scholarly journals Effect of Changing Solvents on Poly(-Caprolactone) Nanofibrous Webs Morphology

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
A. Gholipour Kanani ◽  
S. Hajir Bahrami
Keyword(s):  
Acetic Acid ◽  
Formic Acid ◽  
Glacial Acetic Acid ◽  
Methylene Chloride ◽  
Polymer Concentration ◽  
Average Diameter ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
Poly Caprolactone ◽  
Successful Production

Polycaprolactone nanofibers were prepared using five different solvents (glacial acetic acid, 90% acetic acid, methylene chloride/DMF 4/1, glacial formic acid, and formic acid/acetone 4/1) by electrospinning process. The effect of solution concentrations (5%, 10%, 15% and 20%) and applied voltages during spinning (10 KV to 20 KV) on the nanofibers formation, morphology, and structure were investigated. SEM micrographs showed successful production of PCL nanofibers with different solvents. With increasing the polymer concentration, the average diameter of nanofibers increases. In glacial acetic acid solvent, above 15% concentration bimodal web without beads was obtained. In MC/DMF beads was observed only at 5% solution concentration. However, in glacial formic acid a uniform web without beads were obtained above 10% and the nanofibers were brittle. In formic acid/acetone solution the PCL web formed showed lots of beads along with fine fibers. Increasing applied voltage resulted in fibers with larger diameter.

scholarly journals Thin layer chromatographic compatibility study in preformulation of new transdermal therapeutic systems

2020 ◽  
Vol 66 (1) ◽  
pp. 23-29
Author(s):  
Octavia-Laura Moldovan ◽  
Diana-Nicoleta Brihan ◽  
Nicoleta Todoran ◽  
Aura Rusu
Keyword(s):  
Acetic Acid ◽  
Thin Layer ◽  
Mobile Phase ◽  
Glacial Acetic Acid ◽  
Methylene Chloride ◽  
Hydroxyethyl Cellulose ◽  
Compatibility Study ◽  
Chemical Interactions ◽  
Miconazole Nitrate ◽  
Active Substances

AbstractObjective: The compatibility of four binary active substances combinations adapalene – levofloxacin (ADP-LFX), adapalene – miconazole nitrate (ADP-MCZ), levofloxacin – meloxicam (LFX-MLX) and levofloxacin – miconazole nitrate (LFX-MCZ) was analysed to be comprised in new transdermal therapeutic systems. Also, the compatibility of selected active substances and four polymeric excipients (hydroxypropyl methyl-cellulose - HPMC 15000, hydroxypropyl methylcellulose - HPMC E5, ethyl cellulose - EC 10, and hydroxyethyl cellulose – HEC) was studied.Methods: Thin layer chromatographic method (TLC) and four selected mobile phases were used. On the plate (in situ) were obtained the binary combinations (active substances and active substance-polymer).Results: A good compatibility of ADP-LFX was found using ammonia : methanol : acetonitrile : methylene chloride 2:4:1:4 mobile phase. Using chloroform : acetone : glacial acetic acid 34:4:3 on the chromatogram of ADP-MCZ, only ADP spots appeared but without changes in the shape of the spots and Rf values. Any modifications of LFX and MLX spots (from LFX-MLX mixture) had been observed using toluene : glacial acetic acid : methanol 11:1:0.5 mobile phase, although LFX spots have remained on the baseline. Only LFX spots were visible from LFX-MLX and LFX-MCZ mixtures (ammonia : methanol : acetonitrile : methylene chloride 2:4:1:4 mobile phase). Distinctive spots were observed for ADP, LFX and MLX with variable results from no chemical interactions to limited chemical interactions when the compatibility with polymers was verified.Conclusions: ADP-LFX and LFX-MLX mixtures were found to be compatible. ADP with HPMC polymers and LFX with HPMC E5 and HEC had presented excellent compatibility; for the other binary combinations, different analytical methods will be necessary.

