead to incorrect contact angle and surface energy calculations, leading to an erroneous characterization of their surface properties. Experiments In this study, dynamic wetting experiments of individual CFs were performed in ethylene glycol, diiodomethane, and formamide based on the Wilhelmy method. Capillary forces exerted on the CFs were recorded and analyzed in detail to calculate reliable dynamic contact angles at different contact-line velocities. The molecular-kinetic theory (MKT) and hydrodynamic approach (HD) were then used to model the experimental data and to obtain static contact angles. Findings The analysis shows that the experimental data are in good agreement with the linear MKT suggesting that the dominant channel of energy dissipation at the contact line is the contact-line friction. From the predicted static advancing contact angle values, the surface energy components of the CFs could be obtained thus providing a way to characterize their interfacial properties and predict their compatibility with polymer matrices. This study furthermore points out the importance of choosing the correct combination of test fluids to obtain reliable surface energy results.

Environmental stability is of great interest for sol–gel porous antireflective (AR) coatings. In this work, sol–gel silica AR coatings with excellent environmental stability were prepared via ammonia vapor treatment (AVT) combined with organosilane (hexamethyldisilazane (HMDS) or hexadecyltrimethoxysilane (HTMS)) vapor treatment. The surface free energy (SFE) of the coatings treated with different approaches was estimated through Owens–Wendt method combined with Wenzel equation from the contact angles of water, glycerol and diiodomethane. Scanning electron microscope and Fourier transform infrared spectroscopy were employed to study the surface morphology and chemical composition of the silica coatings treated with different methods. The silica coatings treated by combined vapor phase method possess the SFE of 24.11 mJ·m−2 for N-HD-SiO2 and 34.18 mJ·m−2 for N-HT-SiO2. After being placed in a 90%RH humid environment for 2 months, the peak transmittance of BK7 glasses coated with N-HD-SiO2 and N-HT-SiO2 only decreases by 0.58% and 0.95%, respectively. Meanwhile, N-HD-SiO2 and N-HT-SiO2 coated BK7 glasses also show quite stable optical transmittance after exposure to a vacuum oil environment for 2 months. The mechanism of the combined vapor phase surface treatment is discussed based on the combination analysis of surface morphology, chemical composition and SFE of the coatings.

Application of condition number (CN) approach is critical in selecting appropriate combination of probe liquids for evaluating the surface free energy (SFE) of bitumen. The CN approach recommends use of probe liquids with CN 10 without concerning its adverse effects on the SFE of bitumen. Inappropriate choice of probe liquids may result in incorrect SFE values of bitumen, thereby influencing its compatibility with aggregates. Therefore, the present study is strongly motivated to exhibit the application of CN approach for selecting appropriate probe liquids. Further investigating the impact of CN on aggregate-bitumen compatibility, the present research work also aims at validating CN approach. A polymer modified bitumen (i.e., PMB40) and two types of aggregates namely, quartzite, and basalt aggregates were selected in this study. Five probe liquids namely, water, formamide, diiodomethane, ethylene glycol and glycerol were selected, which formed ten different combinations of probe liquid triplets. The CN of probe liquid triplets was calculated based on singular value decomposition (SVD) method. Thereafter, using the SFE of aggregates and bitumen, compatibility of basalt-PMB40 and quartzite-PMB40 was evaluated using compatibility ratio (CR) parameter. Results revealed that except for probe liquids triplets with CN 10. Therefore, the present study addresses the adverse effect of inappropriate selection of probe liquids on aggregate-bitumen compatibility and also validates the CN approach.

Superhydrophobic and highly oleophobic coatings have the potential for self-cleaning, anti-icing, optoelectronic and antifouling application. In this study, emulsion polymerization and sol-gel methods were employed to prepare a new superhydrophobic and highly oleophobic coating. The structures, surface morphology and the properties of the coating were analyzed by IR, SEM, TG and CA. Pencil scratch test and cross-cut tape test were performed to evaluate the coating mechanical properties. The coating exhibited superhydrophobicity with a water contact angle of greater than 150° and a sliding angle of 4.42° as well as high oleophobicity as demonstrated by a diiodomethane contact angle of 147.41° and a sliding angle of 9.85°. The coating exhibited 6H pencil hardness and 5B cross-cut adhesion properties. These interesting and robust properties make them promising candidates for some applications.

