Novel chiral and achiral bisphenol A and bisphenol AF based benzoxazine monomers were synthesized from the reaction of bisphenol A (bisphenol AF) with paraformaldehyde and primary amines

including (R)-(+)--methylbenzylamine and/or (S)-(-)--methylbenzylamine

via solventless method.The chemical structures and properties of the benzoxazine monomers were identified by Fourier transform infrared spectroscopy (FTIR)

proton nuclear magnetic resonance (1 H-NMR)

polarimeter

and high performance liquid chromatography (HPLC).The curing behavior and thermal properties of benzoxazine monomers and cured polymers were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).The results showed that solventless method provided faster reaction rate

higher yields

and was more environmentally friendly than conventional solvent method.Achiral benzoxazine monomers with double chiral center consisted of four isomers

such as two racemic isomers and two mesomeric isomers.The content of mesomeric isomers was higher than that of racemic isomers.Chiral and achiral benzoxazine monomers underwent the same curing behavior.For achiral polybenzoxazines

the methyl and benzyl chains in racemic and mesomeric structures twined for each other in a disorderly manner to be like a wedge due to the different stereo-configuration of achiral benzoxazine molecules

which resulted in lower free volume and tighter packing of the polymer than those of chiral polybenzoxazines.Consequently

achiral polybenzoxazines showed higher glass transition temperature than that of chiral polybenzoxazines and bisphenol A-aniline based polybenzoxazines.Moreover

CF bond with high dissociation energy contributed to improvement of thermal properties of the polymer.As a result

the bisphenol AF-based polybenzoxazines displayed higher thermal properties than bisphenol A-based polybenzoxazines.