OPTIMIZATION OF ELECTROSPINNING PROCESS PARAMETERS FOR TISSUE ENGINEERING SCAFFOLDS

2006 ◽  
Vol 01 (02) ◽  
pp. 153-178 ◽  
Author(s):  
MING CHEN ◽  
PRABIR K. PATRA ◽  
STEVEN B. WARNER ◽  
SANKHA BHOWMICK
Keyword(s):  
Cell Growth ◽  
Process Parameters ◽  
Growth Kinetics ◽  
Fiber Diameter ◽  
Average Diameter ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
Average Fiber Diameter ◽  
High Concentration ◽  
Cell Growth Kinetics

The goal of the current study was to optimize important process parameters for electrospinning polycaprolactone (PCL) for growing 3T3 fibroblasts. We hypothesized that the smallest obtainable fiber diameter would provide the best cell growth kinetics and we tested this hypothesis for three different process parameters: solution concentration, voltage and collector screen distance. Beaded structures were formed when using low concentration electrospinning solutions (8 wt% to 13 wt%), in which the viscosity ranged from 16.0 c P to 340.0 c P . In this concentration range, cell growth kinetics was impeded when using a high concentration of cells (8–10 × 105). Higher PCL concentration led to an increase in the average fiber diameter from 400 nm to 1600 nm when PCL solution concentration changed from 15 wt% to 20 wt%. Although, the mean values indicated that cell growth kinetics were higher at the lower end of the concentration (15% as opposed to 20%) and this correlated with lower average fiber diameter, the results in this range were not statistically significant (p > 0.05). The average fiber diameter of scaffolds first decreased and then increased when electrospinning voltage was increased. The cell growth kinetics demonstrated that smaller average diameter PCL fiber scaffolds had higher growth kinetics than larger average diameter scaffolds with the best conditions obtained at 15 KV. By increasing the screen distance, the average fiber diameter decreased but had no significant impact on cell growth kinetics. In summary, the optimal parametric space for 3T3 fibroblast growth for our studies was electrospinning a 15 wt% PCL solution using 15 kV voltage and a 25 cm collector distance.

Iodimetric determinations in organic solvents: Determination of manganese oxidation states in methylene chloride solutions

1990 ◽  
Vol 68 (1) ◽  
pp. 79-81 ◽  
Author(s):  
Joaquin F. Perez-Benito ◽  
Enrique Brillas ◽  
Conchita Arias
Keyword(s):  
Acetic Acid ◽  
Quaternary Ammonium ◽  
Glacial Acetic Acid ◽  
Methylene Chloride ◽  
Oxidation States ◽  
Manganese Oxidation ◽  
Chloride Solutions ◽  
Tetrabutylammonium Iodide ◽  
Organic Solutions

An iodimetric technique has been developed to quantitatively analyze the oxidants present in organic solutions. Addition of excess tetrabutylammonium iodide and excess glacial acetic acid results in the formation of tetrabutylammonium triiodide, whose concentration can be measured spectrophotometrically at 295 or 365 nm. Application of this technique to the determination of the final oxidation state of manganese in permanganate reactions in methylene chloride solutions is described. The equilibrium constant for formation of tetrabutylammonium triiodide in methylene chloride has been measured: K = (3.48 ± 0.12) × 104 at 25.0 °C. Keywords: iodimetric determinations, manganese oxidation states, methylene chloride, quaternary ammonium permanganate, quaternary ammonium triiodide.

scholarly journals Controlled Morphology of Porous Polyvinyl Butyral Nanofibers

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Daniela Lubasova ◽  
Lenka Martinova
Keyword(s):  
Applied Voltage ◽  
High Efficiency ◽  
Polymer Concentration ◽  
Polyvinyl Butyral ◽  
Solution Concentration ◽  
Solvent Mixture ◽  
Electrospinning Process ◽  
Filter Materials ◽  
One Step ◽  
Poor Solvent

A simple and effective method for the fabrication of porous nanofibers based on the solvent evaporation methods in one-step electrospinning process from the commercial polyvinyl butyral (PVB) is presented. The obtained nanofibers are prevalently amorphous with diameters ranging from 150 to 4350 nm and specific surface area of approximately 2–20 m2/g. Pore size with irregular shape of the porous PVB fibers ranged approximately from 50 to 200 nm. The effects of polymer solution concentration, composition of the solvents mixture, and applied voltage on fiber diameter and morphology were investigated. The theoretical approach for the choice of poor and good solvents for PVB was explained by the application Hansen solubility parameter (HSP) and two-dimensional graph. Three basic conditions for the production of porous PVB nanofibers were defined: (i) application of good/poor solvent mixture for spinning solution, (ii) differences of the evaporation rate between good/poor solvent, and (iii) correct ratios of good/poor solvent (v/v). The diameter of prepared porous PVB fibers decreased as the polymer concentration was lowered and with higher applied voltage. These nanofiber sheets with porous PVB fibers could be a good candidate for high-efficiency filter materials in comparison to smooth fibers without pores.

