User:Moira M. Esson/Notebook/CHEM-581/2013/02/06

Objectives

1. Prepare PVA(MW 130,000) microspheres through suspension cross-linking of a polymeric solution with glutaraldehyde.
2. Remove prepared MW 130,000 PVA hydrogels from freezer and begin soaking in water.
3. Finish preparing PVA(MW 130,000) hydrogels for freeze-thaw method.
4. Filter prepared clay exchanges.
5. Prepared DSC samples of all used clays.

PVA Microspheres

General Protocol:

• Reaction should be carried out using a reflux condenser and a thermostatic water bath of 55°C.

1. Dissolve 1g total of PVA and clay additive in 5mL hot,deionized water.
2. Acidify the solution using 0.25mL 0.5M H₂SO₄.
3. Dissolve 0.6g Cellulose acetate butyrate(CAB) in 25mL 1,2-dichloroethane.
4. Pour the acidified PVA solution into the 25mL 1,2-dichloroethane solution. Place all in a clean round bottom(RB) flask.
5. Stir the water/1,2-dichlorethane solution for 30 minutes.
6. After 30 minutes stirring, add 0.75mL glutaraldehyde(GA) to the solution.
7. After the addition of glutaraldehyde, allow the reaction to carry out for 3 additional hours at 55°C.
8. Filter the produced microspheres from the solution using a a sintered glass filter and a vacuum.
9. Wash the collected microspheres using the following solvents in the following order:
   1. 1,2-dichloroethane
   2. acetone
   3. hot water
   4. cold water
   5. methanol
10. Dry the microspheres at 60°C overnight.

• The following procedure was adapted from the article Poly(vinyl alcohol) microspheres with pH- and thermosensitive properties as temperature-controlled drug delivery [1]

1,2-dichlorethane safety:

1. 1,2-dichloroethane is highly flammable. Care must be used at all times when dealing with 1,2-dichloroethane
2. Avoid all 1,2-dichloroethane skin contact by wearing gloves and googles.
3. Avoid any 1,2-dichlorethane contact with extreme heat, open flame, or electrical sparks.
4. 1,2-dichloroethane should be kept in the flammable storage safety cabinet when not in use.
5. When in use, 1,2-dichloroethane should be kept in the fume hood.

PVA Microsphere information:

Observations:

• The dispersion agent(hereout referred to as CAB), lamponite clay and PVA formed a sort of suspension in the water/organic solvent solution. It did not appear to fully dissolve. Used a spatula to scrape the side of the RB flask in order to try and break up the large chunks.
• After addition to heat, the large chunks generally broke apart. Small spheres seemed to be forming after approximately an hour spinning.

Hydrogel Preparation

• The general protocol described on January 30th was followed.

Clay Filtration