Objectives
- Prepare PVA(MW 130,000) microspheres through suspension cross-linking of a polymeric solution with glutaraldehyde.
- Remove prepared MW 130,000 PVA hydrogels from freezer and begin soaking in water.
- Finish preparing PVA(MW 130,000) hydrogels for freeze-thaw method.
- Filter prepared clay exchanges.
- 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.
- Dissolve 1g total of PVA and clay additive in 5mL hot,deionized water.
- Acidify the solution using 0.25mL 0.5M H2SO4.
- Dissolve 0.6g Cellulose acetate butyrate(CAB) in 25mL 1,2-dichloroethane.
- Pour the acidified PVA solution into the 25mL 1,2-dichloroethane solution. Place all in a clean round bottom(RB) flask.
- Stir the water/1,2-dichlorethane solution for 30 minutes.
- After 30 minutes stirring, add 0.75mL glutaraldehyde(GA) to the solution.
- After the addition of glutaraldehyde, allow the reaction to carry out for 3 additional hours at 55°C.
- Filter the produced microspheres from the solution using a a sintered glass filter and a vacuum.
- Wash the collected microspheres using the following solvents in the following order:
- 1,2-dichloroethane
- acetone
- hot water
- cold water
- methanol
- Scrap all collected microspheres into a small vial.
- Freeze microspheres in liquid nitrogen for ~2 minutes.
- 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:
- 1,2-dichloroethane is highly flammable. Care must be used at all times when dealing with 1,2-dichloroethane
- Avoid all 1,2-dichloroethane skin contact by wearing gloves and googles.
- Avoid any 1,2-dichlorethane contact with extreme heat, open flame, or electrical sparks.
- 1,2-dichloroethane should be kept in the flammable storage safety cabinet when not in use.
- When in use, 1,2-dichloroethane should be kept in the fume hood.
PVA Microsphere information:
| Preparation of Microspheres using PVA MW 146,000-186,000
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'
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| Amount of PVA added(g) |
0.9001
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| Amount of Lamponite clay added(g) |
0.1004
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| Amount of cellulose acetate butyrate added(g) |
0.6066
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| Amount of GA added(mL) |
0.75
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| Amount of H2SO4 added(mL) |
0.25
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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:
- Sodium Montmorillonite clay will be referred to as NaMT.
- Lamponite clay will be referred to as Lamp.
- Glutaraldehyde will be referred to as GA.
- Dimethyl sulfoxide will be referred to as DMSO.
- Cellulose acetate butyrate will be referred to as CAB.
Hydrogel Preparation
- The six hydrogels prepared on 2013/01/30 were removed from the freezer. Approximately 4mL distilled H2O was added to each beaker. If the hydrogel was sticking to the side of the beaker, a spatula was used to scrape the hydrogel off the edges. The beakers were parafilmed and stored. These films will remain submersed in H2O for 3 days. This will remove any access DMSO.
Observations:
- After three days of the freeze-thaw method, the 6 prepared hydrogels have a firmer consistency than when prepared.
- Each hydrogel shrank in size(were significantly smaller than when originally prepared. The height of the hydrogel grew, but the diameter decreased).
- Although the films became firmer than when originally prepared, they still have some pliability(tested by pulling with a set of tweezers) and hold their shape.
- The hydrogels became more clear in their appearance, so the distribution of the clay is very evident.
- Using tweezers, it seems that the hydrogels with NaMT are the most rigid. This observation will be tested when performing tensile strength tests.
- Each of the six films had a crystal clear film that grew along the edges of the beaker during the freeze thaw method.
Clay Filtration
- After allowing the clays to spin for 4 days, the prepared clays were vacuum filtered following the protocol described on
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Project name
