# User:Moira M. Esson/Notebook/CHEM-581/2013/01/30

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## Objectives

• Prepare all polyvinyl alcohol(MW 146,000-186,000) hydrogels with clay additives
• Preparation of dye stock solutions.

## Preparation of Hydrogels

General Protocol:

1. Using a clean 10mL-20mL beaker, add the desired amount of polyvinyl alcohol. (If preparing a 90:10 ratio of polyvinyl alcohol to clay hydrogel, add ~0.9g PVOH. If preparing a 50:50 ratio of polyvinyl alcohol to clay, ~0.5g polyvinyl alcohol should be added. All hydrogels were prepared on a 1g scale.)
2. Add the desired amount of clay to the sample.
3. Add a magnetic stir bar to the beaker and 6mL of distilled to the reaction mixture.
4. Add 8wt% DMSO to the reaction mixture.
5. Heat the reaction mixture to 80°C. If the reaction mixture begins to boil, immediately reduce heat.
6. Allow the reaction mixture to stir at 80°C for at least 2 hours, or until complete dissolution of polyvinyl alcohol and equal distribution of clay throughout the reaction mixture.
7. Remove reaction mixture from heat and place in freezer(-20°C) for 24 hours. After 24 hours, remove from the freezer and allow to thaw for 24 hours.
8. Repeat this process three times.

The following procedure was adapted from PVA–clay nanocomposite hydrogels for wound dressing
Hydrogel information:

 Preparation of PVOH(MW 146,000-186,000)-clay hydrogels ' ' ' Composition of hydrogel Amount of PVOH(g) Amount of clay(g) Amount of DMSO added(mL) 90:10 PVOH: 50% exchanged NaMT 0.9001 0.1001 0.0655 100% PVOH 1.02193 0 0 50:50 PVOH:50% exchanged NaMT 0.5098 0.4997 0.0364 90:10 PVOH:NaMT 0.90698 0.1002 0.0655 50:50 PVOH:NaMT 0.50399 0.4999 0.0364 90:10 PVOH:Lamponite 0.9062 0.1001 0.0655 50:50 PVOH:Lamponite 0.5105 0.4999 0.0364

Observations:

• Hydrogels containing sodium montmorillonite(NaMT) required the addition of 1mL distilled H2O and required longer heating time. This should be noted when dye is added. A separate, slightly more concentrated stock solution of dye should be prepared for addition to any hydrogels with NaMT additive.
• After preparation of 6 hydrogels, realized that the inclusion of dye will be necessary before the freeze-thaw cross-linking method is performed. I.e. Dye should be added during heating process of PVOH-clay reaction mixture.
• All prepared hydrogels will be reprepared with the addition of dye.

## Calcualtions for dye preparation

• Using Rhodamine 6G as the dye. This is a very bright and fluorescent dye so will want an internal concentration of dye of 1μM.

90:10 ratio

 (1μMx6mL H2O)/0.0655mL DMSO=91.6μM

• This is the molar concentration of the dye will need to be prepared.
 (90μM dye wanted) x (1x10-6M/1μM) x (0.05L) x (479.02gdye/mol)=0.0022g dye added to 50mL volumetric flask


50:50 ratio

 (1μMx6mL H2O)/0.0364mL DMSO= 164.84μM

• This is the molar concentration of the dye that will need to be prepared.
 164.84μMdye x (1x10-6M/1μM) x (0.05L) x (7479.02g dye/mol)= 0.004g dye added to 50mL volumetric flask


Rhodamine 6G safety:

1. Rhodamine 6G is mildly flammable. Care must be used at all times when dealing with 1,2-dichloroethane.
2. Rhodamine 6G is irritating to eyes. Goggles should be worn whenever using Rhodamine 6G. It is also a fine powder, so open away from face.
3. There is limited evidence of the carginogenic effects of Rhodamine 6G. Avoid all Rhodamine 6G skin contact by wearing gloves and goggles.

## Notes

• Please refer to Karlena Brown's notebook for protocol for stock solution dye preparation.