Complex, hierarchic microstructures are prepared by electrophoretic deposition of SiO2 microspheres. A subsequent functionalization via sol-gel technique using perfluorsilanes leads to superoleophobic surfaces. A crucial step of the used process is the application of laser-structured aluminum substrates for electrophoretic deposition leading to complex three-dimensional surface structures. After a chemical functionalization step surfaces are generated that exhibit a huge contact angle against diiodomethane of 157° in air. This is significantly larger than the typically used threshold angle for superoleophobicity of 150°.

In this study, the effect of surface functionalization of poly (methyl methacrylate) (PMMA) layer using [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide, a zwitterion comonomer, on PMMA’s hydrophilicity and antifouling properties was investigated via the utilization of a molecular dynamics (MD) simulation. The modified layers were composed of PMMA chains with 30 repeating units, which were surface functionalized using various amount of zwitterionic comonomers, i.e. 0, 6.66, 9.99 and 16.65 wt%. In this case, the hydrophobicity of the resultant layer was evaluated calculating the contact angle values. Additionally, the calculated contact angles using water and diiodomethane over the PMMA model were compared to experimental values to validate the simulation procedure. To investigate the antifouling property, both the top and bottom models faces were contacted to a given feed composed of a water/hydrocarbon mixed solvent ratio, 60/40 (vol/vol). Likewise, the number density and radial distribution function (RDF) were determined to investigate the change in the solvent molecules repulsion or organic antifouling property of the layer surface, along with increasing the content of the functionalizing groups.

Objective Evaluate the effect of different ceramic primers and post-silanization protocols on physicochemical and morphological characteristics of a lithium disilicate glass ceramic. Methods Lithium disilicate ceramic (IPS e-max CAD) plaques (6 × 10 × 2 mm) were divided into 3 groups according to the ceramic primer used: (1) Silane (RelyX Ceramic Primer-RL); (2) Silane + MDP (Clearfil Ceramic Primer Plus-CP); (3) Self-etching ceramic primer (Monobond Etch and Prime-MB). Specimens from each group were distributed into 5 sub-groups according to post-silanization protocols: (a) Treated as recommended by the manufacturer (MR), (b) MR + Additional drying with air at room temperature for 30 s (RTA), (c) MR + additional drying with hot air for 30 s (HT), (d) MR + Surface rinsing with water at room temperature for 10 s and drying with air at room temperature for 30 s (WT), and (e) Specimens were not silanized (NS). Surface free energy (SFE) was determined using static contact angles measurements with water and diiodomethane. SFE data were submitted to Friedman followed by Wilcoxon post-hoc test (α = 0.05). Morphology was analyzed using scanning electron microscopy. Elemental composition and chemical interactions were determined with X-ray photoelectron spectroscopy analysis. Results RL presented the highest SFE (62.4 mN/m) followed by CP (59.7 mN/m). Post-silanization protocols resulted in similar SFE, but WT and HT induced the highest water contact angles when using CP and RL. CP modified ceramics’ surface morphology compared to the etched and RL treated groups. The presence of water was identified on CP treated specimen. All analyzed primers formed siloxane bonds with ceramic surface. Significance Ceramic primers resulted in different surface free energy and morphology, but siloxane bonds were identified for all tested solutions. HT and WT protocols should be used with RL and CP primers. MB was not influenced by the different silanization protocols.

The 101–000 and 202–101 rotational transitions of a monohalomethylene, HCI, are observed in a discharge plasma of diiodomethane by Fourier-transform microwave (FTMW) and FTMW-microwave double-resonance spectroscopy. The effective rotational constant ( B + C ) / 2 , the centrifugal distortion constant Δ J , and the quadrupole coupling constant of the iodine nucleus are determined from the observed line frequencies. The nuclear spin-rotation coupling constant C bb is required to be included into the set of fitting parameters for a satisfactory analysis of the observed line frequencies.

