User:Karlena L. Brown/Notebook/PVOH Research/2013/02/15

OBJECTIVES

• Continue to run fluorescence testing on samples containing Rhodamine 6G dye
• Prepare new microsphere samples using new method of preparation

New 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 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, quicklya dd some Rhodamine 6G dye to the solution based upon the ratio selection (90:10 vs. 50:50)
7. After the addition of the dye, allow the solution to go through freeze / thaw crosslinking process for ~ 2-3 days
8. Place microsphere solution in a freezer at -20°C for 24 hours and then remove and allow to solution to thaw for 24 hours

Reference: http://www.sciencedirect.com/science/article/pii/S0168365998000893

PVOH 146K Prepared Microsphere Samples & Dye Preparations

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

  M1V1 = M2V2
  1μM (RG6)x 25mL = (92μM)V2    V2 = 271.74μL

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

  M1V1 = M2V2
  1μM (RG6)x 25mL = (165μM)V2    V2 = 152.00μL

Notes

• Hydrogels that completed the freeze / thaw cycle which had ~ 4mL of H₂O added in order for fluorescent analysis include:

  # 50:50 PVOH 130K 110% CEC NaMT w/ DMHXLBR
  # 90:10 PVOH 130K 110% CEC Laponite w/ DMHXLBR
  # 50:50 PVOH 130K 110% CEC Laponite w/ DMHXLBR
  # 90:10 PVOH 130K 110% CEC NaMT w/ DMHXLBR

• For fluorescence analysis, samples were taken every 15 minutes for 2hrs to determine a dye leaching / diffusion rate from hydrogels
• Fluorescent samples run and completed for 2hr diffusion rate determinations:

  # Hydrogel 50:50 PVOH 146K 50% CEC NaMT w/ Bu3HdP+
  # Hydrogel 90:10 PVOH 146K 50% CEC NaMT w/ Bu3HdP+
  # Hydrogel 50:50 PVOH 146K NaMT
  # Hydrogel 90:10 PVOH 146K NaMT
  # Hydrogel control PVOH 146K 
  # Hydrogel 90:10 PVOH 146K Laponite

• In regards to the spectra, all samples maintained a quick diffusion rate indicating that dye crosslinking during the freeze / thaw cycle is pertinent when making hydrogels because it slows down the diffusion rate
• For the hydrogels in which the dye was added, but not crosslinked into the material, their diffusion rate was the quickest -- a significant amount of dye leaked out of those hydrogels throughout the 2 hour period
• Comparing the 50:50 vs. the 90:10 ratio of PVOH / clay, the hydrogels with 50:50 ratio had more dye leak out than the 90:10 ratio hydrogels indicating a more effective pressure stimuli