I am trying to dissolve at 12% in HBSS but it is not dissolving even after 24h of stirring. Is there anything I can adjust like pH or temperature to get the acrylamide to dissolve?
Just leaving it to gointo solution and swell should be adequate however you could look at using 8-10% HBSS. Adjusting pH should be via crosslinking, after the acrylamide has dissolved. You can utilized NaOH or TEA...
If I understand correctly you are trying to dissolve the MBA at 12% (w/v), that is 12 grams per 100 mL. As far as I know that is quite above the limit of solubility of MBA, so what I suppose it is happening is that a part of your compound is in solution, while another part remains as a particulate.
For instance, to achieve a good solubility of MBA in water the correct concentration at 20°C is 2% (w/v) (source: Sigma Aldrich).
Two ways I can suggest to increase the solubility of MBA are the following:
1 - As you mentioned, increase the temperature. Unfortunately I do not have data on the entity of the increase. I am not able to tell you how much you should increase the temperature to reach that 12% or if that is even possible to achieve.
2- Use an additive to boost the solubility. This paper for instance states that the addition of isopropanol increased the solubility from 3 to 10%:Article Polymer Gel Dosimeters with Increased Solubility: A Prelimin...