The objectives for today's lab are making PVOH beads and cross linking the PVOH films made on Friday, 9/2/16.
The full procedure for making the PVOH beads can be found here, scaled to roughly 4.5 g. The procedure we used, with our altered reagent amounts, can be found below:
- 120 mL of ethyl acetate and 2mL of glutaraldehyde was added to a large dish
- 14.85 mL of the 3% montmorillonite clay solution was combined with 33.15 mL of 1.0 M HCl (0.4456 g clay used).2g of PVA was added to this solution and was mixed, while heating, until all PVA crystals have dissolved.
- The PVOH-clay solution was then added, dropwise, to the ethyl acetate and glutaraldehyde solution using a burette. The solution needs to be vigorously stirring during this step.
We did not continue the rest of the procedure because the beads did not correctly form.
Cross Linking PVOH Films
The full procedure we used could be found here.
- Record the mass of the dried films.
- 0.5 mL of glutaraldehye: 1.0429 g
- 0.5 mL of glutaraldehye with bentenite: 1.1424 g
- 1.0 mL of glutaraldehye: 1.1325 g
- 150 mL of sulfate stock solution (made on Friday, 9/2/16) was heated to 70°C.
- 2 of the films were added to the heated solution for 60 minutes and were separated from each other enough to not stick together.
- The films were individually rinsed with DI water for ~5 seconds.
- 150 mL of 1.0 M HCl stock solution (made on Friday, 9/2/16) was heated to 70°C.
- The 3 films were added to the heated solution for 60 minutes and were again separated from each other enough to not stick together.
- The films were rinsed with and soaked in DI water for about 10 minutes.
- The films were then placed in heated 0.2 M NaHCO3 stock solution for 30 min, then rinses and soaked with DI water again for 10-20 minutes.
- The films were left to air dry for 2 days
These protocols are very useful to any reader. Keep it up.
The synthesis of beads did not work. Large clumps formed, not small beads. This was likely due to a number of factors: the montmorillonite clay not being able to form small beads like the bentonite clay, the solution not stirring fast enough, the drops were added too quickly, not enough solvent, or the stir bar being too small.
Good suggestions. We now know that the order of addition is the key factor.