To improve the chemical resistance of non-isocyanate polyurethane (NIPU), two kinds of diglycidyl ether, bisphenol AF (E-AF) and perfluorooctyl glycidyl ether (PFGE), were selected to synthesize two different cyclic carbonates, bisphenol AF (EC-AF) and perfluorooctyl cyclic carbonate (PFGC), respectively. These cyclic carbonates were successfully used to prepare fluorine-containing non-isocyanate polyurethane coatings. The effects of PFGC amounts on the properties of NIPU were studied, and it was found that the contact angles of water, diiodomethane, and hexadecane were increased with the addition of PFGC and up to 106.7°, 80.2°, and 72.7°, respectively, whereas the pendulum hardness of NIPU coatings relatively decreased with the increase in PFGC contents. The NIPU coatings exhibited excellent flexibility, adhesion, and impact resistance. They also displayed good thermal stability with 5% weight loss temperature (T5%) ranging from 249 to 271°C. Moreover, these coatings possessed very low water uptake, excellent hydrophobic/oleophobic properties, and corrosion resistance properties.

Aim The aim of this study was to determine the effect of surface physico-chemico-biological modifications of titanium on critical and theoretical surface free energy. Materials and Methods Cylindrical commercially pure titanium rods (99.9%) 1.27 cm in diameter were sectioned into 2 mm thick disks and polished on silicon carbide paper from 240 to 600 grit. Discs were divided into 3 treatment groups as follows, (a) Chemical treatment group which were treated with HNO3, HF/HNO3, or H2O2/HCL; (b) Physical treatment group, which were treated with autoclaving, autoclaving + Plasma treatment, and HNO3 + Plasma Cleaning and (c) Biological treatment group which were treated with H2O2/HCl followed by attachment of Collagen II or Soaking in simulated body fluid (SBF) Kokubo recipe to form hydroxyapatite. Contact angles of three investigational liquids (20 μl), distilled water, formamide and diiodomethane on the disks were measured using a single-lens reflex camera. Six measurements were made for each treatment. Surface free energies (SFE) were determined using the Zisman method for critical surface energy, the geometric mean method and acid-base theory. Data were compared using Analysis of Variance (ANOVA) and Tukey’s honestly significant difference (HSD) test (α = 0.05). Results/Conclusion Chemical treatment with HNO3 and H2O2/HCl and physical treatment by plasma cleaning of Ti surfaces resulted in significantly higher SFE compared to untreated Ti in all the different approaches for surface free energy determination. The geometric mean method and acid-base theory revealed that increases in SFE were due to increases in the polar and base components of surface energy. Biologically treated surface showed consistent increases in the acid component of surface energy although not statistically significantly different from controls. Information about the effect of surface treatments on SFE and its components provide insights into the preferred surface characteristics for facilitation of cellular activities on implant materials for osseo- and chondro- integration.

In order to reduce the wetting and fouling propensity of polyvinylidene fluoride (PVDF) membrane during coking wastewater treatment by membrane distillation, two kinds of omniphobic PVDF composite membranes were prepared by coating SiO2 nanoparticles on PVDF membrane surface via electrostatic adsorption or chemical bonding respectively, and subsequently fluorination. The coated SiO2 nanoparticles observed as amounts of nano-scale protrusions by scanning electron microscope constructed a re-entrant structure and enhanced membrane surface roughness. The omniphobicity of the modified membranes was confirmed by high contact angles (> 150°) for water, diiodomethane and ethylene glycol on the membrane surface. The omniphobic layer with SiO2 nanoparticles coated via chemical bonding was more stable than electrostatic adsorption. Both the omniphobic PVDF membranes exhibited stable and high rejections of the inorganic and organic contaminants, which were determined by conductivity, total organic carbon and three-dimensional excitation-emission fluorescence spectroscopy of the distillate. The modified omniphobic membranes also showed much less flux decline than the pristine PVDF membrane in direct contact membrane distillation tests (120 h), suggesting their excellent anti-fouling performance. This study indicates that coating silica nanoparticles via chemical bonding is an effective and promising method to fabricate omniphobic PVDF membrane for coking wastewater treatment.

