Improved Characterization of Polyoxazolidinones by Incorporating Solubilizing Side Chains

Carbon dioxide-based polyoxazolidinones
(POxa) are an
emerging
subclass of non-isocyanate polyurethanes for high temperature applications.
Current POxa with rigid linkers suffer from limited solubility that
hinders synthesis and characterization. Herein, we report the addition
of alkyl and alkoxy solubilizing groups to rigid spirocyclic POxa
and their poly(hydroxy­oxazolidinone) (PHO) precursors. The modified
polymers were soluble in up to six organic solvents, enabling characterization
of key properties (e.g., molar mass and polymer structure) using solution-state
methods. Dehydration of PHO to POxa changed solubility from highly
polar to less polar solvents and improved thermal stability by 76–102
°C. The POxa had relatively high glass transition (85–119
°C) and melting (190–238 °C) temperatures tuned by
solubilizing group structure. The improved understanding of factors
affecting solubility, structure–property relationships, and
degradation pathways gained in this study broadens the scope of soluble
POxa and enables more rational design of this promising class of materials.