Solvent-free synthesis of a formaldehyde-free benzoxazine monomer: study of its curing acceleration effect for commercial benzoxazine

Abstract

Polybenzoxazines are very interesting phenolic resins that are obtained from ring-opening polymerisation (ROP) of benzoxazine monomers. However, commercially available resins such as bisphenol A aniline benzoxazine (BA-a) have found limited...

The mechanochemical synthesis of environmentally benign fully biobased 4th generation benzoxazines and their polymers: mechanistic insights into the catalytic activity of latent catalysts

“…Eventually, temperature-guided geometric conformations may offer a possibility of the C 2 –C phenolic bond rotation, enabling the proximity of H phenolic to the other neighbouring proton acceptor (O oxazine ) to create intramolecular O– H phenolic ⋯O oxazine hydrogen bonds via a quasi-chelating ring to assist ROP in the dual mode, both due to the increase in angle strain and latent catalytic effects. 62 As per earlier reported data, the latent catalyst can be activated by simply breaking the hydrogen bonding upon heating and can facilitate the acid-catalyzed polymerization of the BZs.…”

“…To gain better insights of the temperature dependency on the strength of hydrogen bonding for the same crystal, SCXRD data were recorded at three different temperatures (16,40 O-H phenolic ⋯O oxazine hydrogen bonds via a quasi-chelating ring to assist ROP in the dual mode, both due to the increase in angle strain and latent catalytic effects. 62 As per earlier reported data, the latent catalyst can be activated by simply breaking the hydrogen bonding upon heating and can facilitate the acid-catalyzed polymerization of the BZs.…”

“…36,56,57 Recently, the replacement of formaldehyde with other aldehydes has also been employed to form 4 th generation BZs. [58][59][60][61][62] More recently, in this latest generation of BZs with oxazine-ring substitution found to empower structural tailoring close to the oxazine-ring reactive centre and accounted as a strategy to overcome mass loss issues and facilitated polymerization at lower temperature requirements than unsubstituted monomers. 63,64 The progression of structural changes in benzoxazine monomers over the years is illustrated in Fig.…”

Lignin-based bisguaiacol diisocyanate: a green route for the synthesis of biobased polyurethanes

“…[42][43][44] Indeed, this approach already gave excellent results in our hands for monomer or polymer synthesis. [45][46][47] Gratifyingly, using a 20 mL stainless steel milling jar with a 1 cm diameter stainless steel ball agitated at a frequency of 30 Hz, in a vibratory ball-mill, we obtained an excellent yield (90%) of 5 after only 90 minutes of milling. The yield of the transformation was even improved to nearly quantitative (>99%), when running the reaction for 3 h in the presence of potassium iodide catalyst.…”

Hydrogen Bonding-Guided Strategies for Thermal Performance Modulation in Biobased Oxazine Ring-Substituted Benzoxazine Thermosets

“…The Ishida research group pioneered the use of aromatic aldehydes to synthesize this class of oxazine ring-substituted benzoxazines . Such monomers offer excellent opportunities to regulate polymer properties either through the alteration of substitution at 2-/4-position(s) of the oxazine ring, − or through the attachment of an acidic functionality at the C 2 -aryl ring since the concept of the “ built-in catalyst ” in earlier-generation monomers is very well explored. Considering environmental sustainability, the exploration of eco-friendly feedstocks − is becoming popular in this genre.…”