Polymer solutions were sonicated using a QSonica Q500 with a microtip attachment. The microtip QSonica probe was immersed in a polymer solution in MeCN. Water was flowed across the outer surface of the tube using a custom-made jacketed beaker to control bulk temperature (Video S1) (University of Massachusetts Amherst Scientific Glassblowing Laboratory, Amherst, MA). Samples were sonicated at 10% amplitude and 400 kHz for 5 seconds at a time, with 10 second breaks in between pulses to avoid probe overheating. Gelation was determined by the point at which the power output would drop to ~0 W and noise from vibrations would cease when the polymer had formed a solid gel. Samples were then immediately moved to the adjacent needle induced cavitation (NIC) setup to determine the elastic modulus immediately post sonication.