In food processing, insufficient cleaning can result in reduced efficiency, contamination in final product, and energy losses. To optimise widely implemented clean-in-place (CIP) systems, it is critical to understand the influence of the interactions between surfaces, foulant, and chemical agents on the efficiency of the cleaning process. The present work investigates the effect of wall temperature and surface roughness on the surface free energy of stainless steel 316L coupons. Equilibrium contact angles (ECA) of four commonly used liquids, namely ethylene glycol, 1-bromonaphathalene, water, and diiodomethane were measured on the surfaces of interest. Finally, ECAs of liquids were used to quantify surface free energy (SFE) of the solid substrate. Our results show that surface energy is proportional to the roughness and well-prediction of liquids wettability as a function of roughness and temperature. It demonstrates the importance of surface characteristics in determining interfacial energy, and consequently the efficiency of CIP for food engineering.

Synthesis of biodegradable polycarbonates directly from carbon dioxide and diols has seen renewed interest. In the present report, the effect of a series of organic dihalides (CH2X2 and (CHX)2, where X = Cl, Br, and I) in the Cs2CO3-promoted copolymerization of 1 atm CO2 with diols has been studied. Structural analysis of the resultant polymers/oligomers by spectroscopic techniques reveals that a variety of main chain linkages can be obtained, depending on the dihalides used. Specifically, the methylene units from dibromomethane (DBM) are incorporated into the products as carbonate and ether linkages, and the methylene units from diiodomethane (DIM) are incorporated mainly as the ether linkage and without much CO2 incorporation. In comparison, all dihaloethanes examined lead to clean formation of alternating polycarbonates incorporating both the ethylene units from dihaloethanes and the diol units, and the halide is identified as the end group. The mechanistic pathways and the relative activity of the key intermediates are discussed in light of these results.

Amphiphilic diblock copolymers (DC) of 2,3,4,5,6-pentafluorostyrene and 2-hydroxyethyl methacrylate were prepared for the first time by two-step reversible addition–fragmentation chain transfer (RAFT) polymerization. The morphology of films of diblock copolymers that have a composition close to equimolar was studied by transmission electron microscopy. The observed microphase separation and formation of spherical nanodomains is not typical for equimolar diblock copolymers and seems to result from hydrogen bonding between the hydroxyl and carbonyl groups (OH···OH and C=O···HO) in poly(2-hydroxyethyl methacrylate) blocks. Obviously, it is the ability of diblock copolymers to self-organization is the cause of formation of fabric coatings with low surface energy (γ = 11.9 mJ/m2) and relatively large water contact angles ( $${{\theta }^{{{{{\text{H}}}_{{\text{2}}}}{\text{O}}}}}$$ = 120° ± 6°) and diiodomethane ( $${{\theta }^{{{\text{C}}{{{\text{H}}}_{2}}{{{\text{I}}}_{{\text{2}}}}}}}$$ = 93° ± 2°).

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

Superhydrophobic surfaces possess low mechanical strength, and can be easily contaminated by fluids with low surface tension, such as oil, this hinders their practical applications. In this study, fluorinated epoxy was prepared through the thiol-ene click reaction at first. The superhydrophobic surface with high oil-repellency was prepared by the addition of unmodified nano-SiO2 and micron-SiO2 to the fluorinated epoxy. The effect of the ratio of micro- and nano-silica particles on the morphology and wettability of the coating was investigated. It was shown that a re-entrant structure appears and FEP-S coating has good liquid repellency when the amounts of nano-SiO2 and micro-SiO2 are equal. The contact angles of the FEP-S coating (coating with the best liquid repellent performance) for water, glycerol, ethylene glycol, and diiodomethane were 158.6° ± 1.1°, 152.4° ± 0.9°, 153.4° ± 1.3°, and 140.7° ± 0.9°, respectively. In addition, the superhydrophobic coatings possess excellent mechanical and chemical durability, excellent performance in self-cleaning, corrosion resistance, and anti-icing properties. The preparation method of superhydrophobic coating is relatively simple, therefore, it has a wide range of applications and can also be applied to various substrates.

