Mono-, bi-, and trivalent coumarin-containing benzoxazine monomers were synthesized by facile Mannich reactions of 4-methyl-7-hydroxycoumarin and paraformaldehyde with aniline, bisphenol A–NH2, and 1,3,5-tri(4-aminobenzene).

A series of thermally polymerizable dendrimers of various generations, equipped with triphenylamine (TPA) and benzoxazine (BZ) groups, is synthesized through facile one-pot Mannich condensations of N ,N -bis(4-aminophenyl)benzene-1,4-diamine (TPA-3NH , as the core group), 4-(bis(4-aminophenyl)amino)phenol (TPA-2NH -OH, as the AB branching group), and CH O in 1,4-dioxane. The ratios of the integrated areas in the H nuclear magnetic resonance spectra of these dendrimers are consistent with the theoretical numbers of protons, suggesting their successful syntheses. Bathochromic shifts of signals are evident in the UV-vis and photoluminescence spectra upon increasing the generation of the TPA-BZ dendrimers, consistent with an increase in the effective conjugation length. The TPA-BZ dendrimers are able to undergo thermal polymerization and display unique optical physical properties, resulting in thermoset TPA networks after thermal ring-opening polymerization.

Different well-defined benzoxazine/triphenylamine based hyperbranched polymers with controlled degree of branching were prepared and discussed.

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 1 H and 13 C 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.

In this report, we designed a new and simple salicylaldehyde azine-functionalized benzoxazine (Azine-BZ) monomer via Mannich condensation reaction of aniline and paraformaldehyde with 1,2-bis(2,4-dihydroxybenzylidene)hydrazine in 1,4-dioxane. Compared with 10 3-phenyl-3,4-dihydro-2H-benzooxazine monomer (263 °C), the maximum exothermic peak of Azine-BZ was shifted to a lower temperature (213 °C) based on differential scanning calorimetry (DSC) analyses because of the basicity of the phenolic group (OH) in the ortho position and the azine groups. Blending Azine-BZ with different weight ratios of zinc perchlorate [Zn(ClO 4 ) 2 ] to form benzoxazine/zinc ion complexes not only afflicted the thermal properties based on thermogravimetric analysis (TGA) due to physical crosslinking through metal-ligand interactions, but also expedite ring-opening polymerization, decreasing the curing temperature from 15 213 to 184 °C (at 10 wt% Zn 2+ ). Based on the fluorescence results, the Azine-BZ and AZine-BZ/Zn(ClO 4 ) 2 complexes were nonemissive in THF solution. Their fluorescence increased gradually upon on the addition of water contents as poor solvent. Interestingly, both the pure Azine-BZ and blending wotj Zn(ClO 4 ) 2 still emitted light after thermal curing at 150 °C, as determined through photoluminescence measurements, indicating that the azine group could act as a probe of the curing behavior of the benzoxazine monomer, as well as a fluorescent chemosensor for Zn 2+ and, possibly, other transition metal ions through a metal-ligand charge transfer 20 mechanism. 45 polybenozoxazine chemistry offers flexibility of many molecular designs, thereby facilitating the preparation of different PBZ nanocomposites. To control the properties of PBZs, several derivatives functionalized with reactive groups A new salicylaldehyde azine-functionalized benzoxazine (Azine-BZ) monomer formed benzoxazine/zinc ion complexes 5 that not only improved the thermal properties but also facilitated ring-opening polymerization.