User:Karlena L. Brown/Notebook/PVOH Research/2013/02/20

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  • Prepare more microspheres samples expanding upon new previous method developed
  • Begin fluorescence detection through pressure testing analysis of hydrogel samples

Expanded Method of PVOH Clay Microsphere Preparation

  1. In 50mL beaker, dissolve ~ 1.0g total of PVOH 146K or PVOH 130K along with clay additive selected in 25mL hot deionized H2O
  2. Place a stir bar in the 50mL beaker and then heat solution at 100°C for ~ 12-15 minutes until complete dissolution of PVOH / clay sample
  3. Cool solution for ~ 5 minutes, then remove the stir bar, and add PVOH clay sample to a blender.
  4. Afterwards, then add 35mL rather than 25mL of mineral oil to the sample in the blender.
  5. Blend sample solution prepared in blender for ~ 7 minutes on high to form a more homogeneous mixture / emulsion (creating a suspension of microspheres)
  6. After 7 minutes, quickly pour solution into several mini 10mL vials and then add some Rhodamine 6G dye to the solution based upon the ratio selection (90:10 vs. 50:50)
  7. Next, quickly freeze the PVOH clay sample immersed in safflower oil in liquid nitrogen for ~ 5 min. The vial should be held in the liquid nitrogen until the sample is completely frozen throughout.
  8. After the addition of the dye and liquid nitrogen freezing, allow the solution to go through freeze / thaw crosslinking process for ~ 2-3 days
  9. Place microsphere solution in a freezer at -20°C for 24 hours and then remove and allow to solution to thaw for 24 hours

Important Liquid Nitrogen Safety

  • Liquid nitrogen is toxic colorless odorless liquid that freely disintegrates into a gas (MW: 28.00 g/mole)
  • Liquid nitrogen is a cryogenic liquid that readily and instantaneously freezes items
  • Avoid all liquid nitrogen skin contact by wearing gloves and goggles
  • Liquid nitrogen should be kept in a closed cap double barreled metal tin when not in use to inhibit inhalation and asphyxiation
  • When in use, pour liquid nitrogen carefully into double barreled small open metal container -- only small amount necessary
  • If spilled, allow substance to evaporate readily -- do not use a paper towel to wipe up substance because it will instantaneously freeze
  • If spilled, avoid standing too close to the spill or inhaling fumes
  • Keep all spills of liquid nitrogen in a closed space
  • When immersing samples into liquid nitrogen, use beaker tongs while standing at a safe distance away from the solution
  • Limit the contact of liquid nitrogen on gloves or other body parts due to ability to cause severe frostbite
  • To expose of liquid nitrogen, pour solution on the floor in a closed space. Allow substance to freely evaporate into a gas
  • Wash hands after removing gloves that were in contact with liquid nitrogen

PVOH 146K Prepared Microsphere Samples & Dye Preparations 2

1μM Rhodamine 6G Dye Concentration (90:10)

  M1V1 = M2V2
  1μM (RG6)x 10mL = (92μM)V2    V2 = 109μL

1μM Rhodamine 6G Dye Concentration (50:50)

  M1V1 = M2V2
  1μM (RG6)x 10mL = (165μM)V2    V2 = 61μL
PVOH vs. Clay Ratio Clay Selection PVOH 146K Mass (g) Actual Clay Mass (g) H2O Added (mL) Dye Concentration (μM) Dye Amount Added (μL)
50:50 Laponite 0.50220 0.50250 25 165 61
50:50 110% CEC Laponite w/ DMHXLBR 0.50960 0.50460 25 165 61
50:50 NaMT .50250 0.49980 25 92 109

Hydrogel Pressure Testing Protocol (Bent Pippette)

  1. Heat a 9 in. Corning disposable, non-sterile Pasteur pipette using a Bunsen burner in order for the pipette to bend in various directions
  2. Select a hydrogel for pressure analysis and measure out ~ 0.1 grams of the sample
  3. Next, using a razor blade cut the hydrogel for testing into small cubes in order to fit into the Pasteur pippette
  4. Once placing the sample in a Pasteur pipette, attach a rubber bulb to the top of the pipette, and allow 3mL of distilled H2O enter into the pipette by squeezing ribber bulb
  5. Progressively squeeze the bulb in order to expel the 3mL of H2O and apply a pressure to the hydrogels – dispensing Rhodamine 6G dye (dye leaching)
  6. Collect the expelled samples into a small 25mL beaker in order to fluorescence detection analysis

Hydrogel Pressure Samples Tested

90:10 PVOH MW 146K 110% CEC Lamponite w/ DMHXLBR Hydrogel '
Pasteur Pipette Shape Amount of Hydrogel Used(g)
Pasteur pipette w/ no modifications 0.1575
Pipette stem bent at slight angle < less than 90 degrees 0.1134
Pipette stem bent at slight angle < 90 degrees beginning stem of pipette 0.1397
Pipette w/ three pockets at top 0.1039
Pipette bent twice in the stem 0.1158
Pipette bent at top ≈ 90 degree angle w/ pipette sides almost touching 0.1108
Pipette with a twist in middle 0.0993
Pipette bent twice in the middle 0.1416
Pipette w/ two pockets in the top 0.1041
Pipette w/ top bent & sides almost touching = 90 degree angle 0.1258
Plain Pasteur pipette w/ no modifications: Run #2 0.1210


  • Previously prepared microspheres on 2/15/13, formed layer of film at the bottom of each beaker not sole microspheres. The microspheres were actually encompassed into the film
  • Originally the type of oil used to prepare microspheres previously was mineral oil; however, safflower oil was used this time as substitute
  • Safflower oil has a higher freezing point than mineral oil
  • Once samples placed in 10mL vials after being removed from blender began to settle, each sample was then sonicated before freezing in liquid nitrogen -- keeping microspheres immersed in organic layer
  • For the 90:10 PVOH 146K 110% CEC Laponite w/ DMHXLBR, 45mL vs. 35mL of safflower oil was used
  • Rhodamine 6G dye maintains high affinity for organics; therefore, Rhodamine 6G dye will be added later to each microsphere newly prepared
  • DMSO dye prepared hydrogel samples did not leak dye at a quick rate versus dyes prepared in H2O
  • To analyze fluorescence and execute pressure test, hydrogel samples had to be cut into small pieces and smashed up against the glass in order to emulate sheer pressure tests
  • To simulate sheer pressure testing on the hydrogels, Pasteur pipettes were bent at different angles to determine which formation would provide the most sheer pressure and largest fluorescence signal. (Pipette pictures soon to be uploaded)
  • The same sample, 90:10 PVOH 146K 110% Laponite w/ DMHXLBR, was used to determine which Pasteur pipette modification proved useful and most result worthy when providing a fluorescence signal.
  • It appears as if using an unmodified pipette or a pipette with a bend at the top of the pipette so the sides are almost touching produced the maximum amount of sheer pressure.