Amphiphobic surfaces have been developed for various applications. However, the harsh construction conditions and multistep processes limit their practical application. Especially for those with a particular surface roughness and morphology, the amphiphobic property might provide a slight deformation. Here, a facile large-area construction of transparent and flexible amphiphobic coatings with excellent fold resistance has been established by simple casting of the fluorinated liquid nitrile-butadiene rubber (F-LNBR) followed by solvent-free photocuring. It was found that the fluorocarbon groups could concentrate onto the coating surface during the UV-induced photocuring. With a certain coating amount, a stable oleophobic coating was achieved with static contact angles of about 95° and 111° for nonpolar oil (n-hexadecane) and polar oil (diiodomethane). Most importantly, the static contact angles of water and diiodomethane of the amphiphobic coatings on the iron sheet increased after bending and remained around 131° and 120° after being completely folded in half for 100 cycles because the inner fluorocarbon groups could be squeezed out from the flexible cross-linked rubber matrix as a reservoir. Such features indicated the promising self-cleaning and surface protection of the proposed transparent and flexible amphiphobic coatings for deformable substrates.

The compatibility of three types of silicone oil with polydimethylsiloxane, the phase separation of their mixture and the microstructure and properties of their composite coatings were investigated. The existing form of silicone oil in the coating and the precipitation behavior were also studied. The compatibility observed experimentally of the three silicone oils with PDMS is consistent with the results of the thermodynamic calculation. The silicone oil droplet produced by phase separation in the mixture solution can keep its shape in the cured coating, also affecting the microstructure and mechanical properties of the coating. It was found that methyl silicone oil and methyl fluoro silicone oil do not precipitate on the surface, and they have no effect on the surface properties of the coating. In contrast, phenyl silicone oil has obvious effect on the surface, which makes the water contact angle and diiodomethane contact angle of the coating decrease significantly.

Polylactide (PLA) is the second most popular biodegradable plastic in the world currently and is a growing alternative to traditional plastics. Similar to most of the polymers, PLA requires surface activation before further processing, among others plasma activation. Hydrophobic recovery is a major problem of plasma-treated polymer; therefore, authors performed extensive research on the storage stability of the oxygen plasma-treated PLA film. For that purpose the low-temperature plasma with oxygen was applied on PLA film and its influence on surface-free energy (SFE) and contact angle (CA) with water, diiodomethane and ethylene glycol was analysed together with their subsequent hydrophobic recovery during storage. In addition, chemical changes were measured with X-ray photoelectron spectroscopy (XPS), mass loss was determined by weight measurement and the surface topography was measured by means of confocal microscopy. The best wettability of the substrate was observed after 2 and 10 min activation time, which was confirmed by the lowest CA, as well as the highest values of SFE. The degree of hydrophobic recovery depends on treatment time and is most stable for 6 min treatment. The PLA hydrophobic recovery reached its peak after a storage period of 14 days, after which the hydrophilic properties improved again, regardless of the activation time.

Porous scaffolds made of biocompatible and environmental-friendly polymer fibers with diameters in the nano/micro range can find applications in a wide variety of sectors, spanning from the biomedical field to textiles and so on. Their development has received a boost in the last decades thanks to advances in the production methods, such as the electrospinning technique. Conferring antimicrobial properties to these fibrous structures is a primary requirement for many of their applications, but the addition of antimicrobial agents by wet methods can present a series of drawbacks. In this work, strong antibacterial action is successfully provided to electrospun polycaprolactone (PCL) scaffolds by silver (Ag) addition through a simple and flexible way, namely the sputtering deposition of silver onto the PCL fibers. SEM-EDS analyses demonstrate that the polymer fibers get coated by Ag nanoparticles without undergoing any alteration of their morphological integrity upon the deposition process. The influence on wettability is evaluated with polar (water) and non-polar (diiodomethane) liquids, evidencing that this coating method allows preserving the hydrophobic character of the PCL polymer. Excellent antibacterial action (reduction &gt, 99.995% in 4 h) is demonstrated against Escherichia coli. The easy fabrication of these PCL-Ag mats can be applicable to the production of biomedical devices, bioremediation and antifouling systems in filtration, personal protective equipment (PPE), food packaging materials, etc.

