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

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(PVA Microspheres)
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# Finish preparing PVA(MW 130,000) hydrogels for freeze-thaw method.
# Finish preparing PVA(MW 130,000) hydrogels for freeze-thaw method.
# Filter prepared clay exchanges.
# Filter prepared clay exchanges.
-
# Prepared DSC samples of all used clays.
+
# Prepare DSC samples of all used clays.
==PVA Microspheres==
==PVA Microspheres==

Revision as of 10:46, 8 February 2013

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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. Prepare 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:

Preparation of Microspheres using PVA MW 146,000-186,000 '
Amount of PVA added(g)0.9001
Amount of Lamponite clay added(g)0.1004
Amount of cellulose acetate butyrate added(g)0.6066
Amount of GA added(mL)0.75
Amount of H2SO4 added(mL)0.25


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.
  • Many of the microspheres formed large clumps. The next time in lab, the large clumps will be ground in a mortar and pestle to produce smaller microspheres.


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 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 2012/09/19.
  • For the 110% exchanged clays, after 4 hours on the vacuum filter, the clays were not dry. In order to have complete drying of the clays, the remaining wet clay was scraped from the Buchner funnel, placed on a tin tray, and placed in an oven at 90°C.

DSC

DSC sample preparation ' '
Name of sampleMass of pan(g)Mass of sample(g)
NaMT clay0.048130.00316
Lamp clay0.050180.00306
110% Lamp exchange0.049520.00308
110% NaMT exchange0.050140.00301
50% NaMT exchange0.048190.0029
  • The prepared samples will be run the next time in the lab.




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