“…31,32 The absorption band at 1491 cm −1 was attributed to the bending mode in the C–H in-plane of the trisubstituted benzene ring and the bands at 944 cm −1 was related to the out-of-plane bending vibration of the C–H group, due to the characteristic mode of benzene attached to the oxazine ring. 22,31,32 The wide band in the region of 3100–3500 cm −1 was assigned to the symmetric and asymmetric stretching of both N–H and O–H (originating from water absorption). 33,34 The two absorption bands at 1343 and 1565 cm −1 were assigned to the stretching vibration of the –NO 2 group.…”
Section: Resultsmentioning
confidence: 99%
“…33,34 The two absorption bands at 1343 and 1565 cm −1 were assigned to the stretching vibration of the –NO 2 group. 22,35 Figure 7.Fourier transform infrared spectra of the synthesized nitrogen-rich benzoxazines monomers.…”
Section: Resultsmentioning
confidence: 99%
“…The cationic ring-opening polymerization of the developed nitrogen-based–benzoxazine monomers was achieved without initiators or catalysts following the curing program: 160°C/3 h, 200°C/2 h that ensure best thermal properties of the polymer. 22 Figure 3 illustrates the cationic ring-opening polymerization and the final structure of the SC-Bz and DNPH-Bz polymers. The polymerization mechanism has been investigated by several authors, 23–26 so that the N and O heteroatoms act as initiator centers that lead to the formation of repetitive phenoxy bonds, which will rearrange on phenolic structure under further heating.Figure 3.Synthesis of the nitrogen-rich benzoxazine polymers.…”
In a vision to develop new synthetic routes for the preparation of energetic materials, two new energetic benzoxazine monomers were synthesized via a two-step Mannich reaction process involving the incorporation of nitrogen–nitrogen bonds and explosophore groups (NO2) into the monomer backbone. The molecular structures of the synthesized monomers were confirmed by 1H NMR, Fourier transform infrared and elemental analysis techniques. The curing behavior and the degradation phenomena were evaluated by differential scanning calorimetry-thermogravimetric analysis analyses. The two monomers showed two distinct exothermic peaks related to the polymerization and degradation phases. The energetic performances were evaluated by determining the heat of combustion and formation using a bomb calorimeter, in an oxygen atmosphere. The results indicated that the 2,4 dinitrophenylhydrazine–based benzoxazine has better energetic properties than the phenylsemicarbazide-based benzoxazine, and the two developed polymers showed comparable performances with nitrocellulose and glycid azide polymer. Overall, this study has demonstrated that the ease of synthesis of the benzoxazine resins via Mannich reaction can be further extended to the energetic field and further research is undergoing to fully unravel the potential of these exceptional materials.
“…31,32 The absorption band at 1491 cm −1 was attributed to the bending mode in the C–H in-plane of the trisubstituted benzene ring and the bands at 944 cm −1 was related to the out-of-plane bending vibration of the C–H group, due to the characteristic mode of benzene attached to the oxazine ring. 22,31,32 The wide band in the region of 3100–3500 cm −1 was assigned to the symmetric and asymmetric stretching of both N–H and O–H (originating from water absorption). 33,34 The two absorption bands at 1343 and 1565 cm −1 were assigned to the stretching vibration of the –NO 2 group.…”
Section: Resultsmentioning
confidence: 99%
“…33,34 The two absorption bands at 1343 and 1565 cm −1 were assigned to the stretching vibration of the –NO 2 group. 22,35 Figure 7.Fourier transform infrared spectra of the synthesized nitrogen-rich benzoxazines monomers.…”
Section: Resultsmentioning
confidence: 99%
“…The cationic ring-opening polymerization of the developed nitrogen-based–benzoxazine monomers was achieved without initiators or catalysts following the curing program: 160°C/3 h, 200°C/2 h that ensure best thermal properties of the polymer. 22 Figure 3 illustrates the cationic ring-opening polymerization and the final structure of the SC-Bz and DNPH-Bz polymers. The polymerization mechanism has been investigated by several authors, 23–26 so that the N and O heteroatoms act as initiator centers that lead to the formation of repetitive phenoxy bonds, which will rearrange on phenolic structure under further heating.Figure 3.Synthesis of the nitrogen-rich benzoxazine polymers.…”