REARRANGEMENT STUDIES WITH C14: V. THE SOLVOLYSIS OF 2-PHENYLETHYL-1-C14p-TOLUENESULPHONATE

1957 ◽  
Vol 35 (12) ◽  
pp. 1417-1422 ◽  
Author(s):  
C. C. Lee ◽  
G. P. Slater ◽  
J. W. T. Spinks
Keyword(s):  
Acetic Acid ◽  
Formic Acid ◽  
Glacial Acetic Acid ◽  
Ion Pair ◽  
Absolute Ethanol ◽  
Solvent Systems ◽  
Anhydrous Formic Acid

The solvolysis of 2-phenylethyl-1-C14p-toluenesulphonate in absolute ethanol, glacial acetic acid, 90% formic acid, and anhydrous formic acid gave rise to products which showed rearrangements of the C14-labeled atoms from the C-1 to the C-2 positions to the extent of 0.3%, 5.5%, 40%, and 45%, respectively. The results constitute an unequivocal proof that phenyl participation occurs in the reactions studied. The different degrees of rearrangement found for the different solvent systems are in agreement with the concept that the solvolysis process may have a range of mechanisms between the two extremes of the nucleophilic or SN2 type and the limiting or SN1 type. In the solvolysis in absolute ethanol, a small amount of "unreacted" 2-phenylethyl p-toluenesulphonate recovered from the reaction mixture was found to show isotope position rearrangement of almost the same degree as the ethanolysis product. This finding is tentatively attributed to the phenomenon of internal return involving an ethyl-phenonium p-toluenesulphonate ion-pair.

A Simple Method to Prepare Affinity Resins on Cellulose Basis

1984 ◽  
Vol 39 (11-12) ◽  
pp. 1048-1051 ◽  
Author(s):  
Karl Eisele ◽  
Fernando Dias Costa ◽  
Carlos Pascual ◽  
Beatus Ofenloch-Hähnle
Keyword(s):  
Molecular Weight ◽  
Acetic Acid ◽  
Glacial Acetic Acid ◽  
Androgen Receptors ◽  
Methylene Chloride ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Low Molecular Weight ◽  
Amino Acid Residues ◽  
Simple Method

Abstract Affinity resins with different spacer arms were synthesized analogues to the solid phase peptide synthesis using aminoethyl cellulose or carboxymethyl cellulose as matrix. The spacer arms could be varied in length and rigidity. Especially spacer arms consisting of poly am ino acids can be synthesized with a defined amount of amino acid residues specifically in the low molecular weight ranges. The method is also applicable to other matrices w hich are not susceptible to 1 ɴ HCl in glacial acetic acid, trethylamine, methylene chloride and dimethylformamide. The synthesis of affinity resins with different spacer arms for the purification of androgen receptors is described as an example of the method.

Allometric Scaling Relationship between Solution Concentration and Nanofiber Diameter in Bubble Electrospinning and its Experimental Verification

2010 ◽  
Vol 148-149 ◽  
pp. 869-872 ◽  
Author(s):  
Yong Liu ◽  
Liang Dong ◽  
Jie Fan ◽  
Rui Wang ◽  
Ru Dong Chen
Keyword(s):  
Allometric Scaling ◽  
Present Model ◽  
Scaling Law ◽  
Average Diameter ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
Scaling Relationship ◽  
Nanofiber Diameter ◽  
Theoretical Predictions ◽  
High Prediction

An allometrical scaling relationship between the solution concentration and the nanofiber diameter in bubble electrospinning was established. The scaling law was validated with experimental results using bubble-electrospun Polyvinylpyrrolidone (PVP) nanofibers at different concentration PVP solutions. The results showed that the average diameter of PVP nanofibers increased approximately exponentially with solution concentration in bubble electrospinning process. The experimental data agreed well with the theoretical predictions, and showed that the present model had high prediction accuracy.

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