Preparation of oil-modified polycaprolactone and its further modification with benzoxazine for coating purposes

Sunflower oil-modified polyester (SOMPE) was prepared via the ring opening polymerization of ?-caprolactone (CL) using partial glycerides (PGs) and stannous octoate (SO) as the initiator and catalyst, respectively. In addition to being the initiator, PGs participate in the drying process of the film sample for coating purposes. The structure of the sample was characterized by FT-IR and ¹H NMR. The film of SOMPE cannot reach a fully dried state as a result of its less oil moiety content. By increasing the oil fraction, the chain length of polycaprolactone (PCL) decreased by changing the [monomer]/[initiator] mol ratio and shortening the reaction time. Even with these precautions, the molecular weight of SOMPE could not be reduced below 5000 g/mol, and this caused the film to become soft. Therefore, hydroxy-functional benzoxazine monomer (HFB-a) was prepared and used in a further modification of SOMPE. HFB-a was chemically combined with SOMPE via the urethane linkage formed from the reaction of 2,4-toluene diisocyanate, yielding SOMPE-HFB-a. Because the SOMPE-HFB-a sample also had a soft film, additional HFB-a was used to prepare the SOMPE-HFB-a/HFB-a blend. The cured blend prepared with SOMPE-HFB-a and HFB-a in a weight ratio of 1/8, [SOMPE-HFB-a/HFB-a:1/8], had good film properties. The cured film was examined by FT-IR and DSC following the curing process. After our modifications were applied, PCL and polybenzoxazine lost their softness and brittleness, respectively, and a binder with good film properties was formed.     

Cefditorene-Mediated Synthesis of Silver Nanoparticles and Its Catalytic Activity

Ag(0) NPs were prepared by chemical reduction method in which silver nitrate was taken as the metal precursor and cefditorene as a reducing/capping agent and NaOH as the catalyst for reaction enhancement. The formation of the Ag(0) NPs was monitored using UV–Vis absorption spectroscopy confirmed the formation of Ag(0) NPs by exciting the typical surface plasmon absorption maxima at 405 nm. Transmission electron microscopy (TEM) confirmed the spherical morphology of the (Ag(0) NPs). The crystallite (11 ± 3 nm) and particle size (14.1 ± 2.2 nm) obtained from TEM and XRD analysis were coinciding with each other. Prepared Ag(0) NPs were then used as catalyst against 2-nitroaniline, 3-nitroaniline and 4-nitroaniline, which all showed best catalytic activity.     

New monomers and polymers derived from α‐hydroxymethyl methyl vinyl ketone

2‐Hydroxymethyl‐but‐1‐ene‐3‐one [α‐hydroxymethyl methyl vinyl ketone (HMVK)] was synthesized from methyl vinyl ketone using paraformaldehyde and a tertiary amine catalyst. Free‐radical polymerization of this monomer created transparent, tough polymers that were insoluble in organic solvents. HMVK was converted to trimethylsilyl, acetate, and chloride derivatives. When the hydroxyl group was thus protected or removed, all these monomers could be free radically polymerized in bulk to make soluble polymers. The chlorination reaction is complicated by the formation of 1,1‐bischloromethylacetone, which dehydrohalogenated unexpectedly to the desired α‐chloromethyl methyl vinyl ketone. HMVK will self‐condense to an ether dimer in the presence of a catalytic acid. This reagent is capable of crosslinking many alkene monomers through hydrolytically stable ether bonds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 509–516, 2000     

Electrochemical corrosion properties of metal alloys used in orthopaedic implants

This study concerns an investigation of the corrosion behavior of 316 stainless steel, CoCrMo and Ti6Al4V alloys in simulated body conditions (ringer lactate) at 37 °C by the use of Tafel plots, mixed potential and electrochemical impedance spectroscopy (EIS). Ti6Al4V alloy has the highest corrosion resistance followed by CoCr alloy. Ti6Al4V–CoCrMO was the best couple for galvanic corrosion with the minimum galvanic potential and current values according to mixed potential theory and Tafel method. It was concluded that Ti6Al4V was the most suitable material for implant applications in the human body.     

Synthesis of fluorinated/methacrylated epoxy based oligomers and investigation of its performance in the UV curable hybrid coatings

Organic–inorganic hybrid coatings based on fluorinated/methacrylated soybean oil and bisphenol A/F epoxy methacrylate were obtained by combining photopolymerization and sol–gel process. Hard and transparent hybrid coatings were prepared on polycarbonate panels and their physical and mechanical properties such as gel content, hardness, adhesion, gloss, contact angle as well as tensile strength were measured. Results from the mechanical measurements showed that the properties of hybrid coatings improved with the increase in fluorine and sol–gel precursor contents. Thermo gravimetric analysis results demonstrated that fluorine and silica incorporations significantly enhanced the thermal oxidative stability of the hybrid coating materials. The surface morphology was also characterized by scanning electron microscopy (SEM). SEM studies indicated that inorganic particles were dispersed homogenously throughout the organic matrix.     

A theory of thin lamellar eutectic growth with anisotropic interphase boundaries

We present a semiempirical theory of the effects of an orientation dependence of the surface free energy of interphase boundaries (interphase boundary anisotropy) on lamellar eutectic growth in thin samples. We show that, to a good approximation, thin lamellar eutectic patterns with a strong interphase boundary anisotropy travel along the growth front at such a velocity – or, equivalently, at such an inclination angle of the lamellae left behind in the solid – that the surface tension force of the interphase boundary is nearly parallel to the applied thermal gradient. This explains, among other things, the crystallographic locking of lamellar eutectic patterns that occurs in those eutectic grains, which have cusp singularities in the Wulff plot of the interphase boundary. Based on this theory, we show that the rotating directional solidification method, by which a thin sample is rotated with respect to a fixed unidirectional thermal gradient, must yield eutectic lamellae whose trajectories are nearly homothetic to the two-dimensional Wulff form of the interphase boundary. This opens up new possibilities for the experimental study of interphase boundary anisotropy in eutectic alloys.     

Effect on response time and diffraction efficiency of co-usage azo dye and carbon nanoparticle in nematic liquid crystal

In this work, the formation of the photo-induced grating and nonlinear optical properties such as diffraction efficiency (η), refractive index modulation (Δn), nonlinear index coefficient (n₂) of nematic liquid crystal (E7) doped by azo dye (Methyl Red) and C60 have been investigated by diffraction grating measurements. Diffraction efficiencies of 441 nm pump and 632 nm probe beams were measured in two-wave mixing experiment. Maximum diffraction efficiency was found 26% doped with both 1% MR and 0.5% C60, while cells without C60 had maximum diffraction efficiency of 19% under 30 mW laser illumination. Rise time was found to increase with Methyl Red concentration. The nonlinear index coefficient, n₂, was calculated to be 11 × 10⁻³ cm²/W and highly depend on MR concentration.     

The synthesis,characterization, electrochemical character,catalytic and antimicrobial activity of novel,azo-containing Schiff bases and their metal complexes

Three novel Schiff base ligands containing the azo group, 2-((E)-(4-((E)-phenyldiazenyl)phenylimino)methyl)phenol, 3-((E)-(4-((E)-phenyldiazenyl)phenylimino)methyl)benzene-1,2-diol and 4-((E)-(4-((E)-phenyldiazenyl)phenylimino)methyl)benzene-1,2,3-triol, were synthesized from the reaction of p-aminoazobenzene with salicylaldehyde, 2,4-dihydroxybenzaldehyde and 2,3,4-trihydroxybenzaldehyde, respectively. The mononuclear Co(II) and Cu(II) complexes of the Schiff base ligands were prepared and characterized using elemental analyses, IR, UV–visible spectroscopy, magnetic susceptibility and conductance measurements; ¹H NMR and mass spectra of the ligands were also recorded. The Co(II) and Cu(II) metal complexes are formed by the coordination of the N and O atoms of the ligands. The electrochemical properties of the metal complexes were investigated at 100 mV s^?1 scan rate in DMSO; the oxidative C–C coupling properties of the Co(II) and Cu(II) complexes were investigated on the sterically hindered 2,6-di-tert-butylphenol (DTBP). In addition, the Schiff base ligands and their complexes were evaluated for both their in vitro antibacterial activity using the disc diffusion method.     

The effect of alcohol on the passivation of al alloys in 1 N H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

In this study, the influence of different alcohol on the passivation of aluminium alloys have been investigated by using current-potential curves. Experimental results show that the addition of alcohol in H₂SO₄ solution have been changed passivation potential distance of the alloys. Elemental compositions of alloys have also directly affected passivation of alloys. This influence is more effective especially in alloys content higher Si also and less Cu.