We break new ground in the in-depth mechanistic understanding of the molecular behavior of tert-butyl methacrylate (t-BMA) and N-isopropylacrylamide (NIPAM) copolymers upon thermal treatment and correlate this understanding with the mechanical properties of the resulting materials. We explore-via nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic measurements-the formation of cyclic anhydride and imide structures and exploit high-resolution mass spectrometry (HRMS) coupled to size-exclusion chromatography (SEC) as well as tandem MS (MS/MS) to correlate the time and temperature dependent cyclization processes. Critically, we propose a reshuffling mechanism describing dynamic ring-opening events involving the anhydride and imide structures, which enables the in-depth understanding of the dynamic material properties. Drawing on information from low-molecular-weight model systems, we translate our findings to high-molar-mass polymers, showing that our mechanistic model enables the understanding of the material properties of the polymers.