“…Polymer scientists have focused on smart hydrogels that can undergo reversible, three-dimensional, large-scale physical or chemical changes in response to small external changes in environmental conditions, such as temperature, 1 pH, 2 light, 3 magnetic or electric field, 4 ionic strength and biological molecules. 5 Most pH-responsive polymers are polyelectrolytes with weak acidic or basic groups in their structure, which either accept or release protons in response to changes in environmental pH.…”