Abstract
In this study, we synthesized a novel multifunctional benzoxazine monomer (Coumarin-COOH BZ), possessing both coumarin and COOH groups, through the reaction of 4-methyl-7-hydroxycoumarin, 4-aminobenzoic acid, and paraformaldehyde in 1,4-dioxane, with the structure confirmed using 1H and 13C nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC), FTIR spectroscopy, and thermogravimetric analysis were then employed to monitor the thermal curing behavior of Coumarin-COOH BZ and its blends with poly(N-vinyl-2-pyrrolidone) (PVP), both before and after photodimerization of the coumarin moieties. DSC revealed a single glass transition temperature for each Coumarin-COOH BZ/PVP blend composition; a large positive deviation based on the Kwei equation suggested that strong hydrogen bonding existed between the Coumarin-COOH BZ and PVP segments, confirmed through FTIR spectroscopic analyses. The thermal properties improved (i.e., increased glass transition and thermal degradation temperatures) as a result of the increased crosslinking density after photodimerization under UV exposure.
Highlights
Polybenzoxazines (PBZs) are interesting materials for academic research and industrial applications because of their high thermal stability, low flammability, low surface free energy, high chemical resistance, flexible molecular structural design, and low water absorption [1,2,3,4]
We synthesized according toInprocedures weexpected have reported moiety of the monomer to serve an important role by facilitating hydrogen bonding within previously [12]
These 1H and 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectra are consistent with the trisubstituted benzene ring) successful synthesis of Coumarin-COOH
Summary
Polybenzoxazines (PBZs) are interesting materials for academic research and industrial applications because of their high thermal stability, low flammability, low surface free energy, high chemical resistance, flexible molecular structural design, and low water absorption [1,2,3,4]. The behavior of coumarin chromophores can change in response to variations in its chemical structure coumarins: at 250–300 a π-to-π*bands transition of theofconjugated or the light source [25,26].nm, Tworepresenting significant absorption appearofinthe the electrons. We have reported a bifunctional monomer containing coumarin and pyrene stability of the thermally cured BZ after photodimerization of its coumarin moieties [28]. In an proposed the BZ monomer containing both coumarin unit and investigated the possible chemical unrelatedofstudy, we type found miscibility could result instudy, largewe deviations in miscibility the values could of Tg structure this new of that. 4-methyl-7-hydroxycoumarin coumarin and COOH units, through a facile Mannich condensation of 4-methyl-7-hydroxycoumarin (Coumarin-OH), 4-aminobenzoic paraformaldehyde in (Coumarin-OH), 4-aminobenzoic acid, acid, and and paraformaldehyde in 1,4-dioxane We blended this thisBZBZ monomer homopolymeric form miscible poly(Coumarin-COOH blended monomer withwith homopolymeric.
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