Asymmetric block copolymer membrane fabrication mechanism through self-assembly and non-solvent induced phase separation (SNIPS) process

In this paper, the concept of the functional mechanism of copolymer membrane formation is explained and analyzed from the theoretical and experimental points of view. To understand the phase inversion process and control the final membrane morphology, styrene-acrylonitrile copolymer (SAN) membrane morphology through the self-assembly phenomena is investigated. Since the analysis of the membrane morphology requires the study of both thermodynamic and kinetic parameters, the effect of different membrane formation conditions is investigated experimentally; In order to perceive the formation mechanism of the extraordinary structure membrane, a thermodynamic hypothesis is also developed based on the hydrophilic coil migration to the membrane surface. This hypothesis is analyzed according to Hansen Solubility Parameters and proved using EDX, SAXS, and contact angle analysis of SAN25. Moreover, the SAN30 membrane is fabricated under different operating conditions to evaluate the possibility of morphological prediction based on the developed hypothesis.

Contact Angle of Nepenthes alata Slippery Zone: Results from Measurement and Model Analysis

The slippery zone of Nepenthes alata depends on its highly evolved morphology and structure to show remarkable superhydrophobicity, which has gradually become a biomimetic prototype for developing superhydrophobic materials. However, the mechanism governing this phenomenon has not been fully revealed through model analysis. In this paper, the superhydrophobicity of slippery zone is studied by contact angle measurement, morphology/structure examination and model analysis. The slippery zone causes ultrapure water droplet to produce a considerably high contact angle (155.11–158.30°), and has a micro-nano scale hierarchical structures consisting of lunate cells and wax coverings. According to the Cassie-Baxter equation and a self-defined infiltration coefficient, a model was established to analyze the effect of structure characteristic on the contact angle. Analysis result showed that the calculated contact angle (154.67–159.49°) was highly consistent with the measured contact angle, indicating that the established model can quantitatively characterize the relationship between the contact angle and the structure characteristic. Our study provides some evidences to further reveal the superhydrophobic mechanism of Nepenthes alata slippery zone, as well as inspires the biomimetic development of superhydrophobic surfaces.

Contact Angle and Cell Adhesion of Micro/Nano-Structured Poly (Lactic-Co-Glycolic Acid) Membranes for Dental Regenerative Therapy

Biodegradable membranes are used in regenerative dentistry for guided tissue regeneration (GTR) and guided bone regeneration (GBR). In this study, patterned poly (lactic-co-glycolic acid) (PLGA) membranes with groove, pillar, and hole structures were successfully fabricated by thermal nanoimprinting. Their surfaces were evaluated for topography by scanning electron microscopy and laser microscopy, for hydrophobicity/hydrophilicity by contact angle analysis, and for MC3T3-E1 cell adhesion. The sizes of the patterns on the surfaces of the membranes were 0.5, 1.0, and 2.0 μm, respectively, with the height/depth being 1.0 μm. The pillared and holed PLGA membranes were significantly more hydrophobic than the non-patterned PLGA membranes (p < 0.05). However, the 0.5 μm- and 1.0 μm-grooved PLGA membranes were significantly more hydrophilic than the non-patterned PLGA membranes (p < 0.05). The 0.5 μm-grooved, pillared, and holed membranes exhibited significantly superior adhesion to the MC3T3-E1 cells than the non-patterned PLGA (p < 0.05). These results suggest that patterned PLGA membranes can be clinically used for GTR and GBR in the dental regeneration field.

Effect of Zr(IV) to phosphorus ratio on U(VI) adsorption by diethylenetriamine-pentamethylene phosphate Zr(IV) hybrids

In this work, diethylenetriamine pentamethylenephosphonic acid (DTPMP) was ultilized into preparing of Zr(IV) organophosphates hybrids (Zr-DTPMP-x, x was the molar ratio of Zr(IV)/DTPMP in the synthetic process, x = 0.5, 1, 2, and 3) using a hydrothermal method. The physical and chemical properties of Zr-DTPMP-x were characterized by SEM&EDS, FT-IR, XRD, Zeta potential, XPS, TGA and contact angle analysis. Moreover, the adsorptive performances of Zr-DTPMP-x for U(VI) were investigated. The adsorption results showed that the optimum molar ratio of Zr(IV) to phosphine, pH, equilibrium time, and dosage was 0.5, 4.0, 180 min, and 10 mg, respectively. Besides, the adsorption of U(VI) was in accordance with the pseudo-second-order kinetic model and Sips isothermal model. Moreover, the adsorption capacity determined by Sips isothermal model was 181.34 mg g−1 for Zr-DTPMP-0.5. Furthermore, the adsorptive selectivity of Zr-DTPMP-0.5 for U(VI) was superior than the others. Zr-DTPMP-0.5 may be a powerful candidate for diminishing the contamination of U(VI).

