Beads re-swelling
1) The beads had turned into black clumps when we removed them from the freeze-dryer.
- Upon closer observation, the beads seemed greenish and difficult to separate from another.
- We weighed the dried beads, and re-immersed them in water.
- 10% Beads: 0.811 g
- 20% Beads: 1.007g
- 40% Beads: 1.123g
- Upon immersion, the beads remained clumped together, but turned more green. The more clay there is, the less yellow the beads seem to be.
Photo of dry beads:
Photo of immersed beads:
2) We boiled the cabbage to remove the red cabbage dye from the leaves and obtain a colored solution.
- Dye is neutral (cabbage dye is purple at pH 7)
- Checked effect of pH on dye color
- Beaker on the left is acidic. Beaker in the middle is neutral. Beaker on the right is basic.
--> we will need an acidic environment because we need the dye to be a cation.
3) Analysis of cabbage dye via UV Vis:
- performed serial dilutions as follows: Stock solution, 4:1 Stock to water, 3:2 Stock to water, 2:3 Stock to water, and 1:4 Stock
Resulting spectrum:
Notes
- The vacuum likely induced further hydrolysis of the PvOH, similarly to what we observed when we dried the beads in the oven.
- A patent on PvOH synthesis explains the discoloration is due to hydrolysis leading to formation of conjugated double bonds with terminal aldehyde groups.
This paper talks about the pyrolysis reaction of PvOH : http://fire.nist.gov/bfrlpubs/fire95/PDF/f95145.pdf
- If the beads are not re-swollen by Friday, we will have to make new beads and use a different drying technique.
- Most likely, we will vacuum filtrate the beads and then let them sit over several days.
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