Facile Synthesis and In-Depth Characterization of Polymethacrylimides with Tunable Properties

High-performance polymers such as polymethacrylimides have outstanding properties, for example, a unique strength-to-weight ratio and a high thermal stability, usually coupled to a high glass transition temperature. However, the requirement of high processing temperatures caused by these high glass-transition temperatures is often not desired for melt extrusion processes. Herein, a novel and straightforward imidization process of poly(methacrylic anhydrides) is presented with different ratios of ammonia and N-isopropylamine that is induced by thermal treatment. Therefore, polymethacrylimides with a varying degree of N-substitution, and thus a varying number of hydrogen-bond-donating moieties, are synthesized under facile reaction conditions. An in-depth investigation into the structures obtained with this new methodology is undertaken via a combination of nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared spectroscopy (FT-IR), and high-resolution electrospray ionization mass spectrometry (ESI-MS). Additionally, thermal properties of the materials are investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses. These latter measurements highlight the key opportunity available with this novel synthesis to tailor the thermal properties of the polymer by providing a clear correlation between hydrogen bond formation, as observed by FT-IR, and the glass transition temperature.