Made available in DSpace on 2021-06-25T10:45:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This study aimed to investigate the microstructure, failure probabilities, the susceptibility to subcritical crack growth (SCG), and the surface energy of two comercial brands IPS E.max CAD, Ivoclar Vivadent (LD-C) and Celtra DUO, Dentsply (LS-C) and experimental lithium disilicate (LD-E) and metasilicate (LM-E) glass-ceramics. Discs of each material were made to determine the subcritical crack growth parameters and the biaxial flexural strength (ISO 6872). The stresses to failure (MPa) were submitted to Weibull's analysis (CI 95%). The SCG was tested in water at five constant stress rates: 0.005; 0.05; 0.5; 5 and 50 MPa/s. By measuring the contact angles of water and diiodomethane on the glass-ceramics, we calculated the surface energy (mN/m). The characteristic strengths (MPa) and the Weibull moduli were 382.8 ± 8.3 and 10.1 ± 1.5, 148.5 ± 4.0 and 8.4 ± 0.8, 233.5 ± 10.4 and 5 ± 0.6, and 280.4 ± 9.1 and 6.8 ± 0.9 for LD-C, LS-C, LD-E and LM-E, respectively. The parameter of susceptibility to SCG (n) was: LD-C (18.2 ± 2.5), LS-C (25.6 ± 5.8), LD-E (23.2 ± 8.1), and the LM-E (15.1 ± 2.1). The polar and dispersive energy of LD-C was (~45) and (~26) respectively. The microstructures show that the commercial glass-ceramics are more refined and uniform than the experimental ones, which led to less strength variation. The stress corrosion cracking of the glass-ceramics, mainly LD-C, seemed to be a combination of the surface energy and microstructural features. Department of Dental Materials and Prosthodontics São Paulo State University (UNESP) Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue, São José dos Campos Aeronautics Technological Institute (ITA), 50 Marechal Eduardo Gomes Square Department of Sciences State University of Maringá, Reitor Zeferino Vaz Avenue Department of Materials Engineering (DEMa) Center for Research Technology and Education in Vitreous Materials (CeRTEV) Federal University of São Carlos (UFSCar) College of Dentistry São Francisco University (USF), 218 São Francisco de Assis Avenue Department of Dental Materials and Prosthodontics São Paulo State University (UNESP) Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue, São José dos Campos CAPES: 001 CNPq: 104429/2019-4 CNPq: 156600/2018-8 FAPESP: 2013/07793-6

The surface properties, mechanical characteristics, and morphology of the PP/CPA-Fe composite based on a polymer blend of polypropylene (PP) and copolyamide (CPA) filled with dispersed iron (Fe) were studied. The effect of stepwise behavior of the surface energy and its dispersive and polar components was previously unknown and discovered for the first time when the composition of the polymer blend was varied in the entire composition range. The surface parameters were found by measuring the contact angle of the testing liquids (water and diiodomethane) and using Owens and Wendt’s approach. Stepwise behavior of the surface energy was caused by the morphology of the composite. The largest change in the surface parameters occurs in the phase inversion region, where the phases of PP and CPA-Fe are co-continuous. Below (for the structure of PP matrix with the inclusions of CPA-Fe) and above (for the structure of CPA-Fe matrix with the inclusions of PP) this interval, changes in the surface energy are minor. In the phase inversion region, the relative contributions of the polar and dispersive parts to the total surface energy were changed from 1 to 14% and from 99 to 86%, respectively that was caused by the interface interaction of the components of the blend. On the contrary, the values of elastic modulus (E) remain constant in the phase inversion region, while the largest changes occur below and above this region.

