Molecular structure and solution properties of surfactants

Yüksek Lisans teziMolekül yapılarında içerdikleri hidrofil ve hidrofob gruplar nedeniyle surfaktanlar gıda, boya, deterjan, ilaç ve kozmetik sanayide geniş ölçüde kullanılmıştır. Hidrofil ve hidrofob grupların verdiği çeşitlilik ise surfaktan çözeltilerinin fizikokimyasal özelliklerinde değişikliğe sebep olur. Surfaktan çözeltilerinde moleküllerin öz toplaşımı termodinamik bakımdan istemli olup molekül yapısına bağlıdır. Israelachvili v.d. tarafından tanımlanan moleküler paketleme parametresi ile çözeltide oluşan miselin şekli ve büyüklüğü hakkında bilgi edinilebilir. Bu çalışmada, sodyum dodesil sülfat, dodesil trimetil amonyum bromür gibi surfaktanların sudaki çözeltilerinde öz toplaşım yolu ile oluşan miselin şekli ve büyüklüğü moleküler paketleme parametresi ile tayin edilmiştir. Surfaktan çözeltilerinin içsel viskozite, yoğunluk, kısmi spesifik hacim gibi hidrodinamik özelliklerinin ölçülen değerleri yardımıyla da sonuçlar doğrulanmaya çalışılmıştır. Buna göre incelenen surfaktanlardan sodyum dodesil sülfat çözeltisinde oluşan miselin hidrofob grupların iç tarafta, polar grupların da yüzeye yerleştiği oblat küresel bir şekle sahip olduğu, önemli ölçüde hidrate olduğu ve dinamik bir yapıda bulunduğu söylenebilir.AbstractOn account of the hydrofob and hydrophile groups containing in their molecular structure, surfactants have been extensively used in food, dye, detergent, perfume and cosmetic industries. The variety attributed to hydrofob and hidrophile groups causes the change of the physicochemical properties of the surfactant solutions. Molecular selfassembly in surfactant solutions occurs spontaneously and depends on the molecular structure of surfactants. By means of the molecular packing parameter described by Israelachvili et al., it can be possible to derive the information as to micelle shape and size. In this study the size and shape of micelle formed by the self assembly in the surfactant solutions such as sodium dodecyl sulfate, dodecyl trimethyl ammonium bromide has been determined by the molecular packing parameter. By means of the hydrodynamic properties such as intrinsic viscosity, density and partial specific volume obtained by experimentally, the results have been confirmed. Based on this, it can be said that sodium dodecyl sulfate micelles formed in the solution by self assembly have the oblate spherical shape, and the hydrofob groups have been located in the highly hydrate interior of dynamic micelle structure

Biomimetric coating of monophasic brushite on Ti6Al4V in new m-5xSBF

Ti6Al4V plates were exposed to soaking alkali treatment resulted in Na0.23TiO2 phase on the surface before realizing biomimetic Calcium-Phosphate (CaP) coating in prepared m-5xSBF and 5xSBF solutions at 37 degrees C and pH 6. The aim of the present study was to examine CaP nucleation on the Ti6Al4V substrate in the new biomimetic medium, which allows the precipitation of uniform and monophasic CaPs coating within 2 days. Characterizations of coated surfaces were performed by SEM and EDX, FESEM, FTIR, Raman and contact angle measurements. Phase formation (Na0.23TiO2, 22-1404; TiO2, 21-1276; CaHPO4(H2O)(2), 72-0713 and Ca-5(PO4)(3)OH, 09-0432), average particle size distribution (0.1 - 1.8 mu m for HA, 0.5 - 4.7 mu m and 10.7 - 239.4 mu m for width and length of Brushite), the specific surface area (85,623 and 1,169,412 m(2) g(-1) for Brushite and HA, respectively) and phase transformations (from brushite to calcium pyrophosphate) of the coated CaP powders on the surface were also examined by XRD, DLS technique, BET, and TGA, respectively. As a result, it has been possible to obtain for the first time monophasic brushite phase coated on Ti6Al4V in m-5xSBF biomimetic medium and monophasic brushite coated surface characterization was compared with hydroxyapatite coated surface obtained in 5xSBF

