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. Scrap all collected microspheres into a small vial.
11. Freeze microspheres in liquid nitrogen for ~2 minutes.
12. Place on [ask Dr. Hartings name of machine again] overnight to completely dry.

• 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.
• After 3 hour spinning and heat, large clumps of spheres formed. Upon scraping with a spatula these clumps broke apart into what appeared to be smaller spheres.
• Large clumps indicates that we may want to change portion of our method to produce smaller microspheres.
• The spheres were a cloudy, white color throughout.

Abbreviation Guide:

1. Sodium Montmorillonite clay will be referred to as NaMT.
2. Lamponite clay will be referred to as Lamp.
3. Glutaraldehyde will be referred to as GA.
4. Dimethyl sulfoxide will be referred to as DMSO.
5. Cellulose acetate butyrate will be referred to as CAB.

Hydrogel Preparation

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

Clay Filtration