In this work, the hydrophobization of lignocellulosic jute fibers was achieved via the laccase/TEMPO-mediated grafting of octadecylamine (OA) on their surface, with the aim to improve the interfacial compatibility with nonpolar polylactic acid (PLA) resins in fiber-reinforced composites. The modified jute fibers were analyzed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The characteristic vibrations of methylene groups and the increase in the surface C/O ratio of the jute fibers after the enzymatic treatment indicated that OA molecules were successfully grafted onto the jute fiber surface mediated by the laccase/TEMPO system. It was shown that the grafted jute fibers had increased surface hydrophobicity and reduced polarity with water contact angle of 124.2 °, diiodomethane contact angle of 94.1 ° and surface free energy of 11.44 mJ/m2, which were attributed to the presence of the OA nonpolar alkyl chains on their surface. The tensile, bending, and dynamic mechanical properties of the hydrophobized jute/PLA composites were enhanced, which suggested stronger interfacial adhesion between the jute fibers and the PLA matrix. The mechanical stability was investigated by water immersion measurements and it was found that the modified jute/PLA composites were better in this regards than the control jute/PLA composites. Therefore, this enzymatic hydrophobic modification could be used as an effective and eco-friendly method to produce natural lignocellulosic fiber-reinforced composites with excellent performance.

The mechanism of how the solvent type influences photovoltaic performance and thermal stability of non-fullerene organic solar cells remains unexplored. In this article, the well-known PTB7-Th was selected as a donor, while F8IC was used as an acceptor. The PTB7-Th:F8IC processed from chloroform (CF) exhibited a superiorly higher power conversion efficiency (PCE) of 10.5%, in contrast to the specimen processed from chlorobenzene (CB) of 6.8%. In addition, upon thermal annealing at 160 °C for 120 min, the device processed from CF was more stable than that processed from CB. The incorporation of perylene diimide derivative TBDPDI-C11, serving as the third additive, could also obviously improve the PCE value and thermal stability of PTB7-Th:F8IC processed from CB. According to ultraviolet spectroscopy, atomic force microscopy, transmission electron microscopy, and grazing incidence wide-angle X-ray scattering analyses, the enhanced photovoltaic performance and thermal stability are mainly attributed to formation of PTB7-Th nanofibers and appropriate aggregation of F8IC. The interaction free energy calculated using water and diiodomethane contact angles reveals that PTB7-Th well disperses in CB and tends to aggregate in CF, while F8IC aggregates strongly in CB. The preaggregation matching of the donor and acceptor in solution is essential for the optimization of morphology, efficiency, and thermal stability. The findings in this article could provide useful guidelines to fabricate efficient and thermally stable organic solar cells simply by analyzing the surface energy of components processed from different solvents.

Biofilm attached cultivation is a promising method for efficient production of microalgae. Determining the surface property index to select an appropriate substrate benefiting the algae adhesion and biofilm formation is very important for the cultivation method. This work focused on elucidating and quantifying the influence of surface wettability and roughness of substrate on Chlorella vulgaris adhesion. Firstly, surface modified styrene-acrylic (SA) resin films by adding different dosage of perfluoroalkyl ethyl acrylate (FM) were prepared. Property characterization shows that the surface contact angle in water, formamide and diiodomethane of FM modified SA films is significantly associated with the FM dosage, while the other surface properties including zeta potential, surface potential and surface roughness have insignificant difference. The calculated surface free energy parameters show that the SA films belong to the non-polar substrata. A well quantitative correlation that the adhesion capacity of C. vulgaris linearly declines with the increase of water contact angle was obtained. And a near linear relationship between the adhesion capacity and the surface free energy (γ), or the cohesion free energy (ΔGcoh) was also observed. Secondly, the surface roughness solely changed SA films were prepared by replicating the morphology of stainless steel sieves through the PDMS template method. The patterned SA films have alternately arranged rectangular "valleys" and "ridges". A well linear correlation between the microalgae adhesion capacity and the surface roughness was also obtained.