User:Mary Mendoza/Notebook/CHEM 581: Experimental Chemistry I/2014/10/31

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Continuation of Bead Synthesis Trials The burette set-up utilized by Eleni, Melvin, and Becca's group will be used; details of their assembly can be found on Kalivas' entry for 10/29/2014. The assembly was prepared as shown in the picture. Description A column was set up with glutaraldehyde and hexane. Air is being bubbled through the column to mix the two liquids. PVA-Clay will be dropped down the column Hexane Trial The PVA-Clay formed beads within the hexane and floated down the column. They did not cross-link fast enough if at all and they dissolved into the glutaraldehyde. Organic-Glutaraldehyde Solution We attempted to add acetone to glutaraldehyde and then add hexane to get rid of the solvent layers. The solution was not hydrophobic enough to form beads however. When only a slight layer of hexane and stirring were applied, it yielded no good results. We have decided to abandon the beads and begin synthesis of ribbons We filled a column with acetone and 1.5mL of Glutaraldehyde we then dropped in the PVA-Clay Trial of Several Organic Solvents I observed that as soon as the organic phase, formed bead comes into contact with the aqueous phase of the glutaraldehyde, the bead disperses into the aqueous solution. I decided to conduct my own trials and have my group members continue the burette-ribbon experiments. I concluded that the dilemma in the formation of beads is the immiscibility of the organic phase which forms the beads and the aqueous phase that cross-links the beads. Therefore, I thought, I can resolve this issue by choosing several organic solvents slightly miscible with water but hydrophobic enough to form the beads. In an attempt to keep the reaction mixture homogenized, motion is required. Thus, the reaction should be kept stirring on a stir plate. Also, stirring prevents the formed beads from clumping together." I used the solvent miscibility table provided by Dr. Hartings taken from chemical company, phenomenex, as shown in the picture. Acetonitrile Trial A drop of the PVA-clay was added into 3 mL of acetonitrile contained in a 12x100 mm, 8 mL disposable test tube. The PVA-clay did not form beads. Acetonitrile was tested without the use of the solvent miscibility chart. Upon checking the chart, the solubility in water of acetonitrile (%w/w) is 100. DMSO and Ethyl Acetate Hence, I selected the top 5 least immiscible organic solvent according to their solubility in water (%w/w) as shown in the picture. I first tested dimethyl sulfoxide (DMSO) and ethyl acetate. For DMSO, a quick formation of bead was observed but readily dispersed as it settled on the bottom of the tube. On the other hand, as the drop of PVA-clay-HCl passed through the ethyl acetate, the bead retained its shape for at least 5 to 7 seconds and gradually dispersed. Without testing the remaining organic solvents, I chose ethyl acetate as my organic solvent. It had the suitable features such that it enables the bead formation and its slight immiscibility with water. Next, it was time to test ethyl acetate with glutaraldehyde. The following amounts for the ethyl acetate trial were not exactly measured but made by approximation. I took a 50 mL beaker with a magnetic stir bar. I approximately added 15-20 mL of ethyl acetate. In a drop wise manner, I added my PVA-clay-HCl solution using a pasteur pipette. I added at least 500 uL of glutaraldehyde. With this experimental set-up, I was able to form beads but had to resolve the ratio of materials I used since everything was performed by approximation.