Mesogenic Properties of Aromatic Oligoesters Derived from Kink-Structured Monomers

Novel liquid crystalline oligomers were prepared using different compositions of kink-structured aromatic dicarboxylic acids, aromatic diols, and 4-hydroxybenzoic acid via high-temperature polycondensation. The reaction products were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and polarized optical microscopy. As a result, the samples containing kinked units with phenyl or naphthalene moiety had a broad processing window limited by the melting process and the isotropization, whereas one based on diphenic acid was almost entirely in an amorphous state. The surface properties of the oligomers were evaluated by wetting measurements using a static contact angle analysis.

Blocking and Deblocking of Diisocyanate to Synthesize Polyurethanes

Diisocyanates, particularly toluene diisocyanate (TDI), are useful for the preparation of various polyurethanes with specific applications as leather-like materials, adhesives and insoles, etc. Blocking agents can be used for the operational simplicity and to reduce the hazards of TDI. In this paper, we reported the use of 3-(4-bromo-phenyl)-1H-pyrazole to block toluene diisocyanate (TDI). FTIR, NMR, thermogravimetric analysis, contact angle analysis and differential scanning calorimetry (DSC) were used for the characterization. The effectiveness of the blocking was confirmed by spectroscopic techniques. The DSC thermogram showed that blocked adducts deblock at 240 °C, causing the regeneration of TDI, and causing the diisocyanates to react with polyols of different molecular weights, forming polyurethanes. The characterization of the polyurethanes was performed by infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and a contact angle study.

Surface Bioactivation of Polyether Ether Ketone (PEEK) by Sulfuric Acid and Piranha Solution: Influence of the Modification Route in Capacity for Inducing Cell Growth

The aim of this study was to promote bioactivity of the PEEK surface using sulfuric acid and piranha solution. PEEK was functionalized by a sulfuric acid treatment for 90 s and by piranha solution for 60 and 90 s. Chemical modification of the PEEK surface was evaluated by infrared spectroscopy, contact angle analysis, cytotoxicity, cell adhesion and proliferation. The spectroscopy characteristic band associated with sulfonation was observed in all treated samples. PEEK with piranha solution 60 s showed an increase in the intensity of the bands, which was even more significant for the longer treatment (90 s). The introduction of the sulfonic acid functional group reduced the contact angle. In cytotoxicity assays, for all treatments, the number of viable cells was higher when compared to those of untreated PEEK. PEEK treated with sulfuric acid and piranha solution for 60 s were the treatments that showed the highest percentage of cell viability with no statistically significant differences between them. The modified surfaces had a greater capacity for inducing cell growth, indicative of effective cell adhesion and proliferation. The proposed chemical modifications are promising for the functionalization of PEEK-based implants, as they were effective in promoting bioactivation of the PEEK surface and in stimulating cell growth and proliferation.

Analysis of the association of parameters in the formation of ultrafine fibers from PEI and PMMA

Objective: The aim of the study was to fabricate and morphologically characterize ultrafine Polyetherimide fibers (PEI) associated with Polymethylmethacrylate (PMMA) – PP (group formed by the association of PEI with PMMA), produced by the electrospinning process. Material and Methods: A solution of PEI (0.562 g) + PMMA (0.377 g) dissolved in 2.5 mL of chloroform, 0.85 mL of Dimethylformamide (DMF) and 0.85 mL of 1.1.2.2 Tetrachloroethane (TCE) was prepared. For the electrospinning process, different continuous voltages (10 to 18 kV) and two different distances (8 and 12 cm) between the needle tip and the collecting apparatus were used, giving rise to 6 distinct groups of ultrafine fibers (PP 1 to 6) that were observed in Scanning Electron Microscopy to check for defects and calculate the average diameter of the fibers. Results: The best parameter, the parameter that was most effective for the production of fibers, observed was subjected to Energy Dispersion X-ray Spectroscopy (EDS), X-ray Diffraction (XRD) and Contact Angle Analysis tests. The data were analyzed using the ANOVA and Tukey test (p <0.05). From the comparative analysis of the pre-established parameters, the pattern of PP4 ultrafine fibers was shown to be more effective. Conclusion: The PP4 standard (13 kV – 12 cm) had an average diameter of 0.37 µm. An adequate parameter to electrospinning was able to produce ultrafine fibers of PMMA/PEI. Keywords Polymethylmethacrylate; Scanning electron microscopy; Polyetherimide; Electrospinning process.