In a vision to develop new synthetic routes for the preparation of energetic materials, two new energetic benzoxazine monomers were synthesized via a two-step Mannich reaction process involving the incorporation of nitrogen–nitrogen bonds and explosophore groups (NO2) into the monomer backbone. The molecular structures of the synthesized monomers were confirmed by 1H NMR, Fourier transform infrared and elemental analysis techniques. The curing behavior and the degradation phenomena were evaluated by differential scanning calorimetry-thermogravimetric analysis analyses. The two monomers showed two distinct exothermic peaks related to the polymerization and degradation phases. The energetic performances were evaluated by determining the heat of combustion and formation using a bomb calorimeter, in an oxygen atmosphere. The results indicated that the 2,4 dinitrophenylhydrazine–based benzoxazine has better energetic properties than the phenylsemicarbazide-based benzoxazine, and the two developed polymers showed comparable performances with nitrocellulose and glycid azide polymer. Overall, this study has demonstrated that the ease of synthesis of the benzoxazine resins via Mannich reaction can be further extended to the energetic field and further research is undergoing to fully unravel the potential of these exceptional materials.
“…From the value of T g obtained from DSC analysis (Table 1), it is inferred that the biophenol-based benzoxazine matrix and biocarbon-reinforced hybrid composites possess an almost close value of T g and the influence of biocarbon reinforcement has an only marginal effect. 54…”
In the present work, an attempt has been made to develop cow manure carbon-reinforced hybrid biophenol-based benzoxazine composites for antifouling coating applications. Bio-based benzoxazine with unsymmetrical molecular structure was synthesized using the mixture of a combination of cardanol and eugenol with diaminodiphenyl methane and paraformaldehyde, and the hybrid-benzoxazine obtained was characterized using different analytical techniques, viz., Fourier transform infrared, nuclear magnetic resonance and MALDI mass. Bio-based benzoxazine was further reinforced with varying weight percentages (1, 3 and 5 wt%) of biocarbon derived from cow manure to obtain hybrid composite coatings. The hybrid benzoxazine matrix and composites were studied for their thermal behaviour, contact angle (CA), morphology, corrosion-resistant behaviour and antifouling character to utilize them as coatings materials for different industrial applications. Results obtained from different studies inferred that the biocarbon-reinforced composites possess an enhanced value of glass transition temperature (249°C), high char yield (38.4%), improved CA (105.6°), higher efficiency of corrosion protection against mild steel surface (98%) and improved antimicrobial activity.
“…Benzoxazines 1 and 2 could not be obtained when the milling was performed in a zirconia jar, despite the full conversion of substrates, maybe due to the formation of polybenzoxazine network via a thermally induced ring-opening polymerization side-reaction. [57][58][59] The reversible heterolytic scission of the cyclic N,O-acetal moiety is thermally or catalytically induced, leading to phenolic structures by a Mannich base bridge [-CH 2 -N(R 2 )-CH 2 -], very similar to traditional phenolic resin network polymer. 60 It is also worth noticing that diverse procedures (choice of the solvent, reaction time, temperature) were reported for the preparation of benzoxazines in solution, depending on the nature of the product to be obtained.…”
We describe herein an unprecedented mechanochemical "parallel synthesis" of 3,4-dihydro-2H-benzo[e][1,3]oxazine derivatives via a one pot three component reaction. The new milling system uses a multiposition jar (variable sizes are possible), allowing for the processing of up to 12 samples simultaneously, leading to the formation of a fungicide and a building block for polymer preparation with higher throughput compared to standard milling devices.
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