Polanyi's PhD studies at Manchester University focused on measuring the strengths of chemical bonds using thermal dissociation, building on Warhurst's graduate studies using a sodium flame apparatus to determine the likelihood that a collision between a sodium atom and another molecule would lead to a chemical reaction. For the majority of his career, Polanyi's research has focused on chemical dynamics, attempting to determine the mechanics of a chemical reaction, and the properties of chemical species in the transition state. While at the National Research Council (NRC), Polanyi evaluated transition state theory for its predictive powers, coming to the conclusion that the theory was flawed, largely due to a lack of knowledge about the forces at play in the transition state. Near the end of his stay at NRC, Polanyi worked in Gerhard Herzberg's lab, using spectroscopy to examine vibrational and rotational excitation in iodine molecules. During Polanyi's time at Princeton University, he worked with Sir Hugh Taylor and his colleagues, Michael Boudart and David Garvin. He was influenced by studies conducted at Princeton looking at the vibrationally excited reaction products between atomic hydrogen and ozone.