Effect of Solution and Calcination Time on Sol-gel Synthesis of Hydroxyapatite

Nano-sized hydroxyapatite (HA) particles were synthesized by sol-gel through water and ethanol based mediums of phosphoric acid (H3PO4) and calcium hydroxide (Ca(OH)(2)) at pH = 11 for different calcination time (1 h, 2 h, 4 h). The effects of calcination time and solution on the crystallinity, morphology and impurity phases of the HA nanoparticles were examined via Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). It was found that crystallite size and the fraction crystallinity of the synthesized samples increased with calcination time. According to solution medium, only CaO as impurity was appeared in the water-based solvent, CaO and Ca(OH)(2) impurities were appeared in the ethanol-based solvent. The lowest crystallinity was 0.92 and the highest crystallinity was 1.73 respectively, depending on the process parameters. The Ca/P atomic ratio closest to the bone was found as 1.5178. As a result, the employed water-based sol-gel processes for 1 h calcination time was determined as the optimum for the formation of nano-sized HA powders using calcium hydroxide and phosphoric acid

3D porous collagen/functionalized multiwalled carbon nanotube/chitosan/hydroxyapatite composite scaffolds for bone tissue engineering

In this study, we describe new collagen/functionalized multiwalled carbon nanotube/chitosan/hydroxyapatite (Col/f-MWCNT/CS/HA) composite scaffolds which were fabricated by freezing ( - 40 degrees C at 0.9 degrees C/min) and lyophilization (48 h, 0 degrees C and 200 mtorr). The compressive stresses (from 523 to 1112 kPa), swelling (from 513.9 +/- 27 to 481.05 +/- 25%), porosity (from 98 +/- 0.15 to 95.7 +/- 0.1%), contact angle (from 87.8 to 76.7 degrees) properties examined before and after biomineralization for comparison 3D porous Col, CS, Col/f-MWCNT and Col/f-MWCNT/CS scaffolds. Biomineralization was performed by biomimetic method in concentrated SBF (10 x SBF, at 37 degrees C and 6.5 pH). XRD, SEM, EDS, FTIR, TGA, Optical microscopy and BET results showed that compared to Col, CS and Col/f-MWCNT scaffolds, Col/f-MWCNT/CS scaffolds had higher in vitro bioactivity, large surface area (11.746 m(2)/g) and a good pore volume (0.026 cc/g), interconnected porous microstructure (with 20-350 mu m pore size) and incorporates the advantageous properties of both Col, f-MWCNT, CS and HA. Finally, the methyl thiazolyl tetrazolium (MTT) assay was performed to evaluate scaffolds cytotoxicity which showed that Col/f-MWCNT/CS scaffolds have the best biocompatibility

Microwave-assisted biomimetic synthesis of hydroxyapatite using different sources of calcium

In this study, some properties of biomimetic synthesized hydroxyapatite by using different sources of calcium were investigated. Biomimetic synthesis of hydroxyapatite was carried out in microwave oven using 1.5 simulated body fluid (SBF) solution having different calcium sources with 800 W power for 15 min. As phosphorus source di-ammonium hydrogen phosphate ((NH4)(2)HPO4) while for each sample as a calcium sources calcium chloride (CaCl2), calcium nitrate tetra hydrate (Ca(NO3)(2)center dot 4H(2)0) and calcium hydroxide (Ca(OH)(2)) were utilized, respectively. For comparison, precipitation process was also performed in only 1.5 SBF solution without calcium and phosphorus sources. The presence of phases in synthesized hydroxyapatite was confirmed by XRD. The crystallinity and crystalline size of the phases in as synthesized powders were also calculated by using XRD data. It was found that the unique phase is hydroxyapatite (HAp, Cas(PO4)(3)(OH)) by using the calcium nitrate tetra hydrate and calcium hydroxide sources, while the dominant phases are tri-calcium phosphates (TCP) and HAp for CaCl2 source and 1.5SBF which does not contain any additional Ca source. SEM studies revealed that nano hexagonal rods and nano-spherical hydroxyapatites could be synthesized by using this process. Energy dispersive X-ray spectroscopy (EDS) analysis revealed that the Ca/P ratio near to be as 1.5 which is the value for HAp in bone. Raman and Fourier transform-infrared spectroscopy (FT-IR) results combined with the X-ray diffraction (XRD) indicates that dominantly the present of single phase is HAp. The crystal size and fraction crystallinity of as synthesized HAp powders were changed between 29.5 and 45.4 nm and 0.53-2.37, respectively. Results showed that microwave assisted biomimetic synthesis is a promising method for obtaining HAp powders in shorter process time. (C) 2017 Elsevier B.V. All rights reserved

The effect of reduction of graphene oxide on the formation of hydroxyapatite and tricalcium phosphate

