Reaction-Induced Miscibility in Styrene- and Benzoxazine-Based Copolymers with Poly(vinylpyrrolidone) Blends Through Strong Intermolecular Hydrogen-Bonding Interactions

The miscibility behavior of polymer blends has garnered significant interest; however, while most binary polymer blends are immiscible due to thermodynamic challenges, reaction-induced miscibility (RIM) presents a promising yet underexplored phenomenon for achieving homogeneous mixtures through specific intermolecular hydrogen bonding interactions. This study investigates the design and synthesis of novel styrene- and benzoxazine-based copolymers to achieve RIM behavior with a poly(vinylpyrrolidone) (PVP) homopolymer. Two benzoxazine monomers, HPMI-BZ and Ty-BZ, were synthesized via Mannich condensation, incorporating maleimide groups to enable free radical copolymerization with styrene monomer to form PS-alt-P(HPMI-BZ) and PS-alt-P(Ty-BZ) alternating copolymers, which were characterized using Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The thermal and miscibility behaviors of the PS-alt-P(HPMI-BZ)/PVP and PS-alt-P(Ty-BZ)/PVP binary blends were analyzed, focusing on their intermolecular hydrogen bonding after thermal ring-opening polymerization (ROP). Results demonstrated that the incorporation of functional groups such as OH units from benzoxazine units through thermal ROP facilitated strong intermolecular interactions with the C═O units of PVP, enabling RIM in otherwise immiscible blends. This work highlights the interplay between molecular structure, thermal stability, and miscibility behavior, offering insights into the development of next-generation thermoset/thermoplastic materials with tailored properties.