Rational design and molecular engineering of ultrastable porous fluorescent guanidine functionalized polybenzoxazine

Abstract

This study reports the design, synthesis, and characterization of a novel compound, 1,2,3-tris(7-bromo-2H-benzo[e][1], [3]oxazin-3(4H)-yl)guanidine (BGu-BZ), using triaminoguanidinium chloride (Gu-3NH₂) as a precursor through a straightforward Mannich condensation reaction. The resulting benzoxazine monomer exhibited distinct fluorescence properties influenced by solvent polarity, with emission maxima shifting across solvents. Thermal curing of BGu-BZ at 220 °C yielded poly(BGu-BZ), a porous polymer with enhanced fluorescence emission and excellent thermal stability (T_d10 = 381.5 °C). The cured polymer demonstrated a surface area of 43 m²/g and significant fluorescence shifts, confirming alterations in electronic structure and increased conjugation. The study highlights the solvatochromism behavior of both monomer and polymer, underscoring their potential for applications in luminescent technologies such as solvent sensing and optoelectronics. This work provides valuable insights into the structural-functional relationship in guanidine-functionalized benzoxazines, paving the way for advanced material applications.