This study reports on biomimetic mineralization route employing reduced graphene oxide (RGO) at different rates as a template material for biomineralization of biphasic hydroxyapatite/tricalcium phosphate (HAP/TCP). RGO-HAP/TCP hybride composites were synthesized via biomineralization in Simulated Body Fluid (SBF). GO was prepared from pristine graphite by Hummers and Offeman method. GO nanoparticles were reduced with sodium borohydride (NaBH4) before soaking in 5xSBF for 3 weeks at 37 degrees C and 7.4 pH to performing biomineralization. Surface area and average size distribution of fabricated GO were found as 813.2 m(2) g(-1) and 1.2968 mu m by using BET and DLS technique, respectively. All surfaces are overall negatively charged and zeta potentials of GO, R(1)GO, R(2)GO, R(3)GO were found to be -35.05, -30.01, 29.5, -29.01 and -28.9, respectively in the neutral pH. The contact angles of GO, R(1)GO, R(2)GO and R(3)GO are 33.5 degrees, 55.3 degrees, 57.4 degrees and 61.1 degrees, respectively. The ID/IG values determined by Raman are 1.07, 1.04, 1.02 and 1.01 for GO, R(1)GO, R(2)GO and R(3)GO, respectively. After the reduction, its maximum peak at 236 was clearly shifted to 260, 264 and 267 nm for R(1)GO, R(2)GO and R(3)GO. The precipitation of biphasic HAP/TCP on R(1)GO and R(2)GO was confirmed by XRD, FTIR and TGA analysis. (C) 2017 Elsevier Ltd. All rights reserved

Effect of particle size on microstructural and mechanical properties of UHMWPE-TiO2 composites produced by gelation and crystallization method

In this study, Ultra-high-molecular-weight polyethylene (UHMWPE) in 0.5 wt % concentration-0.5, 1, and 2 wt % nanosized and micron-sized TiO2 composites were produced via gelation/crystallization method in decalin + antioxidant solution at 150 degrees C for 45 min by using magnetic stirrer. The gel composites were cooled in an aluminum tray embedded in iced water under ambient conditions and dried in an oven at 130 degrees C for 90 min to remove any residual trace of decalin and to strengthen the UHWMPE matrix. Scanning electron microscopy-EDS images indicate that TiO2 particles were integrated well with the polymer matrix. differential scanning calorimetry studies revealed that the crystallinity of pure UHMWPE was calculated as 56% and an increase of 13.32% for micron sized and 19.25% for nano sized TiO2. Crystalline and amorphous phases of UHMWPE-TiO2 composites confirmed by Raman are in good agreement with the literature. The elastic modulus of test materials ranged from 610 to 791 MPa for micron sized and raised from 675 to 1085 for nano sized reinforcing agents. Ultimate tensile stress increased about 35% for micron sized and 60% for nano sized weight 1% TiO2 reinforced composites. Biomineralization tests (performed in stimulated body fluid, at 37 degrees C and 6.5 pH during 1 month) have shown that produced composites are compatible as acetabular liner replacement for hipjoints due to no accumulation (Ca, P, Na, etc.) on UHMWPE-TiO2 composites. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47402

A comparison of pretreatments on hydroxyapatite formation on Ti by biomimetic method

In this study, hydroxyapatite coating on titanium material substrate was successfully performed by using biomimetic method. Titanium plates immersed in 1.5 SBF at pH 7.4 and 37 degrees C were analyzed at the end of the first, second, and fourth weeks. At the end of the first week, the immersion process was continued with the sample exposed to the optimum selected surface pretreatment. Three different treatments have been applied to determine the optimum surface treatment: each substrate immersed into NaOH, HCl, and NaOH + HCl solutions before heat treatment at 600 degrees C for 1 h and immersed in NaOH solution was selected the optimum surface treatment. The presence of biphasic hydroxyapatite (HA, Ca-5(PO4)(3)(OH)) and tricalcium phosphate (TCP, Ca-3(PO4)(2)) on Ti surfaces were confirmed by XRD. SEM studies showed that denser HA coating which have nano-sphere-like morphology formed on Ti pretreated with NaOH solution at the end of first week than other hydroxyapatite (HA)-coated Ti pretreated with NaCl and NaOH + NaCl solutions and coating thickness increased by increasing immersion time. The HA coating thickness of the samples immersed in optimum pretreatment solution was found as 178 and 340 mu m for at the end of second and fourth weeks, respectively. The particle size analysis of the biphasic HA powders scraped from the coating layer on the substrate before and after sintering was carried out by Zetasizer and it showed that HA powders have 0.58 mu m average particle size and their particle size distribution has less dimensional dispersion after sintering. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed that the Ca/P ratio in HA powders was near to 1.5. Raman and Fourier transform-infrared spectroscopy (FTIR) results combined with the X-ray diffraction (XRD) indicated the presence of biphasic hydroxyapatite after biomimetic coating process and increment in crystallinity of the powders after sintering. It was found that HA nucleation on Ti pretreated with NaOH solution was higher than Ti pretreated with other solutions which is confirmed by electrochemical impedance spectroscopy (EIS)