- Prepare all polyvinyl alcohol(MW 146,000-186,000) hydrogels with clay additives
- Preparation of dye stock solutions.
Preparation of Hydrogels
- 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.)
- Add the desired amount of clay to the sample.
- Add a magnetic stir bar to the beaker and 6mL of distilled to the reaction mixture.
- Add 8wt% DMSO to the reaction mixture.
- Heat the reaction mixture to 80°C. If the reaction mixture begins to boil, immediately reduce heat.
- 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.
- 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.
- Repeat this process three times.
The following procedure was adapted from PVA–clay nanocomposite hydrogels for wound dressing
|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
- 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.
(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
(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:
- Rhodamine 6G is mildly flammable. Care must be used at all times when dealing with 1,2-dichloroethane.
- 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.
- There is limited evidence of the carginogenic effects of Rhodamine 6G. Avoid all Rhodamine 6G skin contact by wearing gloves and goggles.
- Please refer to Karlena Brown's notebook for protocol